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

/// Persists and exposes the app theme mode (system | dark).
class ThemeProvider extends ChangeNotifier {
  static const _key = 'theme_mode';
  ThemeMode _mode = ThemeMode.system;

  ThemeProvider() {
    _load();
  }

  ThemeMode get mode => _mode;

  Future<void> _load() async {
    final prefs = await SharedPreferences.getInstance();
    final v = prefs.getString(_key);
    if (v == 'dark') {
      _mode = ThemeMode.dark;
    } else if (v == 'light') {
      _mode = ThemeMode.light;
    } else {
      _mode = ThemeMode.system;
    }
    notifyListeners();
  }

  Future<void> setMode(ThemeMode mode) async {
    _mode = mode;
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(
        _key,
        mode == ThemeMode.dark
            ? 'dark'
            : mode == ThemeMode.light
                ? 'light'
                : 'system');
    notifyListeners();
  }
}