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

part 'theme_provider.g.dart';

/// User's theme preference setting.
enum ThemeSetting {
  /// Follow system preference
  system,

  /// Always light mode
  light,

  /// Always dark mode
  dark,
}

/// Provider for theme setting state.
@riverpod
class ThemeNotifier extends _$ThemeNotifier {
  static const _prefsKey = 'theme_setting';

  @override
  ThemeSetting build() {
    _loadSavedSetting();
    return ThemeSetting.system;
  }

  Future<void> _loadSavedSetting() async {
    final prefs = await SharedPreferences.getInstance();
    final value = prefs.getString(_prefsKey);
    if (value != null) {
      try {
        state = ThemeSetting.values.byName(value);
      } catch (_) {
        // Invalid value, keep default
      }
    }
  }

  /// Update theme setting and persist to storage.
  Future<void> setSetting(ThemeSetting setting) async {
    state = setting;
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_prefsKey, setting.name);
  }

  /// Get the ThemeMode for MaterialApp.
  ThemeMode get themeMode => switch (state) {
        ThemeSetting.system => ThemeMode.system,
        ThemeSetting.light => ThemeMode.light,
        ThemeSetting.dark => ThemeMode.dark,
      };
}