// lib/metadata/metadata_service.dart
import 'metadata_model.dart';
import 'metadata_cache.dart';

class MetadataService {
  static final MetadataService _instance = MetadataService._internal();
  factory MetadataService() => _instance;
  MetadataService._internal();

  final MetadataCache _cache = MetadataCache();

  /// 临时版本：不进行实际文件读取，只返回基于文件名的 fallback
  Future<FinalMetadata> getMetadata({
    required String url,
    required String fileName,
    required String fileId,
    bool forceRefresh = false,
  }) async {
    // 1. 检查缓存（如果有）
    if (!forceRefresh) {
      final cached = await _cache.get(fileId);
      if (cached != null && cached.isNotEmpty) {
        return cached;
      }
    }

    // 2. 暂时不读取文件，直接 fallback
    final fallback = _fallbackFromFileName(fileName);

    // 3. 缓存结果（即使 fallback 也缓存，避免频繁调用）
    if (fallback.isNotEmpty) {
      await _cache.put(fileId, fallback);
    }

    return fallback;
  }

  FinalMetadata _fallbackFromFileName(String fileName) {
    final dotIndex = fileName.lastIndexOf('.');
    final title = dotIndex > 0 ? fileName.substring(0, dotIndex) : fileName;
    return FinalMetadata(
      title: title,
      artist: '未知艺术家',
      source: 'filename',
    );
  }
}