<?php	/*

  Adds parallel tasks to a queue.
  
  tick() must be called regularly, that arranges addition of new jobs and removal of closed threads.
  
  
  */

require_once("Thread.php");

class ThreadQueue {
  
  const DEFAULT_QUEUE_SIZE = 2;		// default number of parallel tasks
  const TICK_DELAY = 10000;		// delay after tick, in millisecs 
  
  private $callable;	// the function name to call. can be a method of a static class as well
  private $threads = array();	// Thread instances
  private $jobs = array();	// parameters to pass to $callable
  public $queueSize;		// number of parallel tasks. public, to make it variable run-time.
  
  
  /**
   *	Constructor
   *
   *	@param string $callable		function name
   *	@param integer $queueSize	number of parallel tasks
  */
  
  public function __construct($callable, $queueSize = ThreadQueue::DEFAULT_QUEUE_SIZE ){
    if(!is_callable($callable))throw new Exception("$callable is not callable.");
    $this->callable = $callable;
    $this->queueSize = $queueSize;
  }
  
  
  /**
   *	Add a new job
   *
   *	@param mixed $argument	parameter to pass to $callable
   *	@return int	queue size
   */
  
  public function add($argument){
    $this->jobs[] = $argument;
    return $this->tick();
  }
  
  
  /**
   *	Removes closed threads from queue
   *
   */
  
  private function cleanup(){
    foreach($this->threads as $i => $szal)
      if(!$szal->isAlive())
        unset($this->threads[$i]);
    return count($this->threads); 
  }
   
  
  /**
   *	Starts new threads if needed
   *
   *	@return int	queue size
   */
   
  public function tick(){
    $this->cleanup();
    
    if( (count($this->threads) < $this->queueSize) && count($this->jobs) ){
      $this->threads[] = $szal = new Thread($this->callable);
      $szal->start( array_shift($this->jobs) );
    }
     
    usleep(ThreadQueue::TICK_DELAY);
    return $this->queueSize();
  }


  /**
   *	returns queue size with waiting jobs
   *
   *	@return int
   */
   
  public function queueSize(){
    return count($this->jobs);
  }
  
  
  /**
   *	returns thread instances
   *
   *	@return array of Thread
   */
  public function threads(){
    return $this->threads;
  }
  
  
  /**
   *	Removes all remaining jobs (empty queue)
   *
   *	@return int	number of removed jobs
   */
  public function flush(){
    $size = $this->queueSize();
    $this->jobs = array();
    return $size;
  }
  
}