import 'package:fis_i18n/i18n.dart';
import 'package:fis_i18n/types.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/services.dart';
import 'package:flyinsonolite/localization/fis_keybook.dart';

typedef FTrKeybookBuilder = Future<FISTrKeybook> Function();
typedef FI18nLocaleUpdater = void Function(Locale locale);

AssetBundle _assetBundle = rootBundle;

/// 翻译字典选项
///
/// [locale] 语言
///
/// [builder] 字典建造器
class FISTrKeybookOption {
  const FISTrKeybookOption(this.locale, this.builder);
  final Locale locale;
  final FTrKeybookBuilder builder;

  /// 中文字典建造器
  static final FISTrKeybookOption ChineseOption = FISTrKeybookOption(
    CHINESE_LOCALE,
    () => _buildInnerBoook(CHINESE_LOCALE),
  );

  /// 英文字典建造器
  static final FISTrKeybookOption EnglishOption = FISTrKeybookOption(
    ENGLISH_LOCALE,
    () => _buildInnerBoook(ENGLISH_LOCALE),
  );
}

/// 国际化翻译字典
FISTrKeybook get fisI18nBook => FISI18n.ins.currentBook;

/// 国际化
class FISI18n {
  FISI18n._();

  static FISI18n? _singleton;

  /// 单例
  static FISI18n get ins {
    if (_singleton == null) {
      throw Exception("There aren't any instance of FI18n.");
    }
    return _singleton!;
  }

  late FISTrKeybook _currentBook;
  late FI18nLocaleUpdater _localeUpdater;
  final Map<Locale, FTrKeybookBuilder> _bookMap = {};

  /// 当前语言字典
  FISTrKeybook get currentBook => _currentBook;

  /// 当前是否中文
  bool get isCurrentChinese => currentBook.isCurrentChinese;

  /// 支持的语言
  List<Locale> get supportedLocales => _bookMap.keys.toList();

  /// 设置内置资源包
  static void setAssetBundle(AssetBundle bundle) {
    _assetBundle = bundle;
  }

  /// 初始化
  static Future<void> init(
    FI18nLocaleUpdater localeUpdater,
    List<FISTrKeybookOption> bookOptions,
  ) async {
    if (_singleton != null) {
      throw Exception("FI18n has been init.");
    }
    _singleton = FISI18n._();
    _singleton!._localeUpdater = localeUpdater;
    await _singleton!._buildInstance(bookOptions);
  }

  Future<void> _buildInstance(List<FISTrKeybookOption> bookOptions) async {
    for (var option in bookOptions) {
      if (_bookMap.containsKey(option.locale)) {
        throw Exception("FI18n init: The same locale value already exists.");
      }
      setKeyBook(option.locale, option.builder);
    }
  }

  /// 加载（初始语言，init之后）
  static Future<void> load(Locale locale) async {
    // 语言+国家 精准匹配
    var bookBuilder = _singleton!._bookMap[locale];
    // 语言匹配
    if (bookBuilder == null) {
      final matchKey = _singleton!._bookMap.keys.firstWhere(
        (x) => x.languageCode == locale.languageCode,
        orElse: () => ENGLISH_LOCALE,
      );
      bookBuilder = _singleton!._bookMap[matchKey];
    }
    if (bookBuilder == null) {
      throw Exception(
          "FISI18n load error: No book-builder match the target locale.");
    }
    _singleton!._currentBook = await bookBuilder();
  }

  /// 切换语言
  Future<Locale> switchLanguage([Locale? locale]) async {
    Locale matchLocale;
    if (locale == null) {
      // 顺序找下一个字典
      final keys = _bookMap.keys.toList();
      final curIdx = keys.indexOf(currentBook.locale);
      int nextIdx = curIdx + 1;
      if (nextIdx >= keys.length) nextIdx = 0;
      matchLocale = keys[nextIdx];
    } else {
      // 优先语言Code和国家Code双匹配，否则选语言Code匹配
      final langCodeMatchList =
          _bookMap.keys.where((x) => x.languageCode == locale.languageCode);

      if (langCodeMatchList.isEmpty) {
        // 无匹配
        throw Exception(
            "FI18n switchLanguage: No keybook found for the target locale.");
      }
      if (langCodeMatchList.length > 1) {
        // 查找双匹配
        matchLocale = langCodeMatchList.firstWhere(
          (x) => x.countryCode == locale.languageCode,
          orElse: () => langCodeMatchList.first,
        );
      } else {
        // 单匹配
        matchLocale = langCodeMatchList.first;
      }
    }

    FTrKeybookBuilder builder = _bookMap[matchLocale]!;
    _currentBook = await builder();

    _localeUpdater(matchLocale);
    return matchLocale;
  }

  /// 设置翻译字典(相同语言会覆盖)
  void setKeyBook(Locale locale, FTrKeybookBuilder bookBuilder) {
    _bookMap[locale] = bookBuilder;
  }

  /// 根据字典树翻译
  ///
  /// [keyTree] 字典树，以.分隔，例：common.loading
  String translate(String keyTree) {
    final tiers = keyTree.split('.');
    dynamic curr = currentBook;
    for (var key in tiers) {
      if (curr is IPropQueryable) {
        curr = curr.getProp(key);
      } else {
        return keyTree;
      }
    }
    return curr;
  }
}

Future<FISTrKeybook> _buildInnerBoook(Locale locale) async {
  final code = locale.toCodeString();
  final assetKey = "assets/languages/$code.json";
  final text = await _assetBundle.loadString(assetKey, cache: false);
  final book = FISTrKeybook.createFromJson(text);
  return book;
}