Bump version

- Create migration directives & migrators
- Modify Cache classes to support array manipulation
- Create Redis unit and RedisCache implementation
- Create Queueable base class and Queue class that uses Cache backend

.drone.yml

@@ -22,7 +22,7 @@ steps:
         from_secret: docs_deploy_key
       port: 22
       source: extollo_api_documentation.tar.gz
-      target: /var/nfs/general/static/sites/extollo
+      target: /var/nfs/storage/static/sites/extollo
     when:
       event: promote
       target: docs
@@ -38,7 +38,7 @@ steps:
         from_secret: docs_deploy_key
       port: 22
       script:
-        - cd /var/nfs/general/static/sites/extollo
+        - cd /var/nfs/storage/static/sites/extollo
         - rm -rf docs
         - tar xzf extollo_api_documentation.tar.gz
         - rm -rf extollo_api_documentation.tar.gz
@@ -103,10 +103,19 @@ steps:
       event:
         exclude: tag
 
-  - name: build module
+  - name: Install dependencies
     image: glmdev/node-pnpm:latest
     commands:
       - pnpm i
+
+  - name: Lint code
+    image: glmdev/node-pnpm:latest
+    commands:
+      - pnpm lint
+
+  - name: build module
+    image: glmdev/node-pnpm:latest
+    commands:
       - pnpm build
       - mkdir artifacts
       - tar czf artifacts/extollo-lib.tar.gz lib

.idea/codeStyles/Project.xml

@@ -0,0 +1,55 @@
+<component name="ProjectCodeStyleConfiguration">
+  <code_scheme name="Project" version="173">
+    <JSCodeStyleSettings version="0">
+      <option name="USE_SEMICOLON_AFTER_STATEMENT" value="false" />
+      <option name="FORCE_SEMICOLON_STYLE" value="true" />
+      <option name="USE_DOUBLE_QUOTES" value="false" />
+      <option name="FORCE_QUOTE_STYlE" value="true" />
+      <option name="ENFORCE_TRAILING_COMMA" value="WhenMultiline" />
+      <option name="OBJECT_LITERAL_WRAP" value="2" />
+    </JSCodeStyleSettings>
+    <TypeScriptCodeStyleSettings version="0">
+      <option name="USE_SEMICOLON_AFTER_STATEMENT" value="false" />
+      <option name="FORCE_SEMICOLON_STYLE" value="true" />
+      <option name="USE_DOUBLE_QUOTES" value="false" />
+      <option name="FORCE_QUOTE_STYlE" value="true" />
+      <option name="ENFORCE_TRAILING_COMMA" value="WhenMultiline" />
+      <option name="OBJECT_LITERAL_WRAP" value="2" />
+    </TypeScriptCodeStyleSettings>
+    <editorconfig>
+      <option name="ENABLED" value="false" />
+    </editorconfig>
+    <codeStyleSettings language="JavaScript">
+      <option name="INDENT_CASE_FROM_SWITCH" value="false" />
+      <option name="ALIGN_MULTILINE_PARAMETERS" value="false" />
+      <option name="ALIGN_MULTILINE_FOR" value="false" />
+      <option name="METHOD_CALL_CHAIN_WRAP" value="2" />
+      <option name="IF_BRACE_FORCE" value="3" />
+      <option name="DOWHILE_BRACE_FORCE" value="3" />
+      <option name="WHILE_BRACE_FORCE" value="3" />
+      <option name="FOR_BRACE_FORCE" value="3" />
+    </codeStyleSettings>
+    <codeStyleSettings language="PHP">
+      <indentOptions>
+        <option name="USE_TAB_CHARACTER" value="true" />
+        <option name="SMART_TABS" value="true" />
+      </indentOptions>
+    </codeStyleSettings>
+    <codeStyleSettings language="Shell Script">
+      <indentOptions>
+        <option name="INDENT_SIZE" value="4" />
+        <option name="TAB_SIZE" value="4" />
+      </indentOptions>
+    </codeStyleSettings>
+    <codeStyleSettings language="TypeScript">
+      <option name="INDENT_CASE_FROM_SWITCH" value="false" />
+      <option name="ALIGN_MULTILINE_PARAMETERS" value="false" />
+      <option name="ALIGN_MULTILINE_FOR" value="false" />
+      <option name="METHOD_CALL_CHAIN_WRAP" value="2" />
+      <option name="IF_BRACE_FORCE" value="3" />
+      <option name="DOWHILE_BRACE_FORCE" value="3" />
+      <option name="WHILE_BRACE_FORCE" value="3" />
+      <option name="FOR_BRACE_FORCE" value="3" />
+    </codeStyleSettings>
+  </code_scheme>
+</component>

.idea/codeStyles/codeStyleConfig.xml

@@ -0,0 +1,5 @@
+<component name="ProjectCodeStyleConfiguration">
+  <state>
+    <option name="USE_PER_PROJECT_SETTINGS" value="true" />
+  </state>
+</component>

.idea/dataSources.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="DataSourceManagerImpl" format="xml" multifile-model="true">
+    <data-source source="LOCAL" name="mongo@localhost" uuid="b05ce3f5-fadc-47d6-8621-e232ed1ad2f3">
+      <driver-ref>mongo</driver-ref>
+      <synchronize>true</synchronize>
+      <jdbc-driver>com.dbschema.MongoJdbcDriver</jdbc-driver>
+      <jdbc-url>mongodb://localhost:27017/extollo_1</jdbc-url>
+      <working-dir>$ProjectFileDir$</working-dir>
+    </data-source>
+    <data-source source="LOCAL" name="extollo_1@db03.platform.local" uuid="c8dc268d-b69d-497a-9e6d-b5c6e5275835">
+      <driver-ref>postgresql</driver-ref>
+      <synchronize>true</synchronize>
+      <jdbc-driver>org.postgresql.Driver</jdbc-driver>
+      <jdbc-url>jdbc:postgresql://db03.platform.local:5432/extollo_1</jdbc-url>
+      <working-dir>$ProjectFileDir$</working-dir>
+    </data-source>
+  </component>
+</project>

.idea/lib.iml

@@ -4,5 +4,6 @@
     <content url="file://$MODULE_DIR$" />
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="module" module-name="extollo" />
   </component>
 </module>

.idea/modules.xml

@@ -2,6 +2,7 @@
 <project version="4">
   <component name="ProjectModuleManager">
     <modules>
+      <module fileurl="file://$PROJECT_DIR$/../app/.idea/extollo.iml" filepath="$PROJECT_DIR$/../app/.idea/extollo.iml" />
       <module fileurl="file://$PROJECT_DIR$/.idea/lib.iml" filepath="$PROJECT_DIR$/.idea/lib.iml" />
     </modules>
   </component>

.idea/vcs.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="VcsDirectoryMappings">
-    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+    <mapping directory="" vcs="Git" />
   </component>
 </project>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@extollo/lib",
-  "version": "0.4.0",
+  "version": "0.5.11",
   "description": "The framework library that lifts up your code.",
   "main": "lib/index.js",
   "types": "lib/index.d.ts",
@@ -12,6 +12,7 @@
     "@types/bcrypt": "^5.0.0",
     "@types/busboy": "^0.2.3",
     "@types/cli-table": "^0.3.0",
+    "@types/ioredis": "^4.26.6",
     "@types/mime-types": "^2.1.0",
     "@types/mkdirp": "^1.0.1",
     "@types/negotiator": "^0.6.1",
@@ -27,9 +28,11 @@
     "cli-table": "^0.3.6",
     "colors": "^1.4.0",
     "dotenv": "^8.2.0",
+    "ioredis": "^4.27.6",
     "mime-types": "^2.1.31",
     "mkdirp": "^1.0.4",
     "negotiator": "^0.6.2",
+    "node-fetch": "^3",
     "pg": "^8.6.0",
     "pluralize": "^8.0.0",
     "pug": "^3.0.2",
@@ -45,9 +48,7 @@
   },
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
-    "prebuild": "pnpm run lint && rimraf lib",
-    "build": "tsc",
-    "postbuild": "fse copy --all --dereference --preserveTimestamps --keepExisting=false --quiet --errorOnExist=false src/resources lib/resources",
+    "build": "pnpm run lint && rimraf lib && tsc && fse copy --all --dereference --preserveTimestamps --keepExisting=false --quiet --errorOnExist=false src/resources lib/resources",
     "app": "tsc && node lib/index.js",
     "prepare": "pnpm run build",
     "docs:build": "typedoc --options typedoc.json",

src/auth/AuthenticatableAlreadyExistsError.ts

@@ -0,0 +1,5 @@
+import {ErrorWithContext} from '../util'
+
+export class AuthenticatableAlreadyExistsError extends ErrorWithContext {
+
+}

src/auth/SecurityContext.ts

@@ -1,10 +1,11 @@
 import {Inject, Injectable} from '../di'
 import {EventBus} from '../event/EventBus'
 import {Awaitable, Maybe} from '../util'
-import {Authenticatable, AuthenticatableRepository} from './types'
+import {Authenticatable, AuthenticatableCredentials, AuthenticatableRepository} from './types'
 import {UserAuthenticatedEvent} from './event/UserAuthenticatedEvent'
 import {UserFlushedEvent} from './event/UserFlushedEvent'
 import {UserAuthenticationResumedEvent} from './event/UserAuthenticationResumedEvent'
+import {Logging} from '../service/Logging'
 
 /**
  * Base-class for a context that authenticates users and manages security.
@@ -14,6 +15,9 @@ export abstract class SecurityContext {
     @Inject()
     protected readonly bus!: EventBus
 
+    @Inject()
+    protected readonly logging!: Logging
+
     /** The currently authenticated user, if one exists. */
     private authenticatedUser?: Authenticatable
 
@@ -57,7 +61,7 @@ export abstract class SecurityContext {
      * unauthenticated implicitly.
      * @param credentials
      */
-    async attemptOnce(credentials: Record<string, string>): Promise<Maybe<Authenticatable>> {
+    async attemptOnce(credentials: AuthenticatableCredentials): Promise<Maybe<Authenticatable>> {
         const user = await this.repository.getByCredentials(credentials)
         if ( user ) {
             await this.authenticateOnce(user)
@@ -71,7 +75,7 @@ export abstract class SecurityContext {
      * authentication will be persisted.
      * @param credentials
      */
-    async attempt(credentials: Record<string, string>): Promise<Maybe<Authenticatable>> {
+    async attempt(credentials: AuthenticatableCredentials): Promise<Maybe<Authenticatable>> {
         const user = await this.repository.getByCredentials(credentials)
         if ( user ) {
             await this.authenticate(user)
@@ -108,6 +112,8 @@ export abstract class SecurityContext {
      */
     async resume(): Promise<void> {
         const credentials = await this.getCredentials()
+        this.logging.debug('resume:')
+        this.logging.debug(credentials)
         const user = await this.repository.getByCredentials(credentials)
         if ( user ) {
             this.authenticatedUser = user
@@ -125,7 +131,7 @@ export abstract class SecurityContext {
      * Get the credentials for the current user from whatever storage medium
      * the context's host provides.
      */
-    abstract getCredentials(): Awaitable<Record<string, string>>
+    abstract getCredentials(): Awaitable<AuthenticatableCredentials>
 
     /**
      * Get the currently authenticated user, if one exists.
@@ -138,6 +144,8 @@ export abstract class SecurityContext {
      * Returns true if there is a currently authenticated user.
      */
     hasUser(): boolean {
+        this.logging.debug('hasUser?')
+        this.logging.debug(this.authenticatedUser)
         return Boolean(this.authenticatedUser)
     }
 }

src/auth/basic-ui/BasicLoginController.ts

@@ -0,0 +1,145 @@
+import {Controller} from '../../http/Controller'
+import {Inject, Injectable} from '../../di'
+import {ResponseObject, Route} from '../../http/routing/Route'
+import {Request} from '../../http/lifecycle/Request'
+import {view} from '../../http/response/ViewResponseFactory'
+import {ResponseFactory} from '../../http/response/ResponseFactory'
+import {SecurityContext} from '../SecurityContext'
+import {BasicLoginFormRequest} from './BasicLoginFormRequest'
+import {Routing} from '../../service/Routing'
+import {Valid, ValidationError} from '../../forms'
+import {AuthenticatableCredentials} from '../types'
+import {BasicRegisterFormRequest} from './BasicRegisterFormRequest'
+import {AuthenticatableAlreadyExistsError} from '../AuthenticatableAlreadyExistsError'
+import {Session} from '../../http/session/Session'
+import {temporary} from '../../http/response/TemporaryRedirectResponseFactory'
+
+@Injectable()
+export class BasicLoginController extends Controller {
+    public static routes({ enableRegistration = true } = {}): void {
+        Route.group('auth', () => {
+            Route.get('login', (request: Request) => {
+                const controller = <BasicLoginController> request.make(BasicLoginController)
+                return controller.getLogin()
+            })
+                .pre('@auth:guest')
+                .alias('@auth.login')
+
+            Route.post('login', (request: Request) => {
+                const controller = <BasicLoginController> request.make(BasicLoginController)
+                return controller.attemptLogin()
+            })
+                .pre('@auth:guest')
+                .alias('@auth.login.attempt')
+
+            Route.any('logout', (request: Request) => {
+                const controller = <BasicLoginController> request.make(BasicLoginController)
+                return controller.attemptLogout()
+            })
+                .pre('@auth:required')
+                .alias('@auth.logout')
+
+            if ( enableRegistration ) {
+                Route.get('register', (request: Request) => {
+                    const controller = <BasicLoginController> request.make(BasicLoginController)
+                    return controller.getRegistration()
+                })
+                    .pre('@auth:guest')
+                    .alias('@auth.register')
+
+                Route.post('register', (request: Request) => {
+                    const controller = <BasicLoginController> request.make(BasicLoginController)
+                    return controller.attemptRegister()
+                })
+                    .pre('@auth:guest')
+                    .alias('@auth.register.attempt')
+            }
+        }).pre('@auth:web')
+    }
+
+    @Inject()
+    protected readonly security!: SecurityContext
+
+    @Inject()
+    protected readonly routing!: Routing
+
+    @Inject()
+    protected readonly session!: Session
+
+    public getLogin(): ResponseFactory {
+        return this.getLoginView()
+    }
+
+    public getRegistration(): ResponseFactory {
+        return this.getRegistrationView()
+    }
+
+    public async attemptLogin(): Promise<ResponseObject> {
+        const form = <BasicLoginFormRequest> this.request.make(BasicLoginFormRequest)
+
+        try {
+            const data: Valid<AuthenticatableCredentials> = await form.get()
+            const user = await this.security.attempt(data)
+            if ( user ) {
+                const intention = this.session.get('auth.intention', '/')
+                this.session.forget('auth.intention')
+                return temporary(intention)
+            }
+
+            return this.getLoginView(['Invalid username/password.'])
+        } catch (e: unknown) {
+            if ( e instanceof ValidationError ) {
+                return this.getLoginView(e.errors.all())
+            }
+
+            throw e
+        }
+    }
+
+    public async attemptLogout(): Promise<ResponseObject> {
+        await this.security.flush()
+        return this.getMessageView('You have been logged out.')
+    }
+
+    public async attemptRegister(): Promise<ResponseObject> {
+        const form = <BasicRegisterFormRequest> this.request.make(BasicRegisterFormRequest)
+
+        try {
+            const data: Valid<AuthenticatableCredentials> = await form.get()
+            const user = await this.security.repository.createByCredentials(data)
+            await this.security.authenticate(user)
+
+            const intention = this.session.get('auth.intention', '/')
+            this.session.forget('auth.intention')
+            return temporary(intention)
+        } catch (e: unknown) {
+            if ( e instanceof ValidationError ) {
+                return this.getRegistrationView(e.errors.all())
+            } else if ( e instanceof AuthenticatableAlreadyExistsError ) {
+                return this.getRegistrationView(['A user with that username already exists.'])
+            }
+
+            throw e
+        }
+    }
+
+    protected getLoginView(errors?: string[]): ResponseFactory {
+        return view('@extollo:auth:login', {
+            formAction: this.routing.getNamedPath('@auth.login.attempt').toRemote,
+            errors,
+        })
+    }
+
+    protected getRegistrationView(errors?: string[]): ResponseFactory {
+        return view('@extollo:auth:register', {
+            formAction: this.routing.getNamedPath('@auth.register.attempt').toRemote,
+            errors,
+        })
+    }
+
+    protected getMessageView(message: string): ResponseFactory {
+        return view('@extollo:auth:message', {
+            message,
+        })
+    }
+}

src/auth/basic-ui/BasicLoginFormRequest.ts

@@ -0,0 +1,20 @@
+import {FormRequest, ValidationRules} from '../../forms'
+import {Is, Str} from '../../forms/rules/rules'
+import {Singleton} from '../../di'
+import {AuthenticatableCredentials} from '../types'
+
+@Singleton()
+export class BasicLoginFormRequest extends FormRequest<AuthenticatableCredentials> {
+    protected getRules(): ValidationRules {
+        return {
+            identifier: [
+                Is.required,
+                Str.lengthMin(1),
+            ],
+            credential: [
+                Is.required,
+                Str.lengthMin(1),
+            ],
+        }
+    }
+}

src/auth/basic-ui/BasicRegisterFormRequest.ts

@@ -0,0 +1,22 @@
+import {FormRequest, ValidationRules} from '../../forms'
+import {Is, Str} from '../../forms/rules/rules'
+import {Singleton} from '../../di'
+import {AuthenticatableCredentials} from '../types'
+
+@Singleton()
+export class BasicRegisterFormRequest extends FormRequest<AuthenticatableCredentials> {
+    protected getRules(): ValidationRules {
+        return {
+            identifier: [
+                Is.required,
+                Str.lengthMin(1),
+                Str.alphaNum,
+            ],
+            credential: [
+                Is.required,
+                Str.lengthMin(8),
+                Str.confirmed,
+            ],
+        }
+    }
+}

src/auth/config.ts

@@ -1,5 +1,6 @@
 import {Instantiable} from '../di'
 import {ORMUserRepository} from './orm/ORMUserRepository'
+import {OAuth2LoginConfig} from './external/oauth2/OAuth2LoginController'
 
 /**
  * Inferface for type-checking the AuthenticatableRepositories values.
@@ -21,5 +22,8 @@ export const AuthenticatableRepositories: AuthenticatableRepositoryMapping = {
 export interface AuthConfig {
     repositories: {
         session: keyof AuthenticatableRepositoryMapping,
-    }
+    },
+    sources?: {
+        [key: string]: OAuth2LoginConfig,
+    },
 }

src/auth/contexts/SessionSecurityContext.ts

@@ -2,7 +2,7 @@ import {SecurityContext} from '../SecurityContext'
 import {Inject, Injectable} from '../../di'
 import {Session} from '../../http/session/Session'
 import {Awaitable} from '../../util'
-import {AuthenticatableRepository} from '../types'
+import {AuthenticatableCredentials, AuthenticatableRepository} from '../types'
 
 /**
  * Security context implementation that uses the session as storage.
@@ -19,9 +19,10 @@ export class SessionSecurityContext extends SecurityContext {
         super(repository, 'session')
     }
 
-    getCredentials(): Awaitable<Record<string, string>> {
+    getCredentials(): Awaitable<AuthenticatableCredentials> {
         return {
-            securityIdentifier: this.session.get('extollo.auth.securityIdentifier'),
+            identifier: '',
+            credential: this.session.get('extollo.auth.securityIdentifier'),
         }
     }
 

src/auth/external/oauth2/OAuth2LoginController.ts

@@ -0,0 +1,95 @@
+import {Controller} from '../../../http/Controller'
+import {Inject, Injectable} from '../../../di'
+import {Config} from '../../../service/Config'
+import {Request} from '../../../http/lifecycle/Request'
+import {ResponseObject, Route} from '../../../http/routing/Route'
+import {ErrorWithContext} from '../../../util'
+import {OAuth2Repository} from './OAuth2Repository'
+import {json} from '../../../http/response/JSONResponseFactory'
+
+export interface OAuth2LoginConfig {
+    name: string,
+    clientId: string,
+    clientSecret: string,
+    redirectUrl: string,
+    authorizationCodeField: string,
+    tokenEndpoint: string,
+    tokenEndpointMapping?: {
+        clientId?: string,
+        clientSecret?: string,
+        grantType?: string,
+        codeKey?: string,
+    },
+    tokenEndpointResponseMapping?: {
+        token?: string,
+        expiresIn?: string,
+        expiresAt?: string,
+    },
+    userEndpoint: string,
+    userEndpointResponseMapping?: {
+        identifier?: string,
+        display?: string,
+    },
+}
+
+export function isOAuth2LoginConfig(what: unknown): what is OAuth2LoginConfig {
+    return (
+        Boolean(what)
+        && typeof (what as any).name === 'string'
+        && typeof (what as any).clientId === 'string'
+        && typeof (what as any).clientSecret === 'string'
+        && typeof (what as any).redirectUrl === 'string'
+        && typeof (what as any).authorizationCodeField === 'string'
+        && typeof (what as any).tokenEndpoint === 'string'
+        && typeof (what as any).userEndpoint === 'string'
+    )
+}
+
+@Injectable()
+export class OAuth2LoginController extends Controller {
+    public static routes(configName: string): void {
+        Route.group(`/auth/${configName}`, () => {
+            Route.get('login', (request: Request) => {
+                const controller = <OAuth2LoginController> request.make(OAuth2LoginController, configName)
+                return controller.getLogin()
+            }).pre('@auth:guest')
+        }).pre('@auth:web')
+    }
+
+    @Inject()
+    protected readonly config!: Config
+
+    constructor(
+        protected readonly request: Request,
+        protected readonly configName: string,
+    ) {
+        super(request)
+    }
+
+    public async getLogin(): Promise<ResponseObject> {
+        const repo = this.getRepository()
+        if ( repo.shouldRedirect() ) {
+            return repo.redirect()
+        }
+
+        // We were redirected from the auth source
+        const user = await repo.redeem()
+        return json(user)
+    }
+
+    protected getRepository(): OAuth2Repository {
+        return this.request.make(OAuth2Repository, this.getConfig())
+    }
+
+    protected getConfig(): OAuth2LoginConfig {
+        const config = this.config.get(`auth.sources.${this.configName}`)
+        if ( !isOAuth2LoginConfig(config) ) {
+            throw new ErrorWithContext('Invalid OAuth2 source config.', {
+                configName: this.configName,
+                config,
+            })
+        }
+
+        return config
+    }
+}

src/auth/external/oauth2/OAuth2Repository.ts

@@ -0,0 +1,155 @@
+import {
+    Authenticatable,
+    AuthenticatableCredentials,
+    AuthenticatableRepository,
+} from '../../types'
+import {Inject, Injectable} from '../../../di'
+import {
+    Awaitable,
+    dataGetUnsafe,
+    fetch,
+    Maybe,
+    MethodNotSupportedError,
+    UniversalPath,
+    universalPath,
+    uuid4,
+} from '../../../util'
+import {OAuth2LoginConfig} from './OAuth2LoginController'
+import {Session} from '../../../http/session/Session'
+import {ResponseObject} from '../../../http/routing/Route'
+import {temporary} from '../../../http/response/TemporaryRedirectResponseFactory'
+import {Request} from '../../../http/lifecycle/Request'
+import {Logging} from '../../../service/Logging'
+import {OAuth2User} from './OAuth2User'
+
+@Injectable()
+export class OAuth2Repository implements AuthenticatableRepository {
+    @Inject()
+    protected readonly session!: Session
+
+    @Inject()
+    protected readonly request!: Request
+
+    @Inject()
+    protected readonly logging!: Logging
+
+    constructor(
+        protected readonly config: OAuth2LoginConfig,
+    ) { }
+
+    public createByCredentials(): Awaitable<Authenticatable> {
+        throw new MethodNotSupportedError()
+    }
+
+    getByCredentials(credentials: AuthenticatableCredentials): Awaitable<Maybe<Authenticatable>> {
+        return this.getAuthenticatableFromBearer(credentials.credential)
+    }
+
+    getByIdentifier(): Awaitable<Maybe<Authenticatable>> {
+        return undefined
+    }
+
+    public getRedirectUrl(state?: string): UniversalPath {
+        const url = universalPath(this.config.redirectUrl)
+        if ( state ) {
+            url.query.append('state', state)
+        }
+
+        return url
+    }
+
+    public getTokenEndpoint(): UniversalPath {
+        return universalPath(this.config.tokenEndpoint)
+    }
+
+    public getUserEndpoint(): UniversalPath {
+        return universalPath(this.config.userEndpoint)
+    }
+
+    public async redeem(): Promise<Maybe<OAuth2User>> {
+        if ( !this.stateIsValid() ) {
+            return  // FIXME throw
+        }
+
+        const body = new URLSearchParams()
+
+        if ( this.config.tokenEndpointMapping ) {
+            if ( this.config.tokenEndpointMapping.clientId ) {
+                body.append(this.config.tokenEndpointMapping.clientId, this.config.clientId)
+            }
+
+            if ( this.config.tokenEndpointMapping.clientSecret ) {
+                body.append(this.config.tokenEndpointMapping.clientSecret, this.config.clientSecret)
+            }
+
+            if ( this.config.tokenEndpointMapping.codeKey ) {
+                body.append(this.config.tokenEndpointMapping.codeKey, String(this.request.input(this.config.authorizationCodeField)))
+            }
+
+            if ( this.config.tokenEndpointMapping.grantType ) {
+                body.append(this.config.tokenEndpointMapping.grantType, 'authorization_code')
+            }
+        }
+
+        this.logging.debug(`Redeeming auth code: ${body.toString()}`)
+
+        const response = await fetch(this.getTokenEndpoint().toRemote, {
+            method: 'post',
+            body: body,
+            headers: {
+                'Content-Type': 'application/x-www-form-urlencoded',
+                'Accept': 'application/json',
+            },
+        })
+
+        const data = await response.json()
+        if ( typeof data !== 'object' || data === null ) {
+            throw new Error()
+        }
+
+        this.logging.debug(data)
+        const bearer = String(dataGetUnsafe(data, this.config.tokenEndpointResponseMapping?.token ?? 'bearer'))
+
+        this.logging.debug(bearer)
+        if ( !bearer || typeof bearer !== 'string' ) {
+            throw new Error()
+        }
+
+        return this.getAuthenticatableFromBearer(bearer)
+    }
+
+    public async getAuthenticatableFromBearer(bearer: string): Promise<Maybe<OAuth2User>> {
+        const response = await fetch(this.getUserEndpoint().toRemote, {
+            method: 'get',
+            headers: {
+                'Accept': 'application/json',
+                'Authorization': `Bearer ${bearer}`,
+            },
+        })
+
+        const data = await response.json()
+        if ( typeof data !== 'object' || data === null ) {
+            throw new Error()
+        }
+
+        return new OAuth2User(data, this.config)
+    }
+
+    public stateIsValid(): boolean {
+        const correctState = this.session.get('extollo.auth.oauth2.state', '')
+        const inputState = this.request.input('state') || ''
+        return correctState === inputState
+    }
+
+    public shouldRedirect(): boolean {
+        const codeField = this.config.authorizationCodeField
+        const code = this.request.input(codeField)
+        return !code
+    }
+
+    public async redirect(): Promise<ResponseObject> {
+        const state = uuid4()
+        await this.session.set('extollo.auth.oauth2.state', state)
+        return temporary(this.getRedirectUrl(state).toRemote)
+    }
+}

src/auth/external/oauth2/OAuth2User.ts

@@ -0,0 +1,50 @@
+import {Authenticatable, AuthenticatableIdentifier} from '../../types'
+import {OAuth2LoginConfig} from './OAuth2LoginController'
+import {Awaitable, dataGetUnsafe, InvalidJSONStateError, JSONState} from '../../../util'
+
+export class OAuth2User implements Authenticatable {
+    protected displayField: string
+
+    protected identifierField: string
+
+    constructor(
+        protected data: {[key: string]: any},
+        config: OAuth2LoginConfig,
+    ) {
+        this.displayField = config.userEndpointResponseMapping?.display || 'name'
+        this.identifierField = config.userEndpointResponseMapping?.identifier || 'id'
+    }
+
+    getDisplayIdentifier(): string {
+        return String(dataGetUnsafe(this.data, this.displayField || 'name', ''))
+    }
+
+    getIdentifier(): AuthenticatableIdentifier {
+        return String(dataGetUnsafe(this.data, this.identifierField || 'id', ''))
+    }
+
+    async dehydrate(): Promise<JSONState> {
+        return {
+            isOAuth2User: true,
+            data: this.data,
+            displayField: this.displayField,
+            identifierField: this.identifierField,
+        }
+    }
+
+    rehydrate(state: JSONState): Awaitable<void> {
+        if (
+            !state.isOAuth2User
+            || typeof state.data !== 'object'
+            || state.data === null
+            || typeof state.displayField !== 'string'
+            || typeof state.identifierField !== 'string'
+        ) {
+            throw new InvalidJSONStateError('OAuth2User state is invalid', { state })
+        }
+
+        this.data = state.data
+        this.identifierField = state.identifierField
+        this.displayField = state.identifierField
+    }
+}

src/auth/index.ts

@@ -19,3 +19,8 @@ export * from './middleware/SessionAuthMiddleware'
 export * from './Authentication'
 
 export * from './config'
+
+export * from './basic-ui/BasicLoginFormRequest'
+export * from './basic-ui/BasicLoginController'
+
+export * from './external/oauth2/OAuth2LoginController'

src/auth/middleware/AuthRequiredMiddleware.ts

@@ -5,15 +5,30 @@ import {ResponseObject} from '../../http/routing/Route'
 import {error} from '../../http/response/ErrorResponseFactory'
 import {NotAuthorizedError} from '../NotAuthorizedError'
 import {HTTPStatus} from '../../util'
+import {redirect} from '../../http/response/RedirectResponseFactory'
+import {Routing} from '../../service/Routing'
+import {Session} from '../../http/session/Session'
 
 @Injectable()
 export class AuthRequiredMiddleware extends Middleware {
     @Inject()
     protected readonly security!: SecurityContext
 
+    @Inject()
+    protected readonly routing!: Routing
+
+    @Inject()
+    protected readonly session!: Session
+
     async apply(): Promise<ResponseObject> {
         if ( !this.security.hasUser() ) {
-            return error(new NotAuthorizedError(), HTTPStatus.FORBIDDEN)
+            this.session.set('auth.intention', this.request.url)
+
+            if ( this.routing.hasNamedRoute('@auth.login') ) {
+                return redirect(this.routing.getNamedPath('@auth.login').toRemote)
+            } else {
+                return error(new NotAuthorizedError(), HTTPStatus.FORBIDDEN)
+            }
         }
     }
 }

src/auth/middleware/GuestRequiredMiddleware.ts

@@ -5,15 +5,24 @@ import {ResponseObject} from '../../http/routing/Route'
 import {error} from '../../http/response/ErrorResponseFactory'
 import {NotAuthorizedError} from '../NotAuthorizedError'
 import {HTTPStatus} from '../../util'
+import {Routing} from '../../service/Routing'
+import {redirect} from '../../http/response/RedirectResponseFactory'
 
 @Injectable()
 export class GuestRequiredMiddleware extends Middleware {
     @Inject()
     protected readonly security!: SecurityContext
 
+    @Inject()
+    protected readonly routing!: Routing
+
     async apply(): Promise<ResponseObject> {
         if ( this.security.hasUser() ) {
-            return error(new NotAuthorizedError(), HTTPStatus.FORBIDDEN)
+            if ( this.routing.hasNamedRoute('@auth.redirectFromGuest') ) {
+                return redirect(this.routing.getNamedPath('@auth.redirectFromGuest').toRemote)
+            } else {
+                return error(new NotAuthorizedError(), HTTPStatus.FORBIDDEN)
+            }
         }
     }
 }

src/auth/orm/ORMUser.ts

@@ -24,11 +24,11 @@ export class ORMUser extends Model<ORMUser> implements Authenticatable {
 
     /** The user's first name. */
     @Field(FieldType.varchar, 'first_name')
-    public firstName!: string
+    public firstName?: string
 
     /** The user's last name. */
     @Field(FieldType.varchar, 'last_name')
-    public lastName!: string
+    public lastName?: string
 
     /** The hashed and salted password of the user. */
     @Field(FieldType.varchar, 'password_hash')

src/auth/orm/ORMUserRepository.ts

@@ -1,13 +1,22 @@
-import {Authenticatable, AuthenticatableIdentifier, AuthenticatableRepository} from '../types'
+import {
+    Authenticatable,
+    AuthenticatableCredentials,
+    AuthenticatableIdentifier,
+    AuthenticatableRepository,
+} from '../types'
 import {Awaitable, Maybe} from '../../util'
 import {ORMUser} from './ORMUser'
-import {Injectable} from '../../di'
+import {Container, Inject, Injectable} from '../../di'
+import {AuthenticatableAlreadyExistsError} from '../AuthenticatableAlreadyExistsError'
 
 /**
  * A user repository implementation that looks up users stored in the database.
  */
 @Injectable()
 export class ORMUserRepository extends AuthenticatableRepository {
+    @Inject('injector')
+    protected readonly injector!: Container
+
     /** Look up the user by their username. */
     getByIdentifier(id: AuthenticatableIdentifier): Awaitable<Maybe<Authenticatable>> {
         return ORMUser.query<ORMUser>()
@@ -21,21 +30,36 @@ export class ORMUserRepository extends AuthenticatableRepository {
      * If username/password are specified, look up the user and verify the password.
      * @param credentials
      */
-    async getByCredentials(credentials: Record<string, string>): Promise<Maybe<Authenticatable>> {
-        if ( credentials.securityIdentifier ) {
+    async getByCredentials(credentials: AuthenticatableCredentials): Promise<Maybe<Authenticatable>> {
+        if ( !credentials.identifier && credentials.credential ) {
             return ORMUser.query<ORMUser>()
-                .where('username', '=', credentials.securityIdentifier)
+                .where('username', '=', credentials.credential)
                 .first()
         }
 
-        if ( credentials.username && credentials.password ) {
+        if ( credentials.identifier && credentials.credential ) {
             const user = await ORMUser.query<ORMUser>()
-                .where('username', '=', credentials.username)
+                .where('username', '=', credentials.identifier)
                 .first()
 
-            if ( user && await user.verifyPassword(credentials.password) ) {
+            if ( user && await user.verifyPassword(credentials.credential) ) {
                 return user
             }
         }
     }
+
+    async createByCredentials(credentials: AuthenticatableCredentials): Promise<Authenticatable> {
+        if ( await this.getByCredentials(credentials) ) {
+            throw new AuthenticatableAlreadyExistsError(`Authenticatable already exists with credentials.`, {
+                identifier: credentials.identifier,
+            })
+        }
+
+        const user = <ORMUser> this.injector.make(ORMUser)
+        user.username = credentials.identifier
+        await user.setPassword(credentials.credential)
+        await user.save()
+
+        return user
+    }
 }

src/auth/types.ts

@@ -3,6 +3,11 @@ import {Awaitable, JSONState, Maybe, Rehydratable} from '../util'
 /** Value that can be used to uniquely identify a user. */
 export type AuthenticatableIdentifier = string | number
 
+export interface AuthenticatableCredentials {
+    identifier: string,
+    credential: string,
+}
+
 /**
  * Base class for entities that can be authenticated.
  */
@@ -32,5 +37,7 @@ export abstract class AuthenticatableRepository {
      * Returns the user if the credentials are valid.
      * @param credentials
      */
-    abstract getByCredentials(credentials: Record<string, string>): Awaitable<Maybe<Authenticatable>>
+    abstract getByCredentials(credentials: AuthenticatableCredentials): Awaitable<Maybe<Authenticatable>>
+
+    abstract createByCredentials(credentials: AuthenticatableCredentials): Awaitable<Authenticatable>
 }

src/cli/Directive.ts

@@ -169,8 +169,12 @@ export abstract class Directive extends AppClass {
                 const optionValues = this.parseOptions(options, argv)
                 this.setOptionValues(optionValues)
                 await this.handle(argv)
-            } catch (e) {
-                this.nativeOutput(e.message)
+            } catch (e: unknown) {
+                if ( e instanceof Error ) {
+                    this.nativeOutput(e.message)
+                    this.error(e)
+                }
+
                 if ( e instanceof OptionValidationError ) {
                     // expecting, value, requirements
                     if ( e.context.expecting ) {
@@ -187,6 +191,7 @@ export abstract class Directive extends AppClass {
                         this.nativeOutput(`  - ${e.context.value}`)
                     }
                 }
+
                 this.nativeOutput('\nUse --help for more info.')
             }
         }

src/cli/decorators.ts

@@ -0,0 +1,23 @@
+import {ContainerBlueprint, Instantiable, isInstantiableOf} from '../di'
+import {CommandLine} from './service'
+import {Directive} from './Directive'
+import {logIfDebugging} from '../util'
+
+/**
+ * Register a class as a command-line Directive.
+ * The class must extend Directive.
+ * @constructor
+ */
+export const CLIDirective = (): ClassDecorator => {
+    return (target) => {
+        if ( isInstantiableOf(target, Directive) ) {
+            logIfDebugging('extollo.cli.decorators', 'Registering CLIDirective blueprint:', target)
+            ContainerBlueprint.getContainerBlueprint()
+                .onResolve<CommandLine>(CommandLine, cli => {
+                    cli.registerDirective(target as Instantiable<Directive>)
+                })
+        } else {
+            logIfDebugging('extollo.cli.decorators', 'Skipping CLIDirective blueprint:', target)
+        }
+    }
+}

src/cli/index.ts

@@ -11,3 +11,5 @@ export * from './directive/options/PositionalOption'
 export * from './directive/ShellDirective'
 export * from './directive/TemplateDirective'
 export * from './directive/UsageDirective'
+
+export * from './decorators'

src/di/Container.ts

@@ -1,4 +1,4 @@
-import {DependencyKey, InstanceRef, Instantiable, isInstantiable, StaticClass} from './types'
+import {DependencyKey, InstanceRef, Instantiable, isInstantiable, StaticClass, TypedDependencyKey} from './types'
 import {AbstractFactory} from './factory/AbstractFactory'
 import {collect, Collection, globalRegistry, logIfDebugging} from '../util'
 import {Factory} from './factory/Factory'
@@ -7,7 +7,7 @@ import {ClosureFactory} from './factory/ClosureFactory'
 import NamedFactory from './factory/NamedFactory'
 import SingletonFactory from './factory/SingletonFactory'
 import {InvalidDependencyKeyError} from './error/InvalidDependencyKeyError'
-import {ContainerBlueprint} from './ContainerBlueprint'
+import {ContainerBlueprint, ContainerResolutionCallback} from './ContainerBlueprint'
 
 export type MaybeFactory<T> = AbstractFactory<T> | undefined
 export type MaybeDependency = any | undefined
@@ -17,18 +17,36 @@ export type ResolvedDependency = { paramIndex: number, key: DependencyKey, resol
  * A container of resolve-able dependencies that are created via inversion-of-control.
  */
 export class Container {
+    /**
+     * Given a Container instance, apply the ContainerBlueprint to it.
+     * @param container
+     */
+    public static realizeContainer<T extends Container>(container: T): T {
+        ContainerBlueprint.getContainerBlueprint()
+            .resolve()
+            .map(factory => container.registerFactory(factory))
+
+        ContainerBlueprint.getContainerBlueprint()
+            .resolveConstructable()
+            .map((factory: StaticClass<AbstractFactory<any>, any>) => container.registerFactory(container.make(factory)))
+
+        ContainerBlueprint.getContainerBlueprint()
+            .resolveResolutionCallbacks()
+            .map((listener: {key: TypedDependencyKey<any>, callback: ContainerResolutionCallback<any>}) => {
+                container.onResolve(listener.key)
+                    .then(value => listener.callback(value))
+            })
+
+        return container
+    }
+
     /**
      * Get the global instance of this container.
      */
     public static getContainer(): Container {
         const existing = <Container | undefined> globalRegistry.getGlobal('extollo/injector')
         if ( !existing ) {
-            const container = new Container()
-
-            ContainerBlueprint.getContainerBlueprint()
-                .resolve()
-                .map(factory => container.registerFactory(factory))
-
+            const container = Container.realizeContainer(new Container())
             globalRegistry.setGlobal('extollo/injector', container)
             return container
         }
@@ -48,6 +66,12 @@ export class Container {
      */
     protected instances: Collection<InstanceRef> = new Collection<InstanceRef>()
 
+    /**
+     * Collection of callbacks waiting for a dependency key to be resolved.
+     * @protected
+     */
+    protected waitingResolveCallbacks: Collection<{ key: DependencyKey, callback: (t: unknown) => unknown }> = new Collection<{key: DependencyKey; callback:(t: unknown) => unknown}>();
+
     constructor() {
         this.registerSingletonInstance<Container>(Container, this)
         this.registerSingleton('injector', this)
@@ -172,6 +196,26 @@ export class Container {
         return this.instances.where('key', '=', key).isNotEmpty()
     }
 
+    /**
+     * Get a Promise that resolves the first time the given dependency key is resolved
+     * by the application. If it has already been resolved, the Promise will resolve immediately.
+     * @param key
+     */
+    onResolve<T>(key: TypedDependencyKey<T>): Promise<T> {
+        if ( this.hasInstance(key) ) {
+            return new Promise<T>(res => res(this.make<T>(key)))
+        }
+
+        // Otherwise, we haven't instantiated an instance with this key yet,
+        // so put it onto the waitlist.
+        return new Promise<T>(res => {
+            this.waitingResolveCallbacks.push({
+                key,
+                callback: (res as (t: unknown) => unknown),
+            })
+        })
+    }
+
     /**
      * Returns true if the container has a factory for the given key.
      * @param {DependencyKey} key
@@ -234,6 +278,15 @@ export class Container {
             value: newInstance,
         })
 
+        this.waitingResolveCallbacks = this.waitingResolveCallbacks.filter(waiter => {
+            if ( waiter.key === key ) {
+                waiter.callback(newInstance)
+                return false
+            }
+
+            return true
+        })
+
         return newInstance
     }
 

src/di/ContainerBlueprint.ts

@@ -1,9 +1,19 @@
-import {DependencyKey, Instantiable} from './types'
+import {DependencyKey, Instantiable, StaticClass, TypedDependencyKey} from './types'
 import NamedFactory from './factory/NamedFactory'
 import {AbstractFactory} from './factory/AbstractFactory'
 import {Factory} from './factory/Factory'
 import {ClosureFactory} from './factory/ClosureFactory'
 
+/** Simple type alias for a callback to a container's onResolve method. */
+export type ContainerResolutionCallback<T> = (() => unknown) | ((t: T) => unknown)
+
+/**
+ * Blueprint for newly-created containers.
+ *
+ * This is used to allow global helpers like `@Singleton()`
+ * or `@CLIDirective()` while still supporting multiple
+ * global Container instances at once.
+ */
 export class ContainerBlueprint {
     private static instance?: ContainerBlueprint
 
@@ -17,6 +27,19 @@ export class ContainerBlueprint {
 
     protected factories: (() => AbstractFactory<any>)[] = []
 
+    protected constructableFactories: StaticClass<AbstractFactory<any>, any>[] = []
+
+    protected resolutionCallbacks: ({key: TypedDependencyKey<any>, callback: ContainerResolutionCallback<any>})[] = []
+
+    /**
+     * Register some factory class with the container. Should take no construction params.
+     * @param factory
+     */
+    registerFactory(factory: StaticClass<AbstractFactory<any>, any>): this {
+        this.constructableFactories.push(factory)
+        return this
+    }
+
     /**
      * Register a basic instantiable class as a standard Factory with this container,
      * identified by a string name rather than static class.
@@ -47,7 +70,38 @@ export class ContainerBlueprint {
         return this
     }
 
+    /**
+     * Get an array of factory instances in the blueprint.
+     */
     resolve(): AbstractFactory<any>[] {
         return this.factories.map(x => x())
     }
+
+    /**
+     * Register an onResolve callback to be added to all newly-created containers.
+     * @param key
+     * @param callback
+     */
+    onResolve<T>(key: TypedDependencyKey<T>, callback: ContainerResolutionCallback<T>): this {
+        this.resolutionCallbacks.push({
+            key,
+            callback,
+        })
+        return this
+    }
+
+    /**
+     * Get an array of static Factory classes that need to be instantiated by
+     * the container itself.
+     */
+    resolveConstructable(): StaticClass<AbstractFactory<any>, any> {
+        return [...this.constructableFactories]
+    }
+
+    /**
+     * Get an array of DependencyKey-callback pairs to register with new containers.
+     */
+    resolveResolutionCallbacks(): ({key: TypedDependencyKey<any>, callback: ContainerResolutionCallback<any>})[] {
+        return [...this.resolutionCallbacks]
+    }
 }

src/di/InjectionAware.ts

@@ -0,0 +1,37 @@
+import {Container} from './Container'
+import {TypedDependencyKey} from './types'
+
+/**
+ * Base class for Injection-aware classes that automatically
+ * pass along their configured container to instances created
+ * via their `make` method.
+ */
+export class InjectionAware {
+    private ci: Container
+
+    constructor() {
+        this.ci = Container.getContainer()
+    }
+
+    /** Set the container for this instance. */
+    public setContainer(ci: Container): this {
+        this.ci = ci
+        return this
+    }
+
+    /** Get the container for this instance. */
+    public getContainer(): Container {
+        return this.ci
+    }
+
+    /** Instantiate a new injectable using the container. */
+    public make<T>(target: TypedDependencyKey<T>, ...parameters: any[]): T {
+        const inst = this.ci.make<T>(target, ...parameters)
+
+        if ( inst instanceof InjectionAware ) {
+            inst.setContainer(this.ci)
+        }
+
+        return inst
+    }
+}

src/di/decorator/injection.ts

@@ -1,5 +1,5 @@
 import 'reflect-metadata'
-import {collect, Collection} from '../../util'
+import {collect, Collection, logIfDebugging} from '../../util'
 import {
     DependencyKey,
     DependencyRequirement,
@@ -71,9 +71,10 @@ export const Injectable = (): ClassDecorator => {
  * If a `key` is specified, that DependencyKey will be injected.
  * Otherwise, the DependencyKey is inferred from the type annotation.
  * @param key
+ * @param debug
  * @constructor
  */
-export const Inject = (key?: DependencyKey): PropertyDecorator => {
+export const Inject = (key?: DependencyKey, { debug = false } = {}): PropertyDecorator => {
     return (target, property) => {
         let propertyMetadata = Reflect.getMetadata(DEPENDENCY_KEYS_PROPERTY_METADATA_KEY, target?.constructor || target) as Collection<PropertyDependency>
         if ( !propertyMetadata ) {
@@ -91,11 +92,18 @@ export const Inject = (key?: DependencyKey): PropertyDecorator => {
             if ( existing ) {
                 existing.key = key
             } else {
-                propertyMetadata.push({ property,
-                    key })
+                propertyMetadata.push({
+                    property,
+                    key,
+                    debug,
+                })
             }
         }
 
+        if ( debug ) {
+            logIfDebugging('extollo.di.decoration', '[DEBUG] @Inject() - key:', key, 'property:', property, 'target:', target, 'target constructor:', target?.constructor, 'type:', type)
+        }
+
         Reflect.defineMetadata(DEPENDENCY_KEYS_PROPERTY_METADATA_KEY, propertyMetadata, target?.constructor || target)
     }
 }
@@ -152,3 +160,15 @@ export const Singleton = (name?: string): ClassDecorator => {
         }
     }
 }
+
+/**
+ * Register a factory class directly with any created containers.
+ * @constructor
+ */
+export const FactoryProducer = (): ClassDecorator => {
+    return (target) => {
+        if ( isInstantiable(target) ) {
+            ContainerBlueprint.getContainerBlueprint().registerFactory(target)
+        }
+    }
+}

src/di/index.ts

@@ -13,3 +13,4 @@ export * from './ScopedContainer'
 export * from './types'
 
 export * from './decorator/injection'
+export * from './InjectionAware'

src/di/types.ts

@@ -23,6 +23,16 @@ export function isInstantiable<T>(what: unknown): what is Instantiable<T> {
     )
 }
 
+/**
+ * Returns true if the given value is instantiable and, once instantiated,
+ * will create an instance of the given static class.
+ * @param what
+ * @param type
+ */
+export function isInstantiableOf<T>(what: unknown, type: StaticClass<T, any>): what is Instantiable<T> {
+    return isInstantiable(what) && what.prototype instanceof type
+}
+
 /**
  * Type that identifies a value as a static class, even if it is not instantiable.
  */
@@ -41,6 +51,11 @@ export function isStaticClass<T, T2>(something: unknown): something is StaticCla
  */
 export type DependencyKey = Instantiable<any> | StaticClass<any, any> | string
 
+/**
+ * A DependencyKey, but typed
+ */
+export type TypedDependencyKey<T> = Instantiable<T> | StaticClass<T, any> | string
+
 /**
  * Interface used to store dependency requirements by their place in the injectable
  * target's parameters.
@@ -58,6 +73,7 @@ export interface DependencyRequirement {
 export interface PropertyDependency {
     key: DependencyKey,
     property: string | symbol,
+    debug?: boolean,
 }
 
 /**

src/event/EventBus.ts

@@ -1,4 +1,4 @@
-import {Singleton, StaticClass} from '../di'
+import {Instantiable, Singleton, StaticClass} from '../di'
 import {Bus, Dispatchable, EventSubscriber, EventSubscriberEntry, EventSubscription} from './types'
 import {Awaitable, Collection, uuid4} from '../util'
 
@@ -13,7 +13,7 @@ export class EventBus implements Bus {
      */
     protected subscribers: Collection<EventSubscriberEntry<any>> = new Collection<EventSubscriberEntry<any>>()
 
-    subscribe<T extends Dispatchable>(event: StaticClass<T, T>, subscriber: EventSubscriber<T>): Awaitable<EventSubscription> {
+    subscribe<T extends Dispatchable>(event: StaticClass<T, Instantiable<T>>, subscriber: EventSubscriber<T>): Awaitable<EventSubscription> {
         const entry: EventSubscriberEntry<T> = {
             id: uuid4(),
             event,

src/event/types.ts

@@ -1,5 +1,5 @@
 import {Awaitable, Rehydratable} from '../util'
-import {StaticClass} from '../di'
+import {Instantiable, StaticClass} from '../di'
 
 /**
  * A closure that should be executed with the given event is fired.
@@ -14,7 +14,7 @@ export interface EventSubscriberEntry<T extends Dispatchable> {
     id: string
 
     /** The event class subscribed to. */
-    event: StaticClass<T, T>
+    event: StaticClass<T, Instantiable<T>>
 
     /** The closure to execute when the event is fired. */
     subscriber: EventSubscriber<T>
@@ -41,7 +41,7 @@ export interface Dispatchable extends Rehydratable {
  * An event-driven bus that manages subscribers and dispatched items.
  */
 export interface Bus {
-    subscribe<T extends Dispatchable>(eventClass: StaticClass<T, T>, subscriber: EventSubscriber<T>): Awaitable<EventSubscription>
+    subscribe<T extends Dispatchable>(eventClass: StaticClass<T, Instantiable<T>>, subscriber: EventSubscriber<T>): Awaitable<EventSubscription>
     unsubscribe<T extends Dispatchable>(subscriber: EventSubscriber<T>): Awaitable<void>
     dispatch(event: Dispatchable): Awaitable<void>
 }

src/forms/rules/strings.ts

@@ -1,4 +1,4 @@
-import {ValidationResult, ValidatorFunction} from './types'
+import {ValidationResult, ValidatorFunction, ValidatorFunctionParams} from './types'
 import {isJSON} from '../../util'
 
 /**
@@ -221,6 +221,24 @@ function lengthMax(len: number): ValidatorFunction {
     }
 }
 
+/**
+ * Validator function that requires the input value to match a `${field}Confirm` field's value.
+ * @param fieldName
+ * @param inputValue
+ * @param params
+ */
+function confirmed(fieldName: string, inputValue: unknown, params: ValidatorFunctionParams): ValidationResult {
+    const confirmedFieldName = `${fieldName}Confirm`
+    if ( inputValue === params.data[confirmedFieldName] ) {
+        return { valid: true }
+    }
+
+    return {
+        valid: false,
+        message: `confirmation does not match`,
+    }
+}
+
 export const Str = {
     alpha,
     alphaNum,
@@ -242,4 +260,5 @@ export const Str = {
     length,
     lengthMin,
     lengthMax,
+    confirmed,
 }

src/http/Controller.ts

@@ -1,12 +1,12 @@
-import {AppClass} from '../lifecycle/AppClass'
 import {Request} from './lifecycle/Request'
 import {Container} from '../di'
+import {CanonicalItemClass} from '../support/CanonicalReceiver'
 
 /**
  * Base class for controllers that define methods that
  * handle HTTP requests.
  */
-export class Controller extends AppClass {
+export class Controller extends CanonicalItemClass {
     constructor(
         protected readonly request: Request,
     ) {

src/http/kernel/HTTPKernel.ts

@@ -5,6 +5,7 @@ import {Logging} from '../../service/Logging'
 import {AppClass} from '../../lifecycle/AppClass'
 import {Request} from '../lifecycle/Request'
 import {error} from '../response/ErrorResponseFactory'
+import {HTTPError} from '../HTTPError'
 
 /**
  * Interface for fluently registering kernel modules into the kernel.
@@ -105,7 +106,8 @@ export class HTTPKernel extends AppClass {
             }
         } catch (e: any) {
             this.logging.error(e)
-            await error(e).status(HTTPStatus.INTERNAL_SERVER_ERROR)
+            const status = (e instanceof HTTPError && e.status) ? e.status : HTTPStatus.INTERNAL_SERVER_ERROR
+            await error(e).status(status)
                 .write(request)
         }
 

src/http/kernel/module/ParseIncomingBodyHTTPModule.ts

@@ -138,7 +138,6 @@ export class ParseIncomingBodyHTTPModule extends HTTPKernelModule {
             })
 
             busboy.on('finish', () => {
-                this.logging.debug(`Parsed body input: ${JSON.stringify(request.parsedInput)}`)
                 res()
             })
 

src/http/kernel/module/PoweredByHeaderInjectionHTTPModule.ts

@@ -21,6 +21,7 @@ export class PoweredByHeaderInjectionHTTPModule extends HTTPKernelModule {
     public async apply(request: Request): Promise<Request> {
         if ( !this.config.get('server.poweredBy.hide', false) ) {
             request.response.setHeader('X-Powered-By', this.config.get('server.poweredBy.header', 'Extollo'))
+            request.response.setHeader('Server', this.config.get('server.poweredBy.header', 'Extollo'))
         }
 
         return request

src/http/lifecycle/Request.ts

@@ -108,6 +108,7 @@ export class Request extends ScopedContainer implements DataContainer {
         protected serverResponse: ServerResponse,
     ) {
         super(Container.getContainer())
+        this.registerSingletonInstance(Request, this)
 
         this.secure = Boolean((clientRequest.connection as TLSSocket).encrypted)
 
@@ -124,12 +125,6 @@ export class Request extends ScopedContainer implements DataContainer {
             minor: clientRequest.httpVersionMinor,
         }
 
-        this.register(Request)
-        this.instances.push({
-            key: Request,
-            value: this,
-        })
-
         const parts = url.parse(this.url, true)
 
         this.path = parts.pathname ?? '/'

src/http/lifecycle/Response.ts

@@ -229,6 +229,9 @@ export class Response {
             this.setHeader('Content-Length', String(this.body?.length ?? 0))
         }
 
+        this.setHeader('Date', (new Date()).toUTCString())
+        this.setHeader('Permissions-Policy', 'interest-cohort=()')
+
         await this.write(this.body ?? '')
         this.end()
 

src/http/response/FileResponseFactory.ts

@@ -1,6 +1,7 @@
 import {ResponseFactory} from './ResponseFactory'
 import {Request} from '../lifecycle/Request'
 import {ErrorWithContext, UniversalPath} from '../../util'
+import {Logging} from '../../service/Logging'
 
 /**
  * Helper function that creates a FileResponseFactory for the given path.
@@ -28,6 +29,7 @@ export class FileResponseFactory extends ResponseFactory {
             })
         }
 
+        request.make<Logging>(Logging).debug(`Setting Content-Type of ${this.path} to ${this.path.contentType}...`)
         request.response.setHeader('Content-Type', this.path.contentType || 'application/octet-stream')
         request.response.setHeader('Content-Length', String(await this.path.sizeInBytes()))
         request.response.body = await this.path.readStream()

src/http/response/RedirectResponseFactory.ts

@@ -0,0 +1,31 @@
+import {ResponseFactory} from './ResponseFactory'
+import {HTTPStatus} from '../../util'
+import {Request} from '../lifecycle/Request'
+
+/**
+ * Helper function to create a new RedirectResponseFactory to the given destination.
+ * @param destination
+ */
+export function redirect(destination: string): RedirectResponseFactory {
+    return new RedirectResponseFactory(destination)
+}
+
+/**
+ * Response factory that sends an HTTP redirect to the given destination.
+ */
+export class RedirectResponseFactory extends ResponseFactory {
+    protected targetStatus: HTTPStatus = HTTPStatus.MOVED_TEMPORARILY
+
+    constructor(
+        /** THe URL where the client should redirect to. */
+        public readonly destination: string,
+    ) {
+        super()
+    }
+
+    public async write(request: Request): Promise<Request> {
+        request = await super.write(request)
+        request.response.setHeader('Location', this.destination)
+        return request
+    }
+}

src/http/response/RouteResponseFactory.ts

@@ -0,0 +1,40 @@
+import {ResponseFactory} from './ResponseFactory'
+import {HTTPStatus} from '../../util'
+import {Request} from '../lifecycle/Request'
+import {Routing} from '../../service/Routing'
+
+/**
+ * Helper function to create a new RouteResponseFactory to the given destination.
+ * @param nameOrPath
+ */
+export function route(nameOrPath: string): RouteResponseFactory {
+    return new RouteResponseFactory(nameOrPath)
+}
+
+/**
+ * Response factory that sends an HTTP redirect to the given destination.
+ */
+export class RouteResponseFactory extends ResponseFactory {
+    protected targetStatus: HTTPStatus = HTTPStatus.MOVED_TEMPORARILY
+
+    constructor(
+        /** The alias or path of the route to redirect to. */
+        public readonly nameOrPath: string,
+    ) {
+        super()
+    }
+
+    public async write(request: Request): Promise<Request> {
+        const routing = <Routing> request.make(Routing)
+        request = await super.write(request)
+
+        try {
+            const routePath = routing.getNamedPath(this.nameOrPath)
+            request.response.setHeader('Location', routePath.toRemote)
+        } catch (e: unknown) {
+            request.response.setHeader('Location', routing.getAppUrl().concat(this.nameOrPath).toRemote)
+        }
+
+        return request
+    }
+}

src/http/response/TemporaryRedirectResponseFactory.ts

@@ -6,7 +6,7 @@ import {Request} from '../lifecycle/Request'
  * Helper function to create a new TemporaryRedirectResponseFactory to the given destination.
  * @param destination
  */
-export function redirect(destination: string): TemporaryRedirectResponseFactory {
+export function temporary(destination: string): TemporaryRedirectResponseFactory {
     return new TemporaryRedirectResponseFactory(destination)
 }
 

src/http/response/api.ts

@@ -1,10 +1,10 @@
 /**
  * Base type for an API response format.
  */
-export interface APIResponse {
+export interface APIResponse<T> {
     success: boolean,
     message?: string,
-    data?: any,
+    data?: T,
     error?: {
         name: string,
         message: string,
@@ -17,7 +17,7 @@ export interface APIResponse {
  * @param {string} displayMessage
  * @return APIResponse
  */
-export function message(displayMessage: string): APIResponse {
+export function message(displayMessage: string): APIResponse<void> {
     return {
         success: true,
         message: displayMessage,
@@ -29,7 +29,7 @@ export function message(displayMessage: string): APIResponse {
  * @param record
  * @return APIResponse
  */
-export function one(record: unknown): APIResponse {
+export function one<T>(record: T): APIResponse<T> {
     return {
         success: true,
         data: record,
@@ -41,7 +41,7 @@ export function one(record: unknown): APIResponse {
  * @param {array} records
  * @return APIResponse
  */
-export function many(records: any[]): APIResponse {
+export function many<T>(records: T[]): APIResponse<{records: T[], total: number}> {
     return {
         success: true,
         data: {
@@ -56,7 +56,7 @@ export function many(records: any[]): APIResponse {
  * @return APIResponse
  * @param thrownError
  */
-export function error(thrownError: string | Error): APIResponse {
+export function error(thrownError: string | Error): APIResponse<void> {
     if ( typeof thrownError === 'string' ) {
         return {
             success: false,

src/http/routing/Middleware.ts

@@ -1,12 +1,12 @@
-import {AppClass} from '../../lifecycle/AppClass'
 import {Request} from '../lifecycle/Request'
 import {ResponseObject} from './Route'
 import {Container} from '../../di'
+import {CanonicalItemClass} from '../../support/CanonicalReceiver'
 
 /**
  * Base class representing a middleware handler that can be applied to routes.
  */
-export abstract class Middleware extends AppClass {
+export abstract class Middleware extends CanonicalItemClass {
     constructor(
         /** The request that will be handled by this middleware. */
         protected readonly request: Request,

src/http/routing/Route.ts

@@ -215,6 +215,9 @@ export class Route extends AppClass {
     /** Pre-compiled route handler for the main route handler for this route. */
     protected compiledPostflight?: ResolvedRouteHandler[]
 
+    /** Programmatic aliases of this route. */
+    public aliases: string[] = []
+
     constructor(
         /** The HTTP method(s) that this route listens on. */
         protected method: HTTPMethod | HTTPMethod[],
@@ -228,6 +231,15 @@ export class Route extends AppClass {
         super()
     }
 
+    /**
+     * Set a programmatic name for this route.
+     * @param name
+     */
+    public alias(name: string): this {
+        this.aliases.push(name)
+        return this
+    }
+
     /**
      * Get the string-form of the route.
      */

src/http/servers/static.ts

@@ -5,7 +5,7 @@ import {Collection, HTTPStatus, UniversalPath, universalPath} from '../../util'
 import {Application} from '../../lifecycle/Application'
 import {HTTPError} from '../HTTPError'
 import {view, ViewResponseFactory} from '../response/ViewResponseFactory'
-import {redirect} from '../response/TemporaryRedirectResponseFactory'
+import {redirect} from '../response/RedirectResponseFactory'
 import {file} from '../response/FileResponseFactory'
 import {RouteHandler} from '../routing/Route'
 
@@ -24,6 +24,9 @@ export interface StaticServerOptions {
 
     /** If specified, files with these extensions will not be served. */
     excludedExtensions?: string[]
+
+    /** If a file with this name exists in a directory, it will be served. */
+    indexFile?: string
 }
 
 /**
@@ -156,6 +159,22 @@ export function staticServer(options: StaticServerOptions = {}): RouteHandler {
 
         // If the resolved path is a directory, send the directory listing response
         if ( await filePath.isDirectory() ) {
+            if ( options.indexFile ) {
+                const indexFile = filePath.concat(options.indexFile)
+                if ( await indexFile.exists() ) {
+                    return file(indexFile)
+                }
+            }
+
+            if ( !options.directoryListing ) {
+                throw new StaticServerHTTPError(HTTPStatus.NOT_FOUND, 'File not found', {
+                    basePath: basePath.toString(),
+                    filePath: filePath.toString(),
+                    route: route.path,
+                    reason: 'Path is a directory, and directory listing is disabled',
+                })
+            }
+
             if ( !route.path.endsWith('/') ) {
                 return redirect(`${route.path}/`)
             }

src/http/session/MemorySession.ts

@@ -93,4 +93,12 @@ export class MemorySession extends Session {
 
         this.data[key] = value
     }
+
+    public forget(key: string): void {
+        if ( !this.data ) {
+            throw new SessionNotLoadedError()
+        }
+
+        delete this.data[key]
+    }
 }

src/http/session/Session.ts

@@ -57,4 +57,7 @@ export abstract class Session {
 
     /** Set a value in the session by key. */
     public abstract set(key: string, value: unknown): void
+
+    /** Remove a key from the session data. */
+    public abstract forget(key: string): void
 }

src/index.ts

@@ -42,8 +42,10 @@ export * from './http/response/JSONResponseFactory'
 export * from './http/response/ResponseFactory'
 export * from './http/response/StringResponseFactory'
 export * from './http/response/TemporaryRedirectResponseFactory'
+export * from './http/response/RedirectResponseFactory'
 export * from './http/response/ViewResponseFactory'
 export * from './http/response/FileResponseFactory'
+export * from './http/response/RouteResponseFactory'
 
 export * from './http/routing/ActivatedRoute'
 export * from './http/routing/Route'
@@ -60,6 +62,9 @@ export * from './http/Controller'
 
 export * from './http/servers/static'
 
+export * from './support/CanonicalReceiver'
+
+export * from './service/Canon'
 export * from './service/Canonical'
 export * from './service/CanonicalInstantiable'
 export * from './service/CanonicalRecursive'
@@ -72,9 +77,14 @@ export * from './service/HTTPServer'
 export * from './service/Routing'
 export * from './service/Middlewares'
 
+export * from './support/redis/Redis'
 export * from './support/cache/MemoryCache'
+export * from './support/cache/RedisCache'
 export * from './support/cache/CacheFactory'
 export * from './support/NodeModules'
+export * from './support/queue/Queue'
+
+export * from './service/Queueables'
 
 export * from './views/ViewEngine'
 export * from './views/ViewEngineFactory'

src/lifecycle/AppClass.ts

@@ -1,5 +1,5 @@
 import {Application} from './Application'
-import {Container, DependencyKey, Injectable} from '../di'
+import {Container, Injectable, TypedDependencyKey} from '../di'
 
 /**
  * Base type for a class that supports binding methods by string.
@@ -43,7 +43,7 @@ export class AppClass {
     }
 
     /** Call the `make()` method on the global container. */
-    protected make<T>(target: DependencyKey, ...parameters: any[]): T {
+    protected make<T>(target: TypedDependencyKey<T>, ...parameters: any[]): T {
         return this.container().make<T>(target, ...parameters)
     }
 

src/lifecycle/Application.ts

@@ -1,4 +1,4 @@
-import {Container, ContainerBlueprint} from '../di'
+import {Container} from '../di'
 import {
     ErrorWithContext,
     globalRegistry,
@@ -9,12 +9,12 @@ import {
     universalPath,
     UniversalPath,
 } from '../util'
-
 import {Logging} from '../service/Logging'
 import {RunLevelErrorHandler} from './RunLevelErrorHandler'
 import {Unit, UnitStatus} from './Unit'
 import * as dotenv from 'dotenv'
 import {CacheFactory} from '../support/cache/CacheFactory'
+import {FileLogger} from '../util/logging/FileLogger'
 
 /**
  * Helper function that resolves and infers environment variable values.
@@ -57,12 +57,7 @@ export class Application extends Container {
     public static getContainer(): Container {
         const existing = <Container | undefined> globalRegistry.getGlobal('extollo/injector')
         if ( !existing ) {
-            const container = new Application()
-
-            ContainerBlueprint.getContainerBlueprint()
-                .resolve()
-                .map(factory => container.registerFactory(factory))
-
+            const container = Application.realizeContainer(new Application())
             globalRegistry.setGlobal('extollo/injector', container)
             return container
         }
@@ -78,18 +73,12 @@ export class Application extends Container {
         if ( existing instanceof Application ) {
             return existing
         } else if ( existing ) {
-            const app = new Application()
+            const app = Application.realizeContainer(new Application())
             existing.cloneTo(app)
-
             globalRegistry.setGlobal('extollo/injector', app)
             return app
         } else {
-            const app = new Application()
-
-            ContainerBlueprint.getContainerBlueprint()
-                .resolve()
-                .map(factory => app.registerFactory(factory))
-
+            const app = Application.realizeContainer(new Application())
             globalRegistry.setGlobal('extollo/injector', app)
             return app
         }
@@ -225,6 +214,12 @@ export class Application extends Container {
         const logging: Logging = this.make<Logging>(Logging)
 
         logging.registerLogger(standard)
+
+        if ( this.env('EXTOLLO_LOGGING_ENABLE_FILE') ) {
+            const file: FileLogger = this.make<FileLogger>(FileLogger)
+            logging.registerLogger(file)
+        }
+
         logging.verbose('Attempting to load logging level from the environment...')
 
         const envLevel = this.env('EXTOLLO_LOGGING_LEVEL')
@@ -264,8 +259,12 @@ export class Application extends Container {
         try {
             await this.up()
             await this.down()
-        } catch (e) {
-            this.errorHandler(e)
+        } catch (e: unknown) {
+            if ( e instanceof Error ) {
+                this.errorHandler(e)
+            }
+
+            throw e
         }
     }
 
@@ -311,9 +310,14 @@ export class Application extends Container {
             await unit.up()
             unit.status = UnitStatus.Started
             logging.info(`Started ${unit.constructor.name}.`)
-        } catch (e) {
+        } catch (e: unknown) {
             unit.status = UnitStatus.Error
-            throw this.errorWrapContext(e, {unitName: unit.constructor.name})
+
+            if ( e instanceof Error ) {
+                throw this.errorWrapContext(e, {unitName: unit.constructor.name})
+            }
+
+            throw e
         }
     }
 
@@ -332,7 +336,12 @@ export class Application extends Container {
             logging.info(`Stopped ${unit.constructor.name}.`)
         } catch (e) {
             unit.status = UnitStatus.Error
-            throw this.errorWrapContext(e, {unitName: unit.constructor.name})
+
+            if ( e instanceof Error ) {
+                throw this.errorWrapContext(e, {unitName: unit.constructor.name})
+            }
+
+            throw e
         }
     }
 }

src/lifecycle/RunLevelErrorHandler.ts

@@ -79,10 +79,13 @@ ${contextDisplay}
             }
 
             this.logging.error(errorString, true)
-        } catch (displayError) {
-            // The error display encountered an error...
-            // just throw the original so it makes it out
-            console.error('RunLevelErrorHandler encountered an error:', displayError.message)  // eslint-disable-line no-console
+        } catch (displayError: unknown) {
+            if ( displayError instanceof Error ) {
+                // The error display encountered an error...
+                // just throw the original so it makes it out
+                console.error('RunLevelErrorHandler encountered an error:', displayError.message)  // eslint-disable-line no-console
+            }
+
             throw operativeError
         }
     }

src/migrations/2021-07-23T19:44:00.000Z_CreateSessionsTable.migration.ts

@@ -0,0 +1,39 @@
+import {Inject, Injectable} from '../di'
+import {ConstraintType, DatabaseService, FieldType, Migration, Schema} from '../orm'
+
+/**
+ * Migration that creates the sessions table used by the ORMSession backend.
+ */
+@Injectable()
+export default class CreateSessionsTableMigration extends Migration {
+    @Inject()
+    protected readonly db!: DatabaseService
+
+    async up(): Promise<void> {
+        const schema: Schema = this.db.get().schema()
+        const table = await schema.table('sessions')
+
+        table.primaryKey('session_uuid', FieldType.varchar)
+            .required()
+
+        table.column('session_data')
+            .type(FieldType.json)
+            .required()
+            .default('{}')
+
+        table.constraint('session_uuid_ck')
+            .type(ConstraintType.Check)
+            .expression('LENGTH(session_uuid) > 0')
+
+        await schema.commit(table)
+    }
+
+    async down(): Promise<void> {
+        const schema: Schema = this.db.get().schema()
+        const table = await schema.table('sessions')
+
+        table.dropIfExists()
+
+        await schema.commit(table)
+    }
+}

src/migrations/2021-07-24T10:31:00.000Z_CreateUsersTable.migration.ts

@@ -0,0 +1,47 @@
+import {Inject, Injectable} from '../di'
+import {DatabaseService, FieldType, Migration, Schema} from '../orm'
+
+/**
+ * Migration that creates the users table used by @extollo/lib.auth.
+ */
+@Injectable()
+export default class CreateUsersTableMigration extends Migration {
+    @Inject()
+    protected readonly db!: DatabaseService
+
+    async up(): Promise<void> {
+        const schema: Schema = this.db.get().schema()
+        const table = await schema.table('users')
+
+        table.primaryKey('user_id')
+            .required()
+
+        table.column('first_name')
+            .type(FieldType.varchar)
+            .nullable()
+
+        table.column('last_name')
+            .type(FieldType.varchar)
+            .nullable()
+
+        table.column('password_hash')
+            .type(FieldType.text)
+            .nullable()
+
+        table.column('username')
+            .type(FieldType.varchar)
+            .required()
+            .unique()
+
+        await schema.commit(table)
+    }
+
+    async down(): Promise<void> {
+        const schema: Schema = this.db.get().schema()
+        const table = await schema.table('users')
+
+        table.dropIfExists()
+
+        await schema.commit(table)
+    }
+}

src/orm/DatabaseService.ts

@@ -41,7 +41,7 @@ export class DatabaseService extends AppClass {
      * Get a connection instance by its name. Throws if none exists.
      * @param name
      */
-    get(name: string): Connection {
+    get(name = 'default'): Connection {
         if ( !this.has(name) ) {
             throw new ErrorWithContext(`No such connection is registered: ${name}`)
         }

src/orm/builder/AbstractBuilder.ts

@@ -1,4 +1,4 @@
-import {Inject} from '../../di'
+import {Inject, Injectable} from '../../di'
 import {DatabaseService} from '../DatabaseService'
 import {
     Constraint, ConstraintConnectionOperator,
@@ -9,7 +9,7 @@ import {
     SpecifiedField,
 } from '../types'
 import {Connection} from '../connection/Connection'
-import {deepCopy, ErrorWithContext} from '../../util'
+import {deepCopy, ErrorWithContext, Maybe} from '../../util'
 import {EscapeValue, QuerySafeValue, raw} from '../dialect/SQLDialect'
 import {ResultCollection} from './result/ResultCollection'
 import {AbstractResultIterable} from './result/AbstractResultIterable'
@@ -24,6 +24,7 @@ export type ConstraintGroupClosure<T> = (group: AbstractBuilder<T>) => any
  * A base class that facilitates building database queries using a fluent interface.
  * This can be specialized by child-classes to yield query results of the given type `T`.
  */
+@Injectable()
 export abstract class AbstractBuilder<T> extends AppClass {
     @Inject()
     protected readonly databaseService!: DatabaseService
@@ -55,6 +56,9 @@ export abstract class AbstractBuilder<T> extends AppClass {
     /** The connection on which the query should be executed. */
     protected registeredConnection?: Connection
 
+    /** Raw SQL to use instead. Overrides builder methods. */
+    protected rawSql?: string
+
     /**
      * Create a new, empty, instance of the current builder.
      */
@@ -65,6 +69,13 @@ export abstract class AbstractBuilder<T> extends AppClass {
      */
     public abstract getResultIterable(): AbstractResultIterable<T>
 
+    /**
+     * Get a copy of this builder with its values finalized.
+     */
+    public finalize(): AbstractBuilder<T> {
+        return this.clone()
+    }
+
     /**
      * Clone the current query to a new AbstractBuilder instance with the same properties.
      */
@@ -80,6 +91,7 @@ export abstract class AbstractBuilder<T> extends AppClass {
         bldr.registeredGroupings = deepCopy(this.registeredGroupings)
         bldr.registeredOrders = deepCopy(this.registeredOrders)
         bldr.registeredConnection = this.registeredConnection
+        bldr.rawSql = this.rawSql
 
         return bldr
     }
@@ -115,6 +127,11 @@ export abstract class AbstractBuilder<T> extends AppClass {
         return deepCopy(this.registeredOrders)
     }
 
+    /** Get the raw SQL overriding the builder methods, if it exists. */
+    public get appliedRawSql(): Maybe<string> {
+        return this.rawSql
+    }
+
     /** Get the source table for this query. */
     public get querySource(): QuerySource | undefined {
         if ( this.source ) {
@@ -479,7 +496,7 @@ export abstract class AbstractBuilder<T> extends AppClass {
             throw new ErrorWithContext(`No connection specified to execute update query.`)
         }
 
-        const query = this.registeredConnection.dialect().renderUpdate(this, data)
+        const query = this.registeredConnection.dialect().renderUpdate(this.finalize(), data)
         return this.registeredConnection.query(query)
     }
 
@@ -505,7 +522,7 @@ export abstract class AbstractBuilder<T> extends AppClass {
             throw new ErrorWithContext(`No connection specified to execute update query.`)
         }
 
-        const query = this.registeredConnection.dialect().renderDelete(this)
+        const query = this.registeredConnection.dialect().renderDelete(this.finalize())
         return this.registeredConnection.query(query)
     }
 
@@ -538,7 +555,7 @@ export abstract class AbstractBuilder<T> extends AppClass {
             throw new ErrorWithContext(`No connection specified to execute update query.`)
         }
 
-        const query = this.registeredConnection.dialect().renderInsert(this, rowOrRows)
+        const query = this.registeredConnection.dialect().renderInsert(this.finalize(), rowOrRows)
         return this.registeredConnection.query(query)
     }
 
@@ -550,11 +567,26 @@ export abstract class AbstractBuilder<T> extends AppClass {
             throw new ErrorWithContext(`No connection specified to execute update query.`)
         }
 
-        const query = this.registeredConnection.dialect().renderExistential(this)
+        const query = this.registeredConnection.dialect().renderExistential(this.finalize())
         const result = await this.registeredConnection.query(query)
         return Boolean(result.rows.first())
     }
 
+    /**
+     * Set the query manually. Overrides any builder methods.
+     * @example
+     * ```ts
+     * (new Builder())
+     *  .raw('SELECT NOW() AS example_column')
+     *  .get()
+     * ```
+     * @param sql
+     */
+    raw(sql: string): this {
+        this.rawSql = sql
+        return this
+    }
+
     /**
      * Adds a constraint to this query. This is used internally by the various `where`, `whereIn`, `orWhereNot`, &c.
      * @param preop

src/orm/builder/Builder.ts

@@ -1,5 +1,5 @@
 import {ErrorWithContext} from '../../util'
-import {Container} from '../../di'
+import {Container, Injectable} from '../../di'
 import {ResultIterable} from './result/ResultIterable'
 import {QueryRow} from '../types'
 import {AbstractBuilder} from './AbstractBuilder'
@@ -8,6 +8,7 @@ import {AbstractResultIterable} from './result/AbstractResultIterable'
 /**
  * Implementation of the abstract builder class that returns simple QueryRow objects.
  */
+@Injectable()
 export class Builder extends AbstractBuilder<QueryRow> {
     public getNewInstance(): AbstractBuilder<QueryRow> {
         return Container.getContainer().make<Builder>(Builder)
@@ -18,6 +19,6 @@ export class Builder extends AbstractBuilder<QueryRow> {
             throw new ErrorWithContext(`No connection specified to fetch iterator for query.`)
         }
 
-        return Container.getContainer().make<ResultIterable>(ResultIterable, this, this.registeredConnection)
+        return Container.getContainer().make<ResultIterable>(ResultIterable, this.finalize(), this.registeredConnection)
     }
 }

src/orm/connection/Connection.ts

@@ -1,10 +1,11 @@
-import {ErrorWithContext} from '../../util'
+import {Awaitable, ErrorWithContext} from '../../util'
 import {QueryResult} from '../types'
 import {SQLDialect} from '../dialect/SQLDialect'
 import {AppClass} from '../../lifecycle/AppClass'
 import {Inject, Injectable} from '../../di'
 import {EventBus} from '../../event/EventBus'
 import {QueryExecutedEvent} from './event/QueryExecutedEvent'
+import {Schema} from '../schema/Schema'
 
 /**
  * Error thrown when a connection is used before it is ready.
@@ -61,15 +62,18 @@ export abstract class Connection extends AppClass {
      */
     public abstract close(): Promise<void>
 
-    // public abstract databases(): Promise<Collection<Database>>
+    /**
+     * Get a Schema on this connection.
+     * @param name
+     */
+    public abstract schema(name?: string): Schema
 
-    // public abstract database(name: string): Promise<Database | undefined>
-
-    // public abstract database_as_schema(name: string): Promise<Database>
-
-    // public abstract tables(database_name: string): Promise<Collection<Table>>
-
-    // public abstract table(database_name: string, table_name: string): Promise<Table | undefined>
+    /**
+     * Execute all queries logged to this connection during the closure
+     * as a transaction in the database.
+     * @param closure
+     */
+    public abstract asTransaction<T>(closure: () => Awaitable<T>): Awaitable<T>
 
     /**
      * Fire a QueryExecutedEvent for the given query string.

src/orm/connection/PostgresConnection.ts

@@ -2,10 +2,12 @@ import {Connection, ConnectionNotReadyError} from './Connection'
 import {Client} from 'pg'
 import {Inject} from '../../di'
 import {QueryResult} from '../types'
-import {collect} from '../../util'
+import {Awaitable, collect} from '../../util'
 import {SQLDialect} from '../dialect/SQLDialect'
 import {PostgreSQLDialect} from '../dialect/PostgreSQLDialect'
 import {Logging} from '../../service/Logging'
+import {Schema} from '../schema/Schema'
+import {PostgresSchema} from '../schema/PostgresSchema'
 
 /**
  * Type interface representing the config for a PostgreSQL connection.
@@ -61,10 +63,29 @@ export class PostgresConnection extends Connection {
                 rowCount: result.rowCount,
             }
         } catch (e) {
-            throw this.app().errorWrapContext(e, {
-                query,
-                connection: this.name,
-            })
+            if ( e instanceof Error ) {
+                throw this.app().errorWrapContext(e, {
+                    query,
+                    connection: this.name,
+                })
+            }
+
+            throw e
         }
     }
+
+    public async asTransaction<T>(closure: () => Awaitable<T>): Promise<T> {
+        if ( !this.client ) {
+            throw new ConnectionNotReadyError(this.name, { config: JSON.stringify(this.config) })
+        }
+
+        await this.client.query('BEGIN')
+        const result = await closure()
+        await this.client.query('COMMIT')
+        return result
+    }
+
+    public schema(name?: string): Schema {
+        return new PostgresSchema(this, name)
+    }
 }

src/orm/dialect/PostgreSQLDialect.ts

@@ -1,9 +1,13 @@
 import {EscapeValue, QuerySafeValue, raw, SQLDialect} from './SQLDialect'
-import {Constraint, isConstraintGroup, isConstraintItem, SpecifiedField} from '../types'
+import {Constraint, inverseFieldType, isConstraintGroup, isConstraintItem, SpecifiedField} from '../types'
 import {AbstractBuilder} from '../builder/AbstractBuilder'
+import {ColumnBuilder, ConstraintBuilder, ConstraintType, IndexBuilder, TableBuilder} from '../schema/TableBuilder'
+import {ErrorWithContext, Maybe} from '../../util'
 
 /**
  * An implementation of the SQLDialect specific to PostgreSQL.
+ * @todo joins
+ * @todo sub-selects
  */
 export class PostgreSQLDialect extends SQLDialect {
 
@@ -29,7 +33,7 @@ export class PostgreSQLDialect extends SQLDialect {
                 `${pad(value.getSeconds())}`,
             ]
 
-            return new QuerySafeValue(value, `${y}-${m}-${d} ${h}:${i}:${s}`)
+            return new QuerySafeValue(value, `'${y}-${m}-${d} ${h}:${i}:${s}'`)
         } else if ( !isNaN(Number(value)) ) {
             return new QuerySafeValue(value, String(Number(value)))
         } else if ( value === null || typeof value === 'undefined' ) {
@@ -55,7 +59,7 @@ export class PostgreSQLDialect extends SQLDialect {
             'FROM (',
             ...query.split('\n').map(x => `  ${x}`),
             ') AS extollo_target_query',
-            `OFFSET ${start} LIMIT ${(end - start) + 1}`,
+            `OFFSET ${start} LIMIT ${(end - start) + 1}`,  // FIXME - the +1 is only needed when start === end
         ].join('\n')
     }
 
@@ -85,6 +89,11 @@ export class PostgreSQLDialect extends SQLDialect {
     }
 
     public renderSelect(builder: AbstractBuilder<any>): string {
+        const rawSql = builder.appliedRawSql
+        if ( rawSql ) {
+            return rawSql
+        }
+
         const indent = (item: string, level = 1) => Array(level + 1).fill('')
             .join('  ') + item
         const queryLines = [
@@ -147,6 +156,11 @@ export class PostgreSQLDialect extends SQLDialect {
 
     // TODO support FROM, RETURNING
     public renderUpdate(builder: AbstractBuilder<any>, data: {[key: string]: EscapeValue}): string {
+        const rawSql = builder.appliedRawSql
+        if ( rawSql ) {
+            return rawSql
+        }
+
         const queryLines: string[] = []
 
         // Add table source
@@ -171,6 +185,15 @@ export class PostgreSQLDialect extends SQLDialect {
     }
 
     public renderExistential(builder: AbstractBuilder<any>): string {
+        const rawSql = builder.appliedRawSql
+        if ( rawSql ) {
+            return `
+                SELECT EXISTS(
+                    ${rawSql}
+                )
+            `
+        }
+
         const query = builder.clone()
             .clearFields()
             .field(raw('TRUE'))
@@ -181,6 +204,11 @@ export class PostgreSQLDialect extends SQLDialect {
 
     // FIXME: subquery support here and with select
     public renderInsert(builder: AbstractBuilder<any>, data: {[key: string]: EscapeValue}|{[key: string]: EscapeValue}[] = []): string {
+        const rawSql = builder.appliedRawSql
+        if ( rawSql ) {
+            return rawSql
+        }
+
         const indent = (item: string, level = 1) => Array(level + 1).fill('')
             .join('  ') + item
         const queryLines: string[] = []
@@ -188,6 +216,11 @@ export class PostgreSQLDialect extends SQLDialect {
         if ( !Array.isArray(data) ) {
             data = [data]
         }
+
+        if ( data.length < 1 ) {
+            return ''
+        }
+
         const columns = Object.keys(data[0])
 
         // Add table source
@@ -197,7 +230,7 @@ export class PostgreSQLDialect extends SQLDialect {
             const table: string = tableString.split('.').map(x => `"${x}"`)
                 .join('.')
             queryLines.push('INSERT INTO ' + (typeof source === 'string' ? table : `${table} AS "${source.alias}"`)
-                + (columns.length ? ` (${columns.join(', ')})` : ''))
+                + (columns.length ? ` (${columns.map(x => `"${x}"`).join(', ')})` : ''))
         }
 
         if ( Array.isArray(data) && !data.length ) {
@@ -227,6 +260,11 @@ export class PostgreSQLDialect extends SQLDialect {
     }
 
     public renderDelete(builder: AbstractBuilder<any>): string {
+        const rawSql = builder.appliedRawSql
+        if ( rawSql ) {
+            return rawSql
+        }
+
         const indent = (item: string, level = 1) => Array(level + 1).fill('')
             .join('  ') + item
         const queryLines: string[] = []
@@ -270,6 +308,11 @@ export class PostgreSQLDialect extends SQLDialect {
                 if ( isConstraintGroup(constraint) ) {
                     statements.push(`${indent}${statements.length < 1 ? '' : constraint.preop + ' '}(\n${constraintsToSql(constraint.items, level + 1)}\n${indent})`)
                 } else if ( isConstraintItem(constraint) ) {
+                    if ( Array.isArray(constraint.operand) && !constraint.operand.length ) {
+                        statements.push(`${indent}1 = 0  -- ${constraint.field} ${constraint.operator} empty set`)
+                        continue
+                    }
+
                     const field: string = constraint.field.split('.').map(x => `"${x}"`)
                         .join('.')
                     statements.push(`${indent}${statements.length < 1 ? '' : constraint.preop + ' '}${field} ${constraint.operator} ${this.escape(constraint.operand).value}`)
@@ -294,4 +337,247 @@ export class PostgreSQLDialect extends SQLDialect {
 
         return ['SET', ...sets].join('\n')
     }
+
+    public renderCreateTable(builder: TableBuilder): string {
+        const cols = this.renderTableColumns(builder).map(x => `    ${x}`)
+
+        const builderConstraints = builder.getConstraints()
+        const constraints: string[] = []
+        for ( const constraintName in builderConstraints ) {
+            if ( !Object.prototype.hasOwnProperty.call(builderConstraints, constraintName) ) {
+                continue
+            }
+
+            const constraintBuilder = builderConstraints[constraintName]
+            const constraintDefinition = this.renderConstraintDefinition(constraintBuilder)
+            if ( constraintDefinition ) {
+                constraints.push(`    CONSTRAINT ${constraintDefinition}`)
+            }
+        }
+
+        const parts = [
+            `CREATE TABLE ${builder.isSkippedIfExisting() ? 'IF NOT EXISTS ' : ''}${builder.name} (`,
+            [
+                ...cols,
+                ...constraints,
+            ].join(',\n'),
+            `)`,
+        ]
+
+        return parts.join('\n')
+    }
+
+    public renderTableColumns(builder: TableBuilder): string[] {
+        const defined = builder.getColumns()
+        const rendered: string[] = []
+
+        for ( const columnName in defined ) {
+            if ( !Object.prototype.hasOwnProperty.call(defined, columnName) ) {
+                continue
+            }
+
+            const columnBuilder = defined[columnName]
+            rendered.push(this.renderColumnDefinition(columnBuilder))
+        }
+
+        return rendered
+    }
+
+    /**
+     * Given a constraint schema-builder, render the constraint definition.
+     * @param builder
+     * @protected
+     */
+    protected renderConstraintDefinition(builder: ConstraintBuilder): Maybe<string> {
+        const constraintType = builder.getType()
+        if ( constraintType === ConstraintType.Unique ) {
+            const fields = builder.getFields()
+                .map(x => `"${x}"`)
+                .join(',')
+
+            return `${builder.name} UNIQUE(${fields})`
+        } else if ( constraintType === ConstraintType.Check ) {
+            const expression = builder.getExpression()
+            if ( !expression ) {
+                throw new ErrorWithContext('Cannot create check constraint without expression.', {
+                    constraintName: builder.name,
+                    tableName: builder.parent.name,
+                })
+            }
+
+            return `${builder.name} CHECK(${expression})`
+        }
+    }
+
+    /**
+     * Given a column-builder, render the SQL-definition as used in
+     * CREATE TABLE and ALTER TABLE statements.
+     * @fixme Type `serial` only exists on CREATE TABLE... queries
+     * @param builder
+     * @protected
+     */
+    protected renderColumnDefinition(builder: ColumnBuilder): string {
+        const type = builder.getType()
+        if ( !type ) {
+            throw new ErrorWithContext(`Missing field type for column: ${builder.name}`, {
+                columnName: builder.name,
+                columnType: type,
+            })
+        }
+
+        let render = `"${builder.name}"  ${inverseFieldType(type)}`
+
+        if ( builder.getLength() ) {
+            render += `(${builder.getLength()})`
+        }
+
+        const defaultValue = builder.getDefaultValue()
+        if ( typeof defaultValue !== 'undefined' ) {
+            render += ` DEFAULT ${this.escape(defaultValue)}`
+        }
+
+        if ( builder.isPrimary() ) {
+            render += ` CONSTRAINT ${builder.name}_pk PRIMARY KEY`
+        }
+
+        if ( builder.isUnique() ) {
+            render += ` UNIQUE`
+        }
+
+        render += ` ${builder.isNullable() ? 'NULL' : 'NOT NULL'}`
+        return render
+    }
+
+    public renderDropTable(builder: TableBuilder): string {
+        return `DROP TABLE ${builder.isSkippedIfExisting() ? 'IF EXISTS ' : ''}${builder.name}`
+    }
+
+    public renderCreateIndex(builder: IndexBuilder): string {
+        const cols = builder.getFields().map(x => `"${x}"`)
+        const parts = [
+            `CREATE ${builder.isUnique() ? 'UNIQUE ' : ''}INDEX ${builder.isSkippedIfExisting() ? 'IF NOT EXISTS ' : ''}${builder.name}`,
+            `    ON ${builder.parent.name}`,
+            `    (${cols.join(',')})`,
+        ]
+
+        return parts.join('\n')
+    }
+
+    public renderAlterTable(builder: TableBuilder): string {
+        const alters: string[] = []
+        const columns = builder.getColumns()
+
+        for ( const columnName in columns ) {
+            if ( !Object.prototype.hasOwnProperty.call(columns, columnName) ) {
+                continue
+            }
+
+            const columnBuilder = columns[columnName]
+            if ( !columnBuilder.isExisting() ) {
+                // The column doesn't exist on the table, but was added to the schema
+                alters.push(`    ADD COLUMN ${this.renderColumnDefinition(columnBuilder)}`)
+            } else if ( columnBuilder.isDirty() && columnBuilder.originalFromSchema ) {
+                // The column exists in the table, but was modified in the schema
+                if ( columnBuilder.isDropping() || columnBuilder.isDroppingIfExists() ) {
+                    alters.push(`    DROP COLUMN "${columnBuilder.name}"`)
+                    continue
+                }
+
+                // Change the data type of the column
+                if ( columnBuilder.getType() !== columnBuilder.originalFromSchema.getType() ) {
+                    const renderedType = `${columnBuilder.getType()}${columnBuilder.getLength() ? `(${columnBuilder.getLength()})` : ''}`
+                    alters.push(`    ALTER COLUMN "${columnBuilder.name}" TYPE ${renderedType}`)
+                }
+
+                // Change the default value of the column
+                if ( columnBuilder.getDefaultValue() !== columnBuilder.originalFromSchema.getDefaultValue() ) {
+                    alters.push(`    ALTER COLUMN "${columnBuilder.name}" SET default ${this.escape(columnBuilder.getDefaultValue())}`)
+                }
+
+                // Change the nullable-status of the column
+                if ( columnBuilder.isNullable() !== columnBuilder.originalFromSchema.isNullable() ) {
+                    if ( columnBuilder.isNullable() ) {
+                        alters.push(`    ALTER COLUMN "${columnBuilder.name}" DROP NOT NULL`)
+                    } else {
+                        alters.push(`    ALTER COLUMN "${columnBuilder.name}" SET NOT NULL`)
+                    }
+                }
+
+                // Change the name of the column
+                if ( columnBuilder.getRename() ) {
+                    alters.push(`    RENAME COLUMN "${columnBuilder.name}" TO "${columnBuilder.getRename()}"`)
+                }
+            }
+        }
+
+        const constraints = builder.getConstraints()
+        for ( const constraintName in constraints ) {
+            if ( !Object.prototype.hasOwnProperty.call(constraints, constraintName) ) {
+                continue
+            }
+
+            const constraintBuilder = constraints[constraintName]
+
+            // Drop the constraint if specified
+            if ( constraintBuilder.isDropping() ) {
+                alters.push(`    DROP CONSTRAINT ${constraintBuilder.name}`)
+                continue
+            }
+
+            // Drop the constraint with IF EXISTS if specified
+            if ( constraintBuilder.isDroppingIfExists() ) {
+                alters.push(`    DROP CONSTRAINT IF EXISTS ${constraintBuilder.name}`)
+                continue
+            }
+
+            // Otherwise, drop and recreate the constraint if it was modified
+            if ( constraintBuilder.isDirty() ) {
+                if ( constraintBuilder.isExisting() ) {
+                    alters.push(`    DROP CONSTRAINT IF EXISTS ${constraintBuilder.name}`)
+                }
+
+                const constraintDefinition = this.renderConstraintDefinition(constraintBuilder)
+                if ( constraintDefinition ) {
+                    alters.push(`    ADD CONSTRAINT ${constraintDefinition}`)
+                }
+            }
+        }
+
+        if ( builder.getRename() ) {
+            alters.push(`    RENAME TO "${builder.getRename()}"`)
+        }
+
+        return 'ALTER TABLE ' + builder.name + '\n' + alters.join(',\n')
+    }
+
+    public renderDropIndex(builder: IndexBuilder): string {
+        return `DROP INDEX ${builder.isDroppingIfExists() ? 'IF EXISTS ' : ''}${builder.name}`
+    }
+
+    public renderTransaction(queries: string[]): string {
+        const parts = [
+            'BEGIN',
+            ...queries,
+            'COMMIT',
+        ]
+
+        return parts.join(';\n\n')
+    }
+
+    public renderRenameIndex(builder: IndexBuilder): string {
+        return `ALTER INDEX ${builder.name} RENAME TO ${builder.getRename()}`
+    }
+
+    public renderRecreateIndex(builder: IndexBuilder): string {
+        return `${this.renderDropIndex(builder)};\n\n${this.renderCreateIndex(builder)}`
+    }
+
+    public renderDropColumn(builder: ColumnBuilder): string {
+        const parts = [
+            `ALTER TABLE ${builder.parent.name} ${builder.parent.isSkippedIfExisting() ? 'IF EXISTS ' : ''}`,
+            `    DROP COLUMN ${builder.isSkippedIfExisting() ? 'IF EXISTS ' : ''}${builder.name}`,
+        ]
+
+        return parts.join('\n')
+    }
 }

src/orm/dialect/SQLDialect.ts

@@ -1,6 +1,7 @@
 import {Constraint} from '../types'
 import {AbstractBuilder} from '../builder/AbstractBuilder'
 import {AppClass} from '../../lifecycle/AppClass'
+import {ColumnBuilder, IndexBuilder, TableBuilder} from '../schema/TableBuilder'
 
 /**
  * A value which can be escaped to be interpolated into an SQL query.
@@ -160,10 +161,141 @@ export abstract class SQLDialect extends AppClass {
      * This function should escape the values before they are included in the query string.
      *
      * @example
+     * ```ts
      * dialect.renderUpdateSet({field1: 'value', field2: 45})
      * // => "SET field1 = 'value', field2 = 45"
+     * ```
      *
      * @param data
      */
     public abstract renderUpdateSet(data: {[key: string]: EscapeValue}): string;
+
+    /**
+     * Given a table schema-builder, render a `CREATE TABLE...` query.
+     * @param builder
+     */
+    public abstract renderCreateTable(builder: TableBuilder): string;
+
+    /**
+     * Given a table schema-builder, render an `ALTER TABLE...` query.
+     * @param builder
+     */
+    public abstract renderAlterTable(builder: TableBuilder): string;
+
+    /**
+     * Given a table schema-builder, render a `DROP TABLE...` query.
+     * @param builder
+     */
+    public abstract renderDropTable(builder: TableBuilder): string;
+
+    /**
+     * Render the table-column definitions for the table defined by
+     * the given schema-builder.
+     *
+     * @example
+     * ```ts
+     * dialect.renderTableColumns(builder)
+     * // => ['col1 varchar(100) NULL', 'col2 serial NOT NULL']
+     * ```
+     *
+     * @param builder
+     */
+    public abstract renderTableColumns(builder: TableBuilder): string[];
+
+    /**
+     * Given an index schema-builder, render a `CREATE INDEX...` query.
+     * @param builder
+     */
+    public abstract renderCreateIndex(builder: IndexBuilder): string;
+
+    /**
+     * Given a column schema-builder, render an `ALTER TABLE... DROP COLUMN...` query.
+     * @param builder
+     */
+    public abstract renderDropColumn(builder: ColumnBuilder): string;
+
+    /**
+     * Given an index schema-builder, render a `DROP INDEX...` query.
+     * @param builder
+     */
+    public abstract renderDropIndex(builder: IndexBuilder): string;
+
+    /**
+     * Given an index schema-builder, render an `ALTER INDEX... RENAME...` query.
+     * @param builder
+     */
+    public abstract renderRenameIndex(builder: IndexBuilder): string;
+
+    /**
+     * Given an index schema-builder, render either an `ALTER INDEX...` query,
+     * or a `DROP INDEX...; CREATE INDEX...` query.
+     * @param builder
+     */
+    public abstract renderRecreateIndex(builder: IndexBuilder): string;
+
+    /**
+     * Given a series of fully-formed queries, render them as a single transaction.
+     * @example
+     * ```ts
+     * const queries = [
+     *  'SELECT * FROM a',
+     *  'UPDATE b SET col = 123',
+     * ]
+     *
+     * dialect.renderTransaction(queries)
+     * // => 'BEGIN; SELECT * FROM a; UPDATE b SET col = 123; COMMIT;'
+     * ```
+     * @param queries
+     */
+    public abstract renderTransaction(queries: string[]): string;
+
+    /**
+     * Given a table schema-builder, render a series of queries as a transaction
+     * that apply the given schema to database.
+     * @todo handle constraints better - ConstraintBuilder
+     * @param builder
+     */
+    public renderCommitSchemaTransaction(builder: TableBuilder): string {
+        if ( builder.isDropping() || builder.isDroppingIfExists() ) {
+            // If we're dropping the table, just return the DROP TABLE query
+            return this.renderTransaction([
+                this.renderDropTable(builder),
+            ])
+        }
+
+        // Render the queries to create/update/drop indexes
+        const indexes = Object.values(builder.getIndexes())
+            .filter(index => !index.isExisting() || index.isDirty())
+            .map(index => {
+                if ( index.isDropping() || index.isDroppingIfExists() ) {
+                    return this.renderDropIndex(index)
+                }
+
+                if ( index.isExisting() ) {
+                    // The index was changed in the schema, but exists in the DB
+                    return this.renderRecreateIndex(index)
+                }
+
+                return this.renderCreateIndex(index)
+            })
+
+        // Render the queries to rename indexes AFTER the above operations
+        const renamedIndexes = Object.values(builder.getIndexes())
+            .filter(idx => idx.getRename())
+            .map(x => this.renderRenameIndex(x))
+
+        let parts: string[] = []
+
+        // Render the CREATE/ALTER TABLE query
+        if ( !builder.isExisting() && builder.isDirty() ) {
+            parts.push(this.renderCreateTable(builder))
+        } else if ( builder.isExisting() && builder.isDirty() ) {
+            parts.push(this.renderAlterTable(builder))
+        }
+
+        // Render the various schema queries as a single transaction
+        parts = parts.concat(...indexes)
+        parts = parts.concat(...renamedIndexes)
+        return this.renderTransaction(parts)
+    }
 }

src/orm/directive/CreateMigrationDirective.ts

@@ -0,0 +1,50 @@
+import {Directive, OptionDefinition} from '../../cli'
+import {Injectable} from '../../di'
+import {stringToPascal} from '../../util'
+import {templateMigration} from '../template/migration'
+import {CLIDirective} from '../../cli/decorators'
+
+/**
+ * CLI directive that creates migration classes from template.
+ */
+@Injectable()
+@CLIDirective()
+export class CreateMigrationDirective extends Directive {
+    getDescription(): string {
+        return 'create a new migration'
+    }
+
+    getKeywords(): string | string[] {
+        return ['create-migration', 'make-migration']
+    }
+
+    getOptions(): OptionDefinition[] {
+        return [
+            '{description} | Description of what the migration does',
+        ]
+    }
+
+    getHelpText(): string {
+        return [
+            'Creates a new migration file in `src/app/migrations`.',
+            'To use, specify a string describing what the migration does. For example:',
+            './ex create-migration "Add version column to sessions table"',
+        ].join('\n\n')
+    }
+
+    async handle(): Promise<void> {
+        const description = this.option('description')
+        const className = `${stringToPascal(description)}Migration`
+        const fileName = `${(new Date()).toISOString()}_${className}.migration.ts`
+        const path = this.app().path('..', 'src', 'app', 'migrations', fileName)
+
+        // Create the migrations directory, if it doesn't already exist
+        await path.concat('..').mkdir()
+
+        // Render the template
+        const rendered = await templateMigration.render(className, className, path)
+        await path.write(rendered)
+
+        this.success(`Created migration: ${className}`)
+    }
+}

src/orm/directive/MigrateDirective.ts

@@ -0,0 +1,119 @@
+import {Directive, OptionDefinition} from '../../cli'
+import {Container, Inject, Injectable} from '../../di'
+import {EventBus} from '../../event/EventBus'
+import {Migrations} from '../services/Migrations'
+import {Migrator} from '../migrations/Migrator'
+import {ApplyingMigrationEvent} from '../migrations/events/ApplyingMigrationEvent'
+import {AppliedMigrationEvent} from '../migrations/events/AppliedMigrationEvent'
+import {EventSubscription} from '../../event/types'
+import {NothingToMigrateError} from '../migrations/NothingToMigrateError'
+import {CLIDirective} from '../../cli/decorators'
+
+/**
+ * CLI directive that applies migrations using the default Migrator.
+ * @fixme Support dry run mode
+ */
+@Injectable()
+@CLIDirective()
+export class MigrateDirective extends Directive {
+    @Inject()
+    protected readonly bus!: EventBus
+
+    @Inject('injector')
+    protected readonly injector!: Container
+
+    /** Event bus subscriptions. */
+    protected subscriptions: EventSubscription[] = []
+
+    getKeywords(): string | string[] {
+        return ['migrate']
+    }
+
+    getDescription(): string {
+        return 'apply pending migrations'
+    }
+
+    getOptions(): OptionDefinition[] {
+        return [
+            '--package -p {name} | apply migrations for a specific namespace',
+            '--identifier -i {name} | apply a specific migration, by identifier',
+        ]
+    }
+
+    getHelpText(): string {
+        return [
+            'Migrations are single-run code patches used to track changes to things like database schemata.',
+            '',
+            'You can create migrations in your app using the ./ex command and they can be applied and rolled-back.',
+            '',
+            './ex migrate:create "Add version column to sessions table"',
+            '',
+            'Modules and packages can also register their own migrations. These are run by default.',
+            '',
+            'To run the migrations for a specific package, and no others, use the --package option. Example:',
+            '',
+            './ex migrate --package @extollo',
+            '',
+        ].join('\n')
+    }
+
+    async handle(): Promise<void> {
+        await this.registerListeners()
+
+        const namespace = this.option('package')
+        const identifier = this.option('identifier')
+
+        let identifiers
+        if ( namespace ) {
+            identifiers = (this.injector.make<Migrations>(Migrations))
+                .all(namespace)
+                .map(id => `${namespace}:${id}`)
+        }
+
+        if ( identifier ) {
+            if ( !identifiers ) {
+                identifiers = [identifier]
+            }
+
+            identifiers = identifiers.filter(x => x === identifier)
+        }
+
+        let error
+        try {
+            await (this.injector.make<Migrator>(Migrator)).migrate(identifiers)
+        } catch (e) {
+            if ( e instanceof NothingToMigrateError ) {
+                this.info(e.message)
+            } else {
+                error = e
+                this.error(e)
+            }
+        } finally {
+            await this.removeListeners()
+        }
+
+        if ( error ) {
+            throw error
+        }
+    }
+
+    /**
+     * Register event bus listeners to print messages for the user.
+     * @protected
+     */
+    protected async registerListeners(): Promise<void> {
+        this.subscriptions.push(await this.bus.subscribe(ApplyingMigrationEvent, event => {
+            this.info(`Applying migration ${event.migration.identifier}...`)
+        }))
+
+        this.subscriptions.push(await this.bus.subscribe(AppliedMigrationEvent, event => {
+            this.success(`Applied migration: ${event.migration.identifier}`)
+        }))
+    }
+
+    /** Remove event bus listeners before finish. */
+    protected async removeListeners(): Promise<void> {
+        await Promise.all(this.subscriptions.map(x => x.unsubscribe()))
+        this.subscriptions = []
+    }
+}

src/orm/directive/RollbackDirective.ts

@@ -0,0 +1,104 @@
+import {Directive, OptionDefinition} from '../../cli'
+import {Container, Inject, Injectable} from '../../di'
+import {EventBus} from '../../event/EventBus'
+import {Migrator} from '../migrations/Migrator'
+import {Migrations} from '../services/Migrations'
+import {RollingBackMigrationEvent} from '../migrations/events/RollingBackMigrationEvent'
+import {RolledBackMigrationEvent} from '../migrations/events/RolledBackMigrationEvent'
+import {EventSubscription} from '../../event/types'
+import {NothingToMigrateError} from '../migrations/NothingToMigrateError'
+import {CLIDirective} from '../../cli/decorators'
+
+/**
+ * CLI directive that undoes applied migrations using the default Migrator.
+ * @fixme Support dry run mode
+ */
+@Injectable()
+@CLIDirective()
+export class RollbackDirective extends Directive {
+    @Inject()
+    protected readonly bus!: EventBus
+
+    @Inject('injector')
+    protected readonly injector!: Container
+
+    @Inject()
+    protected readonly migrations!: Migrations
+
+    /** Event bus subscriptions. */
+    protected subscriptions: EventSubscription[] = []
+
+    getKeywords(): string | string[] {
+        return ['rollback']
+    }
+
+    getDescription(): string {
+        return 'roll-back applied migrations'
+    }
+
+    getOptions(): OptionDefinition[] {
+        return [
+            '--identifier -i {name} | roll-back a specific migration, by identifier',
+        ]
+    }
+
+    getHelpText(): string {
+        return [
+            'Use this command to undo one or more migrations that were applied.',
+            '',
+            'By default, the command will undo all of the migrations applied the last time the migrate command was run.',
+            '',
+            'To undo a specific migration, pass its identifier using the --identifier option.',
+            '',
+        ].join('\n')
+    }
+
+    async handle(): Promise<void> {
+        await this.registerListeners()
+
+        const identifier = this.option('identifier')
+
+        let identifiers
+        if ( identifier ) {
+            identifiers = [identifier]
+        }
+
+        let error
+        try {
+            await (this.injector.make<Migrator>(Migrator)).rollback(identifiers)
+        } catch (e) {
+            if ( e instanceof NothingToMigrateError ) {
+                this.info(e.message)
+            } else {
+                error = e
+                this.error(e)
+            }
+        } finally {
+            await this.removeListeners()
+        }
+
+        if ( error ) {
+            throw error
+        }
+    }
+
+    /**
+     * Register event-bus listeners to print messages for the user.
+     * @protected
+     */
+    protected async registerListeners(): Promise<void> {
+        this.subscriptions.push(await this.bus.subscribe(RollingBackMigrationEvent, event => {
+            this.info(`Rolling-back migration ${event.migration.identifier}...`)
+        }))
+
+        this.subscriptions.push(await this.bus.subscribe(RolledBackMigrationEvent, event => {
+            this.success(`Rolled-back migration: ${event.migration.identifier}`)
+        }))
+    }
+
+    /** Remove event bus listeners before finish. */
+    protected async removeListeners(): Promise<void> {
+        await Promise.all(this.subscriptions.map(x => x.unsubscribe()))
+        this.subscriptions = []
+    }
+}

src/orm/index.ts

@@ -18,8 +18,15 @@ export * from './model/ModelResultIterable'
 export * from './model/events'
 export * from './model/Model'
 
-export * from './services/Database'
-export * from './services/Models'
+export * from './model/relation/RelationBuilder'
+export * from './model/relation/Relation'
+export * from './model/relation/HasOneOrMany'
+export * from './model/relation/HasOne'
+export * from './model/relation/HasMany'
+export * from './model/relation/decorators'
+
+export * from './model/scope/Scope'
+export * from './model/scope/ActiveScope'
 
 export * from './support/SessionModel'
 export * from './support/ORMSession'
@@ -28,3 +35,26 @@ export * from './support/ORMCache'
 
 export * from './DatabaseService'
 export * from './types'
+
+export * from './schema/TableBuilder'
+export * from './schema/Schema'
+export * from './schema/PostgresSchema'
+
+export * from './services/Migrations'
+export * from './migrations/Migrator'
+export * from './migrations/NothingToMigrateError'
+export * from './migrations/events/MigrationEvent'
+export * from './migrations/events/ApplyingMigrationEvent'
+export * from './migrations/events/AppliedMigrationEvent'
+export * from './migrations/events/RollingBackMigrationEvent'
+export * from './migrations/events/RolledBackMigrationEvent'
+export * from './migrations/Migration'
+export * from './migrations/MigratorFactory'
+export * from './migrations/DatabaseMigrator'
+
+export * from './services/Database'
+export * from './services/Models'
+
+export * from './directive/CreateMigrationDirective'
+export * from './directive/MigrateDirective'
+export * from './directive/RollbackDirective'

src/orm/migrations/DatabaseMigrator.ts

@@ -0,0 +1,179 @@
+import {Container, Inject, Injectable} from '../../di'
+import {Migrator} from './Migrator'
+import {DatabaseService} from '../DatabaseService'
+import {FieldType} from '../types'
+import {Migration} from './Migration'
+import {Builder} from '../builder/Builder'
+
+/**
+ * Migrator implementation that tracks applied migrations in a database table.
+ * @todo allow configuring more of this
+ */
+@Injectable()
+export class DatabaseMigrator extends Migrator {
+    @Inject()
+    protected readonly db!: DatabaseService
+
+    @Inject('injector')
+    protected readonly injector!: Container
+
+    /** True if we've initialized the migrator. */
+    protected initialized = false
+
+    public async initialize(): Promise<void> {
+        await super.initialize()
+
+        if ( this.initialized ) {
+            return
+        }
+
+        const schema = this.db.get().schema()
+        if ( !(await schema.hasTable('migrations')) ) {
+            const table = await schema.table('migrations')
+
+            table.primaryKey('id', FieldType.serial).required()
+
+            table.column('identifier')
+                .type(FieldType.varchar)
+                .required()
+
+            table.column('applygroup')
+                .type(FieldType.integer)
+                .required()
+
+            table.column('applydate')
+                .type(FieldType.timestamp)
+                .required()
+
+            await schema.commit(table)
+        }
+
+        this.initialized = true
+    }
+
+    async has(migration: Migration): Promise<boolean> {
+        return this.builder()
+            .connection('default')
+            .select('id')
+            .from('migrations')
+            .where('identifier', '=', migration.identifier)
+            .exists()
+    }
+
+    async markApplied(migrations: Migration | Migration[], applyDate: Date = new Date()): Promise<void> {
+        if ( !Array.isArray(migrations) ) {
+            migrations = [migrations]
+        }
+
+        const applyGroup = await this.getNextGroupIdentifier()
+        const rows = migrations.map(migration => {
+            return {
+                applygroup: applyGroup,
+                applydate: applyDate,
+                identifier: migration.identifier,
+            }
+        })
+
+        await this.builder()
+            .connection('default')
+            .table('migrations')
+            .insert(rows)
+    }
+
+    async unmarkApplied(migrations: Migration | Migration[]): Promise<void> {
+        if ( !Array.isArray(migrations) ) {
+            migrations = [migrations]
+        }
+
+        const identifiers = migrations.map(migration => migration.identifier)
+
+        await this.builder()
+            .connection('default')
+            .table('migrations')
+            .whereIn('identifier', identifiers)
+            .delete()
+    }
+
+    async getLastApplyGroup(): Promise<string[]> {
+        const applyGroup = await this.builder()
+            .connection('default')
+            .select('applygroup')
+            .from('migrations')
+            .get()
+            .max<number>('applygroup')
+
+        return this.builder()
+            .connection('default')
+            .select('identifier')
+            .from('migrations')
+            .where('applygroup', '=', applyGroup)
+            .get()
+            .asyncPipe()
+            .tap(coll => {
+                return coll.pluck<string>('identifier')
+            })
+            .tap(coll => {
+                return coll.all()
+            })
+            .resolve()
+    }
+
+    /**
+     * Helper method to look up the next `applygroup` that should be used.
+     * @protected
+     */
+    protected async getNextGroupIdentifier(): Promise<number> {
+        const current = await this.builder()
+            .connection('default')
+            .select('applygroup')
+            .from('migrations')
+            .get()
+            .max<number>('applygroup')
+
+        return (current ?? 0) + 1
+    }
+
+    /**
+     * Given a list of migration identifiers, filter out those that have been applied.
+     * @override to make this more efficient
+     * @param identifiers
+     * @protected
+     */
+    protected async filterAppliedMigrations(identifiers: string[]): Promise<string[]> {
+        const existing = await this.builder()
+            .connection('default')
+            .select('identifier')
+            .from('migrations')
+            .whereIn('identifier', identifiers)
+            .get()
+            .pluck<string>('identifier')
+
+        return identifiers.filter(id => !existing.includes(id))
+    }
+
+    /**
+     * Given a list of migration identifiers, filter out those that have not been applied.
+     * @override to make this more efficient
+     * @param identifiers
+     * @protected
+     */
+    protected async filterPendingMigrations(identifiers: string[]): Promise<string[]> {
+        const existing = await this.builder()
+            .connection('default')
+            .select('identifier')
+            .from('migrations')
+            .whereIn('identifier', identifiers)
+            .get()
+            .pluck<string>('identifier')
+
+        return existing.all()
+    }
+
+    /**
+     * Get a query builder instance.
+     * @protected
+     */
+    protected builder(): Builder {
+        return this.injector.make<Builder>(Builder)
+    }
+}

src/orm/migrations/Migration.ts

@@ -0,0 +1,39 @@
+import {Injectable} from '../../di'
+import {Awaitable} from '../../util'
+
+/**
+ * Abstract base-class for one-time migrations.
+ */
+@Injectable()
+export abstract class Migration {
+    /** Set by the Migrations unit on load. */
+    protected migrationIdentifier!: string
+
+    /**
+     * Sets the migration identifier.
+     * This is used internally when the Migrations service loads
+     * the migration files to determine the ID from the file-name.
+     * It shouldn't be used externally.
+     * @param name
+     */
+    public setMigrationIdentifier(name: string): void {
+        this.migrationIdentifier = name
+    }
+
+    /**
+     * Get the unique identifier of this migration.
+     */
+    public get identifier(): string {
+        return this.migrationIdentifier
+    }
+
+    /**
+     * Apply the migration.
+     */
+    abstract up(): Awaitable<void>
+
+    /**
+     * Undo the migration.
+     */
+    abstract down(): Awaitable<void>
+}

src/orm/migrations/Migrator.ts

@@ -0,0 +1,295 @@
+import {Container, Inject, Injectable} from '../../di'
+import {Awaitable, collect, ErrorWithContext} from '../../util'
+import {Migration} from './Migration'
+import {Migrations} from '../services/Migrations'
+import {EventBus} from '../../event/EventBus'
+import {ApplyingMigrationEvent} from './events/ApplyingMigrationEvent'
+import {AppliedMigrationEvent} from './events/AppliedMigrationEvent'
+import {RollingBackMigrationEvent} from './events/RollingBackMigrationEvent'
+import {RolledBackMigrationEvent} from './events/RolledBackMigrationEvent'
+import {NothingToMigrateError} from './NothingToMigrateError'
+
+/**
+ * Manages single-run patches/migrations.
+ */
+@Injectable()
+export abstract class Migrator {
+    @Inject(Migrations, { debug: true })
+    protected readonly migrations!: Migrations
+
+    @Inject()
+    protected readonly bus!: EventBus
+
+    @Inject('injector')
+    protected readonly injector!: Container
+
+    /**
+     * Should resolve true if the given migration has already been applied.
+     * @param migration
+     */
+    public abstract has(migration: Migration): Awaitable<boolean>
+
+    /**
+     * Should mark the given migrations as being applied.
+     *
+     * If a date is specified, then that is the timestamp when the migrations
+     * were applied, otherwise, use `new Date()`.
+     *
+     * @param migrations
+     * @param date
+     */
+    public abstract markApplied(migrations: Migration | Migration[], date?: Date): Awaitable<void>
+
+    /**
+     * Should un-mark the given migrations as being applied.
+     * @param migration
+     */
+    public abstract unmarkApplied(migration: Migration | Migration[]): Awaitable<void>
+
+    /**
+     * Get the identifiers of the last group of migrations that were applied.
+     */
+    public abstract getLastApplyGroup(): Awaitable<string[]>
+
+    /**
+     * Do any initial setup required to get the migrator ready.
+     * This can be overridden by implementation classes to do any necessary setup.
+     */
+    public initialize(): Awaitable<void> {}  // eslint-disable-line @typescript-eslint/no-empty-function
+
+    /**
+     * Apply pending migrations.
+     *
+     * If identifiers are specified, only the pending migrations with those
+     * identifiers are applied. If none are specified, all pending migrations
+     * will be applied.
+     *
+     * @param identifiers
+     */
+    public async migrate(identifiers?: string[]): Promise<void> {
+        await this.initialize()
+
+        if ( !identifiers ) {
+            identifiers = this.getAllMigrationIdentifiers()
+        }
+
+        identifiers = (await this.filterAppliedMigrations(identifiers)).sort()
+        if ( !identifiers.length ) {
+            throw new NothingToMigrateError()
+        }
+
+        const migrations = collect(identifiers)
+            .map(id => {
+                const migration = this.migrations.get(id)
+
+                if ( !migration ) {
+                    throw new ErrorWithContext(`Unable to find migration with identifier: ${id}`, {
+                        identifier: id,
+                    })
+                }
+
+                return migration
+            })
+
+        await migrations.promiseMap(migration => {
+            return this.apply(migration)
+        })
+
+        await this.markApplied(migrations.all())
+    }
+
+    /**
+     * Rollback applied migrations.
+     *
+     * If specified, only applied migrations with the given identifiers will
+     * be rolled back. If not specified, then the last "batch" of applied
+     * migrations will be rolled back.
+     *
+     * @param identifiers
+     */
+    public async rollback(identifiers?: string[]): Promise<void> {
+        await this.initialize()
+
+        if ( !identifiers ) {
+            identifiers = await this.getLastApplyGroup()
+        }
+
+        identifiers = (await this.filterPendingMigrations(identifiers)).sort()
+        if ( !identifiers.length ) {
+            throw new NothingToMigrateError()
+        }
+
+        const migrations = collect(identifiers)
+            .map(id => {
+                const migration = this.migrations.get(id)
+
+                if ( !migration ) {
+                    throw new ErrorWithContext(`Unable to find migration with identifier: ${id}`, {
+                        identifier: id,
+                    })
+                }
+
+                return migration
+            })
+
+        await migrations.promiseMap(migration => {
+            return this.undo(migration)
+        })
+
+        await this.unmarkApplied(migrations.all())
+    }
+
+    /**
+     * Apply a single migration.
+     * @param migration
+     */
+    public async apply(migration: Migration): Promise<void> {
+        await this.initialize()
+
+        await this.applying(migration)
+
+        await migration.up()
+
+        await this.applied(migration)
+    }
+
+    /**
+     * Rollback a single migration.
+     * @param migration
+     */
+    public async undo(migration: Migration): Promise<void> {
+        await this.initialize()
+
+        await this.rollingBack(migration)
+
+        await migration.down()
+
+        await this.rolledBack(migration)
+    }
+
+    /**
+     * Get all registered migrations, by their string-form identifiers.
+     * @protected
+     */
+    protected getAllMigrationIdentifiers(): string[] {
+        return collect<string>(this.migrations.namespaces())
+            .map(nsp => {
+                return this.migrations.all(nsp)
+                    .map(id => `${nsp}:${id}`)
+            })
+            .tap(coll => {
+                // non-namespaced migrations
+                coll.push(this.migrations.all())
+                return coll
+            })
+            .reduce((current, item) => {
+                return current.concat(item)
+            }, [])
+    }
+
+    /**
+     * Given a list of migration identifiers, filter out those that have been applied.
+     * @param identifiers
+     * @protected
+     */
+    protected async filterAppliedMigrations(identifiers: string[]): Promise<string[]> {
+        return collect(identifiers)
+            .partialMap(identifier => {
+                const migration = this.migrations.get(identifier)
+                if ( migration ) {
+                    return {
+                        identifier,
+                        migration,
+                    }
+                }
+            })
+            .asyncPipe()
+            .tap(coll => {
+                return coll.promiseMap(async group => {
+                    return {
+                        ...group,
+                        has: await this.has(group.migration),
+                    }
+                })
+            })
+            .tap(coll => {
+                return coll.filter(group => !group.has)
+                    .pluck<string>('identifier')
+                    .all()
+            })
+            .resolve()
+    }
+
+    /**
+     * Given a list of migration identifiers, filter out those that have not been applied.
+     * @param identifiers
+     * @protected
+     */
+    protected async filterPendingMigrations(identifiers: string[]): Promise<string[]> {
+        return collect(identifiers)
+            .partialMap(identifier => {
+                const migration = this.migrations.get(identifier)
+                if ( migration ) {
+                    return {
+                        identifier,
+                        migration,
+                    }
+                }
+            })
+            .asyncPipe()
+            .tap(coll => {
+                return coll.promiseMap(async group => {
+                    return {
+                        ...group,
+                        has: await this.has(group.migration),
+                    }
+                })
+            })
+            .tap(coll => {
+                return coll.filter(group => group.has)
+                    .pluck<string>('identifier')
+                    .all()
+            })
+            .resolve()
+    }
+
+    /**
+     * Fire the ApplyingMigrationEvent.
+     * @param migration
+     * @protected
+     */
+    protected async applying(migration: Migration): Promise<void> {
+        const event = <ApplyingMigrationEvent> this.injector.make(ApplyingMigrationEvent, migration)
+        await this.bus.dispatch(event)
+    }
+
+    /**
+     * Fire the AppliedMigrationEvent.
+     * @param migration
+     * @protected
+     */
+    protected async applied(migration: Migration): Promise<void> {
+        const event = <AppliedMigrationEvent> this.injector.make(AppliedMigrationEvent, migration)
+        await this.bus.dispatch(event)
+    }
+
+    /**
+     * Fire the RollingBackMigrationEvent.
+     * @param migration
+     * @protected
+     */
+    protected async rollingBack(migration: Migration): Promise<void> {
+        const event = <RollingBackMigrationEvent> this.injector.make(RollingBackMigrationEvent, migration)
+        await this.bus.dispatch(event)
+    }
+
+    /**
+     * Fire the RolledBackMigrationEvent.
+     * @param migration
+     * @protected
+     */
+    protected async rolledBack(migration: Migration): Promise<void> {
+        const event = <RolledBackMigrationEvent> this.injector.make(RolledBackMigrationEvent, migration)
+        await this.bus.dispatch(event)
+    }
+}

src/orm/migrations/MigratorFactory.ts

@@ -0,0 +1,82 @@
+import {
+    AbstractFactory,
+    DependencyRequirement,
+    PropertyDependency,
+    isInstantiable,
+    DEPENDENCY_KEYS_METADATA_KEY,
+    DEPENDENCY_KEYS_PROPERTY_METADATA_KEY, Instantiable, Injectable, Inject, FactoryProducer,
+} from '../../di'
+import {Collection, ErrorWithContext} from '../../util'
+import {Logging} from '../../service/Logging'
+import {Config} from '../../service/Config'
+import {Migrator} from './Migrator'
+import {DatabaseMigrator} from './DatabaseMigrator'
+
+/**
+ * A dependency injection factory that matches the abstract Migrator class
+ * and produces an instance of the configured session driver implementation.
+ */
+@Injectable()
+@FactoryProducer()
+export class MigratorFactory extends AbstractFactory<Migrator> {
+    @Inject()
+    protected readonly logging!: Logging
+
+    @Inject()
+    protected readonly config!: Config
+
+    constructor() {
+        super({})
+    }
+
+    produce(): Migrator {
+        return new (this.getMigratorClass())()
+    }
+
+    match(something: unknown): boolean {
+        return something === Migrator
+    }
+
+    getDependencyKeys(): Collection<DependencyRequirement> {
+        const meta = Reflect.getMetadata(DEPENDENCY_KEYS_METADATA_KEY, this.getMigratorClass())
+        if ( meta ) {
+            return meta
+        }
+
+        return new Collection<DependencyRequirement>()
+    }
+
+    getInjectedProperties(): Collection<PropertyDependency> {
+        const meta = new Collection<PropertyDependency>()
+        let currentToken = this.getMigratorClass()
+
+        do {
+            const loadedMeta = Reflect.getMetadata(DEPENDENCY_KEYS_PROPERTY_METADATA_KEY, currentToken)
+            if ( loadedMeta ) {
+                meta.concat(loadedMeta)
+            }
+            currentToken = Object.getPrototypeOf(currentToken)
+        } while (Object.getPrototypeOf(currentToken) !== Function.prototype && Object.getPrototypeOf(currentToken) !== Object.prototype)
+
+        return meta
+    }
+
+    /**
+     * Return the instantiable class of the configured migrator backend.
+     * @protected
+     * @return Instantiable<Migrator>
+     */
+    protected getMigratorClass(): Instantiable<Migrator> {
+        const MigratorClass = this.config.get('database.migrations.driver', DatabaseMigrator)
+
+        if ( !isInstantiable(MigratorClass) || !(MigratorClass.prototype instanceof Migrator) ) {
+            const e = new ErrorWithContext('Provided migration driver class does not extend from @extollo/lib.Migrator')
+            e.context = {
+                configKey: 'database.migrations.driver',
+                class: MigratorClass.toString(),
+            }
+        }
+
+        return MigratorClass
+    }
+}

src/orm/migrations/NothingToMigrateError.ts

@@ -0,0 +1,14 @@
+import {ErrorWithContext} from '../../util'
+
+/**
+ * Error thrown when the migrator is run, but no migrations need
+ * to be applied/rolled-back.
+ */
+export class NothingToMigrateError extends ErrorWithContext {
+    constructor(
+        message = 'There is nothing to migrate',
+        context?: {[key: string]: any},
+    ) {
+        super(message, context)
+    }
+}

src/orm/migrations/events/AppliedMigrationEvent.ts

@@ -0,0 +1,8 @@
+import {Injectable} from '../../../di'
+import {MigrationEvent} from './MigrationEvent'
+
+/**
+ * Event fired after a migration is applied.
+ */
+@Injectable()
+export class AppliedMigrationEvent extends MigrationEvent {}

src/orm/migrations/events/ApplyingMigrationEvent.ts

@@ -0,0 +1,8 @@
+import {Injectable} from '../../../di'
+import {MigrationEvent} from './MigrationEvent'
+
+/**
+ * Event fired before a migration is applied.
+ */
+@Injectable()
+export class ApplyingMigrationEvent extends MigrationEvent {}

src/orm/migrations/events/MigrationEvent.ts

@@ -0,0 +1,49 @@
+import {Event} from '../../../event/Event'
+import {Migration} from '../Migration'
+import {Inject, Injectable} from '../../../di'
+import {Migrations} from '../../services/Migrations'
+import {ErrorWithContext} from '../../../util'
+
+/**
+ * Generic base-class for migration-related events.
+ */
+@Injectable()
+export abstract class MigrationEvent extends Event {
+    @Inject()
+    protected readonly migrations!: Migrations
+
+    /** The migration relevant to this event. */
+    private internalMigration: Migration
+
+    /**
+     * Get the relevant migration.
+     */
+    public get migration(): Migration {
+        return this.internalMigration
+    }
+
+    constructor(
+        migration: Migration,
+    ) {
+        super()
+        this.internalMigration = migration
+    }
+
+    dehydrate(): {identifier: string} {
+        return {
+            identifier: this.migration.identifier,
+        }
+    }
+
+    rehydrate(state: {identifier: string}): void {
+        const migration = this.migrations.get(state.identifier)
+
+        if ( !migration ) {
+            throw new ErrorWithContext(`Unable to find migration with identifier: ${state.identifier}`, {
+                identifier: state.identifier,
+            })
+        }
+
+        this.internalMigration = migration
+    }
+}

src/orm/migrations/events/RolledBackMigrationEvent.ts

@@ -0,0 +1,8 @@
+import {Injectable} from '../../../di'
+import {MigrationEvent} from './MigrationEvent'
+
+/**
+ * Event fired after a migration has been rolled-back.
+ */
+@Injectable()
+export class RolledBackMigrationEvent extends MigrationEvent {}

src/orm/migrations/events/RollingBackMigrationEvent.ts

@@ -0,0 +1,8 @@
+import {Injectable} from '../../../di'
+import {MigrationEvent} from './MigrationEvent'
+
+/**
+ * Event fired before a migration is rolled back.
+ */
+@Injectable()
+export class RollingBackMigrationEvent extends MigrationEvent {}

src/orm/model/Model.ts

@@ -1,9 +1,9 @@
 import {ModelKey, QueryRow, QuerySource} from '../types'
-import {Container, Inject, StaticClass} from '../../di'
+import {Container, Inject, Instantiable, isInstantiable, StaticClass} from '../../di'
 import {DatabaseService} from '../DatabaseService'
 import {ModelBuilder} from './ModelBuilder'
 import {getFieldsMeta, ModelField} from './Field'
-import {deepCopy, Pipe, Collection, Awaitable, uuid4} from '../../util'
+import {deepCopy, Pipe, Collection, Awaitable, uuid4, isKeyof} from '../../util'
 import {EscapeValueObject} from '../dialect/SQLDialect'
 import {AppClass} from '../../lifecycle/AppClass'
 import {Logging} from '../../service/Logging'
@@ -17,6 +17,11 @@ import {ModelUpdatedEvent} from './events/ModelUpdatedEvent'
 import {ModelCreatingEvent} from './events/ModelCreatingEvent'
 import {ModelCreatedEvent} from './events/ModelCreatedEvent'
 import {EventBus} from '../../event/EventBus'
+import {Relation, RelationValue} from './relation/Relation'
+import {HasOne} from './relation/HasOne'
+import {HasMany} from './relation/HasMany'
+import {HasOneOrMany} from './relation/HasOneOrMany'
+import {Scope, ScopeClosure} from './scope/Scope'
 
 /**
  * Base for classes that are mapped to tables in a database.
@@ -83,6 +88,12 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
      */
     protected static masks: string[] = []
 
+    /**
+     * Relations that should be eager-loaded by default.
+     * @protected
+     */
+    protected with: (keyof T)[] = []
+
     /**
      * The original row fetched from the database.
      * @protected
@@ -95,6 +106,14 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
      */
     protected modelEventBusSubscribers: Collection<EventSubscriberEntry<any>> = new Collection<EventSubscriberEntry<any>>()
 
+    /**
+     * Cache of relation instances by property accessor.
+     * This is used by the `@Relation()` decorator to cache Relation instances.
+     */
+    public relationCache: Collection<{ accessor: string | symbol, relation: Relation<T, any, any> }> = new Collection<{accessor: string | symbol; relation: Relation<T, any, any>}>()
+
+    protected scopes: Collection<{ accessor: string | Instantiable<Scope>, scope: ScopeClosure }> = new Collection<{accessor: string | Instantiable<Scope>; scope: ScopeClosure}>()
+
     /**
      * Get the table name for this model.
      */
@@ -155,6 +174,28 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
             builder.field(field.databaseKey)
         })
 
+        if ( Array.isArray(this.prototype.with) ) {
+            // Try to get the eager-loaded relations statically, if possible
+            for (const relation of this.prototype.with) {
+                // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+                // @ts-ignore
+                builder.with(relation)
+            }
+        } else if ( this.constructor.length < 1 ) {
+            // Otherwise, if we can instantiate the model without any arguments,
+            // do that and get the eager-loaded relations directly.
+            const inst = Container.getContainer().make<Model<any>>(this)
+            if ( Array.isArray(inst.with) ) {
+                for (const relation of inst.with) {
+                    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+                    // @ts-ignore
+                    builder.with(relation)
+                }
+            }
+        }
+
+        builder.withScopes(this.prototype.scopes)
+
         return builder
     }
 
@@ -307,6 +348,12 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
             builder.field(field.databaseKey)
         })
 
+        for ( const relation of this.with ) {
+            builder.with(relation)
+        }
+
+        builder.withScopes(this.scopes)
+
         return builder
     }
 
@@ -612,6 +659,8 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
             }
 
             const row = this.buildInsertFieldObject()
+            this.logging.debug('Insert field object:')
+            this.logging.debug(row)
             const returnable = new Collection<string>([this.keyName(), ...Object.keys(row)])
 
             const result = await this.query()
@@ -625,7 +674,7 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
 
             const data = result.rows.first()
             if ( data ) {
-                await this.assumeFromSource(result)
+                await this.assumeFromSource(data)
             }
 
             await this.dispatch(new ModelCreatedEvent<T>(this as any))
@@ -635,6 +684,30 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
         return this
     }
 
+    /**
+     * Delete the current model from the database, if it exists.
+     */
+    async delete(): Promise<void> {
+        if ( !this.exists() ) {
+            return
+        }
+
+        await this.query()
+            .where(this.qualifyKey(), '=', this.key())
+            .delete()
+
+        const ctor = this.constructor as typeof Model
+        const field = getFieldsMeta(this)
+            .firstWhere('databaseKey', '=', ctor.key)
+
+        if ( field ) {
+            delete (this as any)[field.modelKey]
+            return
+        }
+
+        delete (this as any)[ctor.key]
+    }
+
     /**
      * Cast this model to a simple object mapping model fields to their values.
      *
@@ -784,10 +857,12 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
     private buildInsertFieldObject(): EscapeValueObject {
         const ctor = this.constructor as typeof Model
 
+        this.logging.debug(`buildInsertFieldObject populateKeyOnInsert? ${ctor.populateKeyOnInsert}; keyName: ${this.keyName()}`)
+
         return getFieldsMeta(this)
             .pipe()
             .unless(ctor.populateKeyOnInsert, fields => {
-                return fields.where('modelKey', '!=', this.keyName())
+                return fields.where('databaseKey', '!=', this.keyName())
             })
             .get()
             .keyMap('databaseKey', inst => (this as any)[inst.modelKey])
@@ -804,7 +879,7 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
         (this as any)[thisFieldName] = object[objectFieldName]
     }
 
-    subscribe<EventT extends Dispatchable>(event: StaticClass<EventT, EventT>, subscriber: EventSubscriber<EventT>): Awaitable<EventSubscription> {
+    subscribe<EventT extends Dispatchable>(event: StaticClass<EventT, Instantiable<EventT>>, subscriber: EventSubscriber<EventT>): Awaitable<EventSubscription> {
         const entry: EventSubscriberEntry<EventT> = {
             id: uuid4(),
             event,
@@ -843,4 +918,208 @@ export abstract class Model<T extends Model<T>> extends AppClass implements Bus
             },
         }
     }
+
+    /**
+     * Create a new one-to-one relation instance. Should be called from a method on the model:
+     *
+     * @example
+     * ```ts
+     * class MyModel extends Model<MyModel> {
+     *     @Related()
+     *     public otherModel() {
+     *         return this.hasOne(MyOtherModel)
+     *     }
+     * }
+     * ```
+     *
+     * @param related
+     * @param foreignKeyOverride
+     * @param localKeyOverride
+     */
+    public hasOne<T2 extends Model<T2>>(related: Instantiable<T2>, foreignKeyOverride?: keyof T & string, localKeyOverride?: keyof T2 & string): HasOne<T, T2> {
+        return new HasOne<T, T2>(this as unknown as T, this.make(related), foreignKeyOverride, localKeyOverride)
+    }
+
+
+    /**
+     * Create a new one-to-one relation instance. Should be called from a method on the model:
+     *
+     * @example
+     * ```ts
+     * class MyModel extends Model<MyModel> {
+     *     @Related()
+     *     public otherModels() {
+     *         return this.hasMany(MyOtherModel)
+     *     }
+     * }
+     * ```
+     *
+     * @param related
+     * @param foreignKeyOverride
+     * @param localKeyOverride
+     */
+    public hasMany<T2 extends Model<T2>>(related: Instantiable<T2>, foreignKeyOverride?: keyof T & string, localKeyOverride?: keyof T2 & string): HasMany<T, T2> {
+        return new HasMany<T, T2>(this as unknown as T, this.make(related), foreignKeyOverride, localKeyOverride)
+    }
+
+    /**
+     * Create the inverse of a one-to-one relation. Should be called from a method on the model:
+     *
+     * @example
+     * ```ts
+     * class MyModel extends Model<MyModel> {
+     *     @Related()
+     *     public otherModel() {
+     *         return this.hasOne(MyOtherModel)
+     *     }
+     * }
+     *
+     * class MyOtherModel extends Model<MyOtherModel> {
+     *     @Related()
+     *     public myModel() {
+     *         return this.belongsToOne(MyModel, 'otherModel')
+     *     }
+     * }
+     * ```
+     *
+     * @param related
+     * @param relationName
+     */
+    public belongsToOne<T2 extends Model<T2>>(related: Instantiable<T>, relationName: keyof T2): HasOne<T, T2> {
+        const relatedInst = this.make(related) as T2
+        const relation = relatedInst.getRelation(relationName)
+
+        if ( !(relation instanceof HasOneOrMany) ) {
+            throw new TypeError(`Cannot create belongs to one relation. Inverse relation must be HasOneOrMany.`)
+        }
+
+        const localKey = relation.localKey
+        const foreignKey = relation.foreignKey
+
+        if ( !isKeyof(localKey, this as unknown as T) || !isKeyof(foreignKey, relatedInst) ) {
+            throw new TypeError('Local or foreign keys do not exist on the base model.')
+        }
+
+        return new HasOne<T, T2>(this as unknown as T, relatedInst, localKey, foreignKey)
+    }
+
+
+    /**
+     * Create the inverse of a one-to-many relation. Should be called from a method on the model:
+     *
+     * @example
+     * ```ts
+     * class MyModel extends Model<MyModel> {
+     *     @Related()
+     *     public otherModels() {
+     *         return this.hasMany(MyOtherModel)
+     *     }
+     * }
+     *
+     * class MyOtherModel extends Model<MyOtherModel> {
+     *     @Related()
+     *     public myModels() {
+     *         return this.belongsToMany(MyModel, 'otherModels')
+     *     }
+     * }
+     * ```
+     *
+     * @param related
+     * @param relationName
+     */
+    public belongsToMany<T2 extends Model<T2>>(related: Instantiable<T>, relationName: keyof T2): HasMany<T, T2> {
+        const relatedInst = this.make(related) as T2
+        const relation = relatedInst.getRelation(relationName)
+
+        if ( !(relation instanceof HasOneOrMany) ) {
+            throw new TypeError(`Cannot create belongs to one relation. Inverse relation must be HasOneOrMany.`)
+        }
+
+        const localKey = relation.localKey
+        const foreignKey = relation.foreignKey
+
+        if ( !isKeyof(localKey, this as unknown as T) || !isKeyof(foreignKey, relatedInst) ) {
+            throw new TypeError('Local or foreign keys do not exist on the base model.')
+        }
+
+        return new HasMany<T, T2>(this as unknown as T, relatedInst, localKey, foreignKey)
+    }
+
+    /**
+     * Get the relation instance returned by a method on this model.
+     * @param name
+     * @protected
+     */
+    public getRelation<T2 extends Model<T2>>(name: keyof this): Relation<T, T2, RelationValue<T2>> {
+        const relFn = this[name]
+
+        if ( relFn instanceof Relation ) {
+            return relFn
+        }
+
+        if ( typeof relFn === 'function' ) {
+            const rel = relFn.apply(relFn, this)
+            if ( rel instanceof Relation ) {
+                return rel
+            }
+        }
+
+        throw new TypeError(`Cannot get relation of name: ${name}. Method does not return a Relation.`)
+    }
+
+    /**
+     * Register a scope on the model.
+     * @param scope
+     * @protected
+     */
+    protected scope(scope: Instantiable<Scope> | ScopeClosure): this {
+        if ( isInstantiable(scope) ) {
+            if ( !this.hasScope(scope) ) {
+                this.scopes.push({
+                    accessor: scope,
+                    scope: builder => (this.make<Scope>(scope)).apply(builder),
+                })
+            }
+        } else {
+            this.scopes.push({
+                accessor: uuid4(),
+                scope,
+            })
+        }
+
+        return this
+    }
+
+    /**
+     * Register a scope on the model with a specific name.
+     * @param name
+     * @param scope
+     * @protected
+     */
+    protected namedScope(name: string, scope: Instantiable<Scope> | ScopeClosure): this {
+        if ( isInstantiable(scope) ) {
+            if ( !this.hasScope(scope) ) {
+                this.scopes.push({
+                    accessor: name,
+                    scope: builder => (this.make<Scope>(scope)).apply(builder),
+                })
+            }
+        } else {
+            this.scopes.push({
+                accessor: name,
+                scope,
+            })
+        }
+
+        return this
+    }
+
+    /**
+     * Returns true if the current model has a scope with the given identifier.
+     * @param name
+     * @protected
+     */
+    protected hasScope(name: string | Instantiable<Scope>): boolean {
+        return Boolean(this.scopes.firstWhere('accessor', '=', name))
+    }
 }

src/orm/model/ModelBuilder.ts

@@ -1,25 +1,136 @@
 import {Model} from './Model'
 import {AbstractBuilder} from '../builder/AbstractBuilder'
 import {AbstractResultIterable} from '../builder/result/AbstractResultIterable'
-import {Instantiable} from '../../di'
+import {Instantiable, StaticClass} from '../../di'
 import {ModelResultIterable} from './ModelResultIterable'
+import {Collection} from '../../util'
+import {ConstraintOperator, ModelKey, ModelKeys} from '../types'
+import {EscapeValue} from '../dialect/SQLDialect'
+import {Scope, ScopeClosure} from './scope/Scope'
 
 /**
  * Implementation of the abstract builder whose results yield instances of a given Model, `T`.
  */
 export class ModelBuilder<T extends Model<T>> extends AbstractBuilder<T> {
+    protected eagerLoadRelations: (keyof T)[] = []
+
+    protected appliedScopes: Collection<{ accessor: string | Instantiable<Scope>, scope: ScopeClosure }> = new Collection<{accessor: string | Instantiable<Scope>; scope: ScopeClosure}>()
+
     constructor(
         /** The model class that is created for results of this query. */
-        protected readonly ModelClass: Instantiable<T>,
+        protected readonly ModelClass: StaticClass<T, typeof Model> & Instantiable<T>,
     ) {
         super()
     }
 
+    public withScopes(scopes: Collection<{ accessor: string | Instantiable<Scope>, scope: ScopeClosure }>): this {
+        this.appliedScopes = scopes.clone()
+        return this
+    }
+
     public getNewInstance(): AbstractBuilder<T> {
-        return this.app().make<ModelBuilder<T>>(ModelBuilder)
+        return this.app().make<ModelBuilder<T>>(ModelBuilder, this.ModelClass)
     }
 
     public getResultIterable(): AbstractResultIterable<T> {
-        return this.app().make<ModelResultIterable<T>>(ModelResultIterable, this, this.registeredConnection, this.ModelClass)
+        return this.app().make<ModelResultIterable<T>>(ModelResultIterable, this.finalize(), this.registeredConnection, this.ModelClass)
+    }
+
+    /**
+     * Get a copy of this builder with all of its values finalized.
+     * @override to apply scopes
+     */
+    public finalize(): AbstractBuilder<T> {
+        const inst = super.finalize()
+        this.appliedScopes.each(rec => rec.scope(inst))
+        return inst
+    }
+
+    /**
+     * Apply a WHERE...IN... constraint on the primary key of the model.
+     * @param keys
+     */
+    public whereKey(keys: ModelKeys): this {
+        return this.whereIn(
+            this.ModelClass.qualifyKey(),
+            this.normalizeModelKeys(keys),
+        )
+    }
+
+    /**
+     * Apply a where constraint on the column corresponding the the specified
+     * property on the model.
+     * @param propertyName
+     * @param operator
+     * @param operand
+     */
+    public whereProperty(propertyName: string, operator: ConstraintOperator, operand?: EscapeValue): this {
+        return this.where(
+            this.ModelClass.propertyToColumn(propertyName),
+            operator,
+            operand,
+        )
+    }
+
+    /**
+     * Mark a relation to be eager-loaded.
+     * @param relationName
+     */
+    public with(relationName: keyof T): this {
+        if ( !this.eagerLoadRelations.includes(relationName) ) {
+            // Try to load the Relation so we fail if the name is invalid
+            this.make<T>(this.ModelClass).getRelation(relationName)
+            this.eagerLoadRelations.push(relationName)
+        }
+
+        return this
+    }
+
+    /**
+     * Remove all global scopes from this query.
+     */
+    public withoutGlobalScopes(): this {
+        this.appliedScopes = new Collection<{accessor: string | Instantiable<Scope>; scope: ScopeClosure}>()
+        return this
+    }
+
+    /**
+     * Remove a specific scope from this query by its identifier.
+     * @param name
+     */
+    public withoutGlobalScope(name: string | Instantiable<Scope>): this {
+        this.appliedScopes = this.appliedScopes.where('accessor', '=', name)
+        return this
+    }
+
+    /** Get the list of relations to eager-load. */
+    public getEagerLoadedRelations(): (keyof T)[] {
+        return [...this.eagerLoadRelations]
+    }
+
+    /**
+     * Given some format of keys of the model, try to normalize them to a flat array.
+     * @param keys
+     * @protected
+     */
+    protected normalizeModelKeys(keys: ModelKeys): ModelKey[] {
+        if ( Array.isArray(keys) ) {
+            return keys
+        } else if ( keys instanceof Collection ) {
+            return keys.all()
+        }
+
+        return [keys]
+    }
+
+    /**
+     * Create a copy of this builder.
+     * @override to add implementation-specific pass-alongs.
+     */
+    public clone(): ModelBuilder<T> {
+        const inst = super.clone() as ModelBuilder<T>
+        inst.eagerLoadRelations = [...this.eagerLoadRelations]
+        inst.appliedScopes = this.appliedScopes.clone()
+        return inst
     }
 }

src/orm/model/ModelResultIterable.ts

@@ -4,7 +4,7 @@ import {Connection} from '../connection/Connection'
 import {ModelBuilder} from './ModelBuilder'
 import {Container, Instantiable} from '../../di'
 import {QueryRow} from '../types'
-import {Collection} from '../../util'
+import {collect, Collection} from '../../util'
 
 /**
  * Implementation of the result iterable that returns query results as instances of the defined model.
@@ -28,13 +28,17 @@ export class ModelResultIterable<T extends Model<T>> extends AbstractResultItera
         const row = (await this.connection.query(query)).rows.first()
 
         if ( row ) {
-            return this.inflateRow(row)
+            const inflated = await this.inflateRow(row)
+            await this.processEagerLoads(collect([inflated]))
+            return inflated
         }
     }
 
     async range(start: number, end: number): Promise<Collection<T>> {
         const query = this.connection.dialect().renderRangedSelect(this.selectSQL, start, end)
-        return (await this.connection.query(query)).rows.promiseMap<T>(row => this.inflateRow(row))
+        const inflated = await (await this.connection.query(query)).rows.promiseMap<T>(row => this.inflateRow(row))
+        await this.processEagerLoads(inflated)
+        return inflated
     }
 
     async count(): Promise<number> {
@@ -45,7 +49,9 @@ export class ModelResultIterable<T extends Model<T>> extends AbstractResultItera
 
     async all(): Promise<Collection<T>> {
         const result = await this.connection.query(this.selectSQL)
-        return result.rows.promiseMap<T>(row => this.inflateRow(row))
+        const inflated = await result.rows.promiseMap<T>(row => this.inflateRow(row))
+        await this.processEagerLoads(inflated)
+        return inflated
     }
 
     /**
@@ -58,6 +64,30 @@ export class ModelResultIterable<T extends Model<T>> extends AbstractResultItera
             .assumeFromSource(row)
     }
 
+    /**
+     * Eager-load eager-loaded relations for the models in the query result.
+     * @param results
+     * @protected
+     */
+    protected async processEagerLoads(results: Collection<T>): Promise<void> {
+        const eagers = this.builder.getEagerLoadedRelations()
+        const model = this.make<T>(this.ModelClass)
+
+        for ( const name of eagers ) {
+            // TODO support nested eager loads?
+
+            const relation = model.getRelation(name)
+            const select = relation.buildEagerQuery(this.builder, results)
+
+            const allRelated = await select.get().collect()
+            allRelated.each(result => {
+                const resultRelation = result.getRelation(name as any)
+                const resultRelated = resultRelation.matchResults(allRelated as any)
+                resultRelation.setValue(resultRelated as any)
+            })
+        }
+    }
+
     clone(): ModelResultIterable<T> {
         return new ModelResultIterable(this.builder, this.connection, this.ModelClass)
     }

src/orm/model/relation/HasMany.ts

@@ -0,0 +1,47 @@
+import {Model} from '../Model'
+import {HasOneOrMany} from './HasOneOrMany'
+import {Collection} from '../../../util'
+import {RelationNotLoadedError} from './Relation'
+
+/**
+ * One-to-many relation implementation.
+ */
+export class HasMany<T extends Model<T>, T2 extends Model<T2>> extends HasOneOrMany<T, T2, Collection<T2>> {
+    protected cachedValue?: Collection<T2>
+
+    protected cachedLoaded = false
+
+    constructor(
+        parent: T,
+        related: T2,
+        foreignKeyOverride?: keyof T & string,
+        localKeyOverride?: keyof T2 & string,
+    ) {
+        super(parent, related, foreignKeyOverride, localKeyOverride)
+    }
+
+    /** Resolve the result of this relation. */
+    public get(): Promise<Collection<T2>> {
+        return this.fetch().collect()
+    }
+
+    /** Set the value of this relation. */
+    public setValue(related: Collection<T2>): void {
+        this.cachedValue = related.clone()
+        this.cachedLoaded = true
+    }
+
+    /** Get the value of this relation. */
+    public getValue(): Collection<T2> {
+        if ( !this.cachedValue ) {
+            throw new RelationNotLoadedError()
+        }
+
+        return this.cachedValue
+    }
+
+    /** Returns true if the relation has been loaded. */
+    public isLoaded(): boolean {
+        return this.cachedLoaded
+    }
+}

src/orm/model/relation/HasOne.ts

@@ -0,0 +1,47 @@
+import {Model} from '../Model'
+import {HasOneOrMany} from './HasOneOrMany'
+import {RelationNotLoadedError} from './Relation'
+import {Maybe} from '../../../util'
+
+/**
+ * One-to-one relation implementation.
+ */
+export class HasOne<T extends Model<T>, T2 extends Model<T2>> extends HasOneOrMany<T, T2, Maybe<T2>> {
+    protected cachedValue?: T2
+
+    protected cachedLoaded = false
+
+    constructor(
+        parent: T,
+        related: T2,
+        foreignKeyOverride?: keyof T & string,
+        localKeyOverride?: keyof T2 & string,
+    ) {
+        super(parent, related, foreignKeyOverride, localKeyOverride)
+    }
+
+    /** Resolve the result of this relation. */
+    async get(): Promise<Maybe<T2>> {
+        return this.fetch().first()
+    }
+
+    /** Set the value of this relation. */
+    public setValue(related: T2): void {
+        this.cachedValue = related
+        this.cachedLoaded = true
+    }
+
+    /** Get the value of this relation. */
+    public getValue(): Maybe<T2> {
+        if ( !this.cachedLoaded ) {
+            throw new RelationNotLoadedError()
+        }
+
+        return this.cachedValue
+    }
+
+    /** Returns true if the relation has been loaded. */
+    public isLoaded(): boolean {
+        return this.cachedLoaded
+    }
+}

src/orm/model/relation/HasOneOrMany.ts

@@ -0,0 +1,80 @@
+import {Model} from '../Model'
+import {Relation, RelationValue} from './Relation'
+import {RelationBuilder} from './RelationBuilder'
+import {raw} from '../../dialect/SQLDialect'
+import {AbstractBuilder} from '../../builder/AbstractBuilder'
+import {ModelBuilder} from '../ModelBuilder'
+import {Collection, toString} from '../../../util'
+
+/**
+ * Base class for 1:1 and 1:M relations.
+ */
+export abstract class HasOneOrMany<T extends Model<T>, T2 extends Model<T2>, V extends RelationValue<T2>> extends Relation<T, T2, V> {
+    protected constructor(
+        parent: T,
+        related: T2,
+
+        /** Override the foreign key property. */
+        protected foreignKeyOverride?: keyof T & string,
+
+        /** Override the local key property. */
+        protected localKeyOverride?: keyof T2 & string,
+    ) {
+        super(parent, related)
+    }
+
+    /** Get the name of the foreign key for this relation. */
+    public get foreignKey(): string {
+        return this.foreignKeyOverride || this.parent.keyName()
+    }
+
+    /** Get the name of the local key for this relation. */
+    public get localKey(): string {
+        return this.localKeyOverride || this.foreignKey
+    }
+
+    /** Get the fully-qualified name of the foreign key. */
+    public get qualifiedForeignKey(): string {
+        return this.related.qualify(this.foreignKey)
+    }
+
+    /** Get the fully-qualified name of the local key. */
+    public get qualifiedLocalKey(): string {
+        return this.related.qualify(this.localKey)
+    }
+
+    /** Get the value of the pivot for this relation from the parent model. */
+    public get parentValue(): any {
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
+        return this.parent[this.localKey]
+    }
+
+    /** Create a new query for this relation. */
+    public query(): RelationBuilder<T2> {
+        return this.builder().select(raw('*'))
+    }
+
+    /** Apply the relation's constraints on a model query. */
+    public applyScope(where: AbstractBuilder<T2>): void {
+        where.where(subq => {
+            subq.where(this.qualifiedForeignKey, '=', this.parentValue)
+                .whereRaw(this.qualifiedForeignKey, 'IS NOT', 'NULL')
+        })
+    }
+
+    /** Create an eager-load query matching this relation's models. */
+    public buildEagerQuery(parentQuery: ModelBuilder<T>, result: Collection<T>): ModelBuilder<T2> {
+        const keys = result.pluck(this.localKey as keyof T)
+            .map(toString)
+            .all()
+
+        return this.related.query()
+            .whereIn(this.foreignKey, keys)
+    }
+
+    /** Given a collection of results, filter out those that are relevant to this relation. */
+    public matchResults(possiblyRelated: Collection<T>): Collection<T> {
+        return possiblyRelated.where(this.foreignKey as keyof T, '=', this.parentValue)
+    }
+}

src/orm/model/relation/Relation.ts

@@ -0,0 +1,111 @@
+import {Model} from '../Model'
+import {ModelBuilder} from '../ModelBuilder'
+import {AbstractBuilder} from '../../builder/AbstractBuilder'
+import {ResultCollection} from '../../builder/result/ResultCollection'
+import {Collection, ErrorWithContext, Maybe} from '../../../util'
+import {QuerySource} from '../../types'
+import {RelationBuilder} from './RelationBuilder'
+import {InjectionAware} from '../../../di'
+
+/** Type alias for possible values of a relation. */
+export type RelationValue<T2> = Maybe<Collection<T2> | T2>
+
+/** Error thrown when a relation result is accessed synchronously before it is loaded. */
+export class RelationNotLoadedError extends ErrorWithContext {
+    constructor(
+        context: {[key: string]: any} = {},
+    ) {
+        super('Attempted to get value of relation that has not yet been loaded.', context)
+    }
+}
+
+/**
+ * Base class for inter-model relation implementations.
+ */
+export abstract class Relation<T extends Model<T>, T2 extends Model<T2>, V extends RelationValue<T2>> extends InjectionAware {
+    protected constructor(
+        /** The model related from. */
+        protected parent: T,
+
+        /** The model related to. */
+        public readonly related: T2,
+    ) {
+        super()
+    }
+
+    /** Get the value of the key field from the parent model. */
+    protected abstract get parentValue(): any
+
+    /** Create a new relation builder query for this relation instance. */
+    public abstract query(): RelationBuilder<T2>
+
+    /** Limit the results of the builder to only this relation's rows. */
+    public abstract applyScope(where: AbstractBuilder<T2>): void
+
+    /** Create a relation query that will eager-load the result of this relation for a set of models. */
+    public abstract buildEagerQuery(parentQuery: ModelBuilder<T>, result: Collection<T>): ModelBuilder<T2>
+
+    /** Given a set of possibly-related instances, filter out the ones that are relevant to the parent. */
+    public abstract matchResults(possiblyRelated: Collection<T>): Collection<T>
+
+    /** Set the value of the relation. */
+    public abstract setValue(related: V): void
+
+    /** Get the value of the relation. */
+    public abstract getValue(): V
+
+    /** Returns true if the relation has been loaded. */
+    public abstract isLoaded(): boolean
+
+    /** Get a collection of the results of this relation. */
+    public fetch(): ResultCollection<T2> {
+        return this.query().get()
+    }
+
+    /** Resolve the result of this relation. */
+    public abstract get(): Promise<V>
+
+    /**
+     * Makes the relation "thenable" so relation methods on models can be awaited
+     * to yield the result of the relation.
+     *
+     * @example
+     * ```ts
+     * const rows = await myModelInstance.myHasManyRelation()  -- rows is a Collection
+     * ```
+     *
+     * @param resolve
+     * @param reject
+     */
+    public then(resolve: (result: V) => unknown, reject: (e: Error) => unknown): void {
+        if ( this.isLoaded() ) {
+            resolve(this.getValue())
+        } else {
+            this.get()
+                .then(result => {
+                    if ( result instanceof Collection ) {
+                        this.setValue(result)
+                    }
+
+                    resolve(result)
+                })
+                .catch(reject)
+        }
+    }
+
+    /** Get the value of this relation. */
+    public get value(): V {
+        return this.getValue()
+    }
+
+    /** Get the query source for the related model in this relation. */
+    public get relatedQuerySource(): QuerySource {
+        const related = this.related.constructor as typeof Model
+        return related.querySource()
+    }
+
+    /** Get a new builder instance for this relation. */
+    public builder(): RelationBuilder<T2> {
+        return this.make(RelationBuilder, this)
+    }
+}

src/orm/model/relation/RelationBuilder.ts

@@ -0,0 +1,14 @@
+import {Model} from '../Model'
+import {ModelBuilder} from '../ModelBuilder'
+import {Relation} from './Relation'
+
+/**
+ * ModelBuilder instance that queries the related model in a relation.
+ */
+export class RelationBuilder<T extends Model<T>> extends ModelBuilder<T> {
+    constructor(
+        protected relation: Relation<any, T, any>,
+    ) {
+        super(relation.related.constructor as any)
+    }
+}

src/orm/model/relation/decorators.ts

@@ -0,0 +1,37 @@
+import {Model} from '../Model'
+
+/**
+ * Decorator for relation methods on a Model implementation.
+ * Caches the relation instances between uses for the life of the model.
+ * @constructor
+ */
+export function Related(): MethodDecorator {
+    return (target, propertyKey, descriptor) => {
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
+        const original = descriptor.value
+
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
+        descriptor.value = function(...args) {
+            const model = this as Model<any>
+            const cache = model.relationCache
+
+            const existing = cache.firstWhere('accessor', '=', propertyKey)
+            if ( existing ) {
+                return existing.relation
+            }
+
+            // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+            // @ts-ignore
+            const value = original.apply(this, args)
+
+            cache.push({
+                accessor: propertyKey,
+                relation: value,
+            })
+
+            return value
+        }
+    }
+}

src/orm/model/scope/ActiveScope.ts

@@ -0,0 +1,11 @@
+import {Scope} from './Scope'
+import {AbstractBuilder} from '../../builder/AbstractBuilder'
+
+/**
+ * A basic scope to limit results where `active` = true.
+ */
+export class ActiveScope extends Scope {
+    apply(query: AbstractBuilder<any>): void {
+        query.where('active', '=', true)
+    }
+}

src/orm/model/scope/Scope.ts

@@ -0,0 +1,18 @@
+import {Injectable, InjectionAware} from '../../../di'
+import {Awaitable} from '../../../util'
+import {AbstractBuilder} from '../../builder/AbstractBuilder'
+
+/**
+ * A closure that takes a query and applies some scope to it.
+ */
+export type ScopeClosure = (query: AbstractBuilder<any>) => Awaitable<void>
+
+/**
+ * Base class for scopes that can be applied to queries.
+ */
+@Injectable()
+export abstract class Scope extends InjectionAware {
+
+    abstract apply(query: AbstractBuilder<any>): Awaitable<void>
+
+}

src/orm/schema/PostgresSchema.ts

@@ -0,0 +1,341 @@
+import {Schema} from './Schema'
+import {Awaitable, collect, Collection} from '../../util'
+import {ConstraintType, TableBuilder} from './TableBuilder'
+import {PostgresConnection} from '../connection/PostgresConnection'
+import {Builder} from '../builder/Builder'
+import {raw} from '../dialect/SQLDialect'
+import {QueryRow} from '../types'
+
+/**
+ * A PostgreSQL-compatible schema implementation.
+ */
+export class PostgresSchema extends Schema {
+    constructor(
+        connection: PostgresConnection,
+        public readonly schema: string = 'public',
+    ) {
+        super(connection)
+    }
+
+    hasColumn(table: string, name: string): Awaitable<boolean> {
+        return (new Builder()).connection(this.connection)
+            .select(raw('*'))
+            .from('information_schema.columns')
+            .where('table_schema', '=', this.schema)
+            .where('table_name', '=', table)
+            .where('column_name', '=', name)
+            .exists()
+    }
+
+    async hasColumns(table: string, name: string[]): Promise<boolean> {
+        const num = await (new Builder()).connection(this.connection)
+            .select(raw('*'))
+            .from('information_schema.columns')
+            .where('table_schema', '=', this.schema)
+            .where('table_name', '=', table)
+            .whereIn('column_name', name)
+            .get()
+            .count()
+
+        return num === name.length
+    }
+
+    hasTable(name: string): Awaitable<boolean> {
+        return (new Builder()).connection(this.connection)
+            .select(raw('*'))
+            .from('information_schema.tables')
+            .where('table_schema', '=', this.schema)
+            .where('table_name', '=', name)
+            .exists()
+    }
+
+    async table(table: string): Promise<TableBuilder> {
+        return this.populateTable(new TableBuilder(table))
+    }
+
+    /**
+     * If the table for the given TableBuilder already exists in the
+     * database, fill in the columns, constraints, and indexes.
+     * @param table
+     * @protected
+     */
+    protected async populateTable(table: TableBuilder): Promise<TableBuilder> {
+        if ( await this.hasTable(table.name) ) {
+            // Load the existing columns
+            const cols = await this.getColumns(table.name)
+            cols.each(col => {
+                table.column(col.column_name)
+                    .type(col.data_type)
+                    .pipe()
+                    .when(col.is_nullable, builder => {
+                        builder.isNullable()
+                        return builder
+                    })
+                    .when(col.column_default, builder => {
+                        builder.default(raw(col.column_default))
+                        return builder
+                    })
+            })
+
+            // Load the existing constraints
+            const constraints = await this.getConstraints(table.name)
+
+            // Apply the unique constraints
+            const uniques = constraints.where('constraint_type', '=', 'u')
+                .sortBy('constraint_name')
+                .groupBy('constraint_name')
+
+            for ( const key in uniques ) {
+                if ( !Object.prototype.hasOwnProperty.call(uniques, key) ) {
+                    continue
+                }
+
+                table.constraint(key)
+                    .type(ConstraintType.Unique)
+                    .pipe()
+                    .peek(constraint => {
+                        collect<{column_name: string}>(uniques[key])  // eslint-disable-line camelcase
+                            .pluck<string>('column_name')
+                            .each(column => constraint.field(column))
+                    })
+                    .get()
+                    .flagAsExistingInSchema()
+            }
+
+            // Apply the primary key constraints
+            constraints.where('constraint_type', '=', 'p')
+                .pipe()
+                .when(c => c.count() > 0, pk => {
+                    pk.each(constraint => {
+                        table.column(constraint.column_name)
+                            .primary()
+                    })
+
+                    return pk
+                })
+
+            // Apply the non-null constraints
+            // Builder columns are non-null by default, so mark the others as nullable
+            const nonNullable = constraints.filter(x => !x.constraint_type)
+                .where('is_nullable', '=', 'NO')
+
+            collect<string>(Object.keys(table.getColumns()))
+                .map(column => {
+                    return {
+                        column,
+                    }
+                })
+                .whereNotIn('column', nonNullable.pluck('column_name'))
+                .pluck<string>('column')
+                .each(column => {
+                    table.column(column)
+                        .nullable()
+                })
+
+            // Look up and apply the check constraints
+            const checkConstraints = await this.getCheckConstraints(table.name)
+
+            checkConstraints.each(constraint => {
+                table.constraint(constraint.constraint_name)
+                    .type(ConstraintType.Check)
+                    .expression(constraint.check_clause)
+                    .flagAsExistingInSchema()
+            })
+
+            // Mark the columns as existing in the database
+            cols.each(col => {
+                table.column(col.column_name)
+                    .flagAsExistingInSchema()
+            })
+
+            // Look up table indexes
+            const indexes = await this.getIndexes(table.name)
+            const groupedIndexes = indexes.groupBy('index_name')
+
+            for ( const key in groupedIndexes ) {
+                if ( !Object.prototype.hasOwnProperty.call(groupedIndexes, key) ) {
+                    continue
+                }
+
+                table.index(key)
+                    .pipe()
+                    .peek(idx => {
+                        collect<{column_name: string}>(groupedIndexes[key])  // eslint-disable-line camelcase
+                            .pluck<string>('column_name')
+                            .each(col => idx.field(col))
+                    })
+                    .when(groupedIndexes[key]?.[0]?.indisprimary, idx => idx.primary())
+                    .when(groupedIndexes[key]?.[0]?.indisunique, idx => idx.unique())
+                    .get()
+                    .flagAsExistingInSchema()
+            }
+
+            table.flagAsExistingInSchema()
+        }
+
+        return table
+    }
+
+    /**
+     * Query the database to look up all indexes on a table, by column.
+     * @see https://stackoverflow.com/a/2213199/4971138
+     * @param table
+     * @protected
+     */
+    protected async getIndexes(table: string): Promise<Collection<QueryRow>> {
+        const rawQuery = `
+            select
+                t.relname as table_name,
+                i.relname as index_name,
+                a.attname as column_name,
+                ix.*
+            from pg_class t
+            left join pg_attribute a
+                on a.attrelid = t.oid
+            left join pg_index ix
+                on t.oid = ix.indrelid
+            left join pg_class i
+                on i.oid = ix.indexrelid
+            left join pg_namespace n
+                on n.oid = i.relnamespace
+            where
+                a.attnum = any(ix.indkey)
+                and t.relkind = 'r'
+                and t.relname = '${table}'
+                and n.nspname = '${this.schema}'
+            order by
+                t.relname,
+                i.relname;
+        `
+
+        return (new Builder()).connection(this.connection)
+            .raw(rawQuery)
+            .get()
+            .collect()
+    }
+
+    /**
+     * Query the database to look up all constraints on a table, by column.
+     * @see https://dba.stackexchange.com/a/290854
+     * @param table
+     * @protected
+     */
+    protected async getConstraints(table: string): Promise<Collection<QueryRow>> {
+        const rawQuery = `
+            SELECT * FROM (
+                SELECT
+                    pgc.contype AS constraint_type,
+                    pgc.conname AS constraint_name,
+                    ccu.table_schema AS table_schema,
+                    kcu.table_name AS table_name,
+                    CASE WHEN (pgc.contype = 'f') THEN kcu.COLUMN_NAME ELSE ccu.COLUMN_NAME END AS column_name, 
+                    CASE WHEN (pgc.contype = 'f') THEN ccu.TABLE_NAME ELSE (null) END AS reference_table,
+                    CASE WHEN (pgc.contype = 'f') THEN ccu.COLUMN_NAME ELSE (null) END AS reference_col,
+                    CASE WHEN (pgc.contype = 'p') THEN 'yes' ELSE 'no' END AS auto_inc,
+                    CASE WHEN (pgc.contype = 'p') THEN 'NO' ELSE 'YES' END AS is_nullable,
+                    'integer' AS data_type,
+                    '0' AS numeric_scale,
+                    '32' AS numeric_precision
+                FROM
+                    pg_constraint AS pgc
+                JOIN pg_namespace nsp
+                    ON nsp.oid = pgc.connamespace
+                JOIN pg_class cls
+                    ON pgc.conrelid = cls.oid
+                JOIN information_schema.key_column_usage kcu
+                    ON kcu.constraint_name = pgc.conname
+                LEFT JOIN information_schema.constraint_column_usage ccu
+                    ON pgc.conname = ccu.CONSTRAINT_NAME 
+                    AND nsp.nspname = ccu.CONSTRAINT_SCHEMA
+                WHERE
+                      kcu.table_name = '${table}'
+                UNION
+                    SELECT
+                        NULL AS constraint_type,
+                        NULL AS constraint_name,
+                        table_schema,
+                        table_name,
+                        column_name,
+                        NULL AS refrence_table,
+                        NULL AS refrence_col,
+                        'no' AS auto_inc,
+                        is_nullable,
+                        data_type,
+                        numeric_scale,
+                        numeric_precision
+                    FROM information_schema.columns cols 
+                    WHERE
+                        table_schema = '${this.schema}'
+                        AND table_name = '${table}'
+                ) AS child
+            ORDER BY table_name DESC
+        `
+
+        return (new Builder()).connection(this.connection)
+            .raw(rawQuery)
+            .get()
+            .collect()
+    }
+
+    /**
+     * @see https://dataedo.com/kb/query/postgresql/list-table-check-constraints
+     * @param table
+     * @protected
+     */
+    protected async getCheckConstraints(table: string): Promise<Collection<QueryRow>> {
+        const rawQuery = `
+            SELECT
+                tc.table_schema,
+                tc.table_name,
+                ARRAY_AGG(col.column_name) AS columns,
+                tc.constraint_name,
+                cc.check_clause
+            FROM information_schema.table_constraints tc
+            JOIN information_schema.check_constraints cc
+                ON tc.constraint_schema = cc.constraint_schema
+                    AND tc.constraint_name = cc.constraint_name
+            JOIN pg_namespace nsp
+                ON nsp.nspname = cc.constraint_schema
+            JOIN pg_constraint pgc
+                ON pgc.conname = cc.constraint_name
+                    AND pgc.connamespace = nsp.oid
+                    AND pgc.contype = 'c'
+            JOIN information_schema.columns col
+                ON col.table_schema = tc.table_schema
+                    AND col.table_name = tc.table_name
+                    AND col.ordinal_position = ANY(pgc.conkey)
+            WHERE
+                tc.constraint_schema NOT IN ('pg_catalog', 'information_schema')
+                AND tc.table_schema = '${this.schema}'
+                AND tc.table_name = '${table}'
+            GROUP BY
+                tc.table_schema,
+                tc.table_name,
+                tc.constraint_name,
+                cc.check_clause
+            ORDER BY
+                tc.table_schema,
+                tc.table_name
+        `
+
+        return (new Builder()).connection(this.connection)
+            .raw(rawQuery)
+            .get()
+            .collect()
+    }
+
+    /**
+     * Query the database to look up all columns on a table.
+     * @param table
+     * @protected
+     */
+    protected async getColumns(table: string): Promise<Collection<QueryRow>> {
+        return (new Builder()).connection(this.connection)
+            .select(raw('*'))
+            .from('information_schema.columns')
+            .where('table_schema', '=', this.schema)
+            .where('table_name', '=', table)
+            .get()
+            .collect()
+    }
+}

src/orm/schema/Schema.ts

@@ -1,14 +1,51 @@
 import {Connection} from '../connection/Connection'
 import {Awaitable} from '../../util'
+import {TableBuilder} from './TableBuilder'
 
+/**
+ * Represents a SQL-schema implementation.
+ */
 export abstract class Schema {
     constructor(
+        /** The SQL connection to execute against. */
         protected readonly connection: Connection,
     ) { }
 
+    /**
+     * Resolve true if the schema has a table with the given name.
+     * @param name
+     */
     public abstract hasTable(name: string): Awaitable<boolean>
 
+    /**
+     * Resolve true if the schema table with the given name has a column with the given name.
+     * @param table
+     * @param name
+     */
     public abstract hasColumn(table: string, name: string): Awaitable<boolean>
 
+    /**
+     * Resolve true if the schema table with the given name has all the specified columns.
+     * @param table
+     * @param name
+     */
     public abstract hasColumns(table: string, name: string[]): Awaitable<boolean>
+
+    /**
+     * Get a TableBuilder instance for a table on the schema.
+     * @param table
+     */
+    public abstract table(table: string): Awaitable<TableBuilder>
+
+    /**
+     * Apply the table to the schema.
+     * @param schema
+     */
+    public async commit(schema: TableBuilder): Promise<void> {
+        const query = this.connection
+            .dialect()
+            .renderCommitSchemaTransaction(schema)
+
+        await this.connection.query(query)
+    }
 }

src/orm/schema/TableBuilder.ts

@@ -1,109 +1,770 @@
-import {Pipe} from '../../util'
+import {collect, Maybe, ParameterizedCallback, Pipe} from '../../util'
+import {FieldType} from '../types'
+import {EscapeValue, QuerySafeValue, raw} from '../dialect/SQLDialect'
 
+/**
+ * Base class with shared logic for the various schema
+ * builders (table, column, index).
+ */
 export abstract class SchemaBuilderBase {
+    /**
+     * Whether or not the schema item should be dropped.
+     *  - `exists` - drop if exists
+     * @protected
+     */
     protected shouldDrop: 'yes'|'no'|'exists' = 'no'
 
+    /**
+     * The name the schema item should have if renaming.
+     * @protected
+     */
     protected shouldRenameTo?: string
 
+    /**
+     * If true, apply IF NOT EXISTS syntax.
+     * @protected
+     */
+    protected shouldSkipIfExists = false
+
+    /** True if the schema has been modified since created/loaded. */
+    protected dirty = false
+
+    /** True if this resource exists, in some form, in the schema. */
+    protected existsInSchema = false
+
+    /** If the resource exists in the schema, the unaltered values it has. */
+    public originalFromSchema?: SchemaBuilderBase
+
     constructor(
-        protected readonly name: string,
+        /** The name of the schema item. */
+        public readonly name: string,
     ) { }
 
+    /**
+     * Clone the properties of this resource to a different instance.
+     * @param newBuilder
+     */
+    public cloneTo(newBuilder: SchemaBuilderBase): SchemaBuilderBase {
+        newBuilder.shouldDrop = this.shouldDrop
+        newBuilder.shouldRenameTo = this.shouldRenameTo
+        newBuilder.shouldSkipIfExists = this.shouldSkipIfExists
+        newBuilder.dirty = this.dirty
+        newBuilder.existsInSchema = this.existsInSchema
+        return newBuilder
+    }
+
+    /** True if this resource should be dropped. */
+    public isDropping(): boolean {
+        return this.shouldDrop === 'yes'
+    }
+
+    /** True if this resource should be dropped with IF EXISTS syntax. */
+    public isDroppingIfExists(): boolean {
+        return this.shouldDrop === 'exists'
+    }
+
+    /** True if this resource should be created with IF NOT EXISTS syntax. */
+    public isSkippedIfExisting(): boolean {
+        return this.shouldSkipIfExists
+    }
+
+    /** True if the resource already exists in some form in the schema. */
+    public isExisting(): boolean {
+        return this.existsInSchema
+    }
+
+    /** True if the resource has been modified since created/loaded. */
+    public isDirty(): boolean {
+        return this.dirty
+    }
+
+    /**
+     * Get the name this resource should be renamed to, if it exists.
+     */
+    public getRename(): Maybe<string> {
+        return this.shouldRenameTo
+    }
+
+    /** Mark the resource to be removed. */
     public drop(): this {
+        this.dirty = true
         this.shouldDrop = 'yes'
         return this
     }
 
+    /** Mark the resource to be removed, if it exists. */
     public dropIfExists(): this {
+        this.dirty = true
         this.shouldDrop = 'exists'
         return this
     }
 
+    /**
+     * Rename the resource to a different name.
+     * @param to
+     */
     public rename(to: string): this {
+        this.dirty = true
         this.shouldRenameTo = to
         return this
     }
 
+    /**
+     * Mark the resource to use IF NOT EXISTS syntax.
+     */
+    public ifNotExists(): this {
+        this.shouldSkipIfExists = true
+        return this
+    }
+
+    /**
+     * Used internally.
+     * Mark that the resource exists in the schema in some form,
+     * and reset the `dirty` flag.
+     */
+    public flagAsExistingInSchema(): this {
+        this.existsInSchema = true
+        this.dirty = false
+        this.originalFromSchema = this.cloneTo(this.cloneInstance())
+        return this
+    }
+
+    /** Get a Pipe containing this instance. */
     pipe(): Pipe<this> {
         return Pipe.wrap<this>(this)
     }
+
+    /**
+     * Get a new instance of the concrete implementation of this class.
+     * @protected
+     */
+    protected abstract cloneInstance(): this
 }
 
+/**
+ * Builder to specify the schema of a table column.
+ */
 export class ColumnBuilder extends SchemaBuilderBase {
+    /** The data type of the column. */
+    protected targetType?: FieldType
 
-}
+    /** True if the column should allow NULL values. */
+    protected shouldBeNullable = false
 
-export class IndexBuilder extends SchemaBuilderBase {
+    /** The default value of the column, if one should exist. */
+    protected defaultValue?: EscapeValue
 
-    protected fields: Set<string> = new Set<string>()
-
-    protected removedFields: Set<string> = new Set<string>()
-
-    protected shouldBeUnique = false
+    /** The data length of this column, if set */
+    protected targetLength?: number
 
+    /** True if this is a primary key constraint. */
     protected shouldBePrimary = false
 
-    protected field(name: string): this {
+    /** True if this column should contain distinct values. */
+    protected shouldBeUnique = false
+
+    public originalFromSchema?: ColumnBuilder
+
+    constructor(
+        name: string,
+
+        /** The table this column belongs to. */
+        public readonly parent: TableBuilder,
+    ) {
+        super(name)
+    }
+
+    public cloneTo(newBuilder: ColumnBuilder): ColumnBuilder {
+        super.cloneTo(newBuilder)
+        newBuilder.targetType = this.targetType
+        newBuilder.shouldBeNullable = this.shouldBeNullable
+        newBuilder.defaultValue = this.defaultValue
+        newBuilder.targetLength = this.targetLength
+        newBuilder.shouldBePrimary = this.shouldBePrimary
+        newBuilder.shouldBeUnique = this.shouldBeUnique
+        return newBuilder
+    }
+
+    /** Get the field type of the column, if it exists. */
+    public getType(): Maybe<FieldType> {
+        return this.targetType
+    }
+
+    /** Get the data-type length of the column, if it exists. */
+    public getLength(): Maybe<number> {
+        return this.targetLength
+    }
+
+    /** Get the default value of the column, if it exists. */
+    public getDefaultValue(): Maybe<EscapeValue> {
+        return this.defaultValue
+    }
+
+    /** True if the column should allow NULL values. */
+    public isNullable(): boolean {
+        return this.shouldBeNullable
+    }
+
+    /** True if the column is a primary key. */
+    public isPrimary(): boolean {
+        return this.shouldBePrimary
+    }
+
+    /** True if the column should require unique values. */
+    public isUnique(): boolean {
+        return this.shouldBeUnique
+    }
+
+    /**
+     * Specify the data type of the column.
+     * @param type
+     */
+    public type(type: FieldType): this {
+        if ( this.targetType === type ) {
+            return this
+        }
+
+        this.dirty = true
+        this.targetType = type
+        return this
+    }
+
+    /**
+     * Make the column nullable.
+     */
+    public nullable(): this {
+        if ( this.shouldBeNullable ) {
+            return this
+        }
+
+        this.dirty = true
+        this.shouldBeNullable = true
+        return this
+    }
+
+    /**
+     * Make the column non-nullable.
+     */
+    public required(): this {
+        if ( !this.shouldBeNullable ) {
+            return this
+        }
+
+        this.dirty = true
+        this.shouldBeNullable = false
+        return this
+    }
+
+    /**
+     * Specify the default value of the column.
+     * @param value
+     */
+    public default(value: EscapeValue): this {
+        if ( this.defaultValue === value ) {
+            return this
+        }
+
+        this.dirty = true
+        this.defaultValue = value
+        return this
+    }
+
+    /**
+     * Set the length of this column's data type.
+     * @param value
+     */
+    public length(value: number): this {
+        if ( this.targetLength === value ) {
+            return this
+        }
+
+        this.dirty = true
+        this.targetLength = value
+        return this
+    }
+
+    /**
+     * Make this a primary-key column.
+     */
+    primary(): this {
+        if ( this.shouldBePrimary ) {
+            return this
+        }
+
+        this.dirty = true
+        this.shouldBePrimary = true
+        return this
+    }
+
+    /**
+     * Make this column require distinct values.
+     */
+    unique(): this {
+        if ( this.shouldBeUnique ) {
+            return this
+        }
+
+        this.dirty = true
+        this.shouldBeUnique = true
+        return this
+    }
+
+    protected cloneInstance(): this {
+        return new ColumnBuilder(this.name, this.parent) as this
+    }
+}
+
+/** Valid constraint types. */
+export enum ConstraintType {
+    Unique = 'un',
+    Check = 'ck',
+}
+
+/**
+ * Builder to specify the schema of a table constraint.
+ */
+export class ConstraintBuilder extends SchemaBuilderBase {
+    public originalFromSchema?: ConstraintBuilder
+
+    /** The fields included in this constraint. */
+    protected fields: Set<string> = new Set<string>()
+
+    /** The type of this constraint. */
+    protected constraintType: ConstraintType = ConstraintType.Unique
+
+    /** The expression defining this constraint, if applicable. */
+    protected constraintExpression?: QuerySafeValue
+
+    constructor(
+        name: string,
+
+        /** The table this constraint belongs to. */
+        public readonly parent: TableBuilder,
+    ) {
+        super(name)
+    }
+
+    /** Get the type of this constraint. */
+    public getType(): ConstraintType {
+        return this.constraintType
+    }
+
+    /** Get the fields included in this constraint. */
+    public getFields(): string[] {
+        return [...this.fields]
+    }
+
+    /** Get the expression used to evaluate this constraint, if it exists. */
+    public getExpression(): Maybe<QuerySafeValue> {
+        return this.constraintExpression
+    }
+
+    public cloneTo(newBuilder: ConstraintBuilder): ConstraintBuilder {
+        super.cloneTo(newBuilder)
+        newBuilder.fields = new Set<string>([...this.fields])
+        newBuilder.constraintType = this.constraintType
+        return newBuilder
+    }
+
+    protected cloneInstance(): this {
+        return new ConstraintBuilder(this.name, this.parent) as this
+    }
+
+    /** Add a field to this constraint. */
+    public field(name: string): this {
+        if ( this.fields.has(name) ) {
+            return this
+        }
+
+        this.dirty = true
         this.fields.add(name)
         return this
     }
 
+    /** Remove a field from this constraint. */
+    public removeField(name: string): this {
+        if ( !this.fields.has(name) ) {
+            return this
+        }
+
+        this.dirty = true
+        this.fields.delete(name)
+        return this
+    }
+
+    /** Specify the type of this constraint. */
+    public type(type: ConstraintType): this {
+        if ( this.constraintType === type ) {
+            return this
+        }
+
+        this.dirty = true
+        this.constraintType = type
+        return this
+    }
+
+    /** Specify the expression used to evaluate this constraint, if applicable. */
+    public expression(sql: string | QuerySafeValue): this {
+        if ( String(this.constraintExpression) === String(sql) ) {
+            return this
+        }
+
+        this.dirty = true
+
+        if ( sql instanceof QuerySafeValue ) {
+            this.constraintExpression = sql
+        }
+
+        this.constraintExpression = raw(sql)
+        return this
+    }
+}
+
+/**
+ * Builder to specify the schema of a table index.
+ */
+export class IndexBuilder extends SchemaBuilderBase {
+    /** The fields included in the index. */
+    protected fields: Set<string> = new Set<string>()
+
+    /** Fields to remove from the index. */
+    protected removedFields: Set<string> = new Set<string>()
+
+    /** True if this is a unique index. */
+    protected shouldBeUnique = false
+
+    /** True if this is a primary key index. */
+    protected shouldBePrimary = false
+
+    public originalFromSchema?: IndexBuilder
+
+    constructor(
+        name: string,
+
+        /** The table this index belongs to. */
+        public readonly parent: TableBuilder,
+    ) {
+        super(name)
+    }
+
+    public cloneTo(newBuilder: IndexBuilder): IndexBuilder {
+        super.cloneTo(newBuilder)
+        newBuilder.fields = new Set<string>([...this.fields])
+        newBuilder.removedFields = new Set<string>([...this.removedFields])
+        newBuilder.shouldBeUnique = this.shouldBeUnique
+        newBuilder.shouldBePrimary = this.shouldBePrimary
+        return newBuilder
+    }
+
+    /** Get the fields in this index. */
+    public getFields(): string[] {
+        return [...this.fields]
+    }
+
+    /** True if this index is a unique index. */
+    public isUnique(): boolean {
+        return this.shouldBeUnique
+    }
+
+    /** True if this index is the primary key index. */
+    public isPrimary(): boolean {
+        return this.shouldBePrimary
+    }
+
+    /**
+     * Add the given field to this index.
+     * @param name
+     */
+    public field(name: string): this {
+        if ( this.fields.has(name) ) {
+            return this
+        }
+
+        this.dirty = true
+        this.fields.add(name)
+        return this
+    }
+
+    /**
+     * Remove the given field from this index.
+     * @param name
+     * @protected
+     */
     protected removeField(name: string): this {
+        if ( !this.fields.has(name) ) {
+            return this
+        }
+
+        this.dirty = true
         this.removedFields.add(name)
         this.fields.delete(name)
         return this
     }
 
+    /**
+     * Make this a primary-key index.
+     */
     primary(): this {
+        if ( this.shouldBePrimary ) {
+            return this
+        }
+
+        this.dirty = true
         this.shouldBePrimary = true
         return this
     }
 
+    /**
+     * Make this a unique index.
+     */
     unique(): this {
+        if ( this.shouldBeUnique ) {
+            return this
+        }
+
+        this.dirty = true
         this.shouldBeUnique = true
         return this
     }
+
+    protected cloneInstance(): this {
+        return new IndexBuilder(this.name, this.parent) as this
+    }
 }
 
+/**
+ * Builder to specify the schema of a table.
+ */
 export class TableBuilder extends SchemaBuilderBase {
 
+    /**
+     * Mapping of column name to column schemata.
+     * @protected
+     */
     protected columns: {[key: string]: ColumnBuilder} = {}
 
+    /**
+     * Mapping of index name to index schemata.
+     * @protected
+     */
     protected indexes: {[key: string]: IndexBuilder} = {}
 
+    /**
+     * Mapping of constraint name to constraint schemata.
+     * @protected
+     */
+    protected constraints: {[key: string]: ConstraintBuilder} = {}
+
+    public originalFromSchema?: TableBuilder
+
+    public cloneTo(newBuilder: TableBuilder): TableBuilder {
+        super.cloneTo(newBuilder)
+        newBuilder.columns = {...this.columns}
+        newBuilder.indexes = {...this.indexes}
+        newBuilder.constraints = {...this.constraints}
+        return newBuilder
+    }
+
+    /**
+     * Get the columns defined on this table.
+     */
+    public getColumns(): {[key: string]: ColumnBuilder} {
+        return {
+            ...this.columns,
+        }
+    }
+
+    /**
+     * Get the indices defined on this table.
+     */
+    public getIndexes(): {[key: string]: IndexBuilder} {
+        return {
+            ...this.indexes,
+        }
+    }
+
+    /**
+     * Get the constraints defined on this table.
+     */
+    public getConstraints(): {[key: string]: ConstraintBuilder} {
+        return {
+            ...this.constraints,
+        }
+    }
+
+    /**
+     * Mark a column to be dropped.
+     * @param name
+     */
     public dropColumn(name: string): this {
+        this.dirty = true
         this.column(name).drop()
         return this
     }
 
+    /**
+     * Mark a column to be renamed.
+     * @param from
+     * @param to
+     */
     public renameColumn(from: string, to: string): this {
         this.column(from).rename(to)
         return this
     }
 
+    /**
+     * Mark an index to be dropped.
+     * @param name
+     */
     public dropIndex(name: string): this {
+        this.dirty = true
         this.index(name).drop()
         return this
     }
 
+    /**
+     * Mark an index to be renamed.
+     * @param from
+     * @param to
+     */
     public renameIndex(from: string, to: string): this {
         this.index(from).rename(to)
         return this
     }
 
-    public column(name: string) {
+    /**
+     * Add a column to this table.
+     * @param name
+     * @param callback
+     */
+    public column(name: string, callback?: ParameterizedCallback<ColumnBuilder>): ColumnBuilder {
         if ( !this.columns[name] ) {
-            this.columns[name] = new ColumnBuilder(name)
+            this.dirty = true
+            this.columns[name] = new ColumnBuilder(name, this)
+        }
+
+        if ( callback ) {
+            callback(this.columns[name])
         }
 
         return this.columns[name]
     }
 
-    public index(name: string) {
+    /**
+     * Add an index to this table.
+     * @param name
+     * @param callback
+     */
+    public index(name: string, callback?: ParameterizedCallback<IndexBuilder>): IndexBuilder {
         if ( !this.indexes[name] ) {
-            this.indexes[name] = new IndexBuilder(name)
+            this.dirty = true
+            this.indexes[name] = new IndexBuilder(name, this)
+        }
+
+        if ( callback ) {
+            callback(this.indexes[name])
         }
 
         return this.indexes[name]
     }
+
+    /**
+     * Add a constraint to this table.
+     * @param name
+     * @param callback
+     */
+    public constraint(name: string, callback?: ParameterizedCallback<ConstraintBuilder>): ConstraintBuilder {
+        if ( !this.constraints[name] ) {
+            this.dirty = true
+            this.constraints[name] = new ConstraintBuilder(name, this)
+        }
+
+        if ( callback ) {
+            callback(this.constraints[name])
+        }
+
+        return this.constraints[name]
+    }
+
+    /**
+     * Generate a programmatically-incrementing constraint name.
+     * @param suffix
+     * @protected
+     */
+    protected getNextAvailableConstraintName(suffix: ConstraintType): string {
+        let current = 1
+        let name = `${this.name}_${current}_${suffix}`
+
+        while ( this.constraints[name] ) {
+            current += 1
+            name = `${this.name}_${current}_${suffix}`
+        }
+
+        return name
+    }
+
+    /**
+     * Add a new check constraint with the given expression.
+     * @param expression
+     */
+    public check(expression: string | QuerySafeValue): this {
+        const name = this.getNextAvailableConstraintName(ConstraintType.Check)
+        this.constraint(name)
+            .type(ConstraintType.Check)
+            .expression(expression)
+
+        return this
+    }
+
+    /**
+     * Add a new unique constraint for the given fields.
+     * @param fields
+     */
+    public unique(...fields: string[]): this {
+        // First, check if an existing constraint exists with these fields
+        for ( const key in this.constraints ) {
+            if ( !Object.prototype.hasOwnProperty.call(this.constraints, key) ) {
+                continue
+            }
+
+            if ( this.constraints[key].getType() !== ConstraintType.Unique ) {
+                continue
+            }
+
+            const existingFields = collect<string>(this.constraints[key].getFields())
+            const intersection = existingFields.intersect(fields)
+
+            if ( existingFields.length === fields.length && intersection.length === fields.length ) {
+                return this
+            }
+        }
+
+        // If an existing constraint can't satisfy this, create a new one
+        const name = this.getNextAvailableConstraintName(ConstraintType.Unique)
+        this.constraint(name)
+            .type(ConstraintType.Unique)
+            .pipe()
+            .peek(constraint => {
+                fields.forEach(field => constraint.field(field))
+            })
+
+        return this
+    }
+
+    /**
+     * Add a primary key (column & index) to this table.
+     * @param name
+     * @param type
+     */
+    public primaryKey(name: string, type: FieldType = FieldType.serial): ColumnBuilder {
+        this.dirty = true
+
+        return this.column(name)
+            .type(type)
+            .primary()
+    }
+
+    protected cloneInstance(): this {
+        return new TableBuilder(this.name) as this
+    }
 }

src/orm/services/Database.ts

@@ -1,10 +1,11 @@
-import {Inject, Singleton} from '../../di'
+import {Container, Inject, Singleton} from '../../di'
 import {DatabaseService} from '../DatabaseService'
 import {PostgresConnection} from '../connection/PostgresConnection'
 import {ErrorWithContext} from '../../util'
 import {Unit} from '../../lifecycle/Unit'
 import {Config} from '../../service/Config'
 import {Logging} from '../../service/Logging'
+import {MigratorFactory} from '../migrations/MigratorFactory'
 
 /**
  * Application unit responsible for loading and creating database connections from config.
@@ -12,13 +13,16 @@ import {Logging} from '../../service/Logging'
 @Singleton()
 export class Database extends Unit {
     @Inject()
-    protected readonly config!: Config;
+    protected readonly config!: Config
 
     @Inject()
-    protected readonly dbService!: DatabaseService;
+    protected readonly dbService!: DatabaseService
 
     @Inject()
-    protected readonly logging!: Logging;
+    protected readonly logging!: Logging
+
+    @Inject('injector')
+    protected readonly injector!: Container
 
     /**
      * Load the `database.connections` config and register Connection instances for each config.
@@ -28,6 +32,9 @@ export class Database extends Unit {
         const connections = this.config.get('database.connections')
         const promises = []
 
+        // Register the migrator factory
+        this.injector.registerFactory(this.injector.make(MigratorFactory))
+
         for ( const key in connections ) {
             if ( !Object.prototype.hasOwnProperty.call(connections, key) ) {
                 continue

src/orm/services/Migrations.ts

@@ -0,0 +1,86 @@
+import {Inject, Singleton} from '../../di'
+import {CanonicalInstantiable} from '../../service/CanonicalInstantiable'
+import {Migration} from '../migrations/Migration'
+import {CanonicalDefinition, CanonicalResolver} from '../../service/Canonical'
+import {UniversalPath} from '../../util'
+import {lib} from '../../lib'
+import {CommandLine} from '../../cli'
+
+/**
+ * Service unit that loads and instantiates migration classes.
+ */
+@Singleton()
+export class Migrations extends CanonicalInstantiable<Migration> {
+    @Inject()
+    protected readonly cli!: CommandLine
+
+    protected appPath = ['migrations']
+
+    protected canonicalItem = 'migration'
+
+    protected suffix = '.migration.js'
+
+    async up(): Promise<void> {
+        if ( await this.path.exists() ) {
+            await super.up()
+        } else {
+            this.logging.debug(`Base migration path does not exist, or has no files: ${this.path}`)
+        }
+
+        // Register the migrations for @extollo/lib
+        const basePath = lib().concat('migrations')
+        const resolver = await this.buildMigrationNamespaceResolver('@extollo', basePath)
+        this.registerNamespace('@extollo', resolver)
+    }
+
+    async initCanonicalItem(definition: CanonicalDefinition): Promise<Migration> {
+        const instance = await super.initCanonicalItem(definition)
+
+        if ( !(instance instanceof Migration) ) {
+            throw new TypeError(`Invalid migration: ${definition.originalName}. Migrations must extend from @extollo/lib.Migration.`)
+        }
+
+        instance.setMigrationIdentifier(definition.canonicalName)
+
+        return instance
+    }
+
+    /**
+     * Creates a CanonicalResolver for a directory that contains migration files.
+     *
+     * @example
+     * ```ts
+     * const path = universalPath('path', 'to', 'migrations', 'folder')
+     * const namespace = '@mypackage'
+     *
+     * const resolver = await migrations.buildMigrationNamespaceResolver(namespace, path)
+     * migrations.registerNamespace(namespace, resolver)
+     * ```
+     * @param name
+     * @param basePath
+     */
+    public async buildMigrationNamespaceResolver(name: string, basePath: UniversalPath): Promise<CanonicalResolver<Migration>> {
+        if ( !name.startsWith('@') ) {
+            name = `@${name}`
+        }
+
+        const namespace: {[key: string]: Migration} = {}
+
+        for await ( const entry of basePath.walk() ) {
+            if ( !entry.endsWith(this.suffix) ) {
+                this.logging.debug(`buildMigrationNamespaceResolver - Skipping file with invalid suffix: ${entry}`)
+                continue
+            }
+
+            const definition = await this.buildCanonicalDefinition(entry, basePath)
+            this.logging.verbose(`buildMigrationNamespaceResolver - Discovered canonical ${this.canonicalItem} "${definition.canonicalName}" from ${entry}`)
+            namespace[definition.canonicalName] = await this.initCanonicalItem(definition)
+            namespace[definition.canonicalName].setMigrationIdentifier(`${name}:${namespace[definition.canonicalName].identifier}`)
+        }
+
+        return {
+            get: (key: string) => namespace[key],
+            all: () => Object.keys(namespace),
+        }
+    }
+}

src/orm/support/CacheModel.ts

@@ -1,6 +1,8 @@
 import {Model} from '../model/Model'
 import {Field} from '../model/Field'
 import {FieldType} from '../types'
+import {Maybe} from '../../util'
+import {ModelBuilder} from '../model/ModelBuilder'
 
 /**
  * A model instance which stores records from the ORMCache driver.
@@ -18,4 +20,15 @@ export class CacheModel extends Model<CacheModel> {
 
     @Field(FieldType.timestamp, 'cache_expires')
     public cacheExpires?: Date;
+
+    public static withCacheKey(key: string): ModelBuilder<CacheModel> {
+        return this.query<CacheModel>()
+            .whereKey(key)
+            .whereProperty('cacheExpires', '>', new Date())
+    }
+
+    public static getCacheKey(key: string): Promise<Maybe<CacheModel>> {
+        return this.withCacheKey(key)
+            .first()
+    }
 }

src/orm/support/ORMCache.ts

@@ -1,5 +1,5 @@
 import {Container} from '../../di'
-import {Cache} from '../../util'
+import {Awaitable, Cache, ErrorWithContext, Maybe} from '../../util'
 import {CacheModel} from './CacheModel'
 
 /**
@@ -7,14 +7,7 @@ import {CacheModel} from './CacheModel'
  */
 export class ORMCache extends Cache {
     public async fetch(key: string): Promise<string | undefined> {
-        const model = await CacheModel.query<CacheModel>()
-            .where(CacheModel.qualifyKey(), '=', key)
-            .where(CacheModel.propertyToColumn('cacheExpires'), '>', new Date())
-            .first()
-
-        if ( model ) {
-            return model.cacheValue
-        }
+        return (await CacheModel.getCacheKey(key))?.cacheValue
     }
 
     public async put(key: string, value: string, expires?: Date): Promise<void> {
@@ -31,15 +24,103 @@ export class ORMCache extends Cache {
     }
 
     public async has(key: string): Promise<boolean> {
-        return CacheModel.query()
-            .where(CacheModel.qualifyKey(), '=', key)
-            .where(CacheModel.propertyToColumn('cacheExpires'), '>', new Date())
+        return CacheModel.withCacheKey(key)
             .exists()
     }
 
     public async drop(key: string): Promise<void> {
         await CacheModel.query()
-            .where(CacheModel.qualifyKey(), '=', key)
+            .whereKey(key)
             .delete()
     }
+
+    public async pop(key: string): Promise<string> {
+        return CacheModel.getConnection()
+            .asTransaction<string>(async () => {
+                const model = await CacheModel.getCacheKey(key)
+                if ( !model ) {
+                    throw new ErrorWithContext('Cannot pop cache value: key does not exist.', {
+                        key,
+                    })
+                }
+
+                await model.delete()
+                return model.cacheValue
+            })
+    }
+
+    public increment(key: string, amount = 1): Awaitable<number> {
+        return CacheModel.getConnection()
+            .asTransaction<number>(async () => {
+                const model = await CacheModel.getCacheKey(key)
+                if ( !model ) {
+                    await this.put(key, String(amount))
+                    return amount
+                }
+
+                model.cacheValue = String(parseInt(model.cacheValue, 10) + amount)
+                await model.save()
+                return parseInt(model.cacheValue, 10)
+            })
+    }
+
+    public decrement(key: string, amount = 1): Awaitable<number> {
+        return CacheModel.getConnection()
+            .asTransaction<number>(async () => {
+                const model = await CacheModel.getCacheKey(key)
+                if ( !model ) {
+                    await this.put(key, String(-amount))
+                    return amount
+                }
+
+                model.cacheValue = String(parseInt(model.cacheValue, 10) - amount)
+                await model.save()
+                return parseInt(model.cacheValue, 10)
+            })
+    }
+
+    public async arrayPush(key: string, value: string): Promise<void> {
+        await CacheModel.getConnection()
+            .asTransaction<void>(async () => {
+                const model = await CacheModel.getCacheKey(key)
+                if ( !model ) {
+                    await this.put(key, JSON.stringify([value]))
+                    return
+                }
+
+                const cacheValue = JSON.parse(model.cacheValue)
+                if ( !Array.isArray(cacheValue) ) {
+                    throw new ErrorWithContext('Cannot push value to non-array.', {
+                        key,
+                    })
+                }
+
+                cacheValue.push(value)
+                model.cacheValue = JSON.stringify(cacheValue)
+            })
+
+        throw new Error('Method not implemented.')
+    }
+
+    public async arrayPop(key: string): Promise<Maybe<string>> {
+        return CacheModel.getConnection()
+            .asTransaction<Maybe<string>>(async () => {
+                const model = await CacheModel.getCacheKey(key)
+                if ( !model ) {
+                    return
+                }
+
+                const cacheValue = JSON.parse(model.cacheValue)
+                if ( !Array.isArray(cacheValue) ) {
+                    throw new ErrorWithContext('Cannot pop value from non-array.', {
+                        key,
+                    })
+                }
+
+                const value = cacheValue.pop()
+                model.cacheValue = JSON.stringify(cacheValue)
+                await model.save()
+                return value
+            })
+    }
 }

src/orm/support/ORMSession.ts

@@ -68,6 +68,7 @@ export class ORMSession extends Session {
         if ( !this.data ) {
             throw new SessionNotLoadedError()
         }
+
         return this.data[key] ?? fallback
     }
 
@@ -75,6 +76,15 @@ export class ORMSession extends Session {
         if ( !this.data ) {
             throw new SessionNotLoadedError()
         }
+
         this.data[key] = value
     }
+
+    public forget(key: string): void {
+        if ( !this.data ) {
+            throw new SessionNotLoadedError()
+        }
+
+        delete this.data[key]
+    }
 }

src/orm/support/SessionModel.ts

@@ -6,9 +6,11 @@ import {FieldType} from '../types'
  * Model used to fetch & store sessions from the ORMSession driver.
  */
 export class SessionModel extends Model<SessionModel> {
-    protected static table = 'sessions';  // FIXME allow configuring
+    protected static table = 'sessions'  // FIXME allow configuring
 
-    protected static key = 'session_uuid';
+    protected static key = 'session_uuid'
+
+    protected static populateKeyOnInsert = true
 
     @Field(FieldType.varchar, 'session_uuid')
     public uuid!: string;