require 'logger'
require 'eventbus/queue'

module EventBus
class Service
  
  attr_accessor :listen_queue
  attr_accessor :system_process
  attr_accessor :global_process
  attr_accessor :logger
  
  # Methods expected to be overridden in subclasses
  def handle_exception(message, exception)
    # Just a hook that can be overridden in the subclass. Framework base behavior is in handle_exception_base.
    # It does not need to be overridden, but can provide some custom behaviors.
  end
  
  # process_message is the main business-logic entry point for the subclass. Subclasses _MUST_ override this.
  def process_message(message)
    raise "You need to override the 'process_message' method in your subclass!"
  end
  
  
  def initialize(application_id = nil)
    @listen_queue = self.class.name
    @application_id = application_id || raise("No application ID specified!")
    @logger = Logger.new(STDOUT)
    @system_process = false
    @global_process = false
    
    @connection_driver = ENV["EVENTBUS_CONNECTOR"] || "Stomp"
    
    driver_module = "#{@connection_driver}ConnectionDriver"
    
    require "eventbus/connectors/#{@connection_driver.downcase}"
    
    # Pretty much just swiped from ActiveSupport "constantize"..
    conn_module = Object.const_defined?(driver_module) ? Object.const_get(driver_module) : Object.const_missing(driver_module)
    
    extend conn_module 
    
    connection_driver_initialize
    
  end
  
  
  def start ( opts = {} )
    
    max_workers = opts.delete(:max_workers) || 5
    
    opts[:system_queue] = @system_process
    opts[:global_process] = @global_process
    
    queue_name = Queue.calc_name(listen_queue, @application_id, ENV['PROD_LEVEL'], opts)
    
    watch_queue(queue_name) do |message|

      # The +2 stuff is because the main thread counts in the list, even though it's not a "worker" thread.
      # What makes it worse is that, depending on the broker connector, watch_queue may also start a thread.
      # With this implementation, that extra thread (e.g. with the stomp connector) would count in this.
      # Bottom line is allow a little wiggle room with the :max_workers. Don't tighten down the threads too much 
      # for now. 
      while (Thread.list.length >= max_workers + 2) do
        sleep 0.25
      end
      
      Thread.new do
        process_message_wrapper message 
      end
     
    end 
    
    # Just sleep in the main thread. Nothing going on here anymore.
    loop do
      sleep 6000
    end
    
  end
  
  private
  
  def process_message_wrapper(message)
    
    begin
      puts "Beginning processing of message in new thread:"
      puts message
      
      process_message message
    rescue
      handle_exception_base message, $!
    end
    
  end
  
  def handle_exception_base(message, exception)
    puts "Caught exception. Exception Text: #{exception}"
    puts "Backtrace:"
    exception.backtrace.map { | frame | puts "- #{frame}"}
    
    msg = EventBus::Message.new("CORE")
    msg.load(message)
    msg.set_error exception
    
    self.handle_exception(msg, exception)
    
    msg.send
  end
  
  def puts(message) 
    @logger.info message
  end
  
end

end # module EventBus