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

import "models.dart";

/// App-wide appearance preferences (theme / locale / date format / currency /
/// font size), mirroring the web app's prefs.js. Persisted to SharedPreferences
/// so the chosen theme survives a restart before /api/me loads, and exposed as a
/// ChangeNotifier so MaterialApp and date formatting react to changes.
class AppSettings extends ChangeNotifier {
  static const _kTheme = "cc_theme";
  static const _kLocale = "cc_locale";
  static const _kDateFormat = "cc_dateFormat";
  static const _kTimeFormat = "cc_timeFormat";
  static const _kWeekStart = "cc_weekStart";
  static const _kCurrency = "cc_currency";
  static const _kFontSize = "cc_fontSize";

  String theme = "system"; // light | dark | system
  String locale = "en-US"; // BCP-47 language-REGION
  String dateFormat = "YMD"; // YMD | DMY_NUM | DMY | MDY

  /// Which clock times are written on. "auto" is the chosen region's own
  /// convention, which is what every time in the app read before there was a
  /// setting; the other two are for the people whose region and habit disagree.
  String timeFormat = "auto"; // auto | 24 | 12

  /// The day a week is drawn as starting on, wherever weekdays are laid out in a
  /// row — the charging scheduler's day picker today. See format.dart, which
  /// owns the rule so every such row reads the same.
  String weekStart = "auto"; // auto | monday | sunday

  String currency = "USD"; // ISO 4217 code
  String fontSize = "medium"; // small | medium | large

  /// Language and region are two controls over the one stored tag, so the pair
  /// can be mixed freely (English in Poland, say).
  String get language => locale.split("-").first;
  String get region => locale.split("-").length > 1 ? locale.split("-")[1] : "US";

  Future<void> loadFromStorage() async {
    final prefs = await SharedPreferences.getInstance();
    theme = prefs.getString(_kTheme) ?? theme;
    locale = prefs.getString(_kLocale) ?? locale;
    dateFormat = prefs.getString(_kDateFormat) ?? dateFormat;
    timeFormat = prefs.getString(_kTimeFormat) ?? timeFormat;
    weekStart = prefs.getString(_kWeekStart) ?? weekStart;
    currency = prefs.getString(_kCurrency) ?? currency;
    fontSize = prefs.getString(_kFontSize) ?? fontSize;
    notifyListeners();
  }

  Future<void> _persist() async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_kTheme, theme);
    await prefs.setString(_kLocale, locale);
    await prefs.setString(_kDateFormat, dateFormat);
    await prefs.setString(_kTimeFormat, timeFormat);
    await prefs.setString(_kWeekStart, weekStart);
    await prefs.setString(_kCurrency, currency);
    await prefs.setString(_kFontSize, fontSize);
  }

  /// Sync from a freshly fetched profile (login, boot, settings saves).
  void applyFromProfile(UserProfile p) {
    theme = p.theme;
    locale = p.locale;
    dateFormat = p.dateFormat;
    timeFormat = p.timeFormat;
    weekStart = p.weekStart;
    currency = p.currency;
    fontSize = p.fontSize;
    _persist();
    notifyListeners();
  }

  /// Optimistically apply a single changed field (used by Settings so the UI
  /// reacts instantly while the PATCH is in flight).
  void patch({
    String? theme,
    String? locale,
    String? dateFormat,
    String? timeFormat,
    String? weekStart,
    String? currency,
    String? fontSize,
  }) {
    if (theme != null) this.theme = theme;
    if (locale != null) this.locale = locale;
    if (dateFormat != null) this.dateFormat = dateFormat;
    if (timeFormat != null) this.timeFormat = timeFormat;
    if (weekStart != null) this.weekStart = weekStart;
    if (currency != null) this.currency = currency;
    if (fontSize != null) this.fontSize = fontSize;
    _persist();
    notifyListeners();
  }

  ThemeMode get themeMode => switch (theme) {
        "light" => ThemeMode.light,
        "dark" => ThemeMode.dark,
        _ => ThemeMode.system,
      };

  double get textScale => switch (fontSize) {
        "small" => 0.9375,
        "large" => 1.125,
        _ => 1.0,
      };
}