using System.Runtime.InteropServices;
using NewLife.Log;

namespace NewLife.Model;

/// <summary>轻量级主机服务</summary>
/// <remarks>
/// 文档 https://newlifex.com/core/host
/// </remarks>
public interface IHostedService
{
    /// <summary>开始服务</summary>
    /// <param name="cancellationToken"></param>
    /// <returns></returns>
    Task StartAsync(CancellationToken cancellationToken);

    /// <summary>停止服务</summary>
    /// <param name="cancellationToken"></param>
    /// <returns></returns>
    Task StopAsync(CancellationToken cancellationToken);
}

/// <summary>主机服务扩展</summary>
public static class HostedServiceExtensions
{
    /// <summary>注册主机服务，在主机启动和停止时执行</summary>
    /// <typeparam name="THostedService"></typeparam>
    /// <param name="services"></param>
    /// <returns></returns>
    public static IObjectContainer AddHostedService<THostedService>(this IObjectContainer services) where THostedService : class, IHostedService
    {
        services.AddSingleton<IHostedService, THostedService>();

        return services;
    }

    /// <summary>注册主机服务，在主机启动和停止时执行</summary>
    /// <typeparam name="THostedService"></typeparam>
    /// <param name="services"></param>
    /// <param name="implementationFactory"></param>
    /// <returns></returns>
    public static IObjectContainer AddHostedService<THostedService>(this IObjectContainer services, Func<IServiceProvider, THostedService> implementationFactory) where THostedService : class, IHostedService
    {
        services.AddSingleton<IHostedService>(implementationFactory);

        return services;
    }
}

/// <summary>轻量级应用主机</summary>
/// <remarks>
/// 文档 https://newlifex.com/core/host
/// 销毁主机时，会触发所有服务的停止事件
/// </remarks>
public interface IHost
{
    /// <summary>添加服务</summary>
    /// <param name="service"></param>
    void Add(IHostedService service);

    /// <summary>添加服务</summary>
    /// <typeparam name="TService"></typeparam>
    void Add<TService>() where TService : class, IHostedService;

    /// <summary>同步运行，大循环阻塞</summary>
    void Run();

    /// <summary>异步允许，大循环阻塞</summary>
    /// <returns></returns>
    Task RunAsync();

    /// <summary>关闭主机</summary>
    /// <param name="reason"></param>
    void Close(String? reason);
}

/// <summary>轻量级应用主机</summary>
/// <remarks>
/// 文档 https://newlifex.com/core/host
/// 销毁主机时，会触发所有服务的停止事件
/// </remarks>
public class Host : DisposeBase, IHost
{
    #region 属性
    /// <summary>服务提供者</summary>
    public IServiceProvider ServiceProvider { get; set; }

    //private readonly IList<Type> _serviceTypes = new List<Type>();
    /// <summary>服务集合</summary>
    public IList<IHostedService> Services { get; } = [];
    #endregion

    #region 构造
    static Host()
    {
        AppDomain.CurrentDomain.ProcessExit += OnExit;
        Console.CancelKeyPress += OnExit;
#if NETCOREAPP
        System.Runtime.Loader.AssemblyLoadContext.Default.Unloading += ctx => OnExit(ctx, EventArgs.Empty);
#endif
#if NET6_0_OR_GREATER
        PosixSignalRegistration.Create(PosixSignal.SIGINT, ctx => OnExit(ctx.Signal + "", EventArgs.Empty));
        PosixSignalRegistration.Create(PosixSignal.SIGQUIT, ctx => OnExit(ctx.Signal + "", EventArgs.Empty));
        PosixSignalRegistration.Create(PosixSignal.SIGTERM, ctx => OnExit(ctx.Signal + "", EventArgs.Empty));
#endif
    }

    /// <summary>通过制定服务提供者来实例化一个应用主机</summary>
    /// <param name="serviceProvider"></param>
    public Host(IServiceProvider serviceProvider) => ServiceProvider = serviceProvider;

    /// <summary>销毁</summary>
    /// <param name="disposing"></param>
    protected override void Dispose(Boolean disposing)
    {
        base.Dispose(disposing);

        //_life?.TrySetResult(0);
        Close(disposing ? "Dispose" : "GC");
    }
    #endregion

    #region 服务集合
    /// <summary>添加服务</summary>
    /// <typeparam name="TService"></typeparam>
    public void Add<TService>() where TService : class, IHostedService
    {
        //var type = typeof(TService);
        //_serviceTypes.Add(type);

        // 把服务类型注册到容器中，以便后续获取
        var ioc = (ServiceProvider as ServiceProvider)?.Container ?? ObjectContainer.Current;
        //ioc.TryAddTransient(type, type);
        ioc.AddHostedService<TService>();
    }

    /// <summary>添加服务</summary>
    /// <param name="service"></param>
    public void Add(IHostedService service) => Services.Add(service);
    #endregion

    #region 开始停止
    /// <summary>开始</summary>
    /// <param name="cancellationToken"></param>
    /// <returns></returns>
    public async Task StartAsync(CancellationToken cancellationToken)
    {
        // 从容器中获取所有服务。此时服务是倒序，需要反转
        var svcs = new List<IHostedService>();
        foreach (var item in ServiceProvider.GetServices<IHostedService>())
        {
            svcs.Add(item);
        }
        svcs.Reverse();
        foreach (var item in svcs)
        {
            Services.Add(item);
        }

        //// 从容器中获取所有服务
        //foreach (var item in _serviceTypes)
        //{
        //    if (ServiceProvider.GetService(item) is IHostedService service) Services.Add(service);
        //}

        // 开始所有服务，任意服务出错都导致启动失败
        foreach (var item in Services)
        {
            await item.StartAsync(cancellationToken).ConfigureAwait(false);
        }
    }

    /// <summary>停止</summary>
    /// <param name="cancellationToken"></param>
    /// <returns></returns>
    public async Task StopAsync(CancellationToken cancellationToken)
    {
        foreach (var item in Services)
        {
            try
            {
                await item.StopAsync(cancellationToken).ConfigureAwait(false);
            }
            catch (Exception ex)
            {
                XTrace.WriteException(ex);
            }
        }
    }
    #endregion

    #region 运行大循环
    private TaskCompletionSource<Object>? _life;
    /// <summary>同步运行，大循环阻塞</summary>
    public void Run() => RunAsync().GetAwaiter().GetResult();

    /// <summary>异步允许，大循环阻塞</summary>
    /// <returns></returns>
    public async Task RunAsync()
    {
        XTrace.WriteLine("Starting......");

        using var source = new CancellationTokenSource();

        _life = new TaskCompletionSource<Object>();

        RegisterExit((s, e) => Close(s?.GetType().Name));

        await StartAsync(source.Token);
        XTrace.WriteLine("Application started. Press Ctrl+C to shut down.");

        await _life.Task;

        XTrace.WriteLine("Application is shutting down...");

        await StopAsync(source.Token);

        XTrace.WriteLine("Stopped!");
    }

    /// <summary>关闭主机</summary>
    /// <param name="reason"></param>
    public void Close(String? reason)
    {
        XTrace.WriteLine("Application closed. {0}", reason);

        _life?.TrySetResult(0);
    }
    #endregion

    #region 退出事件
    private static readonly List<EventHandler> _events = [];
    private static readonly List<Action> _events2 = [];
    private static Int32 _exited;
    /// <summary>注册应用退出事件</summary>
    /// <remarks>在不同场景可能被多次执行，调用方需要做判断</remarks>
    /// <param name="onExit">回调函数</param>
    public static void RegisterExit(EventHandler onExit) => _events.Add(onExit);

    /// <summary>注册应用退出事件。仅执行一次</summary>
    /// <param name="onExit">回调函数</param>
    public static void RegisterExit(Action onExit) => _events2.Add(onExit);

    private static void OnExit(Object? sender, EventArgs e)
    {
        foreach (var item in _events)
        {
            try
            {
                item(sender, e);
            }
            catch (Exception ex)
            {
                XTrace.WriteException(ex);
            }
        }

        // 只执行一次
        if (Interlocked.Increment(ref _exited) > 1) return;

        foreach (var item in _events2)
        {
            try
            {
                item();
            }
            catch (Exception ex)
            {
                XTrace.WriteException(ex);
            }
        }
    }
    #endregion
}

/// <summary>后台任务</summary>
/// <remarks>
/// 文档 https://newlifex.com/core/host
/// </remarks>
public abstract class BackgroundService : IHostedService, IDisposable
{
    private Task? _executingTask;

    private CancellationTokenSource? _stoppingCts;

    /// <summary>执行</summary>
    /// <param name="stoppingToken"></param>
    /// <returns></returns>
    protected abstract Task ExecuteAsync(CancellationToken stoppingToken);

    /// <summary>开始</summary>
    /// <param name="cancellationToken"></param>
    /// <returns></returns>
    public virtual Task StartAsync(CancellationToken cancellationToken)
    {
        _stoppingCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
        _executingTask = ExecuteAsync(_stoppingCts.Token);
#if NET45
        return _executingTask.IsCompleted ? _executingTask : Task.FromResult(0);
#else
        return _executingTask.IsCompleted ? _executingTask : Task.CompletedTask;
#endif
    }

    /// <summary>停止</summary>
    /// <param name="cancellationToken"></param>
    /// <returns></returns>
    public virtual async Task StopAsync(CancellationToken cancellationToken)
    {
        if (_executingTask != null)
        {
            try
            {
                _stoppingCts?.Cancel();
            }
            finally
            {
                await Task.WhenAny(_executingTask, Task.Delay(-1, cancellationToken)).ConfigureAwait(continueOnCapturedContext: false);
            }
        }
    }

    /// <summary>销毁</summary>
    public virtual void Dispose() => _stoppingCts?.Cancel();
}