jam-cloud/lib/jam_websockets/router.rb

require 'pry'
require 'set'
require 'hot_bunnies'
require 'thread'
require 'json'
require 'eventmachine'

import java.util.concurrent.Executors

include Jampb

# add new field to client connection
module EventMachine
  module WebSocket
    class Connection < EventMachine::Connection
      attr_accessor :encode_json, :client_id # client_id is uuid we give to each client to track them as we like
    end
  end
end

module JamWebsockets


  class Router

    attr_accessor :user_context_lookup, :session_context_lookup

    def initialize(options={})
      @log = Logging.logger[self]
      @pending_clients = Set.new # clients that have connected to server, but not logged in.
      @clients = {} # clients that have logged in
      @user_context_lookup = {} # lookup a set of client_contexts by user_id
      @session_context_lookup = {} # lookup a set of client_contexts by session_id
      @client_lookup = {} # lookup a client by client_id
      @sessions_exchange = nil
      @connection = nil
      @channel = nil
      @users_exchange = nil
      @message_factory = JamRuby::MessageFactory.new
      @semaphore = Mutex.new
      @user_topic = nil
      @user_subscription = nil
      @session_topic = nil
      @session_subscription = nil
      @client_topic = nil
      @client_subscription = nil
      @thread_pool = nil
    end

    def start(options = {})

      @log.info "startup"

      begin
        @thread_pool = Executors.new_fixed_thread_pool(8)
        @connection = HotBunnies.connect(:host => options[:host], :port => options[:port])
        @channel = @connection.create_channel
        @channel.prefetch = 10

        register_topics
      rescue => e
        cleanup
        raise e
      end

    end

    def add_client(client_id, client)

      # should never occur
      if @client_lookup.has_key?(client_id)
        @log.warn "client_id #{client_id} connected while the old connection has not yet been terminated"
      end

      @client_lookup[client_id] = client
    end

    def remove_client(client_id, client)
      deleted = @client_lookup.delete(client_id)

      if deleted.nil?
        @log.warn "unable to delete #{client_id} from client_lookup"
      elsif deleted == client
        # put it back--this is only possible if add_client hit the 'old connection' path
        # so in other words if this happens:
        # add_client(1, clientX)
        # add_client(1, clientY) # but clientX is essentially defunct - this could happen due to a bug in client, or EM doesn't notify always of connection close in time
        # remove_client(1, clientX) -- this check maintains that clientY stays as the current client in the hash
        @client_lookup[client_id] = client
      end
    end

    def add_user(context)
      user_contexts = @user_context_lookup[context.user.id]
      if user_contexts.nil?
        user_contexts = Set.new
        @user_context_lookup[context.user.id] = user_contexts
      end

      user_contexts.add(context)
    end

    def remove_user(context)
      user_contexts = @user_context_lookup[context.user.id]
      if user_contexts.nil?
        @log.warn "user can not be removed #{context}"
      else
        # delete the context from set of user contexts
        user_contexts.delete(context)

        # if last user context, delete entire set (memory leak concern)
        if user_contexts.length == 0
          @user_context_lookup.delete(context.user.id)
        end
      end
    end

    def add_session(context)
      session_contexts = @session_context_lookup[context.session.id]
      if session_contexts.nil?
        session_contexts = Set.new
        @session_context_lookup[context.session.id] = session_contexts
      end

      session_contexts.add(context)
    end

    def remove_session(context)
      session_contexts = @session_context_lookup[context.session.id]
      if session_contexts.nil?
        @log.warn "session can not be removed #{context}"
      else
        # delete the context from set of session contexts
        session_contexts.delete(context)

        # if last session context, delete entire set (memory leak concern)
        if session_contexts.length == 0
          @session_context_lookup.delete(context.session.id)
        end

        context.session = nil
      end
    end

    # register topic for user messages and session messages
    def register_topics
      @users_exchange = @channel.exchange('users', :type => :topic)
      @sessions_exchange = @channel.exchange('sessions', :type => :topic)
      @clients_exchange = @channel.exchange('clients', :type => :topic)

      # create user messaging topic
      @user_topic = @channel.queue("", :auto_delete => true)
      @user_topic.bind(@users_exchange, :routing_key => "user.#")
      @user_topic.purge

      # TODO: alert friends

      # subscribe for any messages to users

      @user_subscription = @user_topic.subscribe(:ack => false)
      @user_subscription.each(:blocking => false, :executor => @threadpool) do |headers, msg|
        begin
          routing_key = headers.envelope.routing_key
          user_id = routing_key["user.".length..-1]
          @sempahore.synchronize do
            contexts = @user_context_lookup[user_id]

            unless contexts.nil?

              @log.debug "received user-directed message for session: #{user_id}"

              msg = Jampb::ClientMessage.parse(msg)
              contexts.each do |context|
                EM.schedule do
                  @log.debug "sending user message to #{context}"
                  send_to_client(context.client, msg)
                end
              end
            end
          end

        rescue => e
          @log.error "unhandled error in messaging to client"
          @log.error e
        end
      end

      @session_topic = @channel.queue("", :auto_delete => true)
      @session_topic.bind(@sessions_exchange, :routing_key => "session.#")
      @session_topic.purge

      # subscribe for any messages to session
      @session_subscription = @session_topic.subscribe(:ack => false)
      @session_subscription.each(:blocking => false, :executor => @threadpool) do |headers, msg|
        begin
          routing_key = headers.envelope.routing_key
          session_id = routing_key["session.".length..-1]
          @semaphore.synchronize do
            contexts = @session_context_lookup[session_id]

            unless contexts.nil?

              @log.debug "received session-directed message for session: #{session_id}"

              msg = Jampb::ClientMessage.parse(msg)

              # ok, its very odd to have your own message that you sent bounce back to you. 
              # In one small favor to the client, we purposefully disallow messages a client
              # sent from bouncing back to itself.  
              properties = headers.properties unless headers.nil?
              inner_headers = properties.headers unless properties.nil?
              origin_client_id = inner_headers["client_id"]

              # counter-intuitively, even though a string is passed in when you send the header, an (apparently) auto-generated class is sent back which, if you to_s, returns the original value
              origin_client_id = origin_client_id.to_s unless origin_client_id.nil?

              @log.debug "message received from client #{origin_client_id}"
              contexts.each do |context|
                if context.client.client_id != origin_client_id
                  EM.schedule do
                    @log.debug "sending session message to #{context}"
                    send_to_client(context.client, msg)
                  end
                end
              end
            end
          end

        rescue => e
          @log.error "unhandled error in messaging to client"
          @log.error e
        end
      end

      @client_topic = @channel.queue("", :auto_delete => true)
      @client_topic.bind(@clients_exchange, :routing_key => "client.#")
      @client_topic.purge

      # subscribe for any p2p messages to a client
      @client_subscription = @client_topic.subscribe(:ack => false)
      @client_subscription.each(:blocking => false, :executor => @threadpool) do |headers, msg|
        begin
          routing_key = headers.envelope.routing_key
          client_id = routing_key["client.".length..-1]
          @semaphore.synchronize do
            client = @client_lookup[client_id]

            unless client.nil?
              msg = Jampb::ClientMessage.parse(msg)

              properties = headers.properties unless headers.nil?
              inner_headers = properties.headers unless properties.nil?
              origin_client_id = inner_headers["client_id"]

              @log.debug "p2p message received from client #{origin_client_id} to client #{client_id}"
              EM.schedule do
                @log.debug "sending p2p message to #{client_id}"
                send_to_client(client, msg)
              end
            end
          end


        rescue => e
          @log.error "unhandled error in messaging to client"
          @log.error e
        end
      end
    end

    def send_to_client(client, msg)
      if client.encode_json
        client.send(msg.to_json.to_s)
      else
        # this is so odd that this is necessary from an API perspective.  but searching through the source code... it's all I could find in em-websocket for allowing a binary message to be sent
        client.instance_variable_get(:@handler).send_frame(:binary, msg.to_s)
      end
    end

    def cleanup()
      # shutdown topic listeners and mq connection
      begin
        if !@user_subscription.nil? && @user_subscription.active?
          @log.debug "cleaning up user subscription"
          @user_subscription.cancel
          @user_subscription.shutdown!
        end

        if !@session_subscription.nil? && @session_subscription.active?
          @log.debug "cleaning up session subscription"
          @session_subscription.cancel
          @session_subscription.shutdown!
        end

        if !@client_subscription.nil? && @client_subscription.active?
          @log.debug "cleaning up client subscription"
          @client_subscription.cancel
          @client_subscription.shutdown!
        end

      rescue => e
        @log.debug "unable to cancel subscription on cleanup: #{e}"
      end

      @thread_pool.shutdown

      if !@channel.nil?
        @channel.close
      end

      if !@connection.nil?
        @connection.close
      end

      # tear down each individual client
      @clients.each do |client, context|
        cleanup_client(client)
      end
    end

    def stop
      @log.info "shutdown"
      cleanup
    end

    def new_client(client)

      @semaphore.synchronize do
        @pending_clients.add(client)
      end

      # default to using json instead of pb
      client.encode_json = true

      client.onopen {
        #binding.pry
        @log.debug "client connected #{client}"

        # check for '?pb' or '?pb=true' in url query parameters
        query_pb = client.request["query"]["pb"]

        if !query_pb.nil? && (query_pb == "" || query_pb == "true")
          client.encode_json = false
        end

      }

      client.onclose {
        @log.debug "Connection closed"

        cleanup_client(client)
      }

      client.onerror { |error|
        if error.kind_of?(EM::WebSocket::WebSocketError)
          @log.error "websockets error: #{error}"
        else
          @log.error "generic error: #{error} #{error.backtrace}"
        end

        cleanup_client(client)
        client.close_websocket
      }

      client.onmessage { |msg|
        @log.debug("msg received")

        # TODO: set a max message size before we put it through PB?
        # TODO: rate limit?


        begin
          if client.encode_json
            #example: {"type":"LOGIN", "route_to":"server", "login" : {"username":"hi"}}
            parse = JSON.parse(msg)
            pb_msg = Jampb::ClientMessage.json_create(parse)
            self.route(pb_msg, client)
          else
            pb_msg = Jampb::ClientMessage.parse(msg.to_s)
            self.route(pb_msg, client)
          end
        rescue SessionError => e
          @log.info "ending client session deliberately due to malformed client behavior. reason=#{e}"
          begin
            # wrap the message up and send it down
            error_msg = @message_factory.server_rejection_error(e.to_s)
            send_to_client(client, error_msg)
          ensure
            client.close_websocket
            cleanup_client(client)
          end
        rescue PermissionError => e
          @log.info "permission error.  reason=#{e.to_s}"
          @log.info e

          # wrap the message up and send it down
          error_msg = @message_factory.server_permission_error(msg.message_id, e.to_s)
          send_to_client(client, error_msg)
        rescue => e
          @log.error "ending client session due to server programming or runtime error. reason=#{e.to_s}"
          @log.error e

          begin
            # wrap the message up and send it down
            error_msg = @message_factory.server_generic_error(e.to_s)
            send_to_client(client, error_msg)
          ensure
            client.close_websocket
            cleanup_client(client)
          end
        end


      }

    end

    # removes all resources associated with a client
    def cleanup_client(client)

      @semaphore.synchronize do
        pending = @pending_clients.delete?(client)

        if !pending.nil?
          @log.debug "cleaning up pending client #{client}"
        else

          remove_client(client.client_id, client)

          context = @clients.delete(client)

          if !context.nil?

            remove_user(context)

            if !context.session.nil?
              remove_session(context)
            end
          else
            @log.debug "skipping duplicate cleanup attempt of authorized client"
          end

        end
      end
    end

    def route(client_msg, client)
      message_type = @message_factory.get_message_type(client_msg)

      raise SessionError, "unknown message type received: #{client_msg.type}" if message_type.nil?

      @log.debug("msg received #{message_type}")

      raise SessionError, 'client_msg.route_to is null' if client_msg.route_to.nil?

      if @pending_clients.include? client and client_msg.type != ClientMessage::Type::LOGIN
        # this client has not logged in and is trying to send a non-login message
        raise SessionError, "must 'Login' first"
      end

      if @message_factory.server_directed? client_msg

        handle_server_directed(client_msg, client)

      elsif @message_factory.client_directed? client_msg

        to_client_id = client_msg.route_to[MessageFactory::CLIENT_TARGET_PREFIX.length..-1]
        handle_client_directed(to_client_id, client_msg, client)

      elsif @message_factory.session_directed? client_msg

        session = client_msg.route_to[MessageFactory::SESSION_TARGET_PREFIX.length..-1]
        handle_session_directed(session, client_msg, client)

      elsif @message_factory.user_directed? client_msg

        user = client_msg.route_to[MessageFactory::USER_PREFIX_TARGET.length..-1]
        handle_user_directed(user, client_msg, client)

      else
        raise SessionError, "client_msg.route_to is unknown type: #{client_msg.route_to}"
      end

    end

    def handle_server_directed(client_msg, client)

      if client_msg.type == ClientMessage::Type::LOGIN

        handle_login(client_msg.login, client)

      elsif client_msg.type == ClientMessage::Type::HEARTBEAT

        handle_heartbeat(client_msg.heartbeat, client)

      elsif client_msg.type == ClientMessage::Type::LOGIN_MUSIC_SESSION

        handle_join_music_session(client_msg.login_music_session, client)

      elsif client_msg.type == ClientMessage::Type::LEAVE_MUSIC_SESSION

        handle_leave_music_session(client_msg.leave_music_session, client)

      else
        raise SessionError, "unknown message type '#{client_msg.type}' for #{client_msg.route_to}-directed message"
      end
    end

    def handle_login(login, client)

      username = login.username if login.value_for_tag(1)
      password = login.password if login.value_for_tag(2)
      token = login.token if login.value_for_tag(3)
      client_id = login.client_id if login.value_for_tag(4)

      # you don't have to supply client_id in login--if you don't, we'll generate one
      if client_id.nil?
        # give a unique ID to this client.  This is used to prevent session messages
        # from echoing back to the sender, for instance.
        client_id = UUIDTools::UUID.random_create.to_s
      end

      client.client_id = client_id

      user = valid_login(username, password, token, client_id)

      if !user.nil?

        @log.debug "user #{user.email} logged in"

        # respond with LOGIN_ACK to let client know it was successful
        #binding.pry
        remote_port, remote_ip = Socket.unpack_sockaddr_in(client.get_peername)
        login_ack = @message_factory.login_ack(remote_ip, client_id, user.remember_token)
        send_to_client(client, login_ack)

        # remove from pending_queue
        @semaphore.synchronize do
          @pending_clients.delete(client)

          # add a tracker for this user
          context = ClientContext.new(user, client)
          @clients[client] = context
          add_user(context)
          add_client(client_id, client)
        end
      else
        raise SessionError, 'invalid login'
      end
    end

    def handle_heartbeat(heartbeat, client)
      # todo: manage staleness
    end

    def handle_join_music_session(join_music_session, client)
      # verify that the current user has the rights to actually join the music session
      context = @clients[client]

      session_id = join_music_session.music_session

      begin
        session = access_music_session(session_id, context.user)
        @log.debug "user #{context} joining new session #{session}"
        @semaphore.synchronize do
          old_session = context.session
          if !old_session.nil?
            @log.debug "#{context} is already in session.  auto-logging out to join new session."
            remove_session(context)
          end
          context.session = session
          add_session(context)
        end
      rescue => e
        # send back a failure ack and bail
        @log.debug "client requested non-existent session. client:#{client.request['origin']} user:#{context.user.email}"
        login_music_session = @message_factory.login_music_session_ack(true, e.to_s)
        send_to_client(client, login_music_session)
        return
      end

      # respond with LOGIN_MUSIC_SESSION_ACK to let client know it was successful
      login_music_session = @message_factory.login_music_session_ack(false, nil)
      send_to_client(client, login_music_session)

      # send 'new client' message to other members in the session
      handle_session_directed(session_id,
                              @message_factory.user_joined_music_session(context.user.id, context.user.name),
                              client)
    end

    def handle_leave_music_session(leave_music_session, client)

      context = @clients[client]

      raise SessionError, "unsupported"
    end

    def valid_login(username, password, token, client_id)

      if !token.nil? && token != ''
        @log.debug "logging in via token"
        # attempt login with token
        user = User.find_by_remember_token(token)

        if user.nil?
          @log.debug "no user found with token"
          return false
        else
          @log.debug "#{user} login via token"
          return user
        end

      elsif !username.nil? and !password.nil?

        @log.debug "logging in via user/pass '#{username}' '#{password}'"
        # attempt login with username and password
        user = User.find_by_email(username)

        if !user.nil? && user.authenticate(password)
          @log.debug "#{user} login via password"
          return user
        else
          @log.debug "#{username} login failure"
          return nil
        end
      else
        raise SessionError, 'no login data was found in Login message'
      end

    end

    def access_music_session(music_session_id, user)
      music_session = MusicSession.find_by_id(music_session_id)

      if music_session.nil?
        raise SessionError, 'specified session not found'
      end

      if !music_session.access? user
        raise SessionError, 'not allowed to join the specified session'
      end

      return music_session
    end

    # client_id = the id of the client being accessed
    # client = the current client
    def access_p2p(client_id, user, msg)

      # ping_request and ping_ack messages are special in that they are simply allowed
      if msg.type == ClientMessage::Type::PING_REQUEST || msg.type == ClientMessage::Type::PING_ACK
        return nil
      end

      music_session_client = MusicSessionClient.find_by_client_id(client_id)

      if music_session_client.nil?
        raise PermissionError, 'specified client not found'
      end

      if !music_session_client.access_p2p? user

        raise SessionError, 'not allowed to message this client'

      end
    end

    def handle_session_directed(session_id, client_msg, client)

      context = @clients[client]

      # by not catching any exception here, this will kill the connection
      # if for some reason the client is trying to send to a session that it doesn't
      # belong to
      session = access_music_session(session_id, context.user)

      @log.debug "publishing to session #{session} from client_id #{client.client_id}"
      # put it on the topic exchange for sessions
      @sessions_exchange.publish(client_msg.to_s, :routing_key => "session.#{session_id}", :properties => {:headers => {"client_id" => client.client_id}})
    end

    def handle_client_directed(to_client_id, client_msg, client)
      context = @clients[client]

      # by not catching any exception here, a PermissionError will be thrown if this isn't valid
      # if for some reason the client is trying to send to a client that it doesn't
      # belong to
      access_p2p(to_client_id, context.user, client_msg)

      # populate routing data
      client_msg.from = client.client_id

      @log.debug "publishing to client #{to_client_id} from client_id #{client.client_id}"

      # put it on the topic exchange for clients
      @clients_exchange.publish(client_msg.to_s, :routing_key => "client.#{to_client_id}", :properties => {:headers => {"client_id" => client.client_id}})
    end

    def handle_user_directed(user, client_msg, client)

      raise SessionError, 'not implemented'
    end
  end
end