Initialize chat interface

Signed-off-by: Emmy D'Anello <emmy.danello@animath.fr>

chat/static/chat.js

@@ -0,0 +1,52 @@
+(async () => {
+    // check notification permission
+    // This is useful to alert people that they should do something
+    await Notification.requestPermission()
+})()
+
+/**
+ * Display a new notification with the given title and the given body.
+ * @param title The title of the notification
+ * @param body The body of the notification
+ * @param timeout The time (in milliseconds) after that the notification automatically closes. 0 to make indefinite. Default to 5000 ms.
+ * @return Notification
+ */
+function showNotification(title, body, timeout = 5000) {
+    let notif = new Notification(title, {'body': body, 'icon': "/static/tfjm.svg"})
+    if (timeout)
+        setTimeout(() => notif.close(), timeout)
+    return notif
+}
+
+document.addEventListener('DOMContentLoaded', () => {
+    /**
+     * Process the received data from the server.
+     * @param data The received message
+     */
+    function processMessage(data) {
+        // TODO Implement chat protocol
+    }
+
+    function setupSocket(nextDelay = 1000) {
+        // Open a global websocket
+        socket = new WebSocket(
+            (document.location.protocol === 'https:' ? 'wss' : 'ws') + '://' + window.location.host + '/ws/chat/'
+        )
+
+        // Listen on websockets and process messages from the server
+        socket.addEventListener('message', e => {
+            // Parse received data as JSON
+            const data = JSON.parse(e.data)
+
+            processMessage(data)
+        })
+
+        // Manage errors
+        socket.addEventListener('close', e => {
+            console.error('Chat socket closed unexpectedly, restarting…')
+            setTimeout(() => setupSocket(2 * nextDelay), nextDelay)
+        })
+    }
+
+    setupSocket()
+})