import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

/// Color scheme options for the app
enum AppColorScheme { blue, green, purple, orange }

/// Provider for managing app theme and appearance settings
///
/// Handles theme mode (light/dark/system), color scheme selection,
/// and persistence of user preferences
///
/// Usage example:
/// ```dart
/// final themeProvider = Provider.of<ThemeProvider>(context);
///
/// // Change theme mode
/// themeProvider.setThemeMode(ThemeMode.dark);
///
/// // Change color scheme
/// themeProvider.setColorScheme(AppColorScheme.green);
///
/// // Get current theme data
/// final lightTheme = themeProvider.lightTheme;
/// final darkTheme = themeProvider.darkTheme;
/// ```
class ThemeProvider extends ChangeNotifier {
  static const String _themeModeKey = 'theme_mode';
  static const String _colorSchemeKey = 'color_scheme';

  ThemeMode _themeMode = ThemeMode.system;
  AppColorScheme _colorScheme = AppColorScheme.blue;

  ThemeProvider() {
    _loadPreferences();
  }

  /// Get current theme mode
  ThemeMode get themeMode => _themeMode;

  /// Get current color scheme
  AppColorScheme get colorScheme => _colorScheme;

  /// Get light theme data
  ThemeData get lightTheme => _buildLightTheme();

  /// Get dark theme data
  ThemeData get darkTheme => _buildDarkTheme();

  /// Set theme mode
  ///
  /// [mode] - The theme mode to set (light, dark, or system)
  /// Saves preference and notifies listeners
  Future<void> setThemeMode(ThemeMode mode) async {
    if (_themeMode == mode) return;

    _themeMode = mode;
    notifyListeners();
    await savePreferences();
  }

  /// Set color scheme
  ///
  /// [scheme] - The color scheme to set
  /// Saves preference and notifies listeners
  Future<void> setColorScheme(AppColorScheme scheme) async {
    if (_colorScheme == scheme) return;

    _colorScheme = scheme;
    notifyListeners();
    await savePreferences();
  }

  /// Save preferences to local storage
  Future<void> savePreferences() async {
    try {
      final prefs = await SharedPreferences.getInstance();
      await prefs.setString(_themeModeKey, _themeMode.name);
      await prefs.setString(_colorSchemeKey, _colorScheme.name);
    } catch (e) {
      debugPrint('Failed to save theme preferences: $e');
    }
  }

  /// Load preferences from local storage
  Future<void> _loadPreferences() async {
    try {
      final prefs = await SharedPreferences.getInstance();

      // Load theme mode
      final themeModeStr = prefs.getString(_themeModeKey);
      if (themeModeStr != null) {
        _themeMode = ThemeMode.values.firstWhere(
          (mode) => mode.name == themeModeStr,
          orElse: () => ThemeMode.system,
        );
      }

      // Load color scheme
      final colorSchemeStr = prefs.getString(_colorSchemeKey);
      if (colorSchemeStr != null) {
        _colorScheme = AppColorScheme.values.firstWhere(
          (scheme) => scheme.name == colorSchemeStr,
          orElse: () => AppColorScheme.blue,
        );
      }

      notifyListeners();
    } catch (e) {
      debugPrint('Failed to load theme preferences: $e');
    }
  }

  /// Build light theme based on current color scheme
  ThemeData _buildLightTheme() {
    final colorScheme = _getColorScheme(Brightness.light);

    return ThemeData(
      useMaterial3: true,
      brightness: Brightness.light,
      colorScheme: colorScheme,

      // AppBar theme
      appBarTheme: AppBarTheme(
        centerTitle: true,
        elevation: 0,
        backgroundColor: colorScheme.primary,
        foregroundColor: colorScheme.onPrimary,
      ),

      // Card theme
      cardTheme: const CardThemeData(
        elevation: 2,
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.all(Radius.circular(12)),
        ),
      ),

      // Input decoration theme
      inputDecorationTheme: InputDecorationTheme(
        filled: true,
        fillColor: colorScheme.surfaceContainerHighest.withValues(alpha: 0.3),
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide.none,
        ),
        enabledBorder: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide.none,
        ),
        focusedBorder: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide(color: colorScheme.primary, width: 2),
        ),
        errorBorder: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide(color: colorScheme.error, width: 1),
        ),
        focusedErrorBorder: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide(color: colorScheme.error, width: 2),
        ),
      ),

      // Elevated button theme
      elevatedButtonTheme: ElevatedButtonThemeData(
        style: ElevatedButton.styleFrom(
          elevation: 2,
          padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 12),
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(12),
          ),
        ),
      ),

      // Text button theme
      textButtonTheme: TextButtonThemeData(
        style: TextButton.styleFrom(
          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
          shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(8)),
        ),
      ),

      // Floating action button theme
      floatingActionButtonTheme: FloatingActionButtonThemeData(
        elevation: 4,
        shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(16)),
      ),

      // Progress indicator theme
      progressIndicatorTheme: ProgressIndicatorThemeData(
        color: colorScheme.primary,
      ),

      // Divider theme
      dividerTheme: DividerThemeData(
        color: colorScheme.outlineVariant,
        thickness: 1,
      ),
    );
  }

  /// Build dark theme based on current color scheme
  ThemeData _buildDarkTheme() {
    final colorScheme = _getColorScheme(Brightness.dark);

    return ThemeData(
      useMaterial3: true,
      brightness: Brightness.dark,
      colorScheme: colorScheme,

      // AppBar theme
      appBarTheme: AppBarTheme(
        centerTitle: true,
        elevation: 0,
        backgroundColor: colorScheme.surface,
        foregroundColor: colorScheme.onSurface,
      ),

      // Card theme
      cardTheme: const CardThemeData(
        elevation: 2,
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.all(Radius.circular(12)),
        ),
      ),

      // Input decoration theme
      inputDecorationTheme: InputDecorationTheme(
        filled: true,
        fillColor: colorScheme.surfaceContainerHighest.withValues(alpha: 0.3),
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide.none,
        ),
        enabledBorder: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide.none,
        ),
        focusedBorder: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide(color: colorScheme.primary, width: 2),
        ),
        errorBorder: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide(color: colorScheme.error, width: 1),
        ),
        focusedErrorBorder: OutlineInputBorder(
          borderRadius: BorderRadius.circular(12),
          borderSide: BorderSide(color: colorScheme.error, width: 2),
        ),
      ),

      // Elevated button theme
      elevatedButtonTheme: ElevatedButtonThemeData(
        style: ElevatedButton.styleFrom(
          elevation: 2,
          padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 12),
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(12),
          ),
        ),
      ),

      // Text button theme
      textButtonTheme: TextButtonThemeData(
        style: TextButton.styleFrom(
          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
          shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(8)),
        ),
      ),

      // Floating action button theme
      floatingActionButtonTheme: FloatingActionButtonThemeData(
        elevation: 4,
        shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(16)),
      ),

      // Progress indicator theme
      progressIndicatorTheme: ProgressIndicatorThemeData(
        color: colorScheme.primary,
      ),

      // Divider theme
      dividerTheme: DividerThemeData(
        color: colorScheme.outlineVariant,
        thickness: 1,
      ),
    );
  }

  /// Get color scheme based on brightness and selected color
  ColorScheme _getColorScheme(Brightness brightness) {
    switch (_colorScheme) {
      case AppColorScheme.blue:
        return _getBlueColorScheme(brightness);
      case AppColorScheme.green:
        return _getGreenColorScheme(brightness);
      case AppColorScheme.purple:
        return _getPurpleColorScheme(brightness);
      case AppColorScheme.orange:
        return _getOrangeColorScheme(brightness);
    }
  }

  /// Blue color scheme
  ColorScheme _getBlueColorScheme(Brightness brightness) {
    if (brightness == Brightness.light) {
      return ColorScheme.fromSeed(
        seedColor: Colors.blue,
        brightness: Brightness.light,
      );
    } else {
      return ColorScheme.fromSeed(
        seedColor: Colors.blue,
        brightness: Brightness.dark,
      );
    }
  }

  /// Green color scheme
  ColorScheme _getGreenColorScheme(Brightness brightness) {
    if (brightness == Brightness.light) {
      return ColorScheme.fromSeed(
        seedColor: Colors.green,
        brightness: Brightness.light,
      );
    } else {
      return ColorScheme.fromSeed(
        seedColor: Colors.green,
        brightness: Brightness.dark,
      );
    }
  }

  /// Purple color scheme
  ColorScheme _getPurpleColorScheme(Brightness brightness) {
    if (brightness == Brightness.light) {
      return ColorScheme.fromSeed(
        seedColor: Colors.purple,
        brightness: Brightness.light,
      );
    } else {
      return ColorScheme.fromSeed(
        seedColor: Colors.purple,
        brightness: Brightness.dark,
      );
    }
  }

  /// Orange color scheme
  ColorScheme _getOrangeColorScheme(Brightness brightness) {
    if (brightness == Brightness.light) {
      return ColorScheme.fromSeed(
        seedColor: Colors.orange,
        brightness: Brightness.light,
      );
    } else {
      return ColorScheme.fromSeed(
        seedColor: Colors.orange,
        brightness: Brightness.dark,
      );
    }
  }

  /// Get color scheme name for display
  String getColorSchemeName(AppColorScheme scheme) {
    switch (scheme) {
      case AppColorScheme.blue:
        return '蓝色';
      case AppColorScheme.green:
        return '绿色';
      case AppColorScheme.purple:
        return '紫色';
      case AppColorScheme.orange:
        return '橙色';
    }
  }

  /// Get theme mode name for display
  String getThemeModeName(ThemeMode mode) {
    switch (mode) {
      case ThemeMode.light:
        return '浅色模式';
      case ThemeMode.dark:
        return '深色模式';
      case ThemeMode.system:
        return '跟随系统';
    }
  }
}