using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Windows.Threading;
using Microsoft.Data.Sqlite;
using Xunit;
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 is written to the DB after the debounced background save.
/// </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);
    }

    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 by the debounced background save");
            Assert.Equal(expected, SourceNamesInDb(tempDb));
        }
        finally
        {
            if (window != null) window.Close();
            MainViewModel.LayoutPathOverride = null;
            SqliteConnection.ClearAllPools();
            try { File.Delete(tempDb); } catch { /* best-effort cleanup */ }
        }
    }

    /// <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 debounced save may hold the write lock mid-transaction — not yet.
            return [];
        }
    }

    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();
            }
        }
    }
}