using AxiOmron.PcbCheck.Models;
using AxiOmron.PcbCheck.Options;
using AxiOmron.PcbCheck.Services.Implementations;
using AxiOmron.PcbCheck.Services.Interfaces;
using AxiOmron.PcbCheck.ViewModels;
using System.Runtime.ExceptionServices;
using System.Windows.Data;
using System.Windows.Threading;
using Xunit;

namespace AxiOmron.PcbCheck.Tests;

/// <summary>
/// 验证系统设置页视图模型中的 SFTP 测试连接行为。
/// </summary>
public sealed class SystemSettingViewModelTests
{
    /// <summary>
    /// 当 SFTP 测试成功时，应更新成功状态文本。
    /// </summary>
    /// <returns>异步测试任务。</returns>
    [Fact]
    public async Task TestSftpConnectionAsync_ShouldReportSuccess_WhenConnectionSucceeds()
    {
        var configService = new FakeAppConfigService();
        var stateStore = new AppStateStore();
        var dispatcherService = new ImmediateDispatcherService();
        var sftpLookupService = new FakeSftpLookupService
        {
            TestOutcome = new SftpConnectionTestOutcome
            {
                IsSuccess = true,
                RootPathAccessible = true,
                StatusMessage = "SFTP 连接成功，根目录可访问。"
            }
        };
        var viewModel = new SystemSettingViewModel(configService, sftpLookupService, stateStore, dispatcherService);

        await viewModel.TestSftpConnectionCommand.ExecuteAsync(null);

        Assert.Equal("SFTP 连接成功，根目录可访问。", viewModel.StatusMessage);
    }

    /// <summary>
    /// 当 SFTP 测试失败时，应将失败原因展示到状态文本。
    /// </summary>
    /// <returns>异步测试任务。</returns>
    [Fact]
    public async Task TestSftpConnectionAsync_ShouldReportFailure_WhenConnectionFails()
    {
        var configService = new FakeAppConfigService();
        var stateStore = new AppStateStore();
        var dispatcherService = new ImmediateDispatcherService();
        var sftpLookupService = new FakeSftpLookupService
        {
            TestOutcome = new SftpConnectionTestOutcome
            {
                IsSuccess = false,
                IsSystemError = true,
                StatusMessage = "SFTP 连接失败: timeout"
            }
        };
        var viewModel = new SystemSettingViewModel(configService, sftpLookupService, stateStore, dispatcherService);

        await viewModel.TestSftpConnectionCommand.ExecuteAsync(null);

        Assert.Equal("SFTP 连接失败: timeout", viewModel.StatusMessage);
    }

    /// <summary>
    /// 当运行态快照包含 PLC 监控项时，应同步到系统设置页监控列表。
    /// </summary>
    [Fact]
    public void Constructor_ShouldLoadPlcMonitorItems_FromStateStoreSnapshot()
    {
        var configService = new FakeAppConfigService();
        var stateStore = new AppStateStore();
        var dispatcherService = new ImmediateDispatcherService();
        stateStore.UpdateSnapshot(snapshot =>
        {
            snapshot.PlcMonitorItems.Add(new PlcMonitorItem
            {
                GroupName = "Inputs",
                Name = "PcbArrived",
                CurrentValue = "True",
                LastUpdatedAt = DateTimeOffset.Now
            });
        });

        var viewModel = new SystemSettingViewModel(configService, new FakeSftpLookupService(), stateStore, dispatcherService);

        Assert.Single(viewModel.PlcMonitorItems);
        Assert.Equal("PcbArrived", viewModel.PlcMonitorItems[0].Name);
    }

    /// <summary>
    /// 当后台线程发布运行态快照时，不应直接在后台线程修改已绑定到 CollectionView 的 PLC 监控集合。
    /// </summary>
    [Fact]
    public void UpdateSnapshot_ShouldNotThrow_WhenSnapshotChangesFromBackgroundThread()
    {
        Exception? backgroundException = RunInSta(() =>
        {
            var configService = new FakeAppConfigService();
            var stateStore = new AppStateStore();
            var dispatcherService = new CapturedDispatcherService(Dispatcher.CurrentDispatcher);
            var viewModel = new SystemSettingViewModel(configService, new FakeSftpLookupService(), stateStore, dispatcherService);
            _ = CollectionViewSource.GetDefaultView(viewModel.PlcMonitorItems);

            Exception? capturedException = null;
            using var completed = new ManualResetEventSlim(false);
            var workerThread = new Thread(() =>
            {
                try
                {
                    stateStore.UpdateSnapshot(snapshot =>
                    {
                        snapshot.PlcMonitorItems.Clear();
                        snapshot.PlcMonitorItems.Add(new PlcMonitorItem
                        {
                            GroupName = "Inputs",
                            Name = "PcbArrived",
                            CurrentValue = "True",
                            LastUpdatedAt = DateTimeOffset.Now
                        });
                    });
                }
                catch (Exception ex)
                {
                    capturedException = ex;
                }
                finally
                {
                    completed.Set();
                }
            });

            workerThread.IsBackground = true;
            workerThread.Start();

            Assert.True(completed.Wait(TimeSpan.FromSeconds(5)), "后台线程未在预期时间内完成快照更新。");
            workerThread.Join();
            PumpDispatcherUntil(() => viewModel.PlcMonitorItems.Count == 1, TimeSpan.FromSeconds(5));
            Assert.Single(viewModel.PlcMonitorItems);
            return capturedException;
        });

        Assert.Null(backgroundException);
    }

    /// <summary>
    /// 当 UI 调度已被取消时，系统设置页的快照事件不应将取消异常继续抛到同步上下文。
    /// </summary>
    [Fact]
    public void SnapshotChanged_ShouldIgnoreCanceledDispatcherTask()
    {
        var configService = new FakeAppConfigService();
        var stateStore = new AppStateStore();
        var viewModel = new SystemSettingViewModel(
            configService,
            new FakeSftpLookupService(),
            stateStore,
            new CanceledDispatcherService());
        var synchronizationContext = new ExceptionCapturingSynchronizationContext();
        SynchronizationContext? originalContext = SynchronizationContext.Current;

        try
        {
            SynchronizationContext.SetSynchronizationContext(synchronizationContext);

            stateStore.UpdateSnapshot(snapshot =>
            {
                snapshot.PlcMonitorItems.Add(new PlcMonitorItem
                {
                    GroupName = "Inputs",
                    Name = "PcbArrived",
                    CurrentValue = "True",
                    LastUpdatedAt = DateTimeOffset.Now
                });
            });

            Assert.Null(synchronizationContext.CapturedException);
            Assert.Empty(viewModel.PlcMonitorItems);
        }
        finally
        {
            SynchronizationContext.SetSynchronizationContext(originalContext);
        }
    }

    /// <summary>
    /// 在 STA 线程中执行指定委托，并将内部异常重新抛回当前测试线程。
    /// </summary>
    /// <typeparam name="T">委托返回值类型。</typeparam>
    /// <param name="action">待执行的委托。</param>
    /// <returns>委托返回结果。</returns>
    /// <exception cref="ArgumentNullException">当 <paramref name="action"/> 为 <see langword="null"/> 时抛出。</exception>
    private static T RunInSta<T>(Func<T> action)
    {
        ArgumentNullException.ThrowIfNull(action);

        T? result = default;
        Exception? capturedException = null;
        using var completed = new ManualResetEventSlim(false);
        var thread = new Thread(() =>
        {
            try
            {
                result = action();
            }
            catch (Exception ex)
            {
                capturedException = ex;
            }
            finally
            {
                completed.Set();
            }
        });

        thread.SetApartmentState(ApartmentState.STA);
        thread.Start();

        Assert.True(completed.Wait(TimeSpan.FromSeconds(5)), "STA 测试线程未在预期时间内完成。");
        thread.Join();

        if (capturedException is not null)
        {
            ExceptionDispatchInfo.Capture(capturedException).Throw();
        }

        return result!;
    }

    /// <summary>
    /// 在当前 STA 线程中循环处理 Dispatcher 队列，直到满足指定条件。
    /// </summary>
    /// <param name="condition">停止等待的条件。</param>
    /// <param name="timeout">最大等待时长。</param>
    /// <exception cref="ArgumentNullException">当 <paramref name="condition"/> 为 <see langword="null"/> 时抛出。</exception>
    /// <exception cref="TimeoutException">当超时仍未满足条件时抛出。</exception>
    private static void PumpDispatcherUntil(Func<bool> condition, TimeSpan timeout)
    {
        ArgumentNullException.ThrowIfNull(condition);

        DateTime deadline = DateTime.UtcNow.Add(timeout);
        while (!condition())
        {
            if (DateTime.UtcNow > deadline)
            {
                throw new TimeoutException("Dispatcher 队列在预期时间内未完成处理。");
            }

            var frame = new DispatcherFrame();
            _ = Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, new DispatcherOperationCallback(_ =>
            {
                frame.Continue = false;
                return null;
            }), null);
            Dispatcher.PushFrame(frame);
        }
    }

    private sealed class FakeAppConfigService : IAppConfigService
    {
        public AppConfig Config { get; } = new();

        public AppConfig Load()
        {
            return Config;
        }

        public void Save(AppConfig config)
        {
            ArgumentNullException.ThrowIfNull(config);
        }

        public string GetConfigPath()
        {
            return "appConfig.json";
        }
    }

    private sealed class FakeSftpLookupService : ISftpLookupService
    {
        public SftpConnectionTestOutcome TestOutcome { get; set; } = new();

        public Task<SftpCheckOutcome> CheckFileAsync(string barcode, CancellationToken cancellationToken)
        {
            throw new NotSupportedException();
        }

        public Task<SftpConnectionTestOutcome> TestConnectionAsync(SftpOptions? options, CancellationToken cancellationToken)
        {
            return Task.FromResult(TestOutcome);
        }
    }

    /// <summary>
    /// 提供立即执行的测试用 Dispatcher，实现与设计时调度一致的同步行为。
    /// </summary>
    private sealed class ImmediateDispatcherService : IDispatcherService
    {
        public Task InvokeAsync(Action action)
        {
            ArgumentNullException.ThrowIfNull(action);
            action();
            return Task.CompletedTask;
        }
    }

    /// <summary>
    /// 捕获 async void 事件处理器回抛到同步上下文中的异常。
    /// </summary>
    private sealed class ExceptionCapturingSynchronizationContext : SynchronizationContext
    {
        /// <summary>
        /// 获取或设置捕获到的异常。
        /// </summary>
        public Exception? CapturedException { get; private set; }

        /// <summary>
        /// 立即执行回调并记录内部异常，避免测试进程直接崩溃。
        /// </summary>
        /// <param name="d">待执行回调。</param>
        /// <param name="state">回调状态。</param>
        public override void Post(SendOrPostCallback d, object? state)
        {
            ArgumentNullException.ThrowIfNull(d);

            try
            {
                d(state);
            }
            catch (Exception ex)
            {
                CapturedException = ex;
            }
        }
    }

    /// <summary>
    /// 提供始终返回已取消任务的测试调度服务，用于模拟应用关闭阶段的 Dispatcher 中止。
    /// </summary>
    private sealed class CanceledDispatcherService : IDispatcherService
    {
        public Task InvokeAsync(Action action)
        {
            ArgumentNullException.ThrowIfNull(action);
            return Task.FromCanceled(new CancellationToken(canceled: true));
        }
    }

    /// <summary>
    /// 提供绑定到指定 Dispatcher 的测试调度服务，用于验证跨线程回切行为。
    /// </summary>
    private sealed class CapturedDispatcherService : IDispatcherService
    {
        private readonly Dispatcher _dispatcher;

        public CapturedDispatcherService(Dispatcher dispatcher)
        {
            _dispatcher = dispatcher ?? throw new ArgumentNullException(nameof(dispatcher));
        }

        public Task InvokeAsync(Action action)
        {
            ArgumentNullException.ThrowIfNull(action);
            return _dispatcher.InvokeAsync(action).Task;
        }
    }
}