fin-tracker/app/lib/core/theme/app_theme.dart

import 'package:flutter/material.dart';

/// Design tokens for fin-tracker's visual language (`docs/ai/design-system.md`): graphite-violet
/// surfaces, one bright sky-blue accent, flat rounded cards with no outline, filled inputs and
/// pill-shaped navigation — the look of Snowball.
///
/// Both brightnesses share this accent 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._();

  /// The accent: buttons, active tabs, links and the primary chart series.
  /// Matches `ChartColors.slot1Blue`.
  static const seed = Color(0xFF14AFFF);

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

  static ColorScheme _scheme(Brightness brightness) {
    final base = ColorScheme.fromSeed(seedColor: seed, brightness: brightness);
    if (brightness == Brightness.light) {
      return base.copyWith(
        primary: const Color(0xFF0A98E6),
        onPrimary: Colors.white,
        surface: const Color(0xFFF2F2F7),
        surfaceContainerLowest: Colors.white,
        surfaceContainerLow: const Color(0xFFF7F7FB),
        surfaceContainer: Colors.white,
        surfaceContainerHigh: const Color(0xFFE8E8F0),
        surfaceContainerHighest: const Color(0xFFDCDCE6),
        outlineVariant: const Color(0xFFD8D8E2),
      );
    }
    return base.copyWith(
      primary: seed,
      onPrimary: const Color(0xFF04283B),
      primaryContainer: const Color(0xFF0E4B6E),
      onPrimaryContainer: const Color(0xFFD3F0FF),
      surface: const Color(0xFF25252F),
      surfaceContainerLowest: const Color(0xFF1F1F28),
      surfaceContainerLow: const Color(0xFF2A2A35),
      surfaceContainer: const Color(0xFF2F2F3C),
      surfaceContainerHigh: const Color(0xFF3A3A49),
      surfaceContainerHighest: const Color(0xFF474757),
      onSurface: const Color(0xFFEDEDF3),
      onSurfaceVariant: const Color(0xFFB4B4C3),
      outline: const Color(0xFF74748A),
      outlineVariant: const Color(0xFF3F3F4F),
      error: const Color(0xFFF26B6B),
    );
  }

  static ThemeData _build(Brightness brightness) {
    final scheme = _scheme(brightness);
    final dark = brightness == Brightness.dark;
    final outline = scheme.outlineVariant;
    final radius = BorderRadius.circular(12);
    final fieldRadius = BorderRadius.circular(8);

    OutlineInputBorder field([Color? color, double width = 1]) =>
        OutlineInputBorder(
          borderRadius: fieldRadius,
          borderSide: color == null
              ? BorderSide.none
              : BorderSide(color: color, width: width),
        );

    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: radius,
          side: dark ? BorderSide.none : BorderSide(color: outline),
        ),
      ),
      dividerTheme: DividerThemeData(color: outline, space: 1, thickness: 1),
      dialogTheme: DialogThemeData(
        backgroundColor: scheme.surfaceContainer,
        surfaceTintColor: Colors.transparent,
        shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(16)),
      ),
      bottomSheetTheme: BottomSheetThemeData(
        backgroundColor: scheme.surfaceContainer,
        surfaceTintColor: Colors.transparent,
      ),
      inputDecorationTheme: InputDecorationTheme(
        filled: true,
        fillColor: scheme.surfaceContainerHigh,
        border: field(),
        enabledBorder: field(),
        focusedBorder: field(scheme.primary, 1.5),
        errorBorder: field(scheme.error),
        focusedErrorBorder: field(scheme.error, 1.5),
      ),
      filledButtonTheme: FilledButtonThemeData(
        style: FilledButton.styleFrom(
          shape: RoundedRectangleBorder(borderRadius: fieldRadius),
          padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 14),
        ),
      ),
      outlinedButtonTheme: OutlinedButtonThemeData(
        style: OutlinedButton.styleFrom(
          shape: RoundedRectangleBorder(borderRadius: fieldRadius),
          side: BorderSide(color: outline),
        ),
      ),
      textButtonTheme: TextButtonThemeData(
        style: TextButton.styleFrom(
          shape: RoundedRectangleBorder(borderRadius: fieldRadius),
        ),
      ),
      chipTheme: ChipThemeData(
        backgroundColor: scheme.surfaceContainerHigh,
        side: BorderSide.none,
        shape: RoundedRectangleBorder(borderRadius: fieldRadius),
      ),
      tabBarTheme: TabBarThemeData(
        indicatorColor: scheme.primary,
        labelColor: scheme.onSurface,
        unselectedLabelColor: scheme.onSurfaceVariant,
        dividerColor: outline,
        labelStyle: const TextStyle(fontWeight: FontWeight.w600),
      ),
      popupMenuTheme: PopupMenuThemeData(
        color: scheme.surfaceContainerHigh,
        surfaceTintColor: Colors.transparent,
        shape: RoundedRectangleBorder(borderRadius: radius),
      ),
      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.surfaceContainerLowest,
        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,
          ),
        ),
      ),
    );
  }
}