hss.rb

# Heavy State Sync

require 'faye/websocket'
require 'json'

class HeavyStateSync
  KEEPALIVE_INTERVAL = 15

  def initialize(app)
    @app = app
    @clients = []
    @last_state = {}
  end

  def call(env)
    if Faye::WebSocket.websocket?(env)
      ws = Faye::WebSocket.new(env, ['chat', 'whiteboard'], { ping: KEEPALIVE_INTERVAL })

      ws.on :open do |event|
        @clients << ws
        ws.send @last_state.to_json
      end

      ws.on :message do |event|
        @last_state = JSON.parse(event.data)
        ws.send @last_state.to_json
      end

      ws.on :close do |event|
        @clients.delete(ws)
        ws = nil
      end

      ws.rack_response
    else
      if @app
        @app.call(env)
      else
        [200, {"Content-Type" => "application/json"}, [{error: "Unknown error"}.to_json]]
      end
    end
  end
end

EM.error_handler do |e|
  p "*** ERROR ***"
  puts e
  puts e.backtrace
end