优化项目结构

lib/services/epub/epub_stream_service.dart

@@ -0,0 +1,102 @@
+import 'dart:io';
+import 'dart:typed_data';
+import 'package:archive/archive.dart';
+import 'package:flutter/foundation.dart';
+import 'package:path/path.dart' as p;
+
+class EpubStreamService {
+  String? _currentBookPath;
+  String? _pendingBookPath;
+  Future<void>? _openBookFuture;
+
+  /// Cached decoded archive for the current book.
+  Archive? _cachedArchive;
+
+  Future<void> warmUp() async {}
+
+  Future<void> openBook(String epubPath) {
+    if (_currentBookPath == epubPath && _cachedArchive != null) {
+      return Future.value();
+    }
+
+    if (_pendingBookPath == epubPath && _openBookFuture != null) {
+      return _openBookFuture!;
+    }
+
+    _pendingBookPath = epubPath;
+    _openBookFuture = _doOpenBook(epubPath);
+    return _openBookFuture!;
+  }
+
+  Future<void> _doOpenBook(String epubPath) async {
+    try {
+      final bytes = await File(epubPath).readAsBytes();
+      _cachedArchive = ZipDecoder().decodeBytes(bytes);
+      _currentBookPath = epubPath;
+    } catch (e) {
+      _currentBookPath = null;
+      _cachedArchive = null;
+      rethrow;
+    } finally {
+      if (_pendingBookPath == epubPath) {
+        _pendingBookPath = null;
+        _openBookFuture = null;
+      }
+    }
+  }
+
+  /// Read a single file from the currently open EPUB archive.
+  /// Returns the file bytes, or null if not found / no book loaded.
+  Future<Uint8List?> readFileFromEpub({
+    required String targetFilePath,
+    String? epubPath,
+  }) async {
+    if (epubPath != null && epubPath != _currentBookPath) {
+      await openBook(epubPath);
+    }
+
+    if (_currentBookPath == null || _cachedArchive == null) {
+      return null;
+    }
+
+    final file = _cachedArchive!.findFile(targetFilePath);
+    if (file == null || file.content == null) {
+      return null;
+    }
+
+    return file.content is Uint8List
+        ? file.content as Uint8List
+        : Uint8List.fromList(file.content as List<int>);
+  }
+
+  void dispose() {
+    _cachedArchive = null;
+    _currentBookPath = null;
+    _pendingBookPath = null;
+    _openBookFuture = null;
+  }
+
+  String getMimeType(String filePath) {
+    final ext = p.extension(filePath).toLowerCase().replaceAll('.', '');
+    return _mimeTypeMap[ext] ?? 'application/octet-stream';
+  }
+
+  static const _mimeTypeMap = {
+    'html': 'text/html',
+    'htm': 'text/html',
+    'xhtml': 'application/xhtml+xml',
+    'xml': 'application/xml',
+    'css': 'text/css',
+    'jpg': 'image/jpeg',
+    'jpeg': 'image/jpeg',
+    'png': 'image/png',
+    'gif': 'image/gif',
+    'svg': 'image/svg+xml',
+    'webp': 'image/webp',
+    'ttf': 'font/ttf',
+    'otf': 'font/otf',
+    'woff': 'font/woff',
+    'woff2': 'font/woff2',
+    'js': 'application/javascript',
+  };
+}