using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Xunit;
using ytLive.Services;
using ytLive.ViewModels;

namespace ytLive.Tests;

/// <summary>
/// Webcam resource lifecycle, startup slice: the app polls the OS for webcams
/// exactly once at startup and tri-states on the count — none → app runs on,
/// layer inactive, no alarm; exactly one → attempt to allocate and lock it, and a
/// failed lock surfaces a persistent red alert (bottom of the Layers panel) that
/// re-polls and clears itself the moment the camera can be locked again.
/// The multi-camera path (App Settings selector) is a later slice.
/// Real-App + temp-DB + camera-seam pattern (see WebcamMenuGateTests; the camera
/// seams are new — the startup probe must never touch real hardware under test).
/// </summary>
[Collection("RealApp")]
public sealed class WebcamStartupResourceTests
{
    [Fact]
    public void SingleCamera_IsLockedAtStartup_And_AppRunsOn()
    {
        _app.Run(RunSingleLock);
    }

    [Fact]
    public void NoCameras_AppRunsOn_NoLock_NoAlert()
    {
        _app.Run(RunZero);
    }

    [Fact]
    public void SingleCameraLockFails_RedAlertShown_ThenClears_OnceLockSucceeds()
    {
        _app.Run(RunFailThenRecover);
    }

    private readonly RealAppHost _app;

    public WebcamStartupResourceTests(RealAppHost app) => _app = app;

    private void RunSingleLock() => RunWith(sceneBoilerplate: true, cameraCount: 1, failOnStart: false,
        sentinel: (vm, harness) =>
        {
            vm.WebcamStartupValidationTask!.GetAwaiter().GetResult();
            Assert.Null(vm.WebcamLockAlert);
            Assert.Single(harness.Started);
            Assert.Equal("dev1", harness.Started[0]);
            Assert.NotNull(vm.StagedScene);
            Assert.True(vm.CanAddWebcam, "the single camera becomes the app default — the Web Cam layer is offered");
        });

    private void RunZero() => RunWith(sceneBoilerplate: true, cameraCount: 0, failOnStart: false,
        sentinel: (vm, harness) =>
        {
            vm.WebcamStartupValidationTask!.GetAwaiter().GetResult();
            Assert.Null(vm.WebcamLockAlert);
            Assert.Empty(harness.Started);
            Assert.NotNull(vm.StagedScene);
        });

    private void RunFailThenRecover() => RunWith(sceneBoilerplate: true, cameraCount: 1, failOnStart: true,
        sentinel: (vm, harness) =>
        {
            vm.WebcamStartupValidationTask!.GetAwaiter().GetResult();
            Assert.NotNull(vm.WebcamLockAlert);
            Assert.Contains("Web Cam unavailable", vm.WebcamLockAlert);

            harness.FailLock = false;
            vm.RetryWebcamLockCommand.Execute(null);
            vm.ValidateWebcamResourceStartupAsync().GetAwaiter().GetResult();
            Assert.Null(vm.WebcamLockAlert);
            Assert.Contains("dev1", harness.Started);
        });

    private void RunWith(bool sceneBoilerplate, int cameraCount, bool failOnStart,
        Action<MainViewModel, Harness> sentinel)
    {
        var tempDb = Path.Combine(Path.GetTempPath(), $"ytLlive-wcamstart-{Guid.NewGuid():N}.db");
        MainViewModel.LayoutPathOverride = tempDb;
        var harness = new Harness { FailLock = failOnStart };
        MainViewModel.CameraEnumeratorOverride = new FakeEnumerator(cameraCount);
        MainViewModel.CameraFrameSourceFactoryOverride = id => new FakeWebcamSource(id, harness);
        var window = default(MainWindow);
        try
        {
            using (var schema = new ytLive.Services.LayoutStore(tempDb)) { }
            if (sceneBoilerplate) SeedScenes(tempDb);

            window = new MainWindow();
            var vm = (MainViewModel)window.DataContext;
            sentinel(vm, harness);
        }
        finally
        {
            window?.Close();
            MainViewModel.LayoutPathOverride = null;
            MainViewModel.CameraEnumeratorOverride = null;
            MainViewModel.CameraFrameSourceFactoryOverride = null;
            try { File.Delete(tempDb); } catch { /* best-effort cleanup */ }
        }
    }

    private static void SeedScenes(string path)
    {
        using var connection = new Microsoft.Data.Sqlite.SqliteConnection($"Data Source={path}");
        connection.Open();
        var scenes = new[] { "Starting", "Live", "BRB", "Chat", "Ending" };
        for (var i = 0; i < scenes.Length; i++)
        {
            using var cmd = connection.CreateCommand();
            cmd.CommandText =
                "INSERT INTO Scene (Id, Name, HasBackground, SortOrder) VALUES ($id, $name, 1, $order);";
            cmd.Parameters.AddWithValue("$id", $"scene-{scenes[i].ToLowerInvariant()}");
            cmd.Parameters.AddWithValue("$name", scenes[i]);
            cmd.Parameters.AddWithValue("$order", i);
            cmd.ExecuteNonQuery();
        }
    }

    private sealed class Harness
    {
        public bool FailLock;
        public readonly List<string> Started = new();
        public readonly List<string> Stopped = new();
    }

    private sealed class FakeEnumerator : ICameraEnumerator
    {
        private readonly int _count;

        public FakeEnumerator(int count) => _count = count;

        public Task<IReadOnlyList<CameraDeviceInfo>> GetCamerasAsync()
        {
            var list = new List<CameraDeviceInfo>();
            for (var i = 1; i <= _count; i++)
                list.Add(new CameraDeviceInfo($"dev{i}", $"Test Cam {i}"));
            return Task.FromResult<IReadOnlyList<CameraDeviceInfo>>(list);
        }
    }

    private sealed class FakeWebcamSource : ICameraFrameSource
    {
        public string DeviceId { get; }
        private readonly Harness _harness;
        public event Action<VideoFrame>? FrameAvailable;
#pragma warning disable CS0067
        public event Action<string>? SourceFailed;
#pragma warning restore CS0067

        public FakeWebcamSource(string deviceId, Harness harness)
        {
            DeviceId = deviceId;
            _harness = harness;
        }

        public Task StartAsync()
        {
            if (_harness.FailLock) throw new InvalidOperationException("Camera is in use by another app.");
            _harness.Started.Add(DeviceId);
            FrameAvailable?.Invoke(new VideoFrame(2, 2, new byte[16]));
            return Task.CompletedTask;
        }

        public Task StopAsync()
        {
            _harness.Stopped.Add(DeviceId);
            return Task.CompletedTask;
        }
    }
}