BackgroundTaskQueue.cs

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.

using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;

namespace WeChatAdapter;

public class BackgroundTaskQueue : IBackgroundTaskQueue, IDisposable
{
    private readonly ConcurrentQueue<Func<CancellationToken, Task>> _workItems = new ConcurrentQueue<Func<CancellationToken, Task>>();
    private SemaphoreSlim? _signal = new SemaphoreSlim(0);

    /// <summary>
    /// Queue a Task to background task queue.
    /// </summary>
    /// <param name="workItem">The work func need to be queued.</param>
    public void QueueBackgroundWorkItem(Func<CancellationToken, Task> workItem)
    {
        if (workItem == null)
        {
            throw new ArgumentNullException(nameof(workItem));
        }

        _workItems.Enqueue(workItem);
        _signal!.Release();
    }

    /// <summary>
    /// Dequeue a Task in background task queue.
    /// </summary>
    /// <param name="token">The work func need to be queued.</param>
    /// <returns>A <see cref="Task"/> representing the dequeue operation.</returns>
    public async Task<Func<CancellationToken, Task>> DequeueAsync(CancellationToken token)
    {
        await _signal!.WaitAsync(token).ConfigureAwait(false);
        
        _workItems.TryDequeue(out var workItem);

        return workItem!;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (disposing)
        {
            // free managed resources
            if (_signal != null)
            {
                _signal.Dispose();
                _signal = null;
            }
        }
    }
}