chat-client.js

const WebSocket = require('ws');

const CONNECTING = 0;
const OPEN = 1;

const dev = true;
const PRODUCTION_CHAT_SERVER = 'wss://react-chat-server.herokuapp.com';
const DEV_CHAT_SERVER = 'ws://localhost:8080';
const chatServerUrl = dev ? DEV_CHAT_SERVER : PRODUCTION_CHAT_SERVER;

const createClient = token => {
    let ws;
    const listeners = {};

    const handleMessage = m => {
        const action = JSON.parse(m.data);
        (listeners[action.type] || []).forEach(l => l(action));
    };

    return {
        /**
         * Inits the chat connection with the server
         * @param {string} token the google auth session token
         */
        init() {
            if (ws) {
                throw new Error('Chat client already initialized');
            }
            ws = new WebSocket(`${chatServerUrl}/${token}`);
            ws.addEventListener('message', handleMessage);
        },

        /**
         * Fetch the users list from server.
         * @return {Promise} resolves to an array of users:
         * {
         *     fullName: string,
         *     avatar: string,
         *     name: string,
         *     familyName: string,
         *     email: string,
         *     id: string
         * }
         */
        getUsers() {
            this.send({type: 'getUsers', receiver: 'server'});
        },

        /**
         * Sends a chat message to a recipient
         * @param {string} messageText
         * @param {string} receiver userId of the receiver. When not provided,
         * the message is sent to all the users
         */
        sendMessage(messageText, receiver = 'all') {
            this.send({type: 'message', receiver, payload: {text: messageText}});
        },

        /**
         * Sends an action to the chat server
         * @param {object} action an action has the following form:
         * {
         *     type: string, // for example 'message'
         *     receiver: string, // the userId of the recipient or 'all'
         *     [sender]: string, // not needed, the server knows you
         *     [time]: number, // automatically set to current timestamp.
         *     payload: object, // any data associated with the event
         * }
         * @return {[type]} [description]
         */
        send(action) {
            action.time = action.time || Date.now();
            if (ws.readyState === CONNECTING) {
                setTimeout(() => this.send(action), 100);
            } else if (ws.readyState === OPEN) {
                ws.send(JSON.stringify(action));
            }
        },

        /**
         * Registers a listener for a given event type
         * @param {string} event
         * @param {Function} listener will be called with every
         * chat event of the specified type received from the sever
         * @return {Function} dettach function to remove the event
         * listener.
         */
        on(event, listener) {
            if (event in listeners) {
                listeners[event].push(listener);
            } else {
                listeners[event] = [listener];
            }
            return () => this.off(event, listener);
        },

        /**
         * Dettached a previously registered listener
         * @param {string} event the event type
         * @param {Function} listenerToRemove
         */
        off(event, listenerToRemove) {
            if (event in listeners) {
                listeners[event] = listeners[event].filter(l => l !== listenerToRemove);
            }
        },
    };
};

module.exports = createClient;