using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Threading;
using Microsoft.Data.Sqlite;
using Xunit;
using ytLive.Helpers;
using ytLive.Models;
using ytLive.Services;
using ytLive.ViewModels;

namespace ytLive.Tests;

/// <summary>
/// Layer-list drag-to-reorder: the code-behind reorders StagedScene.Elements
/// directly (RemoveAt/Insert), bypassing SceneGraph's mutation surface, so the
/// drop must be trapped as a data change and persisted. Real-App + temp-DB
/// pattern (see WebcamOutputKeyTests); reuses the exact code-behind mutation and
/// asserts the new order AND each layer's geometry (preview layout) are written
/// to the DB — immediately at drop, no debounce window.
/// </summary>
[Collection("RealApp")]
public sealed class LayerReorderPersistenceTests
{
    private readonly RealAppHost _app;

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

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

    /// <summary>
    /// The user's reproduced bug: dragging a layer BELOW the webcam and relaunching
    /// reverted the order. Root cause: Sources and WebcamSceneConfigs each carried
    /// their OWN per-type SortOrder and load appended all Sources before all
    /// configs — a webcam slotted between sources was structurally unrecoverable.
    /// Save now stamps BOTH tables from one shared z-space (the element's index
    /// within scene.Elements); load merges the two lists on that shared z. This
    /// test seeds the real Live layout (sources + HD Pro Webcam C920), physically
    /// reorders "Web Resource-0" down below the webcam, then fresh-loads a NEW
    /// LayoutStore from the same DB — the restart — and asserts the order holds.
    /// </summary>
    [Fact]
    public void CrossTypeReorder_BelowTheWebcam_SurvivesFreshReload()
    {
        _app.Run(RunCrossTypeReload);
    }

    /// <summary>
    /// Same use case as above but driven with REAL injected mouse input
    /// (SetCursorPos + mouse_event against the desktop) so the actual
    /// List_PreviewMouseLeftButtonDown/Move/Up handlers — the seam no synthetic
    /// event can exercise, since e.GetPosition reads the physical cursor — must
    /// run. Requires an interactive desktop session: if the window is covered or
    /// the session is locked, the pointer no-ops and the drag never lands.
    /// </summary>
    [Fact]
    public void RealMouseDrag_OnTheLayerList_PersistsTheReorder()
    {
        _app.Run(RunRealDrag);
    }

    private void RunRealDrag()
    {
        var tempDb = Path.Combine(Path.GetTempPath(), $"ytLlive-realdrag-{Guid.NewGuid():N}.db");
        MainViewModel.LayoutPathOverride = tempDb;
        var window = default(MainWindow);
        try
        {
            using (var schema = new LayoutStore(tempDb)) { }
            SqliteConnection.ClearAllPools();
            SeedThreeLayers(tempDb);

            window = new MainWindow();
            var vm = (MainViewModel)window.DataContext;
            vm.StagedScene = vm.Scenes.Single(s => SceneCatalog.Is(s.Name, SceneCatalog.Live));
            Assert.True(vm.StagedScene!.Elements.OfType<Source>().Count() >= 4,
                "3 seeded layers + the healed Background must load");

            window.Show();
            window.Activate();
            window.Topmost = true;
            window.UpdateLayout();

            var panel = (UserControl)window.FindName("LeftPanel")!;
            var list = (FocusPreservingListBox)panel.FindName("SourceList")!;
            list.UpdateLayout();

            // Elements = [Background, ImgA, ImgB, ImgC]. Physically drag ImgC
            // (row 3) up onto ImgA (row 1): the handlers reorder live elements to
            // [Background, ImgC, ImgA, ImgB] and EndListDrag must persist that.
            var from = RowScreenPoint(list, 3);
            var to = RowScreenPoint(list, 1);

            SetCursorPos((int)from.X, (int)from.Y);
            LetInputSettle(80);
            mouse_event(MOUSEEVENTF_LEFTDOWN, 0, 0, 0, UIntPtr.Zero);
            LetInputSettle(120);
            SetCursorPos((int)to.X, (int)to.Y);
            LetInputSettle(250);
            mouse_event(MOUSEEVENTF_LEFTUP, 0, 0, 0, UIntPtr.Zero);
            LetInputSettle(400);

            var expected = vm.StagedScene.Elements.OfType<Source>().Select(s => s.Name).ToArray();
            Assert.Equal("Background", expected[0]);
            Assert.Equal("ImgC", expected[1]);

            Assert.True(PumpUntil(() => SourceNamesInDb(tempDb).SequenceEqual(expected),
                    TimeSpan.FromSeconds(10)),
                "a real mouse drag-and-drop must be persisted by the background save");
            Assert.Equal(expected, SourceNamesInDb(tempDb));

            // The same drop must persist the PREVIEW LAYOUT too — each layer's
            // geometry (X/Y/W/H) rides in the same Source rows as the SortOrder.
            var dragged = vm.StagedScene.Elements.OfType<Source>().Single(s => s.Name == "ImgC");
            Assert.Equal((dragged.X, dragged.Y, dragged.Width, dragged.Height),
                GeometryInDb(tempDb, "ImgC"));
        }
        finally
        {
            if (window != null) window.Close();
            MainViewModel.LayoutPathOverride = null;
            SqliteConnection.ClearAllPools();
            try { File.Delete(tempDb); } catch { /* best-effort cleanup */ }
        }
    }

    /// <summary>Screen (device-pixel) point one-third into the list row — over the
    /// name TextBlock, away from the per-row buttons/rename TextBox.</summary>
    private static Point RowScreenPoint(FocusPreservingListBox list, int index)
    {
        var item = (ListBoxItem)list.ItemContainerGenerator.ContainerFromIndex(index)!;
        var inList = item.TransformToVisual(list)
            .Transform(new Point(Math.Min(30, item.ActualWidth - 12), item.ActualHeight / 2));
        return list.PointToScreen(inList);
    }

    /// <summary>Pumps the app dispatcher while sleeping in small steps, so real
    /// input messages posted to the thread queue are processed mid-gesture.</summary>
    private static void LetInputSettle(int milliseconds)
    {
        var frame = new DispatcherFrame();
        var timer = new DispatcherTimer { Interval = TimeSpan.FromMilliseconds(milliseconds) };
        timer.Tick += (_, _) =>
        {
            timer.Stop();
            frame.Continue = false;
        };
        timer.Start();
        Dispatcher.PushFrame(frame);
    }

    private const uint MOUSEEVENTF_LEFTDOWN = 0x0002;
    private const uint MOUSEEVENTF_LEFTUP = 0x0004;

    [DllImport("user32.dll")]
    private static extern bool SetCursorPos(int x, int y);

    [DllImport("user32.dll")]
    private static extern void mouse_event(uint dwFlags, uint dx, uint dy, uint dwData, UIntPtr dwExtraInfo);

    private void Run()
    {
        var tempDb = Path.Combine(Path.GetTempPath(), $"ytLlive-reorder-{Guid.NewGuid():N}.db");
        MainViewModel.LayoutPathOverride = tempDb;
        var window = default(MainWindow);
        try
        {
            using (var schema = new LayoutStore(tempDb)) { }
            SqliteConnection.ClearAllPools();
            SeedThreeLayers(tempDb);

            window = new MainWindow();
            var vm = (MainViewModel)window.DataContext;
            vm.StagedScene = vm.Scenes.Single(s => SceneCatalog.Is(s.Name, SceneCatalog.Live));
            Assert.True(vm.StagedScene!.Elements.OfType<Source>().Count() >= 4,
                "3 seeded layers + the healed Background must load");

            // Mirrors Controls/LeftPanel.List_PreviewMouseMove: drag the last layer
            // to the front of the user layers (the healed Background stays pinned
            // at index 0, so index 1 is the first user layer).
            var elements = vm.StagedScene.Elements;
            var dragged = elements[^1];
            elements.RemoveAt(elements.Count - 1);
            elements.Insert(1, dragged);
            var expected = vm.StagedScene.Elements.OfType<Source>().Select(s => s.Name).ToArray();

            vm.OnSceneElementsReordered();

            Assert.True(PumpUntil(() => SourceNamesInDb(tempDb).SequenceEqual(expected),
                    TimeSpan.FromSeconds(10)),
                "the drag reorder must be persisted at drop (immediate save)");
            Assert.Equal(expected, SourceNamesInDb(tempDb));

            // The drop must persist the dragged layer's PREVIEW LAYOUT too — its
            // X/Y/W/H ride in the same Source row, so one immediate save covers
            // both the new layer list and the preview geometry.
            var draggedSource = vm.StagedScene.Elements.OfType<Source>().Single(s => s.Name == dragged.Name);
            Assert.Equal((draggedSource.X, draggedSource.Y, draggedSource.Width, draggedSource.Height),
                GeometryInDb(tempDb, dragged.Name));
        }
        finally
        {
            if (window != null) window.Close();
            MainViewModel.LayoutPathOverride = null;
            SqliteConnection.ClearAllPools();
            try { File.Delete(tempDb); } catch { /* best-effort cleanup */ }
        }
    }

    private void RunCrossTypeReload()
    {
        var tempDb = Path.Combine(Path.GetTempPath(), $"ytLlive-crosstype-{Guid.NewGuid():N}.db");
        MainViewModel.LayoutPathOverride = tempDb;
        var window = default(MainWindow);
        try
        {
            using (var schema = new LayoutStore(tempDb)) { }
            SqliteConnection.ClearAllPools();
            SeedLiveSceneWithWebcam(tempDb);

            window = new MainWindow();
            var vm = (MainViewModel)window.DataContext;
            vm.StagedScene = vm.Scenes.Single(s => SceneCatalog.Is(s.Name, SceneCatalog.Live));

            // The saved architecture (live scene = Background + YouTube Chat +
            // Image + Web Resource-0 sources, plus the HD Pro Webcam C920 config
            // row) plus the healed background.
            Assert.True(vm.StagedScene!.Elements.OfType<Source>().Count() >= 4,
                "seeded sources + healed Background must load");

            // Mirror the user's repro: drag "Web Resource-0" DOWN below the webcam.
            var elements = vm.StagedScene.Elements;
            var webcam = elements.OfType<WebcamSceneConfig>().Single();
            var dragged = elements.OfType<Source>().Single(s => s.Name == "Web Resource-0");
            var from = elements.IndexOf(dragged);
            elements.RemoveAt(from);
            elements.Insert(elements.IndexOf(webcam) + 1, dragged);

            var expected = elements.Select(e => e.Name).ToArray();

            vm.OnSceneElementsReordered();

            // Restart: a brand-new LayoutStore reading the same DB must restore
            // the cross-type order exactly — webcam between Image and Web
            // Resource-0, not appended after all sources.
            Assert.True(PumpUntil(() =>
                    TryReadSceneOrder(tempDb, out var names) && names.SequenceEqual(expected),
                    TimeSpan.FromSeconds(10)),
                "the webcam-between-sources order must survive a fresh reload");
        }
        finally
        {
            if (window != null) window.Close();
            MainViewModel.LayoutPathOverride = null;
            SqliteConnection.ClearAllPools();
            try { File.Delete(tempDb); } catch { /* best-effort cleanup */ }
        }
    }

    /// <summary>Reads one scene's element order from a FRESH store, both tables
    /// merged on the shared z. False on lock/timeout (save mid-transaction).</summary>
    private static bool TryReadSceneOrder(string path, out string[] names)
    {
        try
        {
            using var store = new LayoutStore(path);
            var scene = store.Load().Single(s => SceneCatalog.Is(s.Name, SceneCatalog.Live));
            names = scene.Elements.Select(e => e.Name).ToArray();
            return true;
        }
        catch (SqliteException)
        {
            names = [];
            return false;
        }
    }

    /// <summary>Seeds the user's real Live layout: Background, YouTube Chat,
    /// Image, Web Resource-0 Source rows + a Webcam row and its config.</summary>
    private static void SeedLiveSceneWithWebcam(string path)
    {
        var scenes = new (string Id, string Name)[]
        {
            ("scene-starting", "Starting"),
            ("scene-live", "Live"),
            ("scene-brb", "BRB"),
            ("scene-chat", "Chat"),
            ("scene-ending", "Ending"),
        };

        var sources = new (string Id, string Type, string Name, int Sort)[]
        {
            ("bg-live", "DisplayCapture", "Background", 0),
            ("chat-live", "ChatBox", "YouTube Chat", 1),
            ("img-live", "Image", "Image", 2),
            ("web-live", "WebSource", "Web Resource-0", 3),
        };

        using var connection = new SqliteConnection($"Data Source={path}");
        connection.Open();

        foreach (var (id, name) in scenes)
        {
            using var cmd = connection.CreateCommand();
            cmd.CommandText = "INSERT INTO Scene (Id, Name, HasBackground, SortOrder) VALUES ($id, $name, 1, $order);";
            cmd.Parameters.AddWithValue("$id", id);
            cmd.Parameters.AddWithValue("$name", name);
            cmd.Parameters.AddWithValue("$order", Array.IndexOf(scenes, (id, name)));
            cmd.ExecuteNonQuery();
        }

        using (var source = connection.CreateCommand())
        {
            source.CommandText =
                @"INSERT INTO Source (Id, SceneId, Type, Name, IsEnabled, Width, Height, IsBackground, SortOrder)
                  VALUES ($id, 'scene-live', $type, $name, 1, 640, 480, $bg, $sort);";
            var idP = source.Parameters.Add("$id", SqliteType.Text);
            var typeP = source.Parameters.Add("$type", SqliteType.Text);
            var nameP = source.Parameters.Add("$name", SqliteType.Text);
            var bgP = source.Parameters.Add("$bg", SqliteType.Integer);
            var sortP = source.Parameters.Add("$sort", SqliteType.Integer);
            foreach (var (id, type, name, sort) in sources)
            {
                idP.Value = id;
                typeP.Value = type;
                nameP.Value = name;
                bgP.Value = name == "Background" ? 1 : 0;
                sortP.Value = sort;
                source.ExecuteNonQuery();
            }
        }

        using (var webcam = connection.CreateCommand())
        {
            webcam.CommandText = "INSERT INTO Webcam (Id, DeviceId, Name) VALUES ('wid-live', 'dev-physical-9', 'HD Pro Webcam C920');";
            webcam.ExecuteNonQuery();
        }

        using (var config = connection.CreateCommand())
        {
            config.CommandText =
                @"INSERT INTO WebcamSceneConfig
                  (SceneId, WebcamId, IsVisible, X, Y, Width, Height, Opacity, SortOrder)
                  VALUES ('scene-live', 'wid-live', 1, 100, 100, 480, 270, 1, 0);";
            config.ExecuteNonQuery();
        }
    }

    /// <summary>Pumps the app dispatcher (so the VM's debounce timer fires) until
    /// <paramref name="isDone"/> or the deadline passes. True when the condition
    /// became true, false on deadline.</summary>
    private static bool PumpUntil(Func<bool> isDone, TimeSpan timeout)
    {
        var frame = new DispatcherFrame();
        var poll = new DispatcherTimer { Interval = TimeSpan.FromMilliseconds(100) };
        var deadline = DateTime.UtcNow + timeout;
        poll.Tick += (_, _) =>
        {
            if (isDone() || DateTime.UtcNow >= deadline)
            {
                poll.Stop();
                frame.Continue = false;
            }
        };
        poll.Start();
        Dispatcher.PushFrame(frame);
        return isDone();
    }

    private static string[] SourceNamesInDb(string path)
    {
        try
        {
            using var connection = new SqliteConnection($"Data Source={path}");
            connection.Open();
            using var cmd = connection.CreateCommand();
            cmd.CommandText = "SELECT Name FROM Source WHERE SceneId = 'scene-live' ORDER BY SortOrder;";
            using var reader = cmd.ExecuteReader();
            var names = new List<string>();
            while (reader.Read()) names.Add(reader.GetString(0));
            return names.ToArray();
        }
        catch (SqliteException)
        {
            // The save may hold the write lock mid-transaction — not yet.
            return [];
        }
    }

    private static (double X, double Y, double Width, double Height) GeometryInDb(string path, string name)
    {
        try
        {
            using var connection = new SqliteConnection($"Data Source={path}");
            connection.Open();
            using var cmd = connection.CreateCommand();
            cmd.CommandText = "SELECT X, Y, Width, Height FROM Source WHERE SceneId = 'scene-live' AND Name = $name;";
            cmd.Parameters.AddWithValue("$name", name);
            using var reader = cmd.ExecuteReader();
            reader.Read();
            return (reader.GetDouble(0), reader.GetDouble(1), reader.GetDouble(2), reader.GetDouble(3));
        }
        catch (SqliteException)
        {
            // The save may hold the write lock mid-transaction — not yet.
            return (double.NaN, double.NaN, double.NaN, double.NaN);
        }
    }

    private static void SeedThreeLayers(string path)
    {
        using var connection = new SqliteConnection($"Data Source={path}");
        connection.Open();

        var scenes = new (string Id, string Name)[]
        {
            ("scene-starting", "Starting"),
            ("scene-live", "Live"),
            ("scene-brb", "BRB"),
            ("scene-chat", "Chat"),
            ("scene-ending", "Ending"),
        };
        foreach (var (id, name) in scenes)
        {
            using var cmd = connection.CreateCommand();
            cmd.CommandText = "INSERT INTO Scene (Id, Name, HasBackground, SortOrder) VALUES ($id, $name, 1, $order);";
            cmd.Parameters.AddWithValue("$id", id);
            cmd.Parameters.AddWithValue("$name", name);
            cmd.Parameters.AddWithValue("$order", Array.IndexOf(scenes, (id, name)));
            cmd.ExecuteNonQuery();
        }

        var layers = new[] { "ImgA", "ImgB", "ImgC" };
        using (var source = connection.CreateCommand())
        {
            source.CommandText =
                @"INSERT INTO Source (Id, SceneId, Type, Name, IsEnabled, X, Y, Width, Height, IsBackground, SortOrder)
                  VALUES ($id, 'scene-live', 'Image', $name, 1, 0, 0, 640, 480, 0, $sort);";
            var idP = source.Parameters.Add("$id", SqliteType.Text);
            var nameP = source.Parameters.Add("$name", SqliteType.Text);
            var sortP = source.Parameters.Add("$sort", SqliteType.Integer);
            for (var i = 0; i < layers.Length; i++)
            {
                idP.Value = $"img-{i}";
                nameP.Value = layers[i];
                sortP.Value = i;
                source.ExecuteNonQuery();
            }
        }
    }
}