Lib und Services für PDF Viewer hinzugefügt

lib/tools/pdf_service.dart

@@ -0,0 +1,128 @@
+import 'dart:io';
+import 'package:http/http.dart' as http;
+import 'package:path_provider/path_provider.dart';
+import 'package:stadtbote/tools/util.dart';
+
+class PdfService {
+  static final PdfService _instance = PdfService._internal();
+  factory PdfService() => _instance;
+  PdfService._internal();
+
+  static const String _cacheSubDir = 'pdf_cache';
+
+  /// Generates a unique filename from URL using hash
+  String _getFilenameFromUrl(String url) {
+    final hash = Util.fastHash(url);
+    return '${hash.toRadixString(16)}.pdf';
+  }
+
+  /// Gets the cache directory for PDFs
+  Future<Directory> _getCacheDirectory() async {
+    final appDir = await getApplicationDocumentsDirectory();
+    final cacheDir = Directory('${appDir.path}/$_cacheSubDir');
+
+    if (!await cacheDir.exists()) {
+      await cacheDir.create(recursive: true);
+    }
+
+    return cacheDir;
+  }
+
+  /// Checks if PDF is already cached and returns the file if it exists
+  Future<File?> getCachedPdf(String url) async {
+    try {
+      final cacheDir = await _getCacheDirectory();
+      final filename = _getFilenameFromUrl(url);
+      final file = File('${cacheDir.path}/$filename');
+
+      if (await file.exists()) {
+        Util.logDebug('PDF found in cache: $filename');
+        return file;
+      }
+
+      return null;
+    } catch (e) {
+      Util.logException('Error checking PDF cache: $e');
+      return null;
+    }
+  }
+
+  /// Downloads PDF from URL and saves it to cache
+  Future<File> downloadAndCachePdf(String url) async {
+    Util.logInfo('Downloading PDF from: $url');
+
+    final response = await http.get(Uri.parse(url));
+
+    if (response.statusCode != 200) {
+      throw Exception('Failed to download PDF: HTTP ${response.statusCode}');
+    }
+
+    final cacheDir = await _getCacheDirectory();
+    final filename = _getFilenameFromUrl(url);
+    final file = File('${cacheDir.path}/$filename');
+
+    await file.writeAsBytes(response.bodyBytes);
+
+    Util.logInfo('PDF cached successfully: $filename');
+
+    return file;
+  }
+
+  /// Gets PDF from cache or downloads it if not cached
+  Future<File> getPdf(String url) async {
+    final cachedFile = await getCachedPdf(url);
+
+    if (cachedFile != null) {
+      return cachedFile;
+    }
+
+    return await downloadAndCachePdf(url);
+  }
+
+  /// Clears all cached PDFs
+  Future<void> clearCache() async {
+    try {
+      final cacheDir = await _getCacheDirectory();
+
+      if (await cacheDir.exists()) {
+        await cacheDir.delete(recursive: true);
+        Util.logInfo('PDF cache cleared');
+      }
+    } catch (e) {
+      Util.logException('Error clearing PDF cache: $e');
+    }
+  }
+
+  /// Gets the total size of cached PDFs in bytes
+  Future<int> getCacheSize() async {
+    try {
+      final cacheDir = await _getCacheDirectory();
+
+      if (!await cacheDir.exists()) {
+        return 0;
+      }
+
+      int totalSize = 0;
+      await for (final entity in cacheDir.list()) {
+        if (entity is File) {
+          totalSize += await entity.length();
+        }
+      }
+
+      return totalSize;
+    } catch (e) {
+      Util.logException('Error calculating cache size: $e');
+      return 0;
+    }
+  }
+
+  /// Validates if URL is a valid PDF URL
+  bool isValidPdfUrl(String url) {
+    try {
+      final uri = Uri.parse(url);
+      return uri.scheme == 'https' || uri.scheme == 'http';
+    } catch (e) {
+      return false;
+    }
+  }
+}