Add view engine unit - handlebars - and response helpers

lib/src/external/http.ts

@@ -1,2 +1,3 @@
 export * from 'https://deno.land/std@0.53.0/http/server.ts'
 export * from 'https://deno.land/std@0.53.0/http/cookie.ts'
+export { Handlebars } from 'https://deno.land/x/handlebars/mod.ts'

lib/src/http/response/PartialViewResponseFactory.ts

@@ -0,0 +1,18 @@
+import ResponseFactory from './ResponseFactory.ts'
+import ViewEngine from '../../unit/ViewEngine.ts'
+import {Request} from '../Request.ts'
+
+export default class PartialViewResponseFactory extends ResponseFactory {
+    constructor(
+        public readonly view: string,
+        public readonly context?: any,
+    ) {
+        super()
+    }
+
+    public async write(request: Request) {
+        const views: ViewEngine = this.make(ViewEngine)
+        request.response.body = await views.partial(this.view, this.context)
+        return request
+    }
+}

lib/src/http/response/ViewResponseFactory.ts

@@ -0,0 +1,19 @@
+import ResponseFactory from './ResponseFactory.ts'
+import ViewEngine from '../../unit/ViewEngine.ts'
+import {Request} from '../Request.ts'
+
+export default class ViewResponseFactory extends ResponseFactory {
+    constructor(
+        public readonly view: string,
+        public readonly context?: any,
+        public readonly layout?: string,
+    ) {
+        super()
+    }
+
+    public async write(request: Request) {
+        const views: ViewEngine = this.make(ViewEngine)
+        request.response.body = await views.render(this.view, this.context, this.layout)
+        return request
+    }
+}

lib/src/http/response/helpers.ts

@@ -8,6 +8,8 @@ import TemporaryRedirectResponseFactory from './TemporaryRedirectResponseFactory
 import {HTTPStatus} from '../../const/http.ts'
 import HTTPErrorResponseFactory from './HTTPErrorResponseFactory.ts'
 import HTTPError from '../../error/HTTPError.ts'
+import ViewResponseFactory from './ViewResponseFactory.ts'
+import PartialViewResponseFactory from './PartialViewResponseFactory.ts'
 
 export function json(value: any): JSONResponseFactory {
     return make(JSONResponseFactory, value)
@@ -33,3 +35,11 @@ export function redirect(destination: string): TemporaryRedirectResponseFactory
 export function http(status: HTTPStatus, message?: string): HTTPErrorResponseFactory {
     return make(HTTPErrorResponseFactory, new HTTPError(status, message))
 }
+
+export function view(view: string, context?: any, layout?: string): ViewResponseFactory {
+    return make(ViewResponseFactory, view, context, layout)
+}
+
+export function partial(view: string, context?: any): PartialViewResponseFactory {
+    return make(PartialViewResponseFactory, view, context)
+}

lib/src/lifecycle/Application.ts

@@ -5,8 +5,9 @@ import {container, make} from '../../../di/src/global.ts'
 import {DependencyKey} from '../../../di/src/type/DependencyKey.ts'
 import RunLevelErrorHandler from '../error/RunLevelErrorHandler.ts'
 import {Status} from '../const/status.ts'
-import Instantiable from "../../../di/src/type/Instantiable.ts";
-import {Collection} from "../collection/Collection.ts";
+import Instantiable from '../../../di/src/type/Instantiable.ts'
+import {Collection} from '../collection/Collection.ts'
+import {path} from '../external/std.ts'
 
 @Service()
 export default class Application {
@@ -66,4 +67,20 @@ export default class Application {
             this.logger.verbose(e)
         }
     }
+
+    get root() {
+        return path.resolve('.')
+    }
+
+    get app_root() {
+        return path.resolve('./app')
+    }
+
+    path(...parts: string[]) {
+        return path.resolve(this.root, ...parts)
+    }
+
+    app_path(...parts: string[]) {
+        return path.resolve(this.app_root, ...parts)
+    }
 }

lib/src/unit/ViewEngine.ts

@@ -0,0 +1,60 @@
+import LifecycleUnit from '../lifecycle/Unit.ts'
+import {Unit} from '../lifecycle/decorators.ts'
+import {Handlebars} from '../external/http.ts'
+import {Logging} from '../service/logging/Logging.ts'
+import {fs} from '../external/std.ts'
+
+@Unit()
+export default class ViewEngine extends LifecycleUnit {
+    protected _handlebars!: Handlebars
+
+    // TODO include basic app info in view data
+
+    constructor(
+        protected readonly logger: Logging,
+    ) {
+        super()
+    }
+
+    async up() {
+        this.logger.info(`Setting views base dir: ${this.app.app_path('http', 'views')}`)
+        this._handlebars = new Handlebars({
+            baseDir: this.app.app_path('http', 'views'),
+            extname: '.hbs',
+            layoutsDir: 'layouts',
+            partialsDir: 'partials',
+            defaultLayout: 'main',
+            helpers: undefined,
+            compilerOptions: undefined,
+        })
+
+        const main_layout_path = this.app.app_path('http', 'views', 'layouts', 'main.hbs')
+        if ( !(await fs.exists(main_layout_path)) ) {
+            this.logger.warn(`Unable to open main view layout file: ${main_layout_path}`)
+            this.logger.warn(`Unless you are using a custom layout, this could cause errors.`)
+        }
+
+        const partials_path = this.app.app_path('http', 'views', 'partials')
+        if ( !(await fs.exists(partials_path)) ) {
+            this.logger.warn(`Unable to open view partials directory: ${partials_path}`)
+            this.logger.warn(`This directory must exist for the view engine to function, even if it is empty.`)
+        }
+    }
+
+    get handlebars(): Handlebars {
+        return this._handlebars
+    }
+
+    async render(view: string, args?: any, layout?: string): Promise<string> {
+        this.logger.debug(`Rendering view: ${view}`)
+        return this.handlebars.renderView(view, args, layout)
+    }
+
+    async partial(view: string, args?: any) {
+        const parts = `${view}.hbs`.split(':')
+        const resolved = this.app.app_path('http', 'views', ...parts)
+
+        this.logger.debug(`Rendering partial: ${view} from ${resolved}`)
+        return this.handlebars.render(resolved, args)
+    }
+}