Musare/backend/logic/cache/index.js

'use strict';

const redis = require('redis');
const mongoose = require('mongoose');

// Lightweight / convenience wrapper around redis module for our needs

const pubs = {}, subs = {};
let callbacks = [];
let initialized = false;
let lockdown = false;

const lib = {

	client: null,
	errorCb: null,
	url: '',
	schemas: {
		session: require('./schemas/session'),
		station: require('./schemas/station'),
		playlist: require('./schemas/playlist'),
		officialPlaylist: require('./schemas/officialPlaylist'),
		song: require('./schemas/song'),
		punishment: require('./schemas/punishment')
	},

	/**
	 * Initializes the cache module
	 *
	 * @param {String} url - the url of the redis server
	 * @param {String} password - the password of the redis server
	 * @param {Function} cb - gets called once we're done initializing
	 */
	init: (url, password, errorCb, cb) => {
		lib.errorCb = errorCb;
		lib.url = url;
		lib.password = password;

		lib.client = redis.createClient({ url: lib.url, password: lib.password });
		lib.client.on('error', (err) => {
			if (lockdown) return;
			errorCb('Cache connection error.', err, 'Cache');
		});

		callbacks.forEach((callback) => {
			callback();
		});

		initialized = true;

		if (lockdown) return this._lockdown();
		cb();
	},

	/**
	 * Gracefully closes all the Redis client connections
	 */
	quit: () => {
		if (lib.client.connected) {
			lib.client.quit();
			Object.keys(pubs).forEach((channel) => pubs[channel].quit());
			Object.keys(subs).forEach((channel) => subs[channel].client.quit());
		}
	},

	/**
	 * Sets a single value in a table
	 *
	 * @param {String} table - name of the table we want to set a key of (table === redis hash)
	 * @param {String} key -  name of the key to set
	 * @param {*} value - the value we want to set
	 * @param {Function} cb - gets called when the value has been set in Redis
	 * @param {Boolean} [stringifyJson=true] - stringify 'value' if it's an Object or Array
	 */
	hset: (table, key, value, cb, stringifyJson = true) => {
		if (lockdown) return cb('Lockdown');
		if (mongoose.Types.ObjectId.isValid(key)) key = key.toString();
		// automatically stringify objects and arrays into JSON
		if (stringifyJson && ['object', 'array'].includes(typeof value)) value = JSON.stringify(value);

		lib.client.hset(table, key, value, err => {
			if (cb !== undefined) {
				if (err) return cb(err);
				cb(null, JSON.parse(value));
			}
		});
	},

	/**
	 * Gets a single value from a table
	 *
	 * @param {String} table - name of the table to get the value from (table === redis hash)
	 * @param {String} key - name of the key to fetch
	 * @param {Function} cb - gets called when the value is returned from Redis
	 * @param {Boolean} [parseJson=true] - attempt to parse returned data as JSON
	 */
	hget: (table, key, cb, parseJson = true) => {
		if (lockdown) return cb('Lockdown');
		if (!key || !table) return typeof cb === 'function' ? cb(null, null) : null;
		if (mongoose.Types.ObjectId.isValid(key)) key = key.toString();
		lib.client.hget(table, key, (err, value) => {
			if (err) return typeof cb === 'function' ? cb(err) : null;
			if (parseJson) try {
				value = JSON.parse(value);
			} catch (e) {
			}
			if (typeof cb === 'function') cb(null, value);
		});
	},

	/**
	 * Deletes a single value from a table
	 *
	 * @param {String} table - name of the table to delete the value from (table === redis hash)
	 * @param {String} key - name of the key to delete
	 * @param {Function} cb - gets called when the value has been deleted from Redis or when it returned an error
	 */
	hdel: (table, key, cb) => {
		if (lockdown) return cb('Lockdown');
		if (!key || !table) return cb(null, null);
		if (mongoose.Types.ObjectId.isValid(key)) key = key.toString();
		lib.client.hdel(table, key, (err) => {
			if (err) return cb(err);
			else return cb(null);
		});
	},

	/**
	 * Returns all the keys for a table
	 *
	 * @param {String} table - name of the table to get the values from (table === redis hash)
	 * @param {Function} cb - gets called when the values are returned from Redis
	 * @param {Boolean} [parseJson=true] - attempts to parse all values as JSON by default
	 */
	hgetall: (table, cb, parseJson = true) => {
		if (lockdown) return cb('Lockdown');
		if (!table) return cb(null, null);
		lib.client.hgetall(table, (err, obj) => {
			if (err) return typeof cb === 'function' ? cb(err) : null;
			if (parseJson && obj) Object.keys(obj).forEach((key) => { try { obj[key] = JSON.parse(obj[key]); } catch (e) {} });
			if (parseJson && !obj) obj = [];
			cb(null, obj);
		});
	},

	/**
	 * Publish a message to a channel, caches the redis client connection
	 *
	 * @param {String} channel - the name of the channel we want to publish a message to
	 * @param {*} value - the value we want to send
	 * @param {Boolean} [stringifyJson=true] - stringify 'value' if it's an Object or Array
	 */
	pub: (channel, value, stringifyJson = true) => {

		/*if (pubs[channel] === undefined) {
		 pubs[channel] = redis.createClient({ url: lib.url });
		 pubs[channel].on('error', (err) => console.error);
		 }*/

		if (stringifyJson && ['object', 'array'].includes(typeof value)) value = JSON.stringify(value);

		//pubs[channel].publish(channel, value);
		lib.client.publish(channel, value);
	},

	/**
	 * Subscribe to a channel, caches the redis client connection
	 *
	 * @param {String} channel - name of the channel to subscribe to
	 * @param {Function} cb - gets called when a message is received
	 * @param {Boolean} [parseJson=true] - parse the message as JSON
	 */
	sub: (channel, cb, parseJson = true) => {
		if (lockdown) return;
		if (initialized) subToChannel();
		else {
			callbacks.push(() => {
				subToChannel();
			});
		}
		function subToChannel() {
			if (subs[channel] === undefined) {
				subs[channel] = { client: redis.createClient({ url: lib.url, password: lib.password }), cbs: [] };
				subs[channel].client.on('message', (channel, message) => {
					if (parseJson) try { message = JSON.parse(message); } catch (e) {}
					subs[channel].cbs.forEach((cb) => cb(message));
				});
				subs[channel].client.subscribe(channel);
			}

			subs[channel].cbs.push(cb);
		}
	},

	_lockdown: () => {
		lib.quit();
		lockdown = true;
	}
};

module.exports = lib;