using Serilog;
using ApplicationException = System.ApplicationException;
using TaskExtensions = MesETL.Shared.Helper.TaskExtensions;

namespace MesETL.App.Services;

/// <summary>
/// 快速批量创建和等待任务
/// </summary>
public class TaskManager
{
    private int _runningTaskCount;

    public int RunningTaskCount => _runningTaskCount;
    public int MaxTaskCount { get; }

    public event Action<Exception>? OnException;
    public event Action? OnTaskCompleteSuccessfully;

    public TaskManager(int maxTaskCount)
    {
        MaxTaskCount = maxTaskCount;
    }

    public async ValueTask<Task> CreateTaskAsync(Func<Task> func, CancellationToken cancellationToken = default)
    {
        await TaskExtensions.WaitUntil(() => _runningTaskCount < MaxTaskCount, 25, cancellationToken);
        return RunTask(func, cancellationToken);
    }

    public async ValueTask<Task> CreateTaskAsync(Func<object?, Task> func, object? arg, CancellationToken ct = default)
    {
        await TaskExtensions.WaitUntil(() => _runningTaskCount < MaxTaskCount, 25, ct);
        return RunTaskNoClosure(func, arg, ct);
    }
    
    private Task RunTask(Func<Task> func, CancellationToken cancellationToken = default)
    {
        var task = Task.Run(async () =>
        {
            // Log.Logger.Verbose("[任务管理器] 新的任务已创建");
            Interlocked.Increment(ref _runningTaskCount);
            try
            {
                await func();
                OnTaskCompleteSuccessfully?.Invoke();
            }
            catch(Exception ex)
            {
                OnException?.Invoke(ex);
                Log.Logger.Error(ex, "[任务管理器] 执行任务时出错");
            }
            finally
            {
                Interlocked.Decrement(ref _runningTaskCount);
            }
        }, cancellationToken);
        return task;
    }

    private Task RunTaskNoClosure(Func<object?, Task> func, object? arg, CancellationToken cancellationToken = default)
    {
        var task = Task.Factory.StartNew(async obj => // 性能考虑，这个lambda中不要捕获任何外部变量!
        {
            // Log.Logger.Verbose("[任务管理器] 新的任务已创建");
            if (obj is not Tuple<Func<object?, Task>, object?> tuple)
                throw new ApplicationException("这个异常不该出现");
            Interlocked.Increment(ref _runningTaskCount);
            try
            {
                await tuple.Item1(tuple.Item2);
                OnTaskCompleteSuccessfully?.Invoke();
            }
            catch(Exception ex)
            {
                OnException?.Invoke(ex);
                Log.Logger.Error(ex, "[任务管理器] 执行任务时出错");
            }
            finally
            {
                Interlocked.Decrement(ref _runningTaskCount);
            }
        }, Tuple.Create(func, arg), cancellationToken).Unwrap();
        return task;
    }
}