app.rb

require 'sinatra'
require 'sinatra-websocket'
require 'json'
require 'haml'

set :server, 'thin'
set :sockets, {}

helpers do
  def logger
    request.logger
  end
end

def register(ws, id)
  socket_info = {
    id: id,
    path: "/hook/#{id}"
  }
  settings.sockets[ws] ||= []
  settings.sockets[ws] << socket_info
  message_data = {
    type: 'registered',
    data: socket_info
  }
  
  message = message_data.to_json
  logger.info "sending: #{message}"
  ws.send message
  socket_info
end

def unregister(ws, id)
end

get '/' do
  if !request.websocket?
    haml :index
  else
    logger.info "websocket initializing"
    request.websocket do |ws|
      ws.onopen do
        id = SecureRandom.hex(8)
        register(ws, id)
      end

      ws.onmessage do |message|
        logger.info "received: #{message}"
        data = JSON.parse(message)
        if data['type']=='register' && data['id']
          if /^\w+$/ === data['id']
            register(ws,data['id'])
          else
            ws.send({type:'error', message:'ID must be a letter, number, or underscore'}.to_json) 
          end
        elsif data['type']=='unregister' && data['id']
          unregister(ws,data['id']) 
        else
          ws.send({type:'error', message:'No such command'}.to_json)
        end
      end

      ws.onclose do
        logger.warn "websocket closed"
        settings.sockets.delete(ws)
      end
    end
  end
end

post '/hook/:id' do
  id = params[:id]
  sockets = settings.sockets.select {|ws,hooks| hooks.any?{|hook| hook[:id] == id}}
  halt 404 unless sockets.count > 0

  ['splat','captures','id'].each {|k| params.delete k}

  message_data = {
    type: 'hook',
    id: id,
    data: params
  }
  message = message_data.to_json
  logger.info "sending: #{message}"
  sockets.keys.each { |ws| ws.send message }
  {}.to_json
end