Add basic concepts for event bus, and implement in request and model

src/orm/model/Model.ts

@@ -1,18 +1,26 @@
 import {ModelKey, QueryRow, QuerySource} from '../types'
-import {Container, Inject} from '../../di'
+import {Container, Inject, StaticClass} from '../../di'
 import {DatabaseService} from '../DatabaseService'
 import {ModelBuilder} from './ModelBuilder'
 import {getFieldsMeta, ModelField} from './Field'
-import {deepCopy, BehaviorSubject, Pipe, Collection} from '../../util'
+import {deepCopy, Pipe, Collection, Awaitable, uuid4} from '../../util'
 import {EscapeValueObject} from '../dialect/SQLDialect'
 import {AppClass} from '../../lifecycle/AppClass'
 import {Logging} from '../../service/Logging'
 import {Connection} from '../connection/Connection'
+import {Bus, Dispatchable, EventSubscriber, EventSubscriberEntry, EventSubscription} from '../../event/types'
+import {ModelRetrievedEvent} from './events/ModelRetrievedEvent'
+import {ModelSavingEvent} from './events/ModelSavingEvent'
+import {ModelSavedEvent} from './events/ModelSavedEvent'
+import {ModelUpdatingEvent} from './events/ModelUpdatingEvent'
+import {ModelUpdatedEvent} from './events/ModelUpdatedEvent'
+import {ModelCreatingEvent} from './events/ModelCreatingEvent'
+import {ModelCreatedEvent} from './events/ModelCreatedEvent'
 
 /**
  * Base for classes that are mapped to tables in a database.
  */
-export abstract class Model<T extends Model<T>> extends AppClass {
+export abstract class Model<T extends Model<T>> extends AppClass implements Bus {
     @Inject()
     protected readonly logging!: Logging;
 
@@ -78,49 +86,10 @@ export abstract class Model<T extends Model<T>> extends AppClass {
     protected originalSourceRow?: QueryRow
 
     /**
-     * Behavior subject that fires after the model is populated.
+     * Collection of event subscribers, by their events.
+     * @protected
      */
-    protected retrieved$ = new BehaviorSubject<Model<T>>()
-
-    /**
-     * Behavior subject that fires right before the model is saved.
-     */
-    protected saving$ = new BehaviorSubject<Model<T>>()
-
-    /**
-     * Behavior subject that fires right after the model is saved.
-     */
-    protected saved$ = new BehaviorSubject<Model<T>>()
-
-    /**
-     * Behavior subject that fires right before the model is updated.
-     */
-    protected updating$ = new BehaviorSubject<Model<T>>()
-
-    /**
-     * Behavior subject that fires right after the model is updated.
-     */
-    protected updated$ = new BehaviorSubject<Model<T>>()
-
-    /**
-     * Behavior subject that fires right before the model is inserted.
-     */
-    protected creating$ = new BehaviorSubject<Model<T>>()
-
-    /**
-     * Behavior subject that fires right after the model is inserted.
-     */
-    protected created$ = new BehaviorSubject<Model<T>>()
-
-    /**
-     * Behavior subject that fires right before the model is deleted.
-     */
-    protected deleting$ = new BehaviorSubject<Model<T>>()
-
-    /**
-     * Behavior subject that fires right after the model is deleted.
-     */
-    protected deleted$ = new BehaviorSubject<Model<T>>()
+    protected modelEventBusSubscribers: Collection<EventSubscriberEntry<any>> = new Collection<EventSubscriberEntry<any>>()
 
     /**
      * Get the table name for this model.
@@ -193,9 +162,16 @@ export abstract class Model<T extends Model<T>> extends AppClass {
         values?: {[key: string]: any},
     ) {
         super()
+        this.initialize()
         this.boot(values)
     }
 
+    /**
+     * Called when the model is instantiated. Use for any setup of events, &c.
+     * @protected
+     */
+    protected initialize(): void {}  // eslint-disable-line @typescript-eslint/no-empty-function
+
     /**
      * Initialize the model's properties from the given values and do any other initial setup.
      *
@@ -228,7 +204,7 @@ export abstract class Model<T extends Model<T>> extends AppClass {
             this.setFieldFromObject(field.modelKey, field.databaseKey, row)
         })
 
-        await this.retrieved$.next(this)
+        await this.dispatch(new ModelRetrievedEvent<T>(this as any))
         return this
     }
 
@@ -592,11 +568,11 @@ export abstract class Model<T extends Model<T>> extends AppClass {
      * @param withoutTimestamps
      */
     public async save({ withoutTimestamps = false } = {}): Promise<Model<T>> {
-        await this.saving$.next(this)
+        await this.dispatch(new ModelSavingEvent<T>(this as any))
         const ctor = this.constructor as typeof Model
 
         if ( this.exists() && this.isDirty() ) {
-            await this.updating$.next(this)
+            await this.dispatch(new ModelUpdatingEvent<T>(this as any))
 
             if ( !withoutTimestamps && ctor.timestamps && ctor.UPDATED_AT ) {
                 (this as any)[ctor.UPDATED_AT] = new Date()
@@ -617,9 +593,9 @@ export abstract class Model<T extends Model<T>> extends AppClass {
                 await this.assumeFromSource(data)
             }
 
-            await this.updated$.next(this)
+            await this.dispatch(new ModelUpdatedEvent<T>(this as any))
         } else if ( !this.exists() ) {
-            await this.creating$.next(this)
+            await this.dispatch(new ModelCreatingEvent<T>(this as any))
 
             if ( !withoutTimestamps ) {
                 if ( ctor.timestamps && ctor.CREATED_AT ) {
@@ -647,10 +623,11 @@ export abstract class Model<T extends Model<T>> extends AppClass {
             if ( data ) {
                 await this.assumeFromSource(result)
             }
-            await this.created$.next(this)
+
+            await this.dispatch(new ModelCreatedEvent<T>(this as any))
         }
 
-        await this.saved$.next(this)
+        await this.dispatch(new ModelSavedEvent<T>(this as any))
         return this
     }
 
@@ -822,4 +799,42 @@ export abstract class Model<T extends Model<T>> extends AppClass {
     protected setFieldFromObject(thisFieldName: string | symbol, objectFieldName: string, object: QueryRow): void {
         (this as any)[thisFieldName] = object[objectFieldName]
     }
+
+    subscribe<EventT extends Dispatchable>(event: StaticClass<EventT, EventT>, subscriber: EventSubscriber<EventT>): Awaitable<EventSubscription> {
+        const entry: EventSubscriberEntry<EventT> = {
+            id: uuid4(),
+            event,
+            subscriber,
+        }
+
+        this.modelEventBusSubscribers.push(entry)
+        return this.buildSubscription(entry.id)
+    }
+
+    unsubscribe<EventT extends Dispatchable>(subscriber: EventSubscriber<EventT>): Awaitable<void> {
+        this.modelEventBusSubscribers = this.modelEventBusSubscribers.where('subscriber', '!=', subscriber)
+    }
+
+    async dispatch(event: Dispatchable): Promise<void> {
+        const eventClass: StaticClass<typeof event, typeof event> = event.constructor as StaticClass<Dispatchable, Dispatchable>
+        await this.modelEventBusSubscribers.where('event', '=', eventClass)
+            .promiseMap(entry => entry.subscriber(event))
+    }
+
+    /**
+     * Build an EventSubscription object for the subscriber of the given ID.
+     * @param id
+     * @protected
+     */
+    protected buildSubscription(id: string): EventSubscription {
+        let subscribed = true
+        return {
+            unsubscribe: (): Awaitable<void> => {
+                if ( subscribed ) {
+                    this.modelEventBusSubscribers = this.modelEventBusSubscribers.where('id', '!=', id)
+                    subscribed = false
+                }
+            },
+        }
+    }
 }