namespace Store.Management.Framework.Utilities;

/// <summary>按订阅顺序等待异步处理器；异常向调用者传播并停止后续处理。</summary>
public sealed class AsyncEvent<TEventArgs> where TEventArgs : EventArgs
{
	private readonly object _gate = new();
	private readonly List<Func<object?, TEventArgs, Task>> _handlers = [];

	public void Subscribe(Func<object?, TEventArgs, Task> callback)
	{
		ArgumentNullException.ThrowIfNull(callback);
		lock (_gate) { _handlers.Add(callback); }
	}

	public void Unsubscribe(Func<object?, TEventArgs, Task> callback)
	{
		ArgumentNullException.ThrowIfNull(callback);
		lock (_gate)
		{
			int index = _handlers.LastIndexOf(callback);
			if (index >= 0) _handlers.RemoveAt(index);
		}
	}

	public async Task InvokeAsync(object? sender, TEventArgs eventArgs)
	{
		ArgumentNullException.ThrowIfNull(eventArgs);
		Func<object?, TEventArgs, Task>[] snapshot;
		lock (_gate) { snapshot = _handlers.ToArray(); }
		foreach (var callback in snapshot) await callback(sender, eventArgs);
	}
}