Ember Event Bus

event-bus.js

// event-bus.js
// this is an EmberJS service, compatible and tested with Ember 2.3.1
// manages the EventSource for the entire application
import Ember from 'ember';

// TODO: add a method to remove a channel or handler from _openChannels
export default Ember.Service.extend({

  store: Ember.inject.service(),

  _eventSource: null,
  _openChannels: [{
    name: 'client.command',
    handler: this.clientCommandHandler
  }],

  _keepAliveTimer: null,
  _keepAliveTimeout: 120000,

  // channels should be an array of name/handler objects:
  // [ ... { name: 'channel-name', handler: function() {...}  }, ...]
  open(channels) {
    let openChannels = this.get('_openChannels');

    let reOpenEventSource = false;
    Ember.$(channels).each(
      (i, channel) => {
        // check if the channel is already subscribed to
        let [openChannel] = $.grep(openChannels, function(openChannel) {
          return openChannel.name === channel.name;
        });

        if (openChannel) { // channel is already subscribed to
          let oldHandler = openChannel.handler;
          openChannel.handler = function() {
            oldHandler();
            channel.handler(); // append the new handler
          };
        } else { // channel is not subscribed to
          reOpenEventSource = true; // need to close and re-open the event source to add the new channel
          openChannels.push(channel);
        }
      }
    );

    this.set('_openChannels', openChannels);

    if (reOpenEventSource) {
      this.get('eventSourceReset').call(this);
    }
  },

  eventSourceReset() {
    console.log('resetting event source');
    let adapter = this.get('store').adapterFor('application');
    let source = this.get('_eventSource');
    let openChannels = this.get('_openChannels');

    if (source) {
      source.close();
    }

    let channelNames = $.map(openChannels,
      (channel) => {
        return channel.name;
      }
    ).join(',');

    let streamUrl = `${adapter.buildURL('live-stream')}?channels=${channelNames}`;

    this.get('startKeepAliveTimer').call(this);
    source = new EventSource(streamUrl);
    this.set('_eventSource', source);

    source.addEventListener('message', (event) => {
      this.channelMessageHandler.call(this, event);
    });
  },

  channelMessageHandler(event) {
    // reset the keep alive timer
    this.get('cancelKeepAliveTimer').call(this);
    this.get('startKeepAliveTimer').call(this);

    // get the channel the message is coming in on and call the handler
    let openChannels = this.get('_openChannels');
    let payload = JSON.parse(event.data);
    let [channel] = $.grep(openChannels, function(channel) {
      return channel.name === payload.channel;
    });
    channel.handler(payload.channel, payload.message);
  },

  startKeepAliveTimer() {
    console.log('keep alive started');
    let _keepAliveTimeout = this.get('_keepAliveTimeout');
    let _keepAliveTimer = Ember.run.later(this, function() {
      this.get('keepAliveHandler').call(this);
    }, _keepAliveTimeout);

    this.set('_keepAliveTimer', _keepAliveTimer);
  },

  cancelKeepAliveTimer() {
    console.log('keep alive cancelled');
    Ember.run.cancel(this.get('_keepAliveTimer'));
  },

  keepAliveHandler() {
    // kill the event source and open a new one
    console.log('keep alive fired');
    let _eventSource = this.get('_eventSource');
    _eventSource.close();
    this.get('eventSourceReset').call(this);
  },

  clientCommandHandler(channel, message) {
    switch (message) {
      case 'reload':
        window.location.reload(true);
        break;
    }
  }

});