Add websocket server to emit DB notifications

lib/www/server/ws/db.js

@@ -0,0 +1,41 @@
+const { pool } = require('../lib/db/connection');
+
+var client;
+
+const channels = {};
+
+async function notify (data) {
+	console.log("NOTIFY", data);
+	if (data.channel in channels) {
+		data._received = new Date();
+		for (const listener of channels[data.channel]) {
+			listener(data);
+		}
+	}
+}
+
+async function listen (addChannels, callback) {
+	if (!client) {
+		client = await pool.connect();
+		client.on('notification', notify);
+		console.log("Client connected");
+	}
+
+	if (!Array.isArray(addChannels)) {
+		addChannels = [addChannels];
+	}
+
+	for (const channel of addChannels) {
+		if (!(channel in channels)) {
+			await client.query("LISTEN "+channel);
+			channels[channel] = new Set();
+			console.log("Listening to ", channel);
+		}
+
+		channels[channel].add(callback);
+	}
+}
+
+module.exports = {
+	listen
+}