module Ably::Realtime
  class Client
    # IncomingMessageDispatcher is a (private) class that is used to dispatch {Ably::Models::ProtocolMessage} that are
    # received from Ably via the {Ably::Realtime::Connection}
    class IncomingMessageDispatcher
      ACTION = Ably::Models::ProtocolMessage::ACTION

      def initialize(client, connection)
        @client     = client
        @connection = connection

        subscribe_to_incoming_protocol_messages
      end

      private
      attr_reader :client, :connection

      def channels
        client.channels
      end

      def get_channel(channel_name)
        channels.fetch(channel_name) do
          logger.warn "Received channel message for non-existent channel"
          Ably::Realtime::Models::NilChannel.new
        end
      end

      def logger
        client.logger
      end

      def dispatch_protocol_message(*args)
        protocol_message = args.first

        unless protocol_message.kind_of?(Ably::Models::ProtocolMessage)
          raise ArgumentError, "Expected a ProtocolMessage. Received #{protocol_message}"
        end

        unless [:nack, :error].include?(protocol_message.action)
          logger.debug "#{protocol_message.action} received: #{protocol_message}"
        end

        update_connection_recovery_info protocol_message

        case protocol_message.action
          when ACTION.Heartbeat
          when ACTION.Ack
            ack_pending_queue_for_message_serial(protocol_message) if protocol_message.has_message_serial?

          when ACTION.Nack
            logger.warn "NACK received: #{protocol_message}"
            nack_pending_queue_for_message_serial(protocol_message) if protocol_message.has_message_serial?

          when ACTION.Connect
          when ACTION.Connected
            connection.transition_state_machine :connected, protocol_message.error

          when ACTION.Disconnect, ACTION.Disconnected
            connection.transition_state_machine :disconnected, protocol_message.error

          when ACTION.Close
          when ACTION.Closed
            connection.transition_state_machine :closed

          when ACTION.Error
            if protocol_message.channel && !protocol_message.has_message_serial?
              dispatch_channel_error protocol_message
            else
              process_connection_error protocol_message
            end

          when ACTION.Attach
          when ACTION.Attached
            get_channel(protocol_message.channel).transition_state_machine :attached, protocol_message

          when ACTION.Detach
          when ACTION.Detached
            get_channel(protocol_message.channel).transition_state_machine :detached

          when ACTION.Sync
            presence = get_channel(protocol_message.channel).presence
            protocol_message.presence.each do |presence_message|
              presence.__incoming_msgbus__.publish :sync, presence_message
            end
            presence.update_sync_serial protocol_message.channel_serial

          when ACTION.Presence
            presence = get_channel(protocol_message.channel).presence
            protocol_message.presence.each do |presence_message|
              presence.__incoming_msgbus__.publish :presence, presence_message
            end

          when ACTION.Message
            channel = get_channel(protocol_message.channel)
            protocol_message.messages.each do |message|
              channel.__incoming_msgbus__.publish :message, message
            end

          else
            raise ArgumentError, "Protocol Message Action #{protocol_message.action} is unsupported by this MessageDispatcher"
        end
      end

      def dispatch_channel_error(protocol_message)
        logger.warn "Channel Error message received: #{protocol_message.error}"
        if !protocol_message.has_message_serial?
          get_channel(protocol_message.channel).transition_state_machine :failed, protocol_message.error
        else
          logger.fatal "Cannot process ProtocolMessage as not yet implemented: #{protocol_message}"
        end
      end

      def process_connection_error(protocol_message)
        connection.manager.error_received_from_server protocol_message.error
      end

      def update_connection_recovery_info(protocol_message)
        if protocol_message.connection_key && (protocol_message.connection_key != connection.key)
          logger.debug "New connection ID set to #{protocol_message.connection_id} with connection key #{protocol_message.connection_key}"
          detach_attached_channels protocol_message.error if protocol_message.error
          connection.configure_new protocol_message.connection_id, protocol_message.connection_key, protocol_message.connection_serial
        end

        if protocol_message.has_connection_serial?
          connection.update_connection_serial protocol_message.connection_serial
        end
      end

      def detach_attached_channels(error)
        channels.select do |channel|
          channel.attached? || channel.attaching?
        end.each do |channel|
          logger.warn "Detaching channel '#{channel.name}': #{error}"
          channel.manager.suspend error
        end
      end

      def ack_pending_queue_for_message_serial(ack_protocol_message)
        drop_pending_queue_from_ack(ack_protocol_message) do |protocol_message|
          ack_messages protocol_message.messages
          ack_messages protocol_message.presence
        end
      end

      def nack_pending_queue_for_message_serial(nack_protocol_message)
        drop_pending_queue_from_ack(nack_protocol_message) do |protocol_message|
          nack_messages protocol_message.messages, nack_protocol_message
          nack_messages protocol_message.presence, nack_protocol_message
        end
      end

      def ack_messages(messages)
        messages.each do |message|
          logger.debug "Calling ACK success callbacks for #{message.class.name} - #{message.to_json}"
          message.succeed message
        end
      end

      def nack_messages(messages, protocol_message)
        messages.each do |message|
          logger.debug "Calling NACK failure callbacks for #{message.class.name} - #{message.to_json}, protocol message: #{protocol_message}"
          message.fail message, protocol_message.error
        end
      end

      def drop_pending_queue_from_ack(ack_protocol_message)
        message_serial_up_to = ack_protocol_message.message_serial + ack_protocol_message.count - 1
        connection.__pending_message_queue__.drop_while do |protocol_message|
          if protocol_message.message_serial <= message_serial_up_to
            yield protocol_message
            true
          end
        end
      end

      def subscribe_to_incoming_protocol_messages
        connection.__incoming_protocol_msgbus__.subscribe(:protocol_message) do |*args|
          dispatch_protocol_message *args
        end
      end
    end
  end
end