Added model event to domain event bridge

refs https://github.com/TryGhost/Team/issues/3169

- To make the coupling to Ghost's model events as loose as possible added a bridge that maps model events to domain events. These domain events it what the collections module can subscribe to to make necessary updates.

ghost/collections/package.json

@@ -28,6 +28,7 @@
         "typescript": "5.1.3"
     },
     "dependencies": {
+        "@tryghost/domain-events": "0.0.0",
         "@tryghost/errors": "^1.2.25",
         "@tryghost/in-memory-repository": "0.0.0",
         "@tryghost/tpl": "^0.1.25",

ghost/collections/src/CollectionsService.ts

@@ -3,6 +3,7 @@ import {CollectionResourceChangeEvent} from './CollectionResourceChangeEvent';
 import {CollectionRepository} from './CollectionRepository';
 import tpl from '@tryghost/tpl';
 import {MethodNotAllowedError, NotFoundError} from '@tryghost/errors';
+import DomainEvents from '@tryghost/domain-events';
 
 const messages = {
     cannotDeleteBuiltInCollectionError: {
@@ -132,6 +133,15 @@ export class CollectionsService {
         return mappedDTO;
     }
 
+    /**
+     * @description Subscribes to Domain events to update collections when posts are added, updated or deleted
+     */
+    subscribeToEvents() {
+        DomainEvents.subscribe(CollectionResourceChangeEvent, async (event: CollectionResourceChangeEvent) => {
+            await this.updateCollections(event);
+        });
+    }
+
     async createCollection(data: CollectionInputDTO): Promise<CollectionDTO> {
         const collection = await Collection.create({
             title: data.title,

ghost/collections/src/libraries.d.ts

@@ -1,2 +1,3 @@
 declare module '@tryghost/errors';
 declare module '@tryghost/tpl';
+declare module '@tryghost/domain-events'

ghost/collections/test/collections.test.ts

@@ -1,4 +1,6 @@
-import assert from 'assert';
+import assert from 'assert/strict';
+import sinon from 'sinon';
+import DomainEvents from '@tryghost/domain-events';
 import {
     CollectionsService,
     CollectionsRepositoryInMemory,
@@ -259,6 +261,24 @@ describe('CollectionsService', function () {
         });
     });
 
+    describe('subscribeToEvents', function () {
+        it('Subscribes to Domain Events', function () {
+            const updateCollectionsSpy = sinon.spy(collectionsService, 'updateCollections');
+            const collectionChangeEvent = CollectionResourceChangeEvent.create('post.added', {
+                id: 'test-id',
+                resource: 'post'
+            });
+
+            DomainEvents.dispatch(collectionChangeEvent);
+            assert.equal(updateCollectionsSpy.calledOnce, false, 'updateCollections should not be called yet');
+
+            collectionsService.subscribeToEvents();
+
+            DomainEvents.dispatch(collectionChangeEvent);
+            assert.equal(updateCollectionsSpy.calledOnce, true, 'updateCollections should be called');
+        });
+    });
+
     describe('Automatic Collections', function () {
         it('Can create an automatic collection', async function () {
             const collection = await collectionsService.createCollection({

ghost/core/core/server/services/collections/index.js

@@ -1,7 +1,6 @@
 const {
     CollectionsService,
-    CollectionsRepositoryInMemory,
-    CollectionResourceChangeEvent
+    CollectionsRepositoryInMemory
 } = require('@tryghost/collections');
 const labs = require('../../../shared/labs');
 
@@ -26,8 +25,7 @@ class CollectionsServiceWrapper {
             return;
         }
 
-        const events = require('../../lib/common/events');
-
+        const translateModelEventsToDomainEvents = require('./model-to-domain-events-bridge');
         const existingBuiltins = await this.api.getAll({filter: 'slug:featured'});
 
         if (!existingBuiltins.data.length) {
@@ -50,24 +48,8 @@ class CollectionsServiceWrapper {
             });
         }
 
-        const ghostModelUpdateEvents = require('./update-events');
-
-        const collectionListener = (event, data) => {
-            const change = Object.assign({}, {
-                id: data.id,
-                resource: event.split('.')[0]
-            }, data._changed);
-            const collectionResourceChangeEvent = CollectionResourceChangeEvent.create(event, change);
-            // @NOTE: to avoid race conditions we need a queue here to make sure updates happen
-            //        one by one and not in parallel
-            this.api.updateCollections(collectionResourceChangeEvent);
-        };
-
-        for (const event of ghostModelUpdateEvents) {
-            if (!events.hasRegisteredListener(event, 'collectionListener')) {
-                events.on(event, data => collectionListener(event, data));
-            }
-        }
+        this.api.subscribeToEvents();
+        translateModelEventsToDomainEvents();
     }
 }
 

ghost/core/core/server/services/collections/model-to-domain-events-bridge.js

@@ -0,0 +1,41 @@
+const DomainEvents = require('@tryghost/domain-events');
+const {
+    CollectionResourceChangeEvent
+} = require('@tryghost/collections');
+
+const domainEventDispatcher = (modelEventName, data) => {
+    const change = Object.assign({}, {
+        id: data.id,
+        resource: modelEventName.split('.')[0]
+    }, data._changed);
+    const collectionResourceChangeEvent = CollectionResourceChangeEvent.create(modelEventName, change);
+
+    DomainEvents.dispatch(collectionResourceChangeEvent);
+};
+
+const translateModelEventsToDomainEvents = () => {
+    const events = require('../../lib/common/events');
+    const ghostModelUpdateEvents = [
+        'post.published',
+        'post.published.edited',
+        'post.unpublished',
+        'tag.added',
+        'tag.edited',
+        'tag.attached',
+        'tag.detached',
+        'tag.deleted',
+        'user.activated',
+        'user.activated.edited',
+        'user.attached',
+        'user.detached',
+        'user.deleted'
+    ];
+
+    for (const modelEvent of ghostModelUpdateEvents) {
+        if (!events.hasRegisteredListener(modelEvent, 'collectionListener')) {
+            events.on(modelEvent, data => domainEventDispatcher(modelEvent, data));
+        }
+    }
+};
+
+module.exports = translateModelEventsToDomainEvents;

ghost/core/core/server/services/collections/update-events.js

@@ -1,15 +0,0 @@
-module.exports = [
-    'post.published',
-    'post.published.edited',
-    'post.unpublished',
-    'tag.added',
-    'tag.edited',
-    'tag.attached',
-    'tag.detached',
-    'tag.deleted',
-    'user.activated',
-    'user.activated.edited',
-    'user.attached',
-    'user.detached',
-    'user.deleted'
-];