<?php

/**

 * Zend Framework

 *

 * LICENSE

 *

 * This source file is subject to the new BSD license that is bundled

 * with this package in the file LICENSE.txt.

 * It is also available through the world-wide-web at this URL:

 * http://framework.zend.com/license/new-bsd

 * If you did not receive a copy of the license and are unable to

 * obtain it through the world-wide-web, please send an email

 * to license@zend.com so we can send you a copy immediately.

 *

 * @category   Zend

 * @package    Zend_Stdlib

 * @copyright  Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 */

require_once 'Zend/Stdlib/SplPriorityQueue.php';

/**

 * Re-usable, serializable priority queue implementation

 *

 * SplPriorityQueue acts as a heap; on iteration, each item is removed from the

 * queue. If you wish to re-use such a queue, you need to clone it first. This 

 * makes for some interesting issues if you wish to delete items from the queue,

 * or, as already stated, iterate over it multiple times.

 *

 * This class aggregates items for the queue itself, but also composes an 

 * "inner" iterator in the form of an SplPriorityQueue object for performing

 * the actual iteration.

 *

 * @category   Zend

 * @package    Zend_Stdlib

 * @copyright  Copyright (c) 2005-2012 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 */

class Zend_Stdlib_PriorityQueue implements Countable, IteratorAggregate, Serializable

{

    const EXTR_DATA     = 0x00000001;

    const EXTR_PRIORITY = 0x00000002;

    const EXTR_BOTH     = 0x00000003;

    /**

     * Inner queue class to use for iteration

     * @var string

     */

    protected $queueClass = 'Zend_Stdlib_SplPriorityQueue';

    /**

     * Actual items aggregated in the priority queue. Each item is an array

     * with keys "data" and "priority".

     * @var array

     */

    protected $items      = array();

    /**

     * Inner queue object

     * @var SplPriorityQueue

     */

    protected $queue;

    /**

     * Insert an item into the queue

     *

     * Priority defaults to 1 (low priority) if none provided.

     * 

     * @param  mixed $data 

     * @param  int $priority 

     * @return Zend_Stdlib_PriorityQueue

     */

    public function insert($data, $priority = 1)

    {

        $priority = (int) $priority;

        $this->items[] = array(

            'data'     => $data,

            'priority' => $priority,

        );

        $this->getQueue()->insert($data, $priority);

        return $this;

    }

    /**

     * Remove an item from the queue

     *

     * This is different than {@link extract()}; its purpose is to dequeue an

     * item.

     *

     * This operation is potentially expensive, as it requires 

     * re-initialization and re-population of the inner queue.

     * 

     * Note: this removes the first item matching the provided item found. If

     * the same item has been added multiple times, it will not remove other 

     * instances.

     *

     * @param  mixed $datum

     * @return boolean False if the item was not found, true otherwise.

     */

    public function remove($datum)

    {

        $found = false;

        foreach ($this->items as $key => $item) {

            if ($item['data'] === $datum) {

                $found = true;

                break;

            }

        }

        if ($found) {

            unset($this->items[$key]);

            $this->queue = null;

            $queue = $this->getQueue();

            foreach ($this->items as $item) {

                $queue->insert($item['data'], $item['priority']);

            }

            return true;

        }

        return false;

    }

    /**

     * Is the queue empty?

     * 

     * @return bool

     */

    public function isEmpty()

    {

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

    }

    /**

     * How many items are in the queue?

     * 

     * @return int

     */

    public function count()

    {

        return count($this->items);

    }

    /**

     * Peek at the top node in the queue, based on priority.

     * 

     * @return mixed

     */

    public function top()

    {

        return $this->getIterator()->top();

    }

    /**

     * Extract a node from the inner queue and sift up 

     * 

     * @return mixed

     */

    public function extract()

    {

        return $this->getQueue()->extract();

    }

    /**

     * Retrieve the inner iterator

     *

     * SplPriorityQueue acts as a heap, which typically implies that as items

     * are iterated, they are also removed. This does not work for situations

     * where the queue may be iterated multiple times. As such, this class 

     * aggregates the values, and also injects an SplPriorityQueue. This method 

     * retrieves the inner queue object, and clones it for purposes of 

     * iteration.

     * 

     * @return SplPriorityQueue

     */

    public function getIterator()

    {

        $queue = $this->getQueue();

        return clone $queue;

    }

    /**

     * Serialize the data structure

     * 

     * @return string

     */

    public function serialize()

    {

        return serialize($this->items);

    }

    /**

     * Unserialize a string into a Zend_Stdlib_PriorityQueue object

     *

     * Serialization format is compatible with {@link Zend_Stdlib_SplPriorityQueue}

     * 

     * @param  string $data 

     * @return void

     */

    public function unserialize($data)

    {

        foreach (unserialize($data) as $item) {

            $this->insert($item['data'], $item['priority']);

        }

    }

    /**

     * Serialize to an array

     *

     * By default, returns only the item data, and in the order registered (not

     * sorted). You may provide one of the EXTR_* flags as an argument, allowing

     * the ability to return priorities or both data and priority.

     * 

     * @param  int $flag 

     * @return array

     */

    public function toArray($flag = self::EXTR_DATA)

    {

        switch ($flag) {

            case self::EXTR_BOTH:

                return $this->items;

            case self::EXTR_PRIORITY:

                return array_map(array($this, 'returnPriority'), $this->items);

            case self::EXTR_DATA:

            default:

                return array_map(array($this, 'returnData'), $this->items);

        }

    }

    /**

     * Specify the internal queue class

     *

     * Please see {@link getIterator()} for details on the necessity of an

     * internal queue class. The class provided should extend SplPriorityQueue.

     * 

     * @param  string $class 

     * @return Zend_Stdlib_PriorityQueue

     */

    public function setInternalQueueClass($class)

    {

        $this->queueClass = (string) $class;

        return $this;

    }

    /**

     * Does the queue contain the given datum?

     * 

     * @param  mixed $datum 

     * @return bool

     */

    public function contains($datum)

    {

        foreach ($this->items as $item) {

            if ($item['data'] === $datum) {

                return true;

            }

        }

        return false;

    }

    /**

     * Does the queue have an item with the given priority?

     * 

     * @param  int $priority 

     * @return bool

     */

    public function hasPriority($priority)

    {

        foreach ($this->items as $item) {

            if ($item['priority'] === $priority) {

                return true;

            }

        }

        return false;

    }

    /**

     * Get the inner priority queue instance

     * 

     * @return Zend_Stdlib_SplPriorityQueue

     */

    protected function getQueue()

    {

        if (null === $this->queue) {

            $this->queue = new $this->queueClass();

            if (!$this->queue instanceof SplPriorityQueue) {

                throw new DomainException(sprintf(

                    'Zend_Stdlib_PriorityQueue expects an internal queue of type SplPriorityQueue; received "%s"',

                    get_class($this->queue)

                ));

            }

        }

        return $this->queue;

    }

    /**

     * Return priority from an internal item

     *

     * Used as a lambda in toArray().

     * 

     * @param  array $item 

     * @return mixed

     */

    public function returnPriority($item)

    {

        return $item['priority'];

    }

    /**

     * Return data from an internal item

     *

     * Used as a lambda in toArray().

     * 

     * @param  array $item 

     * @return mixed

     */

    public function returnData($item)

    {

        return $item['data'];

    }

}