import 'package:intl/locale.dart';

abstract class FileMatcher {
  const FileMatcher._();

  static String? matchFile({
    required List<String> files,
    required String name,
    String extension = 'png',
    int scale = 1,
    Locale? locale,
  }) {
    final localized = matchLocale(files: files, name: 'logo', extension: 'png');
    final scaled = matchScale(files: localized, name: 'logo', extension: 'png');
    final file = files.singleWhere((element) => element == scaled);
    return file;
  }

  static List<String> matchLocale({
    required List<String> files,
    Locale? locale,
    required String name,
    required String extension,
  }) {
    files.sort();
    files = files.reversed.toList();
    List<RegExp> expressions = <RegExp>[];

    // adding the fallbacks
    // - match just *any* language
    // - match the five mostly spoken languages of the world, copied from Wikipedia
    expressions.addAll(
      [
        RegExp(
          '^([a-z]+(-[a-z]+)?\\.lproj\\/)?$name(@\\d+x)?\\.$extension\$',
          unicode: true,
          caseSensitive: false,
        ),
        ...['en', 'zh', 'hi', 'es', 'fr'].reversed.map(
              (language) => RegExp(
                '^$language(-[a-z]+)?\\.lproj\\/$name(@\\d+x)?\\.$extension\$',
                unicode: true,
                caseSensitive: false,
              ),
            ),
      ],
    );

    if (locale != null) {
      final language = locale.languageCode;
      expressions.add(
        RegExp(
          '^$language(-[a-z]+)?\\.lproj\\/$name(@\\d+x)?\\.$extension\$',
          unicode: true,
          caseSensitive: false,
        ),
      );

      final region = locale.countryCode;
      if (region != null) {
        expressions.add(
          RegExp(
            '^$language-$region\\.lproj\\/$name(@\\d+x)?\\.$extension\$',
            unicode: true,
            caseSensitive: false,
          ),
        );
      }
    }

    for (final regex in expressions.reversed) {
      final matches = <String>[];
      for (final file in files) {
        final match = regex.stringMatch(file);
        if (match != null) matches.add(match);
      }
      if (matches.isNotEmpty) return matches;
    }
    return [];
  }

  static String matchScale({
    required List<String> files,
    int scale = 1,
    required String name,
    required String extension,
  }) {
    files.sort();
    files = files.reversed.toList();

    final regex = RegExp(
      '$name(@(\\d+)x)?\\.$extension\$',
      unicode: true,
      caseSensitive: false,
    );

    int closestScale = 0;

    final matches = <String>[];
    for (final file in files) {
      final match = regex.firstMatch(file);
      if (match != null) {
        String? group = match[2];
        if (group == null) {
          if (scale == 1) return match.input;
          group = '1';
        }

        final matchedScale = int.parse(group);
        if (matchedScale == scale) return match.input;

        if (matchedScale < scale) {
          if (closestScale < matchedScale) closestScale = matchedScale;
        } else if (closestScale < matchedScale) {
          closestScale = matchedScale;
        }

        matches.add(match.input);
      }
    }
    final scaledMatches = matches
        .where(
          (element) => RegExp(
            '$name(@${closestScale}x)?\\.$extension\$',
            unicode: true,
            caseSensitive: false,
          ).hasMatch(element),
        )
        .toList();
    scaledMatches.sort();
    return scaledMatches.last;
  }
}