using System.Reflection;
using System.Text.RegularExpressions;
using AcDream.Launcher.Core.Installation;
using AcDream.Launcher.Core.Launching;
using AcDream.Launcher.Core.Orchestration;
using AcDream.Launcher.Core.Profiles;
using AcDream.Launcher.ViewModels;
using Avalonia.Controls;
using Avalonia.Headless.XUnit;
using Avalonia.Threading;
using Avalonia.VisualTree;

namespace AcDream.Launcher.Tests;

/// <summary>
/// Closes #399: no test ever constructed <see cref="MainWindow"/>, so the
/// #398 defect class (code-behind dereferencing an x:Name field that
/// <c>AvaloniaXamlLoader.Load(this)</c> never assigns, instead of the
/// generated <c>InitializeComponent()</c>) reached the user gate through
/// 14,012 green tests that were all ViewModel-only.
///
/// Every test here constructs a real <see cref="MainWindow"/> against the
/// real compiled XAML and drives it exactly the way <c>App.axaml.cs</c>
/// does: assign a live <see cref="LauncherWindowViewModel"/> as
/// <c>DataContext</c>, then exercise the modal open/close paths that
/// dereference the named controls (the bug class lives in
/// MainWindow.axaml.cs's <c>OnViewModelPropertyChanged</c> and
/// <c>FocusActiveModal</c>). That focus work is queued via
/// <c>Dispatcher.UIThread.Post</c>, so every test pumps the headless
/// dispatcher with <see cref="Dispatcher.RunJobs"/> before asserting — a
/// test that only sets a property and asserts would pass vacuously
/// without ever running <c>FocusActiveModal</c>.
/// </summary>
public sealed class MainWindowViewTests
{
    // Every x:Name in MainWindow.axaml, kept in sync with the reflection
    // sweep below so a newly-added named control without a matching field
    // fails loudly instead of silently reaching InitializeComponent().
    private static readonly (string Name, Type Type)[] ExpectedNamedControls =
    [
        ("ProfilesTree", typeof(TreeView)),
        ("ServerNameTextBox", typeof(TextBox)),
        ("AccountNameTextBox", typeof(TextBox)),
        ("CharacterNameTextBox", typeof(TextBox)),
        ("EditorSubmitButton", typeof(Button)),
        ("FirstRunDatDirectoryTextBox", typeof(TextBox)),
        ("FirstRunCloseButton", typeof(Button)),
        ("UpdateCloseButton", typeof(Button)),
    ];

    [AvaloniaFact]
    public void EveryExplicitlyNamedControlIsAssignedAfterConstruction()
    {
        var window = new MainWindow();

        foreach ((string name, Type type) in ExpectedNamedControls)
        {
            object? value = GetNamedField(window, name);
            Assert.True(
                value is not null,
                $"x:Name '{name}' was null after construction. Only the "
                    + "generated InitializeComponent() assigns x:Name backing "
                    + "fields; AvaloniaXamlLoader.Load(this) alone leaves them "
                    + "null (this is the #398 defect class).");
            Assert.IsAssignableFrom(type, value);
        }
    }

    [AvaloniaFact]
    public void ReflectionSweepOfEveryXNameInMarkupFindsANonNullBackingField()
    {
        string markupPath = Path.Combine(
            FindRepositoryRoot(),
            "src",
            "AcDream.Launcher",
            "MainWindow.axaml");
        string markup = File.ReadAllText(markupPath);
        List<string> names = Regex
            .Matches(markup, "x:Name=\"([^\"]+)\"")
            .Select(match => match.Groups[1].Value)
            .Distinct(StringComparer.Ordinal)
            .ToList();

        // The markup must still declare at least the controls the
        // code-behind dereferences; an empty sweep would make this test
        // vacuous.
        Assert.True(names.Count >= ExpectedNamedControls.Length);

        var window = new MainWindow();
        foreach (string name in names)
        {
            FieldInfo? field = typeof(MainWindow).GetField(
                name,
                BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
            Assert.True(field is not null, $"No backing field found for x:Name '{name}'.");
            object? value = field!.GetValue(window);
            Assert.True(
                value is not null,
                $"x:Name '{name}' resolved to a field but its value was null "
                    + "after construction.");
        }
    }

    [AvaloniaTheory]
    [InlineData(ProfileEditorKind.AddServer, "ServerNameTextBox")]
    [InlineData(ProfileEditorKind.EditServer, "ServerNameTextBox")]
    [InlineData(ProfileEditorKind.AddAccount, "AccountNameTextBox")]
    [InlineData(ProfileEditorKind.EditAccount, "AccountNameTextBox")]
    [InlineData(ProfileEditorKind.AddCharacter, "CharacterNameTextBox")]
    [InlineData(ProfileEditorKind.EditCharacter, "CharacterNameTextBox")]
    [InlineData(ProfileEditorKind.Remove, "EditorSubmitButton")]
    public void OpeningEachEditorKindFocusesItsPrimaryFieldAndClosingRunsTheFallbackWithoutThrowing(
        ProfileEditorKind kind,
        string expectedFocusFieldName)
    {
        using LauncherWindowViewModel viewModel = CreateViewModel();
        var window = new MainWindow { DataContext = viewModel };
        window.Show();

        viewModel.EditorDialog.Open(kind, "Fixture title", _ => { });
        Assert.True(viewModel.EditorDialog.IsOpen);
        Dispatcher.UIThread.RunJobs();

        Control expectedFocus = (Control)GetNamedField(window, expectedFocusFieldName)!;
        Assert.Same(expectedFocus, CurrentFocus(window));

        viewModel.EditorDialog.Close();
        Assert.False(viewModel.EditorDialog.IsOpen);

        // Nothing held focus before the dialog opened, so
        // OnViewModelPropertyChanged's close branch posts the fallback
        // (ProfilesTree.Focus()). Pumping the dispatcher is what actually
        // *runs* FocusActiveModal's caller and its ProfilesTree
        // dereference — this is the #398 defect class: with
        // AvaloniaXamlLoader.Load(this) instead of InitializeComponent(),
        // ProfilesTree is null here and this throws
        // NullReferenceException out of the dispatcher. TreeView's Fluent
        // template sets Focusable="False" (focus lives on TreeViewItem
        // rows, not the tree itself), so a successful, non-throwing
        // ProfilesTree.Focus() call still leaves focus at null — that is
        // expected, not a failure.
        Dispatcher.UIThread.RunJobs();
        Assert.NotSame(expectedFocus, CurrentFocus(window));
    }

    [AvaloniaFact]
    public void OpeningAndClosingTheFirstRunWizardFocusesAndRunsTheCloseFallbackWithoutThrowing()
    {
        using LauncherWindowViewModel viewModel = CreateViewModel();
        var window = new MainWindow { DataContext = viewModel };
        window.Show();

        viewModel.FirstRunWizardShell.OpenCommand.Execute(null);
        Assert.True(viewModel.FirstRunWizardShell.IsOpen);
        Dispatcher.UIThread.RunJobs();

        Control datDirectoryBox = (Control)GetNamedField(window, "FirstRunDatDirectoryTextBox")!;
        Assert.Same(datDirectoryBox, CurrentFocus(window));

        viewModel.FirstRunWizardShell.CloseCommand.Execute(null);
        Assert.False(viewModel.FirstRunWizardShell.IsOpen);

        // See the comment in the editor-kind theory above: this pump is
        // what actually executes the ProfilesTree.Focus() fallback.
        Dispatcher.UIThread.RunJobs();
        Assert.NotSame(datDirectoryBox, CurrentFocus(window));
    }

    [AvaloniaFact]
    public async Task OpeningAndClosingTheUpdatePromptFocusesAndRunsTheCloseFallbackWithoutThrowing()
    {
        using LauncherWindowViewModel viewModel = CreateViewModel();
        var window = new MainWindow { DataContext = viewModel };
        window.Show();

        await viewModel.UpdatePrompt.OpenCommand.ExecuteAsync();
        Assert.True(viewModel.UpdatePrompt.IsOpen);
        Dispatcher.UIThread.RunJobs();

        Control closeButton = (Control)GetNamedField(window, "UpdateCloseButton")!;
        Assert.Same(closeButton, CurrentFocus(window));

        viewModel.UpdatePrompt.CloseCommand.Execute(null);
        Assert.False(viewModel.UpdatePrompt.IsOpen);

        // See the comment in the editor-kind theory above: this pump is
        // what actually executes the ProfilesTree.Focus() fallback.
        Dispatcher.UIThread.RunJobs();
        Assert.NotSame(closeButton, CurrentFocus(window));
    }

    [AvaloniaFact]
    public void ClosingAModalRestoresThePreviouslyFocusedControlWithoutThrowing()
    {
        using LauncherWindowViewModel viewModel = CreateViewModel();
        var window = new MainWindow { DataContext = viewModel };
        window.Show();

        // ProfilesTree itself is not a Fluent focus target (its template
        // sets Focusable="False"; individual TreeViewItem rows are the
        // real tab stops), so use another genuinely focusable, always
        // visible control from the same non-modal chrome as the
        // "previously focused" anchor for the _focusBeforeModal != null
        // branch of MainWindow.OnViewModelPropertyChanged.
        Control addServerButton = window
            .GetVisualDescendants()
            .OfType<Button>()
            .First(button => Equals(button.Content, "+ Server"));
        addServerButton.Focus();
        Assert.Same(addServerButton, CurrentFocus(window));

        viewModel.EditorDialog.Open(ProfileEditorKind.AddServer, "Fixture title", _ => { });
        Dispatcher.UIThread.RunJobs();
        Control serverName = (Control)GetNamedField(window, "ServerNameTextBox")!;
        Assert.Same(serverName, CurrentFocus(window));

        viewModel.EditorDialog.Close();
        Dispatcher.UIThread.RunJobs();

        // addServerButton was focused before the dialog opened, so the
        // restore branch (focusToRestore.Focus()) is what ran here, not
        // the ProfilesTree.Focus() fallback exercised by the tests above.
        Assert.Same(addServerButton, CurrentFocus(window));
    }

    private static Control? CurrentFocus(MainWindow window) =>
        Avalonia.Controls.TopLevel.GetTopLevel(window)?.FocusManager?.GetFocusedElement()
            as Control;

    private static object? GetNamedField(MainWindow window, string name) =>
        typeof(MainWindow)
            .GetField(name, BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic)
            ?.GetValue(window);

    private static LauncherWindowViewModel CreateViewModel()
    {
        var viewModel = new LauncherWindowViewModel(
            new StubOrchestrator(),
            new ImmediateUiDispatcher());
        viewModel.Initialize();
        return viewModel;
    }

    private static string FindRepositoryRoot()
    {
        foreach (string start in new[] { AppContext.BaseDirectory, Environment.CurrentDirectory })
        {
            DirectoryInfo? directory = new(start);
            while (directory is not null)
            {
                if (File.Exists(Path.Combine(directory.FullName, "AcDream.slnx")))
                {
                    return directory.FullName;
                }

                directory = directory.Parent;
            }
        }

        throw new DirectoryNotFoundException("Could not find AcDream.slnx.");
    }

    /// <summary>
    /// Minimal no-op orchestrator. These tests exercise MainWindow's own
    /// dispatcher/focus wiring, not orchestrator behavior (already covered
    /// by <see cref="LauncherWindowViewModelTests"/>), so every mutation is
    /// a no-op and the snapshot is deliberately empty.
    /// </summary>
    private sealed class StubOrchestrator : ILauncherOrchestrator
    {
        // Never raised: these tests exercise MainWindow's dispatcher/focus
        // wiring directly and never trigger an orchestrator-side refresh.
#pragma warning disable CS0067
        public event EventHandler? StateChanged;
#pragma warning restore CS0067

        public void LoadProfiles()
        {
        }

        public LauncherStateSnapshot GetSnapshot() => new(
            Servers: [],
            Sessions: [],
            Platform: LauncherPlatformCapabilities.Detect(),
            IsInstallationReady: false,
            InstallationStatus: "Fixture: installation not ready.");

        public LauncherCapability GetLaunchCapability(LaunchMode mode) =>
            LauncherCapability.Available;

        public LauncherCapability GetAccountLaunchCapability(
            string serverName,
            string accountName,
            LaunchMode mode) => LauncherCapability.Available;

        public LauncherCapability GetProbeCapability(string serverName, string accountName) =>
            LauncherCapability.Available;

        public void SetInstallRecord(LauncherInstallRecord? installRecord)
        {
        }

        public void AddServer(string name, string host, int port)
        {
        }

        public void EditServer(string name, string newName, string newHost, int newPort)
        {
        }

        public void RemoveServer(string name)
        {
        }

        public void AddAccount(string serverName, string accountName, string password)
        {
        }

        public void EditAccount(
            string serverName,
            string accountName,
            string newAccountName,
            string? newPassword)
        {
        }

        public void RemoveAccount(string serverName, string accountName)
        {
        }

        public void AddCharacter(
            string serverName,
            string accountName,
            string characterName,
            string? characterId)
        {
        }

        public void EditCharacterIdentity(
            string serverName,
            string accountName,
            string characterName,
            string newCharacterName,
            string? newCharacterId)
        {
        }

        public void UpdateCharacterSettings(
            string serverName,
            string accountName,
            string characterName,
            LaunchMode launchMode,
            IReadOnlyList<string> plugins,
            IReadOnlyList<string> loginCommands)
        {
        }

        public void RemoveCharacter(string serverName, string accountName, string characterName)
        {
        }

        public Task<LauncherSessionSnapshot> LaunchAsync(
            string serverName,
            string accountName,
            string? characterName,
            LaunchMode mode,
            CancellationToken cancellationToken = default) =>
            Task.FromResult(CreateSession());

        public Task<LauncherSessionSnapshot> ProbeAsync(
            string serverName,
            string accountName,
            CancellationToken cancellationToken = default) =>
            Task.FromResult(CreateSession());

        public Task StopSessionAsync(
            string sessionId,
            TimeSpan timeout,
            CancellationToken cancellationToken = default) => Task.CompletedTask;

        public void PollStatus()
        {
        }

        public void ClearFinishedSessions()
        {
        }

        public void Dispose()
        {
        }

        private static LauncherSessionSnapshot CreateSession() => new(
            "fixture-session",
            LauncherActivityKind.Play,
            "Fixture server",
            "fixture-account",
            "+Fixture",
            LaunchMode.Gui,
            LauncherActivityState.Connected,
            "Connected.",
            ExitCode: null,
            Error: null,
            CreatedAt: DateTimeOffset.UnixEpoch);
    }
}