## Ruleaza bucati de Ruby pe un numar maxim de thread-uri
#
# Utilizare:
#
#     runner = Scheduler.new :max_threads => 20
#     ary.each { |item| runner.queue { stuff_to_do_in_paralel } }
#     runner.start
#
# Codul este complet netestat.
 
class Scheduler
  MAX_THREADS = 15
  FREQUENCY   = 1
  
  def initialize(opt = {})
    @max_threads = opt[:max_threads] || MAX_THREADS
    @frequency   = opt[:interval] || FREQUENCY
    
    @running_threads = 0
    @working_queue   = Queue.new
    
    @lock = Mutex.new
    
    @logger = Logger.new(STDOUT)
    @logger.datetime_format = "%H:%M:%S"
  end
  
  def queue(&block)
    @working_queue.push block
  end
  
  def start
    while @working_queue.size > 0
      if @running_threads < @max_threads
        spawn :worker => @working_queue.pop
      else
        # Asteapta @frequency secunde si apoi resume
        sleep @frequency
      end
    end
    
    Thread.list.each { |t| t.join unless t == Thread.main or t == Thread.current }
  end
 
  private  
    def spawn(args = {})      
      @running_threads += 1
      logger "Running threads: #{@running_threads}, queue size: #{@working_queue.size}"
      
      proc = args[:worker]
      
      Thread.new do
        proc.call
      
        @lock.synchronize { @running_threads -= 1 }
      end    
    end
    
    def logger(msg)
      @logger.info(msg)
    end
end