import 'package:shared_preferences/shared_preferences.dart';

/// Layout zoom for the in-app reader (`pageWidth = screenWidth * scale`).
class ReaderZoom {
  static const prefKey = 'reader_zoom_scale';
  static const double min = 0.4;
  static const double max = 1.5;
  static const double step = 0.1;
  static const double defaultScale = 1.0;

  static double clamp(double value) {
    final stepped = (value / step).round() * step;
    return stepped.clamp(min, max);
  }

  static Future<double> load() async {
    final prefs = await SharedPreferences.getInstance();
    final raw = prefs.getDouble(prefKey);
    if (raw == null) return defaultScale;
    return clamp(raw);
  }

  static Future<void> save(double scale) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setDouble(prefKey, clamp(scale));
  }

  static String percentLabel(double scale) {
    final pct = (clamp(scale) * 100).round();
    return '$pct%';
  }
}