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<?php
declare(strict_types=1);
namespace Laminas\Stdlib;
use Countable;
use IteratorAggregate;
use ReturnTypeWillChange;
use Serializable;
use UnexpectedValueException;
use function array_map;
use function count;
use function is_array;
use function serialize;
use function sprintf;
use function unserialize;
/**
* 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.
*
* @template TValue
* @template TPriority of int
* @implements IteratorAggregate<array-key, TValue>
*/
class PriorityQueue implements Countable, IteratorAggregate, Serializable
{
public const EXTR_DATA = 0x00000001;
public const EXTR_PRIORITY = 0x00000002;
public const EXTR_BOTH = 0x00000003;
/**
* Inner queue class to use for iteration
*
* @var class-string<\SplPriorityQueue>
*/
protected $queueClass = SplPriorityQueue::class;
/**
* Actual items aggregated in the priority queue. Each item is an array
* with keys "data" and "priority".
*
* @var list<array{data: TValue, priority: TPriority}>
*/
protected $items = [];
/**
* Inner queue object
*
* @var \SplPriorityQueue<TPriority, TValue>|null
*/
protected $queue;
/**
* Insert an item into the queue
*
* Priority defaults to 1 (low priority) if none provided.
*
* @param TValue $data
* @param TPriority $priority
* @return $this
*/
public function insert($data, $priority = 1)
{
/** @psalm-var TPriority $priority */
$priority = (int) $priority;
$this->items[] = [
'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.
*
* @return bool False if the item was not found, true otherwise.
*/
public function remove(mixed $datum)
{
$found = false;
$key = null;
foreach ($this->items as $key => $item) {
if ($item['data'] === $datum) {
$found = true;
break;
}
}
if ($found && $key !== null) {
unset($this->items[$key]);
$this->queue = null;
if (! $this->isEmpty()) {
$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 === $this->count();
}
/**
* How many items are in the queue?
*
* @return int
*/
#[ReturnTypeWillChange]
public function count()
{
return count($this->items);
}
/**
* Peek at the top node in the queue, based on priority.
*
* @return TValue
*/
public function top()
{
$queue = clone $this->getQueue();
return $queue->top();
}
/**
* Extract a node from the inner queue and sift up
*
* @return TValue
*/
public function extract()
{
$value = $this->getQueue()->extract();
$keyToRemove = null;
$highestPriority = null;
foreach ($this->items as $key => $item) {
if ($item['data'] !== $value) {
continue;
}
if (null === $highestPriority) {
$highestPriority = $item['priority'];
$keyToRemove = $key;
continue;
}
if ($highestPriority >= $item['priority']) {
continue;
}
$highestPriority = $item['priority'];
$keyToRemove = $key;
}
if ($keyToRemove !== null) {
unset($this->items[$keyToRemove]);
}
return $value;
}
/**
* 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<TPriority, TValue>
*/
#[ReturnTypeWillChange]
public function getIterator()
{
$queue = $this->getQueue();
return clone $queue;
}
/**
* Serialize the data structure
*
* @return string
*/
public function serialize()
{
return serialize($this->__serialize());
}
/**
* Magic method used for serializing of an instance.
*
* @return list<array{data: TValue, priority: TPriority}>
*/
public function __serialize()
{
return $this->items;
}
/**
* Unserialize a string into a PriorityQueue object
*
* Serialization format is compatible with {@link SplPriorityQueue}
*
* @param string $data
* @return void
*/
public function unserialize($data)
{
$toUnserialize = unserialize($data);
if (! is_array($toUnserialize)) {
throw new UnexpectedValueException(sprintf(
'Cannot deserialize %s instance; corrupt serialization data',
self::class
));
}
/** @psalm-var list<array{data: TValue, priority: TPriority}> $toUnserialize */
$this->__unserialize($toUnserialize);
}
/**
* Magic method used to rebuild an instance.
*
* @param list<array{data: TValue, priority: TPriority}> $data Data array.
* @return void
*/
public function __unserialize($data)
{
foreach ($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 $flag
* @return array<array-key, mixed>
* @psalm-return ($flag is self::EXTR_BOTH
* ? list<array{data: TValue, priority: TPriority}>
* : $flag is self::EXTR_PRIORITY
* ? list<TPriority>
* : list<TValue>
* )
*/
public function toArray($flag = self::EXTR_DATA)
{
return match ($flag) {
self::EXTR_BOTH => $this->items,
self::EXTR_PRIORITY => array_map(static fn($item): int => $item['priority'], $this->items),
default => array_map(static fn($item): mixed => $item['data'], $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 class-string<\SplPriorityQueue> $class
* @return $this
*/
public function setInternalQueueClass($class)
{
/** @psalm-suppress RedundantCastGivenDocblockType */
$this->queueClass = (string) $class;
return $this;
}
/**
* Does the queue contain the given datum?
*
* @param TValue $datum
* @return bool
*/
public function contains($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 TPriority $priority
* @return bool
*/
public function hasPriority($priority)
{
foreach ($this->items as $item) {
if ($item['priority'] === $priority) {
return true;
}
}
return false;
}
/**
* Get the inner priority queue instance
*
* @throws Exception\DomainException
* @return \SplPriorityQueue<TPriority, TValue>
* @psalm-assert !null $this->queue
*/
protected function getQueue()
{
if (null === $this->queue) {
/** @psalm-suppress UnsafeInstantiation */
$queue = new $this->queueClass();
/** @psalm-var \SplPriorityQueue<TPriority, TValue> $queue */
$this->queue = $queue;
/** @psalm-suppress DocblockTypeContradiction */
if (! $this->queue instanceof \SplPriorityQueue) {
throw new Exception\DomainException(sprintf(
'PriorityQueue expects an internal queue of type SplPriorityQueue; received "%s"',
$queue::class
));
}
}
return $this->queue;
}
/**
* Add support for deep cloning
*
* @return void
*/
public function __clone()
{
if (null !== $this->queue) {
$this->queue = clone $this->queue;
}
}
}