refactoring(sync): Simplify the design of the sync engine.

Removes the concept of message dispatcher and message sender, all of
it can be done by the syncengine class, making it easier to grasp.

umap/static/umap/js/modules/sync/engine.js

@@ -3,15 +3,12 @@ import { MapUpdater, DataLayerUpdater, FeatureUpdater } from './updaters.js'
 
 export class SyncEngine {
   constructor(map) {
-    this.map = map
+    this.updaters = {
-    this.dispatcher = new MessagesDispatcher(this.map)
+      map: new MapUpdater(map),
-    this._initialize()
+      feature: new FeatureUpdater(map),
+      datalayer: new DataLayerUpdater(map),
     }
-  _initialize() {
     this.transport = undefined
-    const noop = () => {}
-    // by default, all operations do nothing, until the engine is started.
-    this.upsert = this.update = this.delete = noop
   }
 
   async authenticate(tokenURI, webSocketURI, server) {
@@ -22,16 +19,47 @@ export class SyncEngine {
   }
 
   start(webSocketURI, authToken) {
-    this.transport = new WebSocketTransport(webSocketURI, authToken, this.dispatcher)
+    this.transport = new WebSocketTransport(webSocketURI, authToken, this)
-    this.sender = new MessagesSender(this.transport)
-    this.upsert = this.sender.upsert.bind(this.sender)
-    this.update = this.sender.update.bind(this.sender)
-    this.delete = this.sender.delete.bind(this.sender)
   }
 
   stop() {
     if (this.transport) this.transport.close()
-    this._initialize()
+    this.transport = undefined
+  }
+
+  _getUpdater(subject, metadata) {
+    if (Object.keys(this.updaters).includes(subject)) {
+      return this.updaters[subject]
+    }
+    throw new Error(`Unknown updater ${subject}, ${metadata}`)
+  }
+
+  // This method is called by the transport layer on new messages
+  receive({ kind, ...payload }) {
+    if (kind == 'operation') {
+      let updater = this._getUpdater(payload.subject, payload.metadata)
+      updater.applyMessage(payload)
+    } else {
+      throw new Error(`Unknown dispatch kind: ${kind}`)
+    }
+  }
+
+  _send(message) {
+    if (this.transport) {
+      this.transport.send('operation', message)
+    }
+  }
+
+  upsert(subject, metadata, value) {
+    this._send({ verb: 'upsert', subject, metadata, value })
+  }
+
+  update(subject, metadata, key, value) {
+    this._send({ verb: 'update', subject, metadata, key, value })
+  }
+
+  delete(subject, metadata, key) {
+    this._send({ verb: 'delete', subject, metadata, key })
   }
 
   /**
@@ -63,60 +91,3 @@ export class SyncEngine {
     return new Proxy(this, handler)
   }
 }
-
-export class MessagesDispatcher {
-  constructor(map) {
-    this.map = map
-    this.updaters = {
-      map: new MapUpdater(this.map),
-      feature: new FeatureUpdater(this.map),
-      datalayer: new DataLayerUpdater(this.map),
-    }
-  }
-
-  getUpdater(subject, metadata) {
-    if (Object.keys(this.updaters).includes(subject)) {
-      return this.updaters[subject]
-    }
-    throw new Error(`Unknown updater ${subject}, ${metadata}`)
-  }
-
-  dispatch({ kind, ...payload }) {
-    if (kind == 'operation') {
-      let updater = this.getUpdater(payload.subject, payload.metadata)
-      updater.applyMessage(payload)
-    } else {
-      throw new Error(`Unknown dispatch kind: ${kind}`)
-    }
-  }
-}
-
-/**
- * Send messages to other connected peers, using the specified transport.
- *
- * - `subject` is the type of object this is referering to (map, feature, layer)
- * - `metadata` contains information about the object we're refering to (id, layerId for instance)
- * - `key` and
- * - `value` are the keys and values that are being modified.
- */
-export class MessagesSender {
-  constructor(transport) {
-    this._transport = transport
-  }
-
-  send(message) {
-    this._transport.send('operation', message)
-  }
-
-  upsert(subject, metadata, value) {
-    this.send({ verb: 'upsert', subject, metadata, value })
-  }
-
-  update(subject, metadata, key, value) {
-    this.send({ verb: 'update', subject, metadata, key, value })
-  }
-
-  delete(subject, metadata, key) {
-    this.send({ verb: 'delete', subject, metadata, key })
-  }
-}

umap/static/umap/js/modules/sync/updaters.js

@@ -15,7 +15,7 @@ class BaseUpdater {
     // Reduce the current list of attributes,
     // to find the object to set the property onto
     const objectToSet = parts.reduce((currentObj, part) => {
-      if (part in currentObj) return currentObj[part]
+      if (currentObj !== undefined && part in currentObj) return currentObj[part]
     }, obj)
 
     // In case the given path doesn't exist, stop here

umap/static/umap/js/modules/sync/websocket.js

@@ -9,7 +9,7 @@ export class WebSocketTransport {
   }
 
   onMessage(wsMessage) {
-    this.receiver.dispatch(JSON.parse(wsMessage.data))
+    this.receiver.receive(JSON.parse(wsMessage.data))
   }
 
   send(kind, payload) {

umap/static/umap/unittests/sync.js

@@ -5,7 +5,7 @@ import pkg from 'chai'
 const { expect } = pkg
 
 import { MapUpdater } from '../js/modules/sync/updaters.js'
-import { MessagesDispatcher, SyncEngine } from '../js/modules/sync/engine.js'
+import { SyncEngine } from '../js/modules/sync/engine.js'
 
 describe('SyncEngine', () => {
   it('should initialize methods even before start', function () {
@@ -16,10 +16,9 @@ describe('SyncEngine', () => {
   })
 })
 
-describe('MessageDispatcher', () => {
+describe('#dispatch', function () {
-  describe('#dispatch', function () {
   it('should raise an error on unknown updater', function () {
-      const dispatcher = new MessagesDispatcher({})
+    const dispatcher = new SyncEngine({})
     expect(() => {
       dispatcher.dispatch({
         kind: 'operation',
@@ -29,7 +28,7 @@ describe('MessageDispatcher', () => {
     }).to.throw(Error)
   })
   it('should produce an error on malformated messages', function () {
-      const dispatcher = new MessagesDispatcher({})
+    const dispatcher = new SyncEngine({})
     expect(() => {
       dispatcher.dispatch({
         yeah: 'yeah',
@@ -38,14 +37,13 @@ describe('MessageDispatcher', () => {
     }).to.throw(Error)
   })
   it('should raise an unknown operations', function () {
-      const dispatcher = new MessagesDispatcher({})
+    const dispatcher = new SyncEngine({})
     expect(() => {
       dispatcher.dispatch({
         kind: 'something-else',
       })
     }).to.throw(Error)
   })
-  })
 })
 
 describe('Updaters', () => {