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<?php
/**
* This file is part of the ramsey/collection library
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*
* @copyright Copyright (c) Ben Ramsey <ben@benramsey.com>
* @license http://opensource.org/licenses/MIT MIT
*/
declare(strict_types=1);
namespace Ramsey\Collection;
use Ramsey\Collection\Exception\InvalidArgumentException;
use Ramsey\Collection\Exception\NoSuchElementException;
use Ramsey\Collection\Tool\TypeTrait;
use Ramsey\Collection\Tool\ValueToStringTrait;
/**
* This class provides a basic implementation of `QueueInterface`, to minimize
* the effort required to implement this interface.
*/
class Queue extends AbstractArray implements QueueInterface
{
use TypeTrait;
use ValueToStringTrait;
/**
* The type of elements stored in this queue.
*
* A queue's type is immutable once it is set. For this reason, this
* property is set private.
*
* @var string
*/
private $queueType;
/**
* The index of the head of the queue.
*
* @var int
*/
protected $index = 0;
/**
* Constructs a queue object of the specified type, optionally with the
* specified data.
*
* @param string $queueType The type (FQCN) associated with this queue.
* @param mixed[] $data The initial items to store in the collection.
*/
public function __construct(string $queueType, array $data = [])
{
$this->queueType = $queueType;
parent::__construct($data);
}
/**
* Sets the given value to the given offset in the queue.
*
* Since arbitrary offsets may not be manipulated in a queue, this method
* serves only to fulfill the `ArrayAccess` interface requirements. It is
* invoked by other operations when adding values to the queue.
*
* @link http://php.net/manual/en/arrayaccess.offsetset.php ArrayAccess::offsetSet()
*
* @param mixed|null $offset The offset is ignored and is treated as `null`.
* @param mixed $value The value to set at the given offset.
*
* @throws InvalidArgumentException when the value does not match the
* specified type for this queue.
*/
public function offsetSet($offset, $value): void
{
if ($this->checkType($this->getType(), $value) === false) {
throw new InvalidArgumentException(
'Value must be of type ' . $this->getType() . '; value is '
. $this->toolValueToString($value)
);
}
$this->data[] = $value;
}
/**
* Ensures that this queue contains the specified element.
*
* This method differs from `offer()` only in that it throws an exception if
* it cannot add the element to the queue.
*
* @see self::offer()
*
* @param mixed $element The element to add to this queue.
*
* @return bool `true` if this queue changed as a result of the call.
*
* @throws InvalidArgumentException when the element does not match the
* specified type for this queue.
*/
public function add($element): bool
{
$this[] = $element;
return true;
}
/**
* Retrieves, but does not remove, the head of this queue.
*
* This method differs from `peek()` only in that it throws an exception if
* this queue is empty.
*
* @see self::peek()
*
* @return mixed the head of this queue.
*
* @throws NoSuchElementException if this queue is empty.
*/
public function element()
{
if ($this->count() === 0) {
throw new NoSuchElementException(
'Can\'t return element from Queue. Queue is empty.'
);
}
return $this[$this->index];
}
/**
* Inserts the specified element into this queue.
*
* This method differs from `add()` only in that it does not throw an
* exception if it cannot add the element to the queue.
*
* @see self::add()
*
* @param mixed $element The element to add to this queue.
*
* @return bool `true` if the element was added to this queue, else `false`.
*/
public function offer($element): bool
{
try {
return $this->add($element);
} catch (InvalidArgumentException $e) {
return false;
}
}
/**
* Retrieves, but does not remove, the head of this queue, or returns `null`
* if this queue is empty.
*
* @see self::element()
*
* @return mixed|null the head of this queue, or `null` if this queue is empty.
*/
public function peek()
{
if ($this->count() === 0) {
return null;
}
return $this[$this->index];
}
/**
* Retrieves and removes the head of this queue, or returns `null`
* if this queue is empty.
*
* @see self::remove()
*
* @return mixed|null the head of this queue, or `null` if this queue is empty.
*/
public function poll()
{
if ($this->count() === 0) {
return null;
}
$head = $this[$this->index];
unset($this[$this->index]);
$this->index++;
return $head;
}
/**
* Retrieves and removes the head of this queue.
*
* This method differs from `poll()` only in that it throws an exception if
* this queue is empty.
*
* @see self::poll()
*
* @return mixed the head of this queue.
*
* @throws NoSuchElementException if this queue is empty.
*/
public function remove()
{
if ($this->count() === 0) {
throw new NoSuchElementException('Can\'t return element from Queue. Queue is empty.');
}
$head = $this[$this->index];
unset($this[$this->index]);
$this->index++;
return $head;
}
/**
* Returns the type associated with this queue.
*/
public function getType(): string
{
return $this->queueType;
}
}
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