// Copyright (C) 2026 SharpEmu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

using System.Collections.Concurrent;
using System.Collections.ObjectModel;
using System.Reflection;
using System.Text.Json;
using Avalonia.Controls;
using Avalonia.Input;
using Avalonia.Media;
using Avalonia.Platform.Storage;
using Avalonia.Threading;

namespace SharpEmu.GUI;

public partial class MainWindow : Window
{
    private const int MaxConsoleLines = 4000;

    private static readonly IBrush DefaultLineBrush = new SolidColorBrush(Color.Parse("#C7CFDE"));
    private static readonly IBrush DimLineBrush = new SolidColorBrush(Color.Parse("#6B7488"));
    private static readonly IBrush InfoLineBrush = new SolidColorBrush(Color.Parse("#6FA8FF"));
    private static readonly IBrush WarningLineBrush = new SolidColorBrush(Color.Parse("#E8B341"));
    private static readonly IBrush ErrorLineBrush = new SolidColorBrush(Color.Parse("#F2777C"));
    private static readonly IBrush SuccessLineBrush = new SolidColorBrush(Color.Parse("#63D489"));

    private readonly List<GameEntry> _allGames = new();
    private readonly ObservableCollection<GameEntry> _visibleGames = new();
    private readonly ObservableCollection<LogLine> _consoleLines = new();
    private readonly ConcurrentQueue<(string Line, bool IsError)> _pendingLines = new();
    private readonly DispatcherTimer _consoleFlushTimer;

    private GuiSettings _settings = new();
    private EmulatorProcess? _emulator;
    private string? _emulatorExePath;
    private bool _isRunning;
    private int _autoScrollTicks;

    public MainWindow()
    {
        InitializeComponent();

        GameList.ItemsSource = _visibleGames;
        ConsoleList.ItemsSource = _consoleLines;

        _consoleFlushTimer = new DispatcherTimer
        {
            Interval = TimeSpan.FromMilliseconds(80),
        };
        _consoleFlushTimer.Tick += (_, _) =>
        {
            FlushPendingConsoleLines();
            MaybeAutoScroll();
        };
        _consoleFlushTimer.Start();

        TitleBar.PointerPressed += OnTitleBarPointerPressed;
        GameList.SelectionChanged += (_, _) => UpdateSelectedGame();
        GameList.DoubleTapped += (_, _) => LaunchSelected();
        SearchBox.TextChanged += (_, _) => RefreshVisibleGames();
        AddFolderButton.Click += async (_, _) => await AddFolderAsync();
        RescanButton.Click += async (_, _) => await RescanLibraryAsync();
        OpenFileButton.Click += async (_, _) => await OpenFileAsync();
        LaunchButton.Click += (_, _) => LaunchSelected();
        StopButton.Click += (_, _) => _emulator?.Stop();
        ClearLogButton.Click += (_, _) => _consoleLines.Clear();
        CopyLogButton.Click += async (_, _) => await CopyConsoleAsync();

        Opened += async (_, _) => await OnOpenedAsync();
        Closing += (_, _) => OnWindowClosing();
    }

    private async Task OnOpenedAsync()
    {
        var version = Assembly.GetExecutingAssembly().GetName().Version;
        if (version is not null)
        {
            VersionText.Text = $"v{version.ToString(3)}";
        }

        _settings = GuiSettings.Load();
        ApplySettingsToControls();
        LocateEmulator();
        await RescanLibraryAsync();
    }

    private void OnWindowClosing()
    {
        ReadControlsIntoSettings();
        _settings.Save();
        _consoleFlushTimer.Stop();
        _emulator?.Dispose();
    }

    private void OnTitleBarPointerPressed(object? sender, PointerPressedEventArgs e)
    {
        if (e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
        {
            BeginMoveDrag(e);
        }
    }

    // ---- Settings <-> controls ----

    private void ApplySettingsToControls()
    {
        LogLevelBox.SelectedIndex = _settings.LogLevel.ToLowerInvariant() switch
        {
            "trace" => 0,
            "debug" => 1,
            "info" => 2,
            "warning" or "warn" => 3,
            "error" => 4,
            "critical" or "fatal" => 5,
            _ => 2,
        };
        TraceImportsBox.Value = Math.Clamp(_settings.ImportTraceLimit, 0, 4096);
        StrictToggle.IsChecked = _settings.StrictDynlibResolution;
    }

    private void ReadControlsIntoSettings()
    {
        _settings.LogLevel = SelectedLogLevel();
        _settings.ImportTraceLimit = (int)(TraceImportsBox.Value ?? 0);
        _settings.StrictDynlibResolution = StrictToggle.IsChecked == true;
    }

    private string SelectedLogLevel()
    {
        return LogLevelBox.SelectedIndex switch
        {
            0 => "Trace",
            1 => "Debug",
            2 => "Info",
            3 => "Warning",
            4 => "Error",
            5 => "Critical",
            _ => "Info",
        };
    }

    // ---- Emulator discovery ----

    private void LocateEmulator()
    {
        var exeName = OperatingSystem.IsWindows() ? "SharpEmu.exe" : "SharpEmu";
        var baseDirectory = AppContext.BaseDirectory;
        var candidates = new List<string>();
        if (!string.IsNullOrWhiteSpace(_settings.EmulatorPath))
        {
            candidates.Add(_settings.EmulatorPath);
        }

        // The GUI and the CLI are the same executable: with arguments it runs
        // the emulator, so the preferred child process is this process itself.
        if (Environment.ProcessPath is { } selfPath &&
            Path.GetFileNameWithoutExtension(selfPath).Equals("SharpEmu", StringComparison.OrdinalIgnoreCase))
        {
            candidates.Add(selfPath);
        }

        candidates.Add(Path.Combine(baseDirectory, exeName));
        candidates.Add(Path.Combine(baseDirectory, "win-x64", exeName));
        candidates.Add(Path.Combine(baseDirectory, "..", exeName));

        _emulatorExePath = candidates.FirstOrDefault(File.Exists) is { } found
            ? Path.GetFullPath(found)
            : null;

        EmulatorPathText.Text = _emulatorExePath is not null
            ? $"Emulator: {_emulatorExePath}"
            : "Emulator: SharpEmu executable not found — build SharpEmu.CLI first.";
    }

    // ---- Game library ----

    private async Task AddFolderAsync()
    {
        var folders = await StorageProvider.OpenFolderPickerAsync(new FolderPickerOpenOptions
        {
            Title = "Choose a folder containing games",
            AllowMultiple = false,
        });

        var path = folders.FirstOrDefault()?.TryGetLocalPath();
        if (string.IsNullOrEmpty(path))
        {
            return;
        }

        if (!_settings.GameFolders.Contains(path, StringComparer.OrdinalIgnoreCase))
        {
            _settings.GameFolders.Add(path);
            _settings.Save();
        }

        await RescanLibraryAsync();
    }

    private async Task RescanLibraryAsync()
    {
        var folders = _settings.GameFolders.ToArray();
        StatusBarRight.Text = "Scanning library…";

        var games = await Task.Run(() => ScanFolders(folders));

        _allGames.Clear();
        _allGames.AddRange(games);
        RefreshVisibleGames();
        StatusBarRight.Text = folders.Length == 0
            ? "Add a game folder to populate the library."
            : $"Library scanned: {games.Count} game(s) in {folders.Length} folder(s).";
    }

    private static List<GameEntry> ScanFolders(IReadOnlyList<string> folders)
    {
        var games = new List<GameEntry>();
        var seen = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
        var enumeration = new EnumerationOptions
        {
            IgnoreInaccessible = true,
            RecurseSubdirectories = true,
            MaxRecursionDepth = 8,
        };

        foreach (var folder in folders)
        {
            if (!Directory.Exists(folder))
            {
                continue;
            }

            try
            {
                foreach (var file in Directory.EnumerateFiles(folder, "eboot.bin", enumeration))
                {
                    var fullPath = Path.GetFullPath(file);
                    if (!seen.Add(fullPath))
                    {
                        continue;
                    }

                    long size = 0;
                    try
                    {
                        size = new FileInfo(fullPath).Length;
                    }
                    catch (IOException)
                    {
                    }

                    var (title, titleId) = TryReadParamJson(fullPath);
                    games.Add(new GameEntry(title ?? GameNameFor(fullPath), titleId, fullPath, size));
                }
            }
            catch (Exception)
            {
                // Skip folders that fail to enumerate.
            }
        }

        games.Sort((a, b) => string.Compare(a.Name, b.Name, StringComparison.OrdinalIgnoreCase));
        return games;
    }

    /// <summary>
    /// Reads the game title and title id from sce_sys/param.json next to the
    /// executable, when present.
    /// </summary>
    private static (string? Title, string? TitleId) TryReadParamJson(string ebootPath)
    {
        try
        {
            var directory = Path.GetDirectoryName(ebootPath);
            if (directory is null)
            {
                return (null, null);
            }

            var paramPath = Path.Combine(directory, "sce_sys", "param.json");
            if (!File.Exists(paramPath))
            {
                return (null, null);
            }

            // ReadAllText handles a UTF-8 BOM, which JsonDocument rejects in
            // raw bytes.
            using var document = JsonDocument.Parse(File.ReadAllText(paramPath));
            var root = document.RootElement;

            string? titleId = null;
            if (root.TryGetProperty("titleId", out var idElement) && idElement.ValueKind == JsonValueKind.String)
            {
                titleId = idElement.GetString();
            }

            string? title = null;
            if (root.TryGetProperty("localizedParameters", out var localized) &&
                localized.ValueKind == JsonValueKind.Object)
            {
                if (localized.TryGetProperty("defaultLanguage", out var language) &&
                    language.ValueKind == JsonValueKind.String &&
                    localized.TryGetProperty(language.GetString()!, out var defaultBlock) &&
                    defaultBlock.ValueKind == JsonValueKind.Object &&
                    defaultBlock.TryGetProperty("titleName", out var titleName) &&
                    titleName.ValueKind == JsonValueKind.String)
                {
                    title = titleName.GetString();
                }
                else
                {
                    foreach (var property in localized.EnumerateObject())
                    {
                        if (property.Value.ValueKind == JsonValueKind.Object &&
                            property.Value.TryGetProperty("titleName", out var anyTitleName) &&
                            anyTitleName.ValueKind == JsonValueKind.String)
                        {
                            title = anyTitleName.GetString();
                            break;
                        }
                    }
                }
            }

            return (
                string.IsNullOrWhiteSpace(title) ? null : title,
                string.IsNullOrWhiteSpace(titleId) ? null : titleId);
        }
        catch (Exception)
        {
            return (null, null);
        }
    }

    private static string GameNameFor(string ebootPath)
    {
        var directory = Path.GetDirectoryName(ebootPath);
        var name = directory is not null ? Path.GetFileName(directory) : null;
        return string.IsNullOrEmpty(name) ? Path.GetFileName(ebootPath) : name;
    }

    private void RefreshVisibleGames()
    {
        var query = SearchBox.Text?.Trim() ?? string.Empty;
        var selected = GameList.SelectedItem as GameEntry;

        _visibleGames.Clear();
        foreach (var game in _allGames)
        {
            if (query.Length == 0 ||
                game.Name.Contains(query, StringComparison.OrdinalIgnoreCase) ||
                game.Path.Contains(query, StringComparison.OrdinalIgnoreCase))
            {
                _visibleGames.Add(game);
            }
        }

        GameCountText.Text = _visibleGames.Count.ToString();
        if (selected is not null && _visibleGames.Contains(selected))
        {
            GameList.SelectedItem = selected;
        }

        UpdateSelectedGame();
    }

    private void UpdateSelectedGame()
    {
        if (GameList.SelectedItem is GameEntry game)
        {
            SelectedGameTitle.Text = game.Name;
            SelectedGamePath.Text = game.Path;
        }
        else
        {
            SelectedGameTitle.Text = "No game selected";
            SelectedGamePath.Text = "Pick a game from the library, or open an eboot.bin directly.";
        }

        UpdateRunButtons();
    }

    // ---- Launching ----

    private async Task OpenFileAsync()
    {
        var files = await StorageProvider.OpenFilePickerAsync(new FilePickerOpenOptions
        {
            Title = "Open an executable to launch",
            AllowMultiple = false,
            FileTypeFilter = new[]
            {
                new FilePickerFileType("PS executables") { Patterns = new[] { "eboot.bin", "*.bin", "*.self", "*.elf" } },
                FilePickerFileTypes.All,
            },
        });

        var path = files.FirstOrDefault()?.TryGetLocalPath();
        if (!string.IsNullOrEmpty(path))
        {
            Launch(path, Path.GetFileName(path));
        }
    }

    private void LaunchSelected()
    {
        if (GameList.SelectedItem is GameEntry game)
        {
            Launch(game.Path, game.Name);
        }
    }

    private void Launch(string ebootPath, string displayName)
    {
        if (_isRunning)
        {
            return;
        }

        if (_emulatorExePath is null)
        {
            LocateEmulator();
            if (_emulatorExePath is null)
            {
                AppendConsoleLine("SharpEmu executable not found. Build the SharpEmu.CLI project first (dotnet build).", ErrorLineBrush);
                return;
            }
        }

        ReadControlsIntoSettings();
        _settings.Save();

        var arguments = new List<string>
        {
            "--cpu-engine=native",
            $"--log-level={_settings.LogLevel.ToLowerInvariant()}",
        };
        if (_settings.StrictDynlibResolution)
        {
            arguments.Add("--strict");
        }

        if (_settings.ImportTraceLimit > 0)
        {
            arguments.Add($"--trace-imports={_settings.ImportTraceLimit}");
        }

        arguments.Add(ebootPath);

        _consoleLines.Clear();
        AppendConsoleLine($"$ SharpEmu {string.Join(' ', arguments)}", DimLineBrush);

        var emulator = new EmulatorProcess();
        emulator.OutputReceived += (line, isError) => _pendingLines.Enqueue((line, isError));
        emulator.Exited += code => Dispatcher.UIThread.Post(() => OnEmulatorExited(code));

        try
        {
            emulator.Start(_emulatorExePath, arguments, Path.GetDirectoryName(ebootPath));
        }
        catch (Exception ex)
        {
            emulator.Dispose();
            AppendConsoleLine($"Failed to start the emulator: {ex.Message}", ErrorLineBrush);
            return;
        }

        _emulator = emulator;
        _isRunning = true;
        StatusDot.Fill = SuccessLineBrush;
        StatusText.Text = $"Running — {displayName}";
        StatusBarRight.Text = $"Running {displayName}";
        UpdateRunButtons();
    }

    private void OnEmulatorExited(int exitCode)
    {
        FlushPendingConsoleLines();
        _isRunning = false;
        _emulator?.Dispose();
        _emulator = null;

        var meaning = exitCode switch
        {
            0 => "OK",
            1 => "invalid arguments",
            2 => "eboot not found",
            3 => "runtime exception",
            4 => "emulation error",
            _ => "unknown",
        };
        var brush = exitCode == 0 ? SuccessLineBrush : ErrorLineBrush;
        AppendConsoleLine($"Process exited with code {exitCode} ({meaning}).", brush);

        StatusDot.Fill = exitCode == 0 ? (IBrush)SuccessLineBrush : ErrorLineBrush;
        StatusText.Text = $"Exited with code {exitCode} ({meaning})";
        StatusBarRight.Text = "Idle";
        UpdateRunButtons();
    }

    private void UpdateRunButtons()
    {
        LaunchButton.IsEnabled = !_isRunning && GameList.SelectedItem is GameEntry;
        StopButton.IsEnabled = _isRunning;
        OpenFileButton.IsEnabled = !_isRunning;
    }

    // ---- Console ----

    private void FlushPendingConsoleLines()
    {
        if (_pendingLines.IsEmpty)
        {
            return;
        }

        var incoming = new List<LogLine>();
        while (_pendingLines.TryDequeue(out var pending))
        {
            incoming.Add(new LogLine(pending.Line, BrushForLine(pending.Line)));
        }

        if (incoming.Count >= MaxConsoleLines)
        {
            // A burst larger than the cap: keep only the newest lines.
            _consoleLines.Clear();
            for (var i = incoming.Count - MaxConsoleLines; i < incoming.Count; i++)
            {
                _consoleLines.Add(incoming[i]);
            }
        }
        else
        {
            var overflow = _consoleLines.Count + incoming.Count - MaxConsoleLines;
            for (var i = 0; i < overflow; i++)
            {
                _consoleLines.RemoveAt(0);
            }

            foreach (var line in incoming)
            {
                _consoleLines.Add(line);
            }
        }

        _autoScrollTicks = 3;
    }

    private void AppendConsoleLine(string text, IBrush brush)
    {
        _consoleLines.Add(new LogLine(text, brush));
        _autoScrollTicks = 3;
        MaybeAutoScroll();
    }

    private void MaybeAutoScroll()
    {
        // ScrollToEnd is applied over a few flush-timer ticks because the
        // virtualizing panel re-estimates its extent after large batches, and
        // a single scroll can land short of the true end. A synchronous
        // ScrollIntoView during rapid adds is avoided entirely — it can crash
        // the panel with "Invalid Arrange rectangle".
        if (_autoScrollTicks <= 0 || AutoScrollCheck.IsChecked != true)
        {
            return;
        }

        _autoScrollTicks--;
        (ConsoleList.Scroll as ScrollViewer)?.ScrollToEnd();
    }

    private static IBrush BrushForLine(string line)
    {
        if (line.Contains("[ERROR]", StringComparison.Ordinal) ||
            line.Contains("[CRITICAL]", StringComparison.Ordinal))
        {
            return ErrorLineBrush;
        }

        if (line.Contains("[WARNING]", StringComparison.Ordinal))
        {
            return WarningLineBrush;
        }

        if (line.Contains("[INFO]", StringComparison.Ordinal))
        {
            return InfoLineBrush;
        }

        if (line.Contains("[DEBUG]", StringComparison.Ordinal) ||
            line.Contains("[TRACE]", StringComparison.Ordinal))
        {
            return DimLineBrush;
        }

        return DefaultLineBrush;
    }

    private async Task CopyConsoleAsync()
    {
        if (_consoleLines.Count == 0 || Clipboard is null)
        {
            return;
        }

        var text = string.Join(Environment.NewLine, _consoleLines.Select(line => line.Text));
        await Clipboard.SetTextAsync(text);
    }
}