namespace Fleet.Hosting;

/// <summary>
/// 当前生效的定时重启：节点本地的设置优先；本地没有写时用面板下发的，面板改了之后立即重新排下一次，不需要重启进程。
/// </summary>
public sealed class RestartController : IDisposable
{
    private readonly RestartSchedule? _local;
    private readonly object _gate = new();
    private RestartSchedule? _remote;
    private readonly CancellationTokenSource _now = new();
    private CancellationTokenSource _changed = new();
    private string? _nowReason;

    public RestartController(RestartSchedule? local = null)
    {
        _local = local;
    }

    /// <summary>本地有设置时为 true：面板下发的不生效。</summary>
    public bool IsLocal => _local is not null;

    public RestartSchedule? Current
    {
        get
        {
            lock (_gate)
            {
                return _local ?? _remote;
            }
        }
    }

    /// <summary>当前设置被改动时会被取消的令牌；先取令牌、再取 <see cref="Current"/>，就不会漏掉中间的改动。</summary>
    public CancellationToken ChangeToken
    {
        get
        {
            lock (_gate)
            {
                return _changed.Token;
            }
        }
    }

    /// <summary>应用要求现在就有序退出（比如管理员请求更新）；退出的原因，没有就是 null。</summary>
    public string? NowReason
    {
        get
        {
            lock (_gate)
            {
                return _nowReason;
            }
        }
    }

    /// <summary>应用要求现在就退出的令牌。</summary>
    public CancellationToken NowToken => _now.Token;

    /// <summary>要求进程现在就有序退出，由服务管理器拉起；不管有没有设置定时重启。</summary>
    public void RequestNow(string reason)
    {
        lock (_gate)
        {
            _nowReason ??= reason;
        }

        _now.Cancel();
    }

    /// <summary>面板下发的设置；为空表示面板关闭了定时重启。返回 false 表示文本不合法（节点忽略它）。</summary>
    public bool SetRemote(string? text)
    {
        RestartSchedule? schedule = null;
        if (!string.IsNullOrWhiteSpace(text) && !RestartSchedule.TryParse(text, out schedule))
        {
            return false;
        }

        CancellationTokenSource previous;
        lock (_gate)
        {
            _remote = schedule;
            previous = _changed;
            _changed = new CancellationTokenSource();
        }

        previous.Cancel();
        previous.Dispose();
        return true;
    }

    public void Dispose()
    {
        lock (_gate)
        {
            _changed.Dispose();
            _now.Dispose();
        }
    }
}