// *******************************************************************************
// 
//  *******   ***   ***               *
//     *     *     *                  *
//     *    *      *                *****
//     *    *       ***  *   *   **   *    **    ***
//     *    *          *  * *   *     *   ****  * * *
//     *     *         *   *      *   * * *     * * *
//     *      ***   ***    *     **   **   **   *   *
//                         *
// *******************************************************************************
//  see https://github.com/tgoessler/TCSystemCS for details.
//  Copyright (C) 2003 - 2026 Thomas Goessler. All Rights Reserved.
// *******************************************************************************
// 
//  TCSystem is the legal property of its developers.
//  Please refer to the COPYRIGHT file distributed with this source distribution.
// 
// *******************************************************************************

#region Usings

using System.Threading;
using System.Threading.Tasks;

#endregion

namespace TCSystem.Thread;

internal sealed class AsyncUpdateHelper : IAsyncUpdateHelper
{
#region Public

    public async Task BeginUpdateAsync()
    {
        Interlocked.Increment(ref _numPendingStops);
        Interlocked.Increment(ref _numPendingUpdates);

        await _semaphore.WaitAsync();

        Interlocked.Decrement(ref _numPendingStops);
        Interlocked.Decrement(ref _numPendingUpdates);
    }

    public async Task WaitAsync()
    {
        Interlocked.Increment(ref _numPendingUpdates);

        await _semaphore.WaitAsync();

        Interlocked.Decrement(ref _numPendingUpdates);
    }

    public void EndUpdate()
    {
        _semaphore.Release();
    }

    public bool ShouldStop => Interlocked.Read(ref _numPendingStops) > 0;
    public bool IsUpdatePending => Interlocked.Read(ref _numPendingUpdates) > 0;

#endregion

#region Private

    private long _numPendingStops;
    private long _numPendingUpdates;
    private readonly SemaphoreSlim _semaphore = new(1, 1);

#endregion
}