dougal-software/lib/www/server/ws/db.js

const { pool } = require('../lib/db/connection');

var client;

const channels = {};

async function 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
}