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vendor/yomitan/js/comm/shared-worker-bridge.js

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+/*
+ * Copyright (C) 2024-2025  Yomitan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import {createApiMap, invokeApiMapHandler} from '../core/api-map.js';
+import {ExtensionError} from '../core/extension-error.js';
+import {log} from '../core/log.js';
+
+/**
+ * This serves as a bridge between the application and the backend on Firefox
+ * where we don't have service workers.
+ *
+ * It is designed to have extremely short lifetime on the application side,
+ * as otherwise it will stay alive across extension updates (which only restart
+ * the backend) which can lead to extremely difficult to debug situations where
+ * the bridge is running an old version of the code.
+ *
+ * All it does is broker a handshake between the application and the backend,
+ * where they establish a connection between each other with a MessageChannel.
+ *
+ * # On backend startup
+ *  backend
+ *    ↓↓<"registerBackendPort" via SharedWorker.port.postMessage>↓↓
+ *  bridge: store the port in state
+ *
+ * # On application startup
+ *  application: create a new MessageChannel, bind event listeners to one of the ports, and send the other port to the bridge
+ *    ↓↓<"connectToBackend1" via SharedWorker.port.postMessage>↓↓
+ *  bridge
+ *    ↓↓<"connectToBackend2" via MessageChannel.port.postMessage which is stored in state from backend startup phase>↓↓
+ *  backend: bind event listeners to the other port
+ */
+export class SharedWorkerBridge {
+    constructor() {
+        /** @type {MessagePort?} */
+        this._backendPort = null;
+
+        /** @type {import('shared-worker').ApiMap} */
+        this._apiMap = createApiMap([
+            ['registerBackendPort', this._onRegisterBackendPort.bind(this)],
+            ['connectToBackend1', this._onConnectToBackend1.bind(this)],
+        ]);
+    }
+
+    /**
+     *
+     */
+    prepare() {
+        addEventListener('connect', (connectEvent) => {
+            const interlocutorPort = (/** @type {MessageEvent} */ (connectEvent)).ports[0];
+            interlocutorPort.addEventListener('message', (/** @type {MessageEvent<import('shared-worker').ApiMessageAny>} */ event) => {
+                const {action, params} = event.data;
+                return invokeApiMapHandler(this._apiMap, action, params, [interlocutorPort, event.ports], () => {});
+            });
+            interlocutorPort.addEventListener('messageerror', (/** @type {MessageEvent} */ event) => {
+                const error = new ExtensionError('SharedWorkerBridge: Error receiving message from interlocutor port when establishing connection');
+                error.data = event;
+                log.error(error);
+            });
+            interlocutorPort.start();
+        });
+    }
+
+    /** @type {import('shared-worker').ApiHandler<'registerBackendPort'>} */
+    _onRegisterBackendPort(_params, interlocutorPort, _ports) {
+        this._backendPort = interlocutorPort;
+    }
+
+    /** @type {import('shared-worker').ApiHandler<'connectToBackend1'>} */
+    _onConnectToBackend1(_params, _interlocutorPort, ports) {
+        if (this._backendPort !== null) {
+            this._backendPort.postMessage(void 0, [ports[0]]); // connectToBackend2
+        } else {
+            log.warn('SharedWorkerBridge: backend port is not registered; this can happen if one of the content scripts loads faster than the backend when extension is reloading');
+        }
+    }
+}
+
+const bridge = new SharedWorkerBridge();
+bridge.prepare();