Immediate backend event handlers (#555)

* Add function to await until prepare is completed

* Create BackendEventHandler to synchronously set up event handling

2 files changed, 106 insertions, 18 deletions

diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index 7971d16f..faba6c42 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -75,9 +75,15 @@ class Backend {
 
         this.popupWindow = null;
 
-        this._defaultBrowserActionTitle = null;
         this._isPrepared = false;
         this._prepareError = false;
+        this._preparePromise = null;
+        this._prepareCompletePromise = new Promise((resolve, reject) => {
+            this._prepareCompleteResolve = resolve;
+            this._prepareCompleteReject = reject;
+        });
+
+        this._defaultBrowserActionTitle = null;
         this._badgePrepareDelayTimer = null;
         this._logErrorLevel = null;
 
@@ -134,7 +140,26 @@ class Backend {
         ]);
     }
 
-    async prepare() {
+    prepare() {
+        if (this._preparePromise === null) {
+            const promise = this._prepareInternal();
+            promise.then(
+                (value) => {
+                    this._isPrepared = true;
+                    this._prepareCompleteResolve(value);
+                },
+                (error) => {
+                    this._prepareError = true;
+                    this._prepareCompleteReject(error);
+                }
+            );
+            promise.finally(() => this._updateBadge());
+            this._preparePromise = promise;
+        }
+        return this._prepareCompletePromise;
+    }
+
+    async _prepareInternal() {
         try {
             this._defaultBrowserActionTitle = await this._getBrowserIconTitle();
             this._badgePrepareDelayTimer = setTimeout(() => {
@@ -156,15 +181,6 @@ class Backend {
 
             this.onOptionsUpdated('background');
 
-            if (isObject(chrome.commands) && isObject(chrome.commands.onCommand)) {
-                chrome.commands.onCommand.addListener(this._runCommand.bind(this));
-            }
-            if (isObject(chrome.tabs) && isObject(chrome.tabs.onZoomChange)) {
-                chrome.tabs.onZoomChange.addListener(this._onZoomChange.bind(this));
-            }
-            chrome.runtime.onMessage.addListener(this.onMessage.bind(this));
-            chrome.runtime.onConnect.addListener(this._onConnect.bind(this));
-
             const options = this.getOptions(this.optionsContext);
             if (options.general.showGuide) {
                 chrome.tabs.create({url: chrome.runtime.getURL('/bg/guide.html')});
@@ -175,10 +191,7 @@ class Backend {
             this._sendMessageAllTabs('backendPrepared');
             const callback = () => this.checkLastError(chrome.runtime.lastError);
             chrome.runtime.sendMessage({action: 'backendPrepared'}, callback);
-
-            this._isPrepared = true;
         } catch (e) {
-            this._prepareError = true;
             yomichan.logError(e);
             throw e;
         } finally {
@@ -186,15 +199,33 @@ class Backend {
                 clearTimeout(this._badgePrepareDelayTimer);
                 this._badgePrepareDelayTimer = null;
             }
-
-            this._updateBadge();
         }
     }
 
+    prepareComplete() {
+        return this._prepareCompletePromise;
+    }
+
     isPrepared() {
         return this._isPrepared;
     }
 
+    handleCommand(...args) {
+        return this._runCommand(...args);
+    }
+
+    handleZoomChange(...args) {
+        return this._onZoomChange(...args);
+    }
+
+    handleConnect(...args) {
+        return this._onConnect(...args);
+    }
+
+    handleMessage(...args) {
+        return this.onMessage(...args);
+    }
+
     _sendMessageAllTabs(action, params={}) {
         const callback = () => this.checkLastError(chrome.runtime.lastError);
         chrome.tabs.query({}, (tabs) => {
@@ -1293,3 +1324,57 @@ class Backend {
         }
     }
 }
+
+class BackendEventHandler {
+    constructor(backend) {
+        this._backend = backend;
+    }
+
+    prepare() {
+        if (isObject(chrome.commands) && isObject(chrome.commands.onCommand)) {
+            const onCommand = this._createGenericEventHandler((...args) => this._backend.handleCommand(...args));
+            chrome.commands.onCommand.addListener(onCommand);
+        }
+
+        if (isObject(chrome.tabs) && isObject(chrome.tabs.onZoomChange)) {
+            const onZoomChange = this._createGenericEventHandler((...args) => this._backend.handleZoomChange(...args));
+            chrome.tabs.onZoomChange.addListener(onZoomChange);
+        }
+
+        const onConnect = this._createGenericEventHandler((...args) => this._backend.handleConnect(...args));
+        chrome.runtime.onConnect.addListener(onConnect);
+
+        const onMessage = this._onMessage.bind(this);
+        chrome.runtime.onMessage.addListener(onMessage);
+    }
+
+    // Event handlers
+
+    _createGenericEventHandler(handler) {
+        return this._onGenericEvent.bind(this, handler);
+    }
+
+    _onGenericEvent(handler, ...args) {
+        if (this._backend.isPrepared()) {
+            handler(...args);
+            return;
+        }
+
+        this._backend.prepareComplete().then(
+            () => { handler(...args); },
+            () => {} // NOP
+        );
+    }
+
+    _onMessage(message, sender, sendResponse) {
+        if (this._backend.isPrepared()) {
+            return this._backend.handleMessage(message, sender, sendResponse);
+        }
+
+        this._backend.prepareComplete().then(
+            () => { this._backend.handleMessage(message, sender, sendResponse); },
+            () => { sendResponse(); } // NOP
+        );
+        return true;
+    }
+}
diff --git a/ext/bg/js/background-main.js b/ext/bg/js/background-main.js
index 345b4a77..9dd447c4 100644
--- a/ext/bg/js/background-main.js
+++ b/ext/bg/js/background-main.js
@@ -17,12 +17,15 @@
 
 /* global
  * Backend
+ * BackendEventHandler
  */
 
-(async () => {
+(() => {
     const backend = new Backend();
+    const backendEventHandler = new BackendEventHandler(backend);
+    backendEventHandler.prepare();
     if (typeof window === 'object' && window !== null) {
         window.yomichanBackend = backend;
     }
-    await backend.prepare();
+    backend.prepare();
 })();