namespace MoShiro.Measurement;

/// <summary>一个运行中的积木：自己的取消令牌和后台任务。拨号方和监听方共用。</summary>
public sealed class RunningBlock : IDisposable
{
    private readonly CancellationTokenSource _cts = new();

    private RunningBlock(IBlock block, string signature)
    {
        Block = block;
        Signature = signature;
        Completion = Task.CompletedTask;
    }

    public IBlock Block { get; }

    /// <summary>参数、端口或流编号变化时调和器据此重启积木。</summary>
    public string Signature { get; }

    /// <summary>积木自己结束（单向数据流的发送端）或失败（<see cref="BlockFaultException"/>）时完成；被 <see cref="StopAsync"/> 停止时正常完成。</summary>
    public Task Completion { get; private set; }

    public static RunningBlock Start(IBlock block, string signature)
    {
        var running = new RunningBlock(block, signature);
        running.Completion = Task.Run(() => block.RunAsync(running._cts.Token), CancellationToken.None);
        return running;
    }

    /// <summary>停止积木并等它退出（最多 5 秒）。</summary>
    public async Task StopAsync()
    {
        await _cts.CancelAsync();
        try
        {
            await Completion.WaitAsync(TimeSpan.FromSeconds(5));
        }
        catch (Exception ex) when (ex is OperationCanceledException or TimeoutException or BlockFaultException)
        {
            // 没有及时退出或者已经失败：不再等
        }

        Dispose();
    }

    public void Dispose() => _cts.Dispose();
}