import 'package:flutter/material.dart';

/// Design tokens for fin-tracker's visual language (`docs/ai/design-system.md`): dark
/// surfaces tinted blue-indigo rather than neutral grey, flat bordered cards instead of
/// Material's default elevation shadow, and one accent seed shared with
/// `ChartColors.slot1Blue` so UI chrome and the primary data series read as the same color.
///
/// Both brightnesses share this seed and this shape language — only the surface tones
/// differ — so the dark theme is not a special case bolted onto a default light Material
/// theme, and switching `themeModeProvider` never changes which widgets exist.
class AppTheme {
  const AppTheme._();

  /// Matches `ChartColors.slot1Blue`.
  static const seed = Color(0xFF2A78D6);

  static ThemeData light() => _build(Brightness.light);
  static ThemeData dark() => _build(Brightness.dark);

  static ThemeData _build(Brightness brightness) {
    final scheme = ColorScheme.fromSeed(seedColor: seed, brightness: brightness);
    final outline = scheme.outlineVariant.withValues(alpha: brightness == Brightness.dark ? 0.4 : 0.7);

    return ThemeData(
      useMaterial3: true,
      brightness: brightness,
      colorScheme: scheme,
      scaffoldBackgroundColor: scheme.surface,
      appBarTheme: AppBarTheme(
        backgroundColor: scheme.surface,
        surfaceTintColor: Colors.transparent,
        elevation: 0,
        scrolledUnderElevation: 0,
      ),
      cardTheme: CardThemeData(
        elevation: 0,
        color: scheme.surfaceContainer,
        surfaceTintColor: Colors.transparent,
        clipBehavior: Clip.antiAlias,
        margin: EdgeInsets.zero,
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(16),
          side: BorderSide(color: outline),
        ),
      ),
      dividerTheme: DividerThemeData(color: outline, space: 1, thickness: 1),
      navigationRailTheme: NavigationRailThemeData(
        backgroundColor: scheme.surfaceContainerLow,
        indicatorColor: scheme.primaryContainer,
        useIndicator: true,
        selectedIconTheme: IconThemeData(color: scheme.primary),
        unselectedIconTheme: IconThemeData(color: scheme.onSurfaceVariant),
        selectedLabelTextStyle: TextStyle(color: scheme.primary, fontWeight: FontWeight.w600),
        unselectedLabelTextStyle: TextStyle(color: scheme.onSurfaceVariant),
      ),
      navigationBarTheme: NavigationBarThemeData(
        backgroundColor: scheme.surfaceContainerLow,
        indicatorColor: scheme.primaryContainer,
        elevation: 0,
        iconTheme: WidgetStateProperty.resolveWith(
          (states) => IconThemeData(
            color: states.contains(WidgetState.selected) ? scheme.primary : scheme.onSurfaceVariant,
          ),
        ),
        labelTextStyle: WidgetStateProperty.resolveWith(
          (states) => TextStyle(
            fontSize: 12,
            fontWeight: states.contains(WidgetState.selected) ? FontWeight.w600 : FontWeight.w400,
            color: states.contains(WidgetState.selected) ? scheme.primary : scheme.onSurfaceVariant,
          ),
        ),
      ),
    );
  }
}