cozylife/hackfastalgos

<?HH
/**
 * Hack Fast Algos
 *
 * Implementation of a queue
 * @Learn more @link https://en.wikipedia.org/wiki/Queue_(abstract_data_type)
 */

namespace HackFastAlgos\DataStructure;

class QueueEmptyException extends \Exception{}

class Queue implements \Countable
{
    private array $queueData = [];
    private int $count = 0;

    public function count() : int
    {
        return $this->count;
    }

    public function enqueue<T>(T $item)
    {
        $this->queueData[] = $item;
        $this->count++;
    }

    public function dequeue<T>() : T
    {
        $this->throwIfEmptyQueue();
        $item = array_shift($this->queueData);
        $this->count--;
        return $item;
    }

    public function manuallyDequeue<T>() : T
    {
        $this->throwIfEmptyQueue();

        $count = count($this->queueData);
        $first = array_key_exists(0, $this->queueData) ? $this->queueData[0] : null;

        // Re-index the queue
        $k = 0;
        $newQueue = [];
        for ($i = 1; $i < $count; $i++) {
            $newQueue[$k++] = $this->queueData[$i];
        }

        $this->queueData = $newQueue;
        return $first;
    }

    private function throwIfEmptyQueue()
    {
        if (empty($this->queueData)) {
            throw new QueueEmptyException();
        }
    }
}