WebSockets: shared JS client initial implementation

share/web_surfaces/shared/ardour.js

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+/*
+ * Copyright © 2020 Luciano Iam <lucianito@gmail.com>
+ *
+ * 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 2 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, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+import { Channel } from './channel.js';
+
+export class Ardour {
+
+	constructor () {
+		this.channel = new Channel(location.host);
+	}
+
+	async open () {
+		await this.channel.open();
+	}
+
+	close () {
+		this.channel.close();
+	}
+
+	async getAvailableSurfaces () {
+		const response = await fetch('/index.json');
+		
+		if (response.status == 200) {
+			return await response.json();
+		} else {
+			throw new Error(`HTTP response status ${response.status}`);
+		}
+	}
+
+	// TO DO - add methods for dealing with messages flowing from/to the WebSockets channel
+
+}

share/web_surfaces/shared/channel.js

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+/*
+ * Copyright © 2020 Luciano Iam <lucianito@gmail.com>
+ *
+ * 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 2 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, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+const JSON_INF = 1.0e+128;
+
+export class Channel {
+
+    constructor (host) {
+        // https://developer.mozilla.org/en-US/docs/Web/API/URL/host
+        this.host = host;
+    }
+
+    open () {
+        return new Promise((resolve, reject) => {
+            this.socket = new WebSocket(`ws://${this.host}`);
+            this.socket.onerror = (error) => this.errorCallback(error);
+            this.socket.onmessage = (event) => this._onMessage(event);
+            this.socket.onopen = resolve;
+        });
+    }
+    
+    errorCallback (error) {
+        // empty
+    }
+
+    messageCallback (node, addr, val) {
+        // empty
+    }
+
+    send (node, addr, val) {
+        for (const i in val) {
+            if (val[i] == Infinity) {
+                val[i] = JSON_INF;
+            } else if (val[i] == -Infinity) {
+                val[i] = -JSON_INF;
+            }
+        }
+        
+        const json = JSON.stringify({node: node, addr: addr, val: val});
+
+        this.socket.send(json);
+    }
+
+    _onMessage (event) {
+        const msg = JSON.parse(event.data);
+
+        for (const i in msg.val) {
+            if (msg.val[i] >= JSON_INF) {
+                msg.val[i] = Infinity;
+            } else if (msg.val[i] <= -JSON_INF) {
+                msg.val[i] = -Infinity;
+            }
+        }
+
+        this.messageCallback(msg.node, msg.addr || [], msg.val);
+    }
+
+}