<?php

/*

 * This file is part of SwiftMailer.

 * (c) 2004-2009 Chris Corbyn

 *

 * For the full copyright and license information, please view the LICENSE

 * file that was distributed with this source code.

 */

/**

 * Redudantly and rotationally uses several Transports when sending.

 * 

 * @package Swift

 * @subpackage Transport

 * @author Chris Corbyn

 */

class Swift_Transport_LoadBalancedTransport implements Swift_Transport

{

  /** Transports which are deemed useless */

  private $_deadTransports = array();

  /**

   * The Transports which are used in rotation.

   * 

   * @var array Swift_Transport

   * @access protected

   */

  protected $_transports = array();

  /**

   * Creates a new LoadBalancedTransport.

   */

  public function __construct()

  {

  }

  /**

   * Set $transports to delegate to.

   * 

   * @param array $transports Swift_Transport

   */

  public function setTransports(array $transports)

  {

    $this->_transports = $transports;

    $this->_deadTransports = array();

  }

  /**

   * Get $transports to delegate to.

   * 

   * @return array Swift_Transport

   */

  public function getTransports(array $transports)

  {

    return array_merge($this->_transports, $this->_deadTransports);

  }

  /**

   * Test if this Transport mechanism has started.

   * 

   * @return boolean

   */

  public function isStarted()

  {

    return count($this->_transports) > 0;

  }

  /**

   * Start this Transport mechanism.

   */

  public function start()

  {

    $this->_transports = array_merge($this->_transports, $this->_deadTransports);

  }

  /**

   * Stop this Transport mechanism.

   */

  public function stop()

  {

    foreach ($this->_transports as $transport)

    {

      $transport->stop();

    }

  }

  /**

   * Send the given Message.

   * 

   * Recipient/sender data will be retreived from the Message API.

   * The return value is the number of recipients who were accepted for delivery.

   * 

   * @param Swift_Mime_Message $message

   * @param string[] &$failedRecipients to collect failures by-reference

   * @return int

   */

  public function send(Swift_Mime_Message $message, &$failedRecipients = null)

  {

    $maxTransports = count($this->_transports);

    $sent = 0;

    for ($i = 0; $i < $maxTransports

      && $transport = $this->_getNextTransport(); ++$i)

    {

      try

      {

        if (!$transport->isStarted())

        {

          $transport->start();

        }

        if ($sent = $transport->send($message, $failedRecipients))

        {

          break;

        }

      }

      catch (Swift_TransportException $e)

      {

        $this->_killCurrentTransport();

      }

    }

    if (count($this->_transports) == 0)

    {

      throw new Swift_TransportException(

        'All Transports in LoadBalancedTransport failed, or no Transports available'

        );

    }

    return $sent;

  }

  /**

   * Register a plugin.

   * 

   * @param Swift_Events_EventListener $plugin

   */

  public function registerPlugin(Swift_Events_EventListener $plugin)

  {

    foreach ($this->_transports as $transport)

    {

      $transport->registerPlugin($plugin);

    }

  }

  // -- Protected methods

  /**

   * Rotates the transport list around and returns the first instance.

   * 

   * @return Swift_Transport

   * @access protected

   */

  protected function _getNextTransport()

  {

    if ($next = array_shift($this->_transports))

    {

      $this->_transports[] = $next;

    }

    return $next;

  }

  /**

   * Tag the currently used (top of stack) transport as dead/useless.

   * 

   * @access protected

   */

  protected function _killCurrentTransport()

  {

    if ($transport = array_pop($this->_transports))

    {

      try

      {

        $transport->stop();

      }

      catch (Exception $e)

      {

      }

      $this->_deadTransports[] = $transport;

    }

  }

}