import "package:flutter/widgets.dart";

sealed class AppMenuItem {
  const AppMenuItem();
}

class AppMenuGroup extends AppMenuItem {
  const AppMenuGroup({
    required this.label,
    required this.children,
    this.icon,
    this.visible = true,
  });

  final String label;
  final IconData? icon;
  final List<AppMenuItem> children;
  final bool visible;

  List<AppMenuItem> get visibleChildren => children.where((item) {
    return switch (item) {
      AppMenuGroup group => group.visible,
      AppMenuAction action => action.visible,
      _ => true,
    };
  }).toList();
}

class AppMenuAction extends AppMenuItem {
  const AppMenuAction({
    required this.label,
    this.icon,
    this.trailingIcon,
    this.onTap,
    this.shortcut,
    this.visible = true,
  });

  final String label;
  final IconData? icon;
  final IconData? trailingIcon;
  final VoidCallback? onTap;
  final SingleActivator? shortcut;
  final bool visible;

  bool get enabled => onTap != null;
}

class AppMenuCheck extends AppMenuItem {
  const AppMenuCheck({
    required this.label,
    required this.checked,
    this.checkedLabel,
    this.onToggle,
    this.shortcut,
  });

  final String label;
  final String? checkedLabel;
  final bool checked;
  final VoidCallback? onToggle;
  final SingleActivator? shortcut;
}

class AppMenuPlatformProvided extends AppMenuItem {
  const AppMenuPlatformProvided(this.type);

  final PlatformProvidedMenuItemType type;
}

class AppMenuSeparator extends AppMenuItem {
  const AppMenuSeparator({this.visible = true});

  final bool visible;
}

/// Converts the shared menu model to Flutter's native platform menu model.
class AppMenuNativeRenderer {
  static List<PlatformMenuItem> build(
    List<AppMenuGroup> menus, {
    String appName = "Garage App",
  }) {
    final appItems = <PlatformMenuItem>[
      for (final type in [
        PlatformProvidedMenuItemType.about,
        PlatformProvidedMenuItemType.servicesSubmenu,
        PlatformProvidedMenuItemType.hide,
        PlatformProvidedMenuItemType.hideOtherApplications,
        PlatformProvidedMenuItemType.showAllApplications,
        PlatformProvidedMenuItemType.quit,
      ])
        if (PlatformProvidedMenuItem.hasMenu(type))
          PlatformProvidedMenuItem(type: type),
    ];

    return [
      if (appItems.isNotEmpty) PlatformMenu(label: appName, menus: appItems),
      for (final group in menus)
        if (group.visible)
          PlatformMenu(
            label: group.label,
            menus: _convertItems(group.visibleChildren),
          ),
    ];
  }

  static String signature(List<AppMenuGroup> menus) {
    final buffer = StringBuffer();
    for (final group in menus) {
      if (!group.visible) continue;
      _writeSignature(buffer, group);
      buffer.write(";");
    }
    return buffer.toString();
  }

  static List<PlatformMenuItem> _convertItems(List<AppMenuItem> items) {
    final groups = <List<AppMenuItem>>[<AppMenuItem>[]];
    for (final item in items) {
      if (item case AppMenuSeparator(visible: true)) {
        groups.add(<AppMenuItem>[]);
      } else if (item is! AppMenuSeparator) {
        groups.last.add(item);
      }
    }

    final result = <PlatformMenuItem>[];
    for (var index = 0; index < groups.length; index++) {
      final native = groups[index]
          .map(_toNativeItem)
          .whereType<PlatformMenuItem>();
      final items = native.toList();
      if (items.isEmpty) continue;
      if (index == 0) {
        result.addAll(items);
      } else {
        result.add(PlatformMenuItemGroup(members: items));
      }
    }
    return result;
  }

  static PlatformMenuItem? _toNativeItem(AppMenuItem item) {
    return switch (item) {
      AppMenuGroup group when group.visible => PlatformMenu(
        label: group.label,
        menus: _convertItems(group.visibleChildren),
      ),
      AppMenuAction action when action.visible => PlatformMenuItem(
        label: action.label,
        shortcut: action.shortcut,
        onSelected: action.onTap,
      ),
      AppMenuCheck check => PlatformMenuItem(
        label: check.checked && check.checkedLabel != null
            ? check.checkedLabel!
            : check.label,
        shortcut: check.shortcut,
        onSelected: check.onToggle,
      ),
      AppMenuPlatformProvided provided
          when PlatformProvidedMenuItem.hasMenu(provided.type) =>
        PlatformProvidedMenuItem(type: provided.type),
      _ => null,
    };
  }

  static void _writeSignature(StringBuffer buffer, AppMenuItem item) {
    switch (item) {
      case AppMenuGroup group:
        if (!group.visible) return;
        buffer
          ..write("G(")
          ..write(group.label)
          ..write("|")
          ..write(group.icon?.codePoint ?? -1)
          ..write(")[");
        for (final child in group.visibleChildren) {
          _writeSignature(buffer, child);
          buffer.write(",");
        }
        buffer.write("]");
      case AppMenuAction action:
        if (!action.visible) return;
        buffer
          ..write("A(")
          ..write(action.label)
          ..write("|")
          ..write(action.icon?.codePoint ?? -1)
          ..write("|")
          ..write(action.enabled ? 1 : 0)
          ..write("|")
          ..write(_shortcutSignature(action.shortcut))
          ..write(")");
      case AppMenuCheck check:
        buffer
          ..write("C(")
          ..write(check.label)
          ..write("|")
          ..write(check.checkedLabel ?? "-")
          ..write("|")
          ..write(check.checked ? 1 : 0)
          ..write("|")
          ..write(check.onToggle != null ? 1 : 0)
          ..write("|")
          ..write(_shortcutSignature(check.shortcut))
          ..write(")");
      case AppMenuPlatformProvided provided:
        buffer
          ..write("P(")
          ..write(provided.type.name)
          ..write(")");
      case AppMenuSeparator separator:
        if (separator.visible) buffer.write("S");
    }
  }

  // SingleActivator has no value-based toString (it's Diagnosticable, so the
  // default one embeds the object's identity hash) - and menu_def.dart builds
  // a fresh activator on every rebuild, so hashing the instance itself would
  // make the signature change every frame and defeat the whole point of this
  // gate. build it off the actual key/modifier fields instead, those are what
  // we care about being stable.
  static String _shortcutSignature(SingleActivator? shortcut) {
    if (shortcut == null) return "-";
    return [
      shortcut.trigger.keyLabel,
      shortcut.trigger.keyId.toRadixString(16),
      shortcut.alt ? "a" : "",
      shortcut.control ? "c" : "",
      shortcut.meta ? "m" : "",
      shortcut.shift ? "s" : "",
    ].join(":");
  }
}