class Concurrent::CachedThreadPool

def <<(block)
  self.post(&block)
  return self
end

def create_worker_thread
  wrkr = Worker.new(self)
  Thread.new(wrkr, self) do |worker, parent|
    Thread.current.abort_on_exception = false
    worker.run
    parent.on_worker_exit(worker)
  end
  return wrkr
end

def initialize(opts = {})
  @idletime = (opts[:idletime] || DEFAULT_THREAD_IDLETIME).to_i
  raise ArgumentError.new('idletime must be greater than zero') if @idletime <= 0
  @max_threads = opts[:max_threads] || opts[:max] || MAX_POOL_SIZE
  if @max_threads < MIN_POOL_SIZE || @max_threads > MAX_POOL_SIZE
    raise ArgumentError.new("size must be from #{MIN_POOL_SIZE} to #{MAX_POOL_SIZE}")
  end
  @state = :running
  @pool = []
  @terminator = Event.new
  @mutex = Mutex.new
  @busy = []
  @idle = []
end

def kill
  @mutex.synchronize do
    break if @state == :shutdown
    @state = :shutdown
      @idle.each{|worker| worker.kill }
      @busy.each{|worker| worker.kill }
    @terminator.set
  end
end

def length
  @mutex.synchronize do
    @state == :running ? @busy.length + @idle.length : 0
  end
end

def on_end_task(worker)
  @mutex.synchronize do
    break unless @state == :running
    @busy.delete(worker)
    @idle.push(worker)
  end
end

def on_worker_exit(worker)
  @mutex.synchronize do
    @idle.delete(worker)
    @busy.delete(worker)
    if @idle.empty? && @busy.empty? && @state != :running
      @state = :shutdown
      @terminator.set
    end
  end
end

def post(*args, &block)
  raise ArgumentError.new('no block given') if block.nil?
  @mutex.synchronize do
    break false unless @state == :running
    if @idle.empty?
      if @idle.length + @busy.length < @max_threads
        worker = create_worker_thread
      else
        worker = @busy.shift
      end
    else
      worker = @idle.pop
    end
    @busy.push(worker)
    worker.signal(*args, &block)
    prune_stale_workers
    true
  end
end

def prune_stale_workers
  @idle.reject! do |worker|
    if worker.idletime > @idletime
      worker.stop
      true
    else
      worker.dead?
    end
  end
end

def running?
  return @state == :running
end

def shutdown
  @mutex.synchronize do
    break unless @state == :running
    if @idle.empty? && @busy.empty?
      @state = :shutdown
      @terminator.set
    else
      @state = :shuttingdown
      @idle.each{|worker| worker.stop }
      @busy.each{|worker| worker.stop }
    end
  end
end

def wait_for_termination(timeout = nil)
  return @terminator.wait(timeout)
end