require 'nats/client'
require 'google/protobuf'

require 'rubypitaya/core/protos/nats_connector_pb'

module RubyPitaya

  class NatsConnector

    REQUEST_TYPE_SYS  = 0
    REQUEST_TYPE_USER = 1

    MESSAGE_TYPE_REQUEST  = 0
    MESSAGE_TYPE_NOTIFY   = 1
    MESSAGE_TYPE_RESPONSE = 2
    MESSAGE_TYPE_PUSH     = 3

    def initialize(nats_address, server_uuid, server_name)
      @server_uuid = server_uuid
      @server_name = server_name
      @nats_address = nats_address
      @nats = nil
      @subscribe = nil
    end

    def connect
      self.disconnect

      @nats = NATS.connect(servers: [@nats_address])
      @subscribe = @nats.subscribe(subscribe_topic)

      loop do
        message = @subscribe.pending_queue.pop
        @subscribe.synchronize do
          @subscribe.pending_size -= message.data.size
        end

        request = NatsRequest.decode(message.data).to_h

        response = yield request

        nats_response = NatsResponse.new(data: response.force_encoding('ascii-8bit'))
        nats_response_encoded = NatsResponse.encode(nats_response)

        @nats.publish(message.reply, nats_response_encoded)
      end
    end

    def disconnect
      @subscribe.unsubscribe unless @subscribe.nil?
      @nats.close unless @nats.nil?

      @nats = nil
      @subscribe = nil
    end

    def push_to_frontend(session, message_route, payload)
      frontend_topic = get_frontend_topic(session.frontend_id)

      nats_message = NatsMessage.new(
        route: message_route,
        data: payload,
        reply: @server_uuid,
        type: MESSAGE_TYPE_REQUEST,
      )

      nats_session = NatsSession.new(
        id: session.id,
        uid: session.uid,
        data: session.data.to_json,
      )

      nats_request = NatsRequest.new(
        type: REQUEST_TYPE_USER,
        session: nats_session,
        msg: nats_message,
        frontendID: session.frontend_id,
        metadata: session.metadata.to_json,
      )

      request = NatsRequest.encode(nats_request)

      nats_response = @nats.request(frontend_topic, request)

      response = NatsResponse.decode(nats_response.data).to_h

      response
    end

    def push_to_user(uid, message_route, payload)
      user_topic = get_user_message_topic(uid)

      nats_push = NatsPush.new(
        route: message_route,
        uid: uid,
        data: payload.to_json,
      )

      @nats.publish(user_topic, nats_push)

      0
    end

    def subscribe_topic
      "pitaya/servers/#{@server_name}/#{@server_uuid}"
    end

    def get_frontend_topic(frontend_id)
      "pitaya/servers/connector/#{frontend_id}"
    end

    def get_user_message_topic(uid)
      "pitaya/connector/user/#{uid}/push"
    end
  end
end