import 'package:signals/signals.dart';

import '../../database/database.dart';
import '../../l10n/locales.dart';
import '../fonts.dart';

/// The reader's presentation choices (spec 8.2) plus the per-app limits they
/// move within. Values persist through ReaderSettings in the database.
class ReaderSettingsController {
  ReaderSettingsController(this._db);

  final MewsDatabase _db;

  static const minScale = 0.75;
  static const maxScale = 2.0;
  static const scaleStep = 0.125;

  /// The accepted values, in the order the settings page offers them. A
  /// setting arrives as a link the reader can also type, so a value outside
  /// these lists is refused rather than stored.
  static const themeModes = ['light', 'dark', 'system'];
  static const variants = ['site', 'warm', 'cool', 'green', 'mono'];

  final font = signal(defaultFontFamily);
  final fontScale = signal(1.0);
  final themeMode = signal('system');
  final variant = signal('site');

  /// The interface language: a shipped locale tag, or [systemLanguage] to take
  /// whatever the device asks for.
  final language = signal(systemLanguage);

  Future<void> load() async {
    final settings = await _db.readSettings();
    if (settings == null) return;
    font.value = settings.font;
    fontScale.value = settings.fontScale;
    themeMode.value = settings.themeMode;
    variant.value = settings.variant;
    language.value = settings.language;
  }

  Future<bool> setFont(String family) async {
    // Only a family this build bundles: an unknown one would silently render
    // in the platform's font instead.
    if (!readerFonts.any((f) => f.family == family) || family == font.value) {
      return false;
    }
    font.value = family;
    await _persist();
    return true;
  }

  Future<bool> decreaseSize() => _setScale(fontScale.value - scaleStep);
  Future<bool> increaseSize() => _setScale(fontScale.value + scaleStep);

  Future<bool> _setScale(double value) async {
    if (value < minScale || value > maxScale) return false;
    fontScale.value = value;
    await _persist();
    return true;
  }

  Future<bool> setThemeMode(String mode) async {
    if (!themeModes.contains(mode) || mode == themeMode.value) return false;
    themeMode.value = mode;
    await _persist();
    return true;
  }

  Future<bool> setVariant(String variant) async {
    if (!variants.contains(variant) || variant == this.variant.value) {
      return false;
    }
    this.variant.value = variant;
    await _persist();
    return true;
  }

  Future<bool> setLanguage(String tag) async {
    if (tag != systemLanguage && matchLocale(tag) == null) return false;
    if (tag == language.value) return false;
    language.value = tag;
    await _persist();
    return true;
  }

  Future<void> _persist() => _db.saveSettings(
        font: font.value,
        fontScale: fontScale.value,
        themeMode: themeMode.value,
        variant: variant.value,
        language: language.value,
      );
}