using System.Threading;

namespace SimpleAdmin.Application;

/// <summary>
/// 使同一异步调用链可重入，独立请求仍须取得外部互斥锁。
/// 不在 Acquire 中设置 AsyncLocal，避免值不能流回调用方的问题。
/// </summary>
internal static class OnboardingOperationGate
{
    private sealed record Frame(string Key, Frame Parent);
    private static readonly AsyncLocal<Frame> Held = new();

    internal static async Task<T> Run<T>(
        string key,
        Func<Task<IAsyncDisposable>> acquire,
        Func<Task<T>> action)
    {
        for (var frame = Held.Value; frame != null; frame = frame.Parent)
            if (frame.Key == key)
                return await action();

        await using var lease = await acquire();
        var previous = Held.Value;
        Held.Value = new Frame(key, previous);
        try
        {
            return await action();
        }
        finally
        {
            Held.Value = previous;
        }
    }
}