1 files changed, 125 insertions, 0 deletions
diff --git a/ext/fg/js/frontend-api-sender.js b/ext/fg/js/frontend-api-sender.js
new file mode 100644
index 00000000..e2becb90
--- /dev/null
+++ b/ext/fg/js/frontend-api-sender.js
@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2019 Alex Yatskov <alex@foosoft.net>
+ * Author: Alex Yatskov <alex@foosoft.net>
+ *
+ * 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 <http://www.gnu.org/licenses/>.
+ */
+
+
+class FrontendApiSender {
+    constructor() {
+        this.ackTimeout = 3000; // 3 seconds
+        this.responseTimeout = 10000; // 10 seconds
+        this.callbacks = {};
+        this.disconnected = false;
+        this.nextId = 0;
+
+        this.port = chrome.runtime.connect(null, {name: 'backend-api-forwarder'});
+        this.port.onDisconnect.addListener(this.onDisconnect.bind(this));
+        this.port.onMessage.addListener(this.onMessage.bind(this));
+    }
+
+    invoke(action, params, target) {
+        if (this.disconnected) {
+            return Promise.reject('Disconnected');
+        }
+
+        const id = `${this.nextId}`;
+        ++this.nextId;
+
+        return new Promise((resolve, reject) => {
+            const info = {id, resolve, reject, ack: false, timer: null};
+            this.callbacks[id] = info;
+            info.timer = setTimeout(() => this.onError(id, 'Timeout (ack)'), this.ackTimeout);
+
+            this.port.postMessage({id, action, params, target});
+        });
+    }
+
+    onMessage({type, id, data}) {
+        switch (type) {
+            case 'ack':
+                this.onAck(id);
+                break;
+            case 'result':
+                this.onResult(id, data);
+                break;
+        }
+    }
+
+    onDisconnect() {
+        this.disconnected = true;
+
+        const ids = Object.keys(this.callbacks);
+        for (const id of ids) {
+            this.onError(id, 'Disconnected');
+        }
+    }
+
+    onAck(id) {
+        if (!this.callbacks.hasOwnProperty(id)) {
+            console.warn(`ID ${id} not found`);
+            return;
+        }
+
+        const info = this.callbacks[id];
+        if (info.ack) {
+            console.warn(`Request ${id} already ack'd`);
+            return;
+        }
+
+        info.ack = true;
+        clearTimeout(info.timer);
+        info.timer = setTimeout(() => this.onError(id, 'Timeout (response)'), this.responseTimeout);
+    }
+
+    onResult(id, data) {
+        if (!this.callbacks.hasOwnProperty(id)) {
+            console.warn(`ID ${id} not found`);
+            return;
+        }
+
+        const info = this.callbacks[id];
+        if (!info.ack) {
+            console.warn(`Request ${id} not ack'd`);
+            return;
+        }
+
+        delete this.callbacks[id];
+        clearTimeout(info.timer);
+        info.timer = null;
+
+        if (typeof data.error === 'string') {
+            info.reject(data.error);
+        } else {
+            info.resolve(data.result);
+        }
+    }
+
+    onError(id, reason) {
+        if (!this.callbacks.hasOwnProperty(id)) { return; }
+        const info = this.callbacks[id];
+        delete this.callbacks[id];
+        info.timer = null;
+        info.reject(reason);
+    }
+
+    static generateId(length) {
+        let id = '';
+        for (let i = 0; i < length; ++i) {
+            id += Math.floor(Math.random() * 256).toString(16).padStart(2, '0');
+        }
+        return id;
+    }
+}