/*
 * Copyright (C) 2012-2020 CypherCore <http://github.com/CypherCore>
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

using System.Collections.Generic;
using System.Threading;

namespace Framework.Threading
{
    public class ProducerConsumerQueue<T>
    {
        object _queueLock = new();
        Queue<T> _queue = new();
        volatile bool _shutdown;

        public ProducerConsumerQueue()
        {
            _shutdown = false;
        }

        public void Push(T value)
        {
            lock (_queueLock)
            {
                _queue.Enqueue(value);
                Monitor.PulseAll(_queueLock);
            }
        }

        public bool Empty()
        {
            lock (_queueLock)
                return _queue.Count == 0;
        }

        public bool Pop(out T value)
        {
            value = default;
            lock (_queueLock)
            {
                if (_queue.Count == 0 || _shutdown)
                    return false;

                value = _queue.Dequeue();
                return true;
            }
        }

        public void WaitAndPop(out T value)
        {
            value = default;
            lock (_queueLock)
            {
                while (_queue.Count == 0 && !_shutdown)
                    Monitor.Wait(_queueLock);

                if (_queue.Count == 0 || _shutdown)
                    return;

                value = _queue.Dequeue();
            }
        }

        public void Cancel()
        {
            lock (_queueLock)
            {
                while (_queue.Count != 0)
                {
                    _queue.Dequeue();
                }

                _shutdown = true;
                Monitor.PulseAll(_queueLock);
            }
        }
    }
}