/// Shared menu helpers for Wolf3D hosts.
library;

import 'package:wolf_3d_dart/wolf_3d_data_types.dart';

/// Known VGA picture indexes used by the original Wolf3D control-panel menus.
///
/// Values below are picture-table indexes (not raw chunk ids).
/// For example, `C_CONTROLPIC` is chunk 26 in `GFXV_WL6.H`, so its picture
/// index is `26 - STARTPICS(3) = 23`.
abstract class WolfMenuPic {
  static const int hBj = 0; // H_BJPIC
  static const int hTopWindow = 3; // H_TOPWINDOWPIC
  static const int cOptions = 7; // C_OPTIONSPIC
  static const int cCursor1 = 8; // C_CURSOR1PIC
  static const int cCursor2 = 9; // C_CURSOR2PIC
  static const int cNotSelected = 10; // C_NOTSELECTEDPIC
  static const int cSelected = 11; // C_SELECTEDPIC
  static const int cBabyMode = 16; // C_BABYMODEPIC
  static const int cEasy = 17; // C_EASYPIC
  static const int cNormal = 18; // C_NORMALPIC
  static const int cHard = 19; // C_HARDPIC
  static const int cControl = 23; // C_CONTROLPIC
  static const int cEpisode1 = 27; // C_EPISODE1PIC
  static const int cEpisode2 = 28; // C_EPISODE2PIC
  static const int cEpisode3 = 29; // C_EPISODE3PIC
  static const int cEpisode4 = 30; // C_EPISODE4PIC
  static const int cEpisode5 = 31; // C_EPISODE5PIC
  static const int cEpisode6 = 32; // C_EPISODE6PIC
  static const int statusBar = 83; // STATUSBARPIC
  static const int title = 84; // TITLEPIC
  static const int pg13 = 85; // PG13PIC
  static const int credits = 86; // CREDITSPIC
  static const int highScores = 87; // HIGHSCORESPIC

  static const List<int> episodePics = [
    cEpisode1,
    cEpisode2,
    cEpisode3,
    cEpisode4,
    cEpisode5,
    cEpisode6,
  ];
}

/// Shared menu text colors resolved from the VGA palette.
///
/// Keep menu color choices centralized so renderers don't duplicate
/// hard-coded palette slots or RGB conversion logic.
abstract class WolfMenuPalette {
  static const int selectedTextIndex = 19;
  static const int unselectedTextIndex = 23;
  static const int _headerTargetRgb = 0xFFF700;

  static int? _cachedHeaderTextIndex;

  static int get headerTextIndex =>
      _cachedHeaderTextIndex ??= _nearestPaletteIndex(_headerTargetRgb);

  static int get selectedTextColor => ColorPalette.vga32Bit[selectedTextIndex];

  static int get unselectedTextColor =>
      ColorPalette.vga32Bit[unselectedTextIndex];

  static int get headerTextColor => ColorPalette.vga32Bit[headerTextIndex];

  static int _nearestPaletteIndex(int rgb) {
    final int targetR = (rgb >> 16) & 0xFF;
    final int targetG = (rgb >> 8) & 0xFF;
    final int targetB = rgb & 0xFF;

    int bestIndex = 0;
    int bestDistance = 1 << 30;

    for (int i = 0; i < 256; i++) {
      final int color = ColorPalette.vga32Bit[i];
      final int r = color & 0xFF;
      final int g = (color >> 8) & 0xFF;
      final int b = (color >> 16) & 0xFF;

      final int dr = targetR - r;
      final int dg = targetG - g;
      final int db = targetB - b;
      final int distance = (dr * dr) + (dg * dg) + (db * db);
      if (distance < bestDistance) {
        bestDistance = distance;
        bestIndex = i;
      }
    }

    return bestIndex;
  }
}

/// Structured accessors for classic Wolf3D menu art.
class WolfClassicMenuArt {
  final WolfensteinData data;

  WolfClassicMenuArt(this.data);

  int? _resolvedIndexOffset;

  VgaImage? get controlBackground {
    final preferred = mappedPic(WolfMenuPic.cControl);
    if (_looksLikeMenuBackdrop(preferred)) {
      return preferred;
    }

    // Older data layouts may shift/control-panel art around nearby indices.
    for (int delta = -4; delta <= 4; delta++) {
      final candidate = mappedPic(WolfMenuPic.cControl + delta);
      if (_looksLikeMenuBackdrop(candidate)) {
        return candidate;
      }
    }

    return preferred;
  }

  VgaImage? get title => mappedPic(WolfMenuPic.title);

  VgaImage? get heading => mappedPic(WolfMenuPic.hTopWindow);

  VgaImage? get selectedMarker => mappedPic(WolfMenuPic.cSelected);

  VgaImage? get unselectedMarker => mappedPic(WolfMenuPic.cNotSelected);

  VgaImage? get optionsLabel => mappedPic(WolfMenuPic.cOptions);

  VgaImage? get credits => mappedPic(WolfMenuPic.credits);

  VgaImage? episodeOption(int episodeIndex) {
    if (episodeIndex < 0 || episodeIndex >= WolfMenuPic.episodePics.length) {
      return null;
    }
    return mappedPic(WolfMenuPic.episodePics[episodeIndex]);
  }

  VgaImage? difficultyOption(Difficulty difficulty) {
    switch (difficulty) {
      case Difficulty.baby:
        return mappedPic(WolfMenuPic.cBabyMode);
      case Difficulty.easy:
        return mappedPic(WolfMenuPic.cEasy);
      case Difficulty.medium:
        return mappedPic(WolfMenuPic.cNormal);
      case Difficulty.hard:
        return mappedPic(WolfMenuPic.cHard);
    }
  }

  /// Returns [index] after applying a detected version/layout offset.
  VgaImage? mappedPic(int index) {
    return pic(index + _indexOffset);
  }

  int get _indexOffset {
    if (_resolvedIndexOffset != null) {
      return _resolvedIndexOffset!;
    }

    // Retail and shareware generally place STATUSBAR/TITLE/PG13/CREDITS as a
    // contiguous block. If files are from a different release, infer a shift.
    for (int i = 0; i < data.vgaImages.length - 3; i++) {
      final status = data.vgaImages[i];
      if (!_looksLikeStatusBar(status)) {
        continue;
      }

      final title = data.vgaImages[i + 1];
      final pg13 = data.vgaImages[i + 2];
      final credits = data.vgaImages[i + 3];
      if (_looksLikeFullScreen(title) &&
          _looksLikeFullScreen(pg13) &&
          _looksLikeFullScreen(credits)) {
        _resolvedIndexOffset = i - WolfMenuPic.statusBar;
        return _resolvedIndexOffset!;
      }
    }

    _resolvedIndexOffset = 0;
    return 0;
  }

  bool _looksLikeStatusBar(VgaImage image) {
    return image.width >= 280 && image.height >= 24 && image.height <= 64;
  }

  bool _looksLikeFullScreen(VgaImage image) {
    return image.width >= 280 && image.height >= 140;
  }

  bool _looksLikeMenuBackdrop(VgaImage? image) {
    if (image == null) {
      return false;
    }
    return image.width >= 180 && image.height >= 100;
  }

  VgaImage? pic(int index) {
    if (index < 0 || index >= data.vgaImages.length) {
      return null;
    }
    final image = data.vgaImages[index];

    // Ignore known gameplay HUD art in menu composition.
    if (index == WolfMenuPic.statusBar + _indexOffset) {
      return null;
    }
    if (image.width <= 0 || image.height <= 0) {
      return null;
    }

    return image;
  }
}