require 'resque' rescue nil # optional dependency

module Pwwka
  # Primary interface for sending messages.
  #
  # Example:
  #
  #     # Send a message, blowing up if there's any problem
  #     Pwwka::Transmitter.send_message!({ user_id: @user.id }, "users.user.activated")
  #
  #     # Send a message, logging if there's any problem
  #     Pwwka::Transmitter.send_message_safely({ user_id: @user.id }, "users.user.activated")
  class Transmitter

    extend Pwwka::Logging
    include Pwwka::Logging

    DEFAULT_DELAY_BY_MS = 5000

    attr_reader :channel_connector

    def initialize
      @channel_connector = ChannelConnector.new
    end

    # Send an important message that must go through.  This method allows any raised exception 
    # to pass through.
    #
    # payload:: Hash of what you'd like to include in your message
    # routing_key:: String routing key for the message
    # delayed:: Boolean send this message later
    # delay_by:: Integer milliseconds to delay the message
    # on_error:: What is the behavior of
    # - :ignore (aka as send_message_safely)
    # - :raise
    # - :resque -- use Resque to try to send the message later
    #
    # Returns true
    #
    # Raises any exception generated by the innerworkings of this library.
    def self.send_message!(payload, routing_key, on_error: :raise,
        delayed: false, delay_by: nil)
      if delayed
        new.send_delayed_message!(*[payload, routing_key, delay_by].compact)
      else
        new.send_message!(payload, routing_key)
      end
      info "AFTER Transmitting Message on #{routing_key} -> #{payload}"

    rescue => e

      error "ERROR Transmitting Message on #{routing_key} -> #{payload}: #{e}"

      case on_error

        when :raise
          raise e

        when :resque
          begin
            send_message_async(payload, routing_key, delay_by_ms: delayed ? delay_by || DEFAULT_DELAY_BY_MS : 0)
          rescue => resque_exception
            warn(resque_exception.message)
            raise e
          end
        else # ignore
      end
      false
    end

    # Use Resque to enqueue the message.
    # - :delay_by_ms:: Integer milliseconds to delay the message. Default is 0.
    def self.send_message_async(payload, routing_key, delay_by_ms: 0)
      Resque.enqueue_in(delay_by_ms/1000, SendMessageAsyncJob, payload, routing_key)
    end

    # Send a less important message that doesn't have to go through. This eats
    # any `StandardError` and logs it, returning false rather than blowing up.
    #
    # payload:: Hash of what you'd like to include in your message
    # routing_key:: String routing key for the message
    # delayed:: Boolean send this message later
    # delay_by:: Integer milliseconds to delay the message
    #
    # Returns true if the message was sent, false otherwise
    # @deprecated This is ignoring a message. ::send_message supports this explicitly.
    def self.send_message_safely(payload, routing_key, delayed: false, delay_by: nil)
      send_message!(payload, routing_key, delayed: delayed, delay_by: delay_by, on_error: :ignore)
    end

    def send_message!(payload, routing_key)
      info "START Transmitting Message on #{routing_key} -> #{payload}"
      channel_connector.topic_exchange.publish(
          payload.to_json,
          routing_key: routing_key,
          persistent:  true)
      channel_connector.connection_close
      # if it gets this far it has succeeded
      info "END Transmitting Message on #{routing_key} -> #{payload}"
      true
    end


    def send_delayed_message!(payload, routing_key, delay_by = DEFAULT_DELAY_BY_MS)
      channel_connector.raise_if_delayed_not_allowed
      info "START Transmitting Delayed Message on #{routing_key} -> #{payload}"
      channel_connector.create_delayed_queue
      channel_connector.delayed_exchange.publish(
          payload.to_json,
          routing_key: routing_key,
          expiration:  delay_by,
          persistent:  true)
      channel_connector.connection_close
      # if it gets this far it has succeeded
      info "END Transmitting Delayed Message on #{routing_key} -> #{payload}"
      true
    end

  end
end