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File Upload and Storage

Modern web applications frequently need to handle file uploads, from simple profile pictures to complex document management systems. Hypermodern provides a comprehensive file upload and storage system that handles everything from basic uploads to enterprise-grade features like virus scanning, image processing, and chunked uploads for large files.

Understanding File Upload Architecture

The Hypermodern file upload system is built around several key components that work together to provide a secure, scalable, and flexible solution:

  • Upload Middleware: Handles multipart form parsing and initial validation
  • File Storage Service: Abstracts storage backends (local, cloud)
  • Processing Pipeline: Handles file transformation and optimization
  • Security Layer: Provides virus scanning and content validation
  • Metadata Management: Tracks file information and relationships

Core Components

import 'package:hypermodern_server/hypermodern_server.dart';

class FileUploadSystem {
  final FileUploadMiddleware uploadMiddleware;
  final FileStorageService storageService;
  final FileProcessingPipeline processingPipeline;
  final FileSecurityService securityService;
  final FileMetadataService metadataService;

  FileUploadSystem({
    required this.uploadMiddleware,
    required this.storageService,
    required this.processingPipeline,
    required this.securityService,
    required this.metadataService,
  });
}

Basic File Upload Setup

Configuration

Start by configuring the file upload system with appropriate limits and validation rules:

class FileUploadConfig {
  static FileUploadConfig get standard => FileUploadConfig(
    uploadDir: 'temp_uploads',
    maxFileSize: 50 * 1024 * 1024, // 50MB
    maxFiles: 10,
    allowedExtensions: ['.jpg', '.jpeg', '.png', '.pdf', '.txt', '.doc', '.docx'],
    allowedMimeTypes: [
      'image/jpeg',
      'image/png',
      'application/pdf',
      'text/plain',
      'application/msword',
      'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
    ],
    autoSave: false, // Handle saving manually for more control
    virusScanEnabled: true,
    generateThumbnails: true,
  );

  static FileUploadConfig get restrictive => FileUploadConfig(
    uploadDir: 'secure_uploads',
    maxFileSize: 10 * 1024 * 1024, // 10MB
    maxFiles: 5,
    allowedExtensions: ['.pdf', '.txt'],
    allowedMimeTypes: ['application/pdf', 'text/plain'],
    autoSave: false,
    virusScanEnabled: true,
    requireAuthentication: true,
  );
}

Server Setup

Configure your Hypermodern server with file upload capabilities:

void configureFileUploads(HypermodernServer server) {
  // Configure upload middleware
  final uploadConfig = FileUploadConfig.standard;
  server.addMiddleware(FileUploadMiddleware(config: uploadConfig));
  
  // Set up storage service
  final storageConfig = FileStorageConfig(
    baseDirectory: 'storage/uploads',
    organizeByDate: true,
    preserveOriginalNames: true,
    maxFileSize: uploadConfig.maxFileSize,
  );
  final storageService = FileStorageService(config: storageConfig);
  
  // Set up processing pipeline
  final processingPipeline = FileProcessingPipeline([
    VirusScanProcessor(),
    ImageOptimizationProcessor(),
    ThumbnailGenerationProcessor(),
    MetadataExtractionProcessor(),
  ]);
  
  // Register upload endpoints
  _registerFileUploadEndpoints(server, storageService, processingPipeline);
}

Single File Upload

Basic Implementation

class FileUploadController {
  static Future<dynamic> uploadSingle(RequestData data) async {
    final uploadedFiles = data.files.values.toList();
    
    if (uploadedFiles.isEmpty) {
      return {'error': 'No files uploaded', 'code': 400};
    }
    
    if (uploadedFiles.length > 1) {
      return {'error': 'Only one file allowed', 'code': 400};
    }
    
    final file = uploadedFiles.first;
    
    try {
      // Validate file
      await _validateFile(file);
      
      // Process file
      final processedFile = await FileProcessingService.process(file);
      
      // Store file
      final storedFile = await FileStorageService.store(processedFile);
      
      // Create database record
      final fileRecord = await FileMetadataService.create(
        storedFile: storedFile,
        uploadedBy: data.user?.id,
        metadata: {
          'original_name': file.filename,
          'upload_ip': data.clientIP,
          'upload_time': DateTime.now().toIso8601String(),
        },
      );
      
      return {
        'success': true,
        'file': {
          'id': fileRecord.id,
          'filename': storedFile.originalName,
          'size': storedFile.size,
          'contentType': storedFile.contentType,
          'url': '/api/files/${fileRecord.id}',
          'uploadedAt': fileRecord.createdAt.toIso8601String(),
        },
      };
    } catch (e) {
      return {'error': e.toString(), 'code': 500};
    }
  }

  static Future<void> _validateFile(UploadedFile file) async {
    // Size validation
    if (file.size > 50 * 1024 * 1024) {
      throw ValidationException('File too large (max 50MB)');
    }
    
    // Extension validation
    final allowedExtensions = ['.jpg', '.jpeg', '.png', '.pdf', '.txt'];
    final extension = file.filename.toLowerCase().split('.').last;
    if (!allowedExtensions.contains('.$extension')) {
      throw ValidationException('File type not allowed');
    }
    
    // Content type validation
    final allowedTypes = ['image/jpeg', 'image/png', 'application/pdf', 'text/plain'];
    if (!allowedTypes.contains(file.contentType)) {
      throw ValidationException('Invalid content type');
    }
    
    // Virus scan
    final scanResult = await VirusScanService.scan(file.bytes);
    if (!scanResult.isClean) {
      throw SecurityException('File failed security scan');
    }
  }
}

Advanced Single Upload with Processing

class AdvancedFileUploadController {
  static Future<dynamic> uploadWithProcessing(RequestData data) async {
    final file = _extractSingleFile(data);
    final options = _extractProcessingOptions(data);
    
    try {
      // Pre-upload validation
      await FileValidator.validate(file, options.validationRules);
      
      // Security scanning
      await SecurityScanner.scan(file);
      
      // Process based on file type
      final processedFiles = await _processFile(file, options);
      
      // Store all versions
      final storedFiles = await _storeFiles(processedFiles);
      
      // Create database records
      final fileRecord = await _createFileRecord(file, storedFiles, data.user);
      
      // Generate response
      return _generateSuccessResponse(fileRecord, storedFiles);
      
    } catch (e) {
      await _handleUploadError(e, file);
      rethrow;
    }
  }

  static Future<List<ProcessedFile>> _processFile(
    UploadedFile file, 
    ProcessingOptions options,
  ) async {
    switch (file.contentType) {
      case 'image/jpeg':
      case 'image/png':
        return await ImageProcessor.process(file, options.imageOptions);
      
      case 'application/pdf':
        return await PDFProcessor.process(file, options.pdfOptions);
      
      case 'video/mp4':
        return await VideoProcessor.process(file, options.videoOptions);
      
      default:
        return [ProcessedFile.fromOriginal(file)];
    }
  }
}

Multiple File Upload

Batch Upload Implementation

class BatchUploadController {
  static Future<dynamic> uploadMultiple(RequestData data) async {
    final uploadedFiles = data.files.values.toList();
    
    if (uploadedFiles.isEmpty) {
      return {'error': 'No files uploaded'};
    }
    
    if (uploadedFiles.length > 10) {
      return {'error': 'Too many files (max 10)'};
    }
    
    // Validate total size
    final totalSize = uploadedFiles.fold<int>(0, (sum, file) => sum + file.size);
    if (totalSize > 100 * 1024 * 1024) { // 100MB total
      return {'error': 'Total file size too large (max 100MB)'};
    }
    
    final results = <Map<String, dynamic>>[];
    final errors = <Map<String, dynamic>>[];
    
    // Process files concurrently
    final futures = uploadedFiles.map((file) => _processFileAsync(file, data));
    final outcomes = await Future.wait(futures, eagerError: false);
    
    for (int i = 0; i < outcomes.length; i++) {
      final outcome = outcomes[i];
      final file = uploadedFiles[i];
      
      if (outcome.isSuccess) {
        results.add({
          'fieldName': file.fieldName,
          'filename': file.filename,
          'fileId': outcome.fileId,
          'url': outcome.url,
        });
      } else {
        errors.add({
          'fieldName': file.fieldName,
          'filename': file.filename,
          'error': outcome.error,
        });
      }
    }
    
    return {
      'success': errors.isEmpty,
      'uploaded': results.length,
      'failed': errors.length,
      'files': results,
      'errors': errors,
    };
  }

  static Future<UploadOutcome> _processFileAsync(
    UploadedFile file, 
    RequestData data,
  ) async {
    try {
      await FileValidator.validate(file);
      final processed = await FileProcessor.process(file);
      final stored = await FileStorage.store(processed);
      final record = await FileMetadata.create(stored, data.user?.id);
      
      return UploadOutcome.success(
        fileId: record.id,
        url: '/api/files/${record.id}',
      );
    } catch (e) {
      return UploadOutcome.failure(error: e.toString());
    }
  }
}

Image Upload and Processing

Comprehensive Image Handling

class ImageUploadController {
  static Future<dynamic> uploadImage(RequestData data) async {
    final file = _extractImageFile(data);
    final options = ImageProcessingOptions.fromRequest(data);
    
    try {
      // Validate image
      await ImageValidator.validate(file);
      
      // Extract metadata
      final metadata = await ImageMetadataExtractor.extract(file);
      
      // Process image
      final processedImages = await ImageProcessor.process(file, options);
      
      // Store all versions
      final storedFiles = await _storeImageVersions(processedImages);
      
      // Create database record
      final imageRecord = await ImageRecord.create(
        originalFile: storedFiles.original,
        thumbnails: storedFiles.thumbnails,
        metadata: metadata,
        uploadedBy: data.user?.id,
      );
      
      return {
        'success': true,
        'image': {
          'id': imageRecord.id,
          'original': {
            'url': storedFiles.original.publicUrl,
            'width': metadata.width,
            'height': metadata.height,
            'size': storedFiles.original.size,
          },
          'thumbnails': storedFiles.thumbnails.map((thumb) => {
            'size': thumb.size,
            'url': thumb.publicUrl,
            'width': thumb.width,
            'height': thumb.height,
          }).toList(),
          'metadata': {
            'format': metadata.format,
            'colorSpace': metadata.colorSpace,
            'hasAlpha': metadata.hasAlpha,
            'exif': metadata.exifData,
          },
        },
      };
    } catch (e) {
      return {'error': e.toString()};
    }
  }
}

class ImageProcessor {
  static Future<ProcessedImageSet> process(
    UploadedFile file, 
    ImageProcessingOptions options,
  ) async {
    final image = await decodeImage(file.bytes);
    if (image == null) {
      throw ProcessingException('Invalid image format');
    }
    
    final results = ProcessedImageSet();
    
    // Optimize original
    if (options.optimizeOriginal) {
      final optimized = await _optimizeImage(image, options);
      results.original = ProcessedImage(
        data: optimized,
        width: image.width,
        height: image.height,
        format: options.outputFormat,
      );
    }
    
    // Generate thumbnails
    for (final size in options.thumbnailSizes) {
      final thumbnail = await _generateThumbnail(image, size, options);
      results.thumbnails.add(thumbnail);
    }
    
    // Generate responsive versions
    if (options.generateResponsive) {
      final responsive = await _generateResponsiveVersions(image, options);
      results.responsive.addAll(responsive);
    }
    
    return results;
  }

  static Future<Uint8List> _optimizeImage(
    Image image, 
    ImageProcessingOptions options,
  ) async {
    // Resize if needed
    if (options.maxWidth != null || options.maxHeight != null) {
      image = copyResize(
        image,
        width: options.maxWidth,
        height: options.maxHeight,
        maintainAspect: true,
      );
    }
    
    // Apply filters
    if (options.sharpen) {
      image = convolution(image, [0, -1, 0, -1, 5, -1, 0, -1, 0]);
    }
    
    // Encode with quality settings
    switch (options.outputFormat) {
      case ImageFormat.jpeg:
        return Uint8List.fromList(encodeJpg(image, quality: options.quality));
      case ImageFormat.png:
        return Uint8List.fromList(encodePng(image));
      case ImageFormat.webp:
        return Uint8List.fromList(encodeWebP(image, quality: options.quality));
      default:
        return Uint8List.fromList(encodeJpg(image, quality: options.quality));
    }
  }
}

Large File Upload with Chunking

Chunked Upload Implementation

class ChunkedUploadController {
  static Future<dynamic> initiateUpload(RequestData data) async {
    final filename = data.body['filename'] as String;
    final fileSize = data.body['fileSize'] as int;
    final chunkSize = data.body['chunkSize'] as int? ?? (5 * 1024 * 1024); // 5MB default
    
    // Validate file size
    if (fileSize > 1024 * 1024 * 1024) { // 1GB limit
      return {'error': 'File too large (max 1GB)'};
    }
    
    // Create upload session
    final uploadSession = await ChunkedUploadSession.create(
      filename: filename,
      fileSize: fileSize,
      chunkSize: chunkSize,
      userId: data.user?.id,
    );
    
    return {
      'success': true,
      'uploadId': uploadSession.id,
      'chunkSize': chunkSize,
      'totalChunks': uploadSession.totalChunks,
      'uploadUrl': '/api/upload/chunk',
    };
  }

  static Future<dynamic> uploadChunk(RequestData data) async {
    final uploadId = data.body['uploadId'] as String;
    final chunkIndex = data.body['chunkIndex'] as int;
    final file = data.files.values.first;
    
    try {
      // Get upload session
      final session = await ChunkedUploadSession.get(uploadId);
      if (session == null) {
        return {'error': 'Upload session not found'};
      }
      
      // Validate chunk
      if (chunkIndex >= session.totalChunks) {
        return {'error': 'Invalid chunk index'};
      }
      
      // Store chunk
      await ChunkStorage.store(uploadId, chunkIndex, file.bytes);
      
      // Update session
      await session.markChunkReceived(chunkIndex);
      
      // Check if upload is complete
      if (session.isComplete) {
        final assembledFile = await _assembleFile(session);
        await _finalizeUpload(session, assembledFile);
        
        return {
          'success': true,
          'completed': true,
          'fileId': session.finalFileId,
          'url': '/api/files/${session.finalFileId}',
        };
      }
      
      return {
        'success': true,
        'completed': false,
        'chunksReceived': session.chunksReceived.length,
        'totalChunks': session.totalChunks,
        'progress': session.progress,
      };
    } catch (e) {
      return {'error': e.toString()};
    }
  }

  static Future<AssembledFile> _assembleFile(ChunkedUploadSession session) async {
    final chunks = <Uint8List>[];
    
    for (int i = 0; i < session.totalChunks; i++) {
      final chunkData = await ChunkStorage.get(session.id, i);
      chunks.add(chunkData);
    }
    
    // Combine chunks
    final totalSize = chunks.fold<int>(0, (sum, chunk) => sum + chunk.length);
    final assembledData = Uint8List(totalSize);
    
    int offset = 0;
    for (final chunk in chunks) {
      assembledData.setRange(offset, offset + chunk.length, chunk);
      offset += chunk.length;
    }
    
    return AssembledFile(
      filename: session.filename,
      data: assembledData,
      contentType: _detectContentType(session.filename),
    );
  }

  static Future<void> _finalizeUpload(
    ChunkedUploadSession session, 
    AssembledFile file,
  ) async {
    // Process the assembled file
    final processedFile = await FileProcessor.process(file);
    
    // Store the file
    final storedFile = await FileStorage.store(processedFile);
    
    // Create database record
    final fileRecord = await FileRecord.create(
      storedFile: storedFile,
      uploadedBy: session.userId,
      uploadMethod: 'chunked',
    );
    
    // Update session with final file ID
    await session.setFinalFileId(fileRecord.id);
    
    // Clean up chunks
    await ChunkStorage.cleanup(session.id);
  }
}

File Security and Validation

Comprehensive Security Layer

class FileSecurityService {
  static Future<SecurityScanResult> scanFile(UploadedFile file) async {
    final results = <SecurityCheck>[];
    
    // Virus scan
    final virusScan = await VirusScanner.scan(file.bytes);
    results.add(virusScan);
    
    // Content validation
    final contentValidation = await ContentValidator.validate(file);
    results.add(contentValidation);
    
    // Malware detection
    final malwareDetection = await MalwareDetector.scan(file);
    results.add(malwareDetection);
    
    // File structure analysis
    final structureAnalysis = await FileStructureAnalyzer.analyze(file);
    results.add(structureAnalysis);
    
    return SecurityScanResult(
      isClean: results.every((check) => check.passed),
      checks: results,
      riskLevel: _calculateRiskLevel(results),
    );
  }

  static Future<void> quarantineFile(String fileId, String reason) async {
    await QuarantineService.quarantine(fileId, reason);
    await NotificationService.notifyAdmins('File quarantined: $fileId - $reason');
  }
}

class ContentValidator {
  static Future<SecurityCheck> validate(UploadedFile file) async {
    final checks = <String>[];
    
    // Check file signature matches extension
    final actualType = await FileTypeDetector.detect(file.bytes);
    final expectedType = _getExpectedType(file.filename);
    
    if (actualType != expectedType) {
      checks.add('File signature mismatch');
    }
    
    // Check for embedded executables
    if (await _containsExecutableCode(file.bytes)) {
      checks.add('Contains executable code');
    }
    
    // Check for suspicious patterns
    final suspiciousPatterns = await _scanForSuspiciousPatterns(file.bytes);
    checks.addAll(suspiciousPatterns);
    
    return SecurityCheck(
      name: 'Content Validation',
      passed: checks.isEmpty,
      issues: checks,
    );
  }

  static Future<bool> _containsExecutableCode(Uint8List data) async {
    // Check for common executable signatures
    final signatures = [
      [0x4D, 0x5A], // PE executable
      [0x7F, 0x45, 0x4C, 0x46], // ELF executable
      [0xCA, 0xFE, 0xBA, 0xBE], // Mach-O executable
    ];
    
    for (final signature in signatures) {
      if (_hasSignature(data, signature)) {
        return true;
      }
    }
    
    return false;
  }
}

File Type Validation

class FileTypeValidator {
  static const Map<String, List<String>> allowedTypes = {
    'image': ['image/jpeg', 'image/png', 'image/gif', 'image/webp'],
    'document': ['application/pdf', 'text/plain', 'application/msword'],
    'video': ['video/mp4', 'video/webm', 'video/quicktime'],
    'audio': ['audio/mpeg', 'audio/wav', 'audio/ogg'],
  };

  static Future<ValidationResult> validate(
    UploadedFile file, 
    String category,
  ) async {
    final allowedMimeTypes = allowedTypes[category];
    if (allowedMimeTypes == null) {
      return ValidationResult.failure('Unknown file category');
    }
    
    // Check MIME type
    if (!allowedMimeTypes.contains(file.contentType)) {
      return ValidationResult.failure('File type not allowed for category $category');
    }
    
    // Verify file signature
    final detectedType = await FileSignatureDetector.detect(file.bytes);
    if (!allowedMimeTypes.contains(detectedType)) {
      return ValidationResult.failure('File signature does not match declared type');
    }
    
    // Category-specific validation
    switch (category) {
      case 'image':
        return await _validateImage(file);
      case 'document':
        return await _validateDocument(file);
      case 'video':
        return await _validateVideo(file);
      default:
        return ValidationResult.success();
    }
  }

  static Future<ValidationResult> _validateImage(UploadedFile file) async {
    try {
      final image = await decodeImage(file.bytes);
      if (image == null) {
        return ValidationResult.failure('Invalid image format');
      }
      
      // Check dimensions
      if (image.width > 10000 || image.height > 10000) {
        return ValidationResult.failure('Image dimensions too large');
      }
      
      // Check for suspicious metadata
      final metadata = await ImageMetadataExtractor.extract(file);
      if (metadata.hasSuspiciousData) {
        return ValidationResult.failure('Image contains suspicious metadata');
      }
      
      return ValidationResult.success();
    } catch (e) {
      return ValidationResult.failure('Image validation failed: $e');
    }
  }
}

File Storage Backends

Local Storage Implementation

class LocalFileStorage implements FileStorageBackend {
  final String baseDirectory;
  final bool organizeByDate;

  LocalFileStorage({
    required this.baseDirectory,
    this.organizeByDate = true,
  });

  @override
  Future<StoredFile> store(ProcessedFile file) async {
    final storagePath = _generateStoragePath(file.filename);
    final fullPath = path.join(baseDirectory, storagePath);
    
    // Ensure directory exists
    await Directory(path.dirname(fullPath)).create(recursive: true);
    
    // Write file
    final fileHandle = File(fullPath);
    await fileHandle.writeAsBytes(file.data);
    
    return StoredFile(
      id: _generateFileId(),
      originalName: file.filename,
      storagePath: storagePath,
      size: file.data.length,
      contentType: file.contentType,
      uploadedAt: DateTime.now(),
      backend: StorageBackend.local,
    );
  }

  @override
  Future<Uint8List?> retrieve(String storagePath) async {
    final fullPath = path.join(baseDirectory, storagePath);
    final file = File(fullPath);
    
    if (!await file.exists()) {
      return null;
    }
    
    return await file.readAsBytes();
  }

  @override
  Future<bool> delete(String storagePath) async {
    final fullPath = path.join(baseDirectory, storagePath);
    final file = File(fullPath);
    
    if (await file.exists()) {
      await file.delete();
      return true;
    }
    
    return false;
  }

  String _generateStoragePath(String filename) {
    final now = DateTime.now();
    final fileId = _generateFileId();
    final extension = path.extension(filename);
    
    if (organizeByDate) {
      final year = now.year.toString();
      final month = now.month.toString().padLeft(2, '0');
      final day = now.day.toString().padLeft(2, '0');
      
      return '$year/$month/$day/$fileId$extension';
    } else {
      return '$fileId$extension';
    }
  }
}

Database Integration

class FileMetadataService {
  static Future<FileRecord> createRecord({
    required StoredFile storedFile,
    String? uploadedBy,
    Map<String, dynamic>? metadata,
    String? description,
    String? category,
  }) async {
    final record = FileRecord(
      id: storedFile.id,
      originalName: storedFile.originalName,
      storagePath: storedFile.storagePath,
      size: storedFile.size,
      contentType: storedFile.contentType,
      uploadedBy: uploadedBy,
      uploadedAt: storedFile.uploadedAt,
      metadata: metadata ?? {},
      description: description,
      category: category,
      backend: storedFile.backend,
    );
    
    await Database.insert('files', record.toJson());
    
    // Index for search if it's a document
    if (_isSearchableDocument(record)) {
      await SearchIndexService.indexFile(record);
    }
    
    return record;
  }

  static Future<FileRecord?> getRecord(String fileId) async {
    final result = await Database.query(
      'SELECT * FROM files WHERE id = ?',
      [fileId],
    );
    
    if (result.isEmpty) {
      return null;
    }
    
    return FileRecord.fromJson(result.first);
  }

  static Future<List<FileRecord>> getUserFiles(
    String userId, {
    String? category,
    int limit = 50,
    int offset = 0,
  }) async {
    var query = 'SELECT * FROM files WHERE uploaded_by = ?';
    final params = <dynamic>[userId];
    
    if (category != null) {
      query += ' AND category = ?';
      params.add(category);
    }
    
    query += ' ORDER BY uploaded_at DESC LIMIT ? OFFSET ?';
    params.addAll([limit, offset]);
    
    final results = await Database.query(query, params);
    return results.map((row) => FileRecord.fromJson(row)).toList();
  }
}

Performance Optimization

Caching Strategy

class FileCache {
  static final Map<String, CachedFile> _cache = {};
  static const maxCacheSize = 100 * 1024 * 1024; // 100MB
  static int _currentCacheSize = 0;

  static Future<Uint8List?> get(String fileId) async {
    final cached = _cache[fileId];
    if (cached != null && cached.isValid) {
      // Move to end (LRU)
      _cache.remove(fileId);
      _cache[fileId] = cached;
      return cached.data;
    }
    
    return null;
  }

  static void put(String fileId, Uint8List data) {
    // Don't cache large files
    if (data.length > 10 * 1024 * 1024) return; // 10MB limit
    
    // Evict old entries if needed
    while (_currentCacheSize + data.length > maxCacheSize && _cache.isNotEmpty) {
      final oldestKey = _cache.keys.first;
      final removed = _cache.remove(oldestKey)!;
      _currentCacheSize -= removed.data.length;
    }
    
    _cache[fileId] = CachedFile(
      data: data,
      cachedAt: DateTime.now(),
      ttl: Duration(minutes: 30),
    );
    _currentCacheSize += data.length;
  }
}

Async Processing

class AsyncFileProcessor {
  static final Queue<ProcessingJob> _queue = Queue();
  static bool _isProcessing = false;

  static Future<void> queueForProcessing(
    String fileId, 
    ProcessingOptions options,
  ) async {
    final job = ProcessingJob(
      fileId: fileId,
      options: options,
      queuedAt: DateTime.now(),
    );
    
    _queue.add(job);
    await JobQueue.add('file_processing', job.toJson());
    
    _processQueue();
  }

  static Future<void> _processQueue() async {
    if (_isProcessing || _queue.isEmpty) return;
    
    _isProcessing = true;
    
    try {
      while (_queue.isNotEmpty) {
        final job = _queue.removeFirst();
        await _processJob(job);
      }
    } finally {
      _isProcessing = false;
    }
  }

  static Future<void> _processJob(ProcessingJob job) async {
    try {
      final fileRecord = await FileMetadataService.getRecord(job.fileId);
      if (fileRecord == null) return;
      
      final fileData = await FileStorage.retrieve(fileRecord.storagePath);
      if (fileData == null) return;
      
      // Process based on options
      final processedFiles = await FileProcessor.process(
        UploadedFile.fromData(fileData, fileRecord.originalName),
        job.options,
      );
      
      // Store processed versions
      for (final processed in processedFiles) {
        await FileStorage.store(processed);
      }
      
      // Update database
      await FileMetadataService.updateProcessingStatus(
        job.fileId, 
        ProcessingStatus.completed,
      );
      
    } catch (e) {
      await FileMetadataService.updateProcessingStatus(
        job.fileId, 
        ProcessingStatus.failed,
        error: e.toString(),
      );
    }
  }
}

Best Practices and Security

1. Input Validation

Always validate files thoroughly:

class ComprehensiveFileValidator {
  static Future<ValidationResult> validate(UploadedFile file) async {
    final checks = <ValidationCheck>[];
    
    // Size check
    checks.add(await _validateSize(file));
    
    // Type check
    checks.add(await _validateType(file));
    
    // Content check
    checks.add(await _validateContent(file));
    
    // Security check
    checks.add(await _validateSecurity(file));
    
    final failedChecks = checks.where((check) => !check.passed).toList();
    
    return ValidationResult(
      passed: failedChecks.isEmpty,
      checks: checks,
      errors: failedChecks.map((check) => check.error).toList(),
    );
  }
}

2. Error Handling

Implement comprehensive error handling:

class FileUploadErrorHandler {
  static Map<String, dynamic> handleError(Exception error, UploadedFile? file) {
    switch (error.runtimeType) {
      case ValidationException:
        return _handleValidationError(error as ValidationException);
      
      case SecurityException:
        return _handleSecurityError(error as SecurityException, file);
      
      case StorageException:
        return _handleStorageError(error as StorageException);
      
      case ProcessingException:
        return _handleProcessingError(error as ProcessingException);
      
      default:
        return _handleGenericError(error);
    }
  }

  static Map<String, dynamic> _handleSecurityError(
    SecurityException error, 
    UploadedFile? file,
  ) {
    // Log security incident
    SecurityLogger.logIncident(
      type: 'file_upload_security_violation',
      details: error.toString(),
      file: file?.filename,
      timestamp: DateTime.now(),
    );
    
    return {
      'error': 'File failed security validation',
      'code': 'SECURITY_VIOLATION',
      'details': error.userMessage,
    };
  }
}

3. Monitoring and Analytics

Track file upload metrics:

class FileUploadAnalytics {
  static Future<void> trackUpload(FileRecord record) async {
    await AnalyticsService.track('file_upload', {
      'file_id': record.id,
      'file_size': record.size,
      'content_type': record.contentType,
      'category': record.category,
      'user_id': record.uploadedBy,
      'timestamp': record.uploadedAt.toIso8601String(),
    });
  }

  static Future<Map<String, dynamic>> getUploadStats(
    String userId, {
    DateTime? startDate,
    DateTime? endDate,
  }) async {
    final stats = await Database.query('''
      SELECT 
        COUNT(*) as total_uploads,
        SUM(size) as total_size,
        AVG(size) as avg_size,
        content_type,
        COUNT(*) as type_count
      FROM files 
      WHERE uploaded_by = ? 
        AND uploaded_at BETWEEN ? AND ?
      GROUP BY content_type
    ''', [
      userId,
      startDate?.toIso8601String() ?? '1970-01-01',
      endDate?.toIso8601String() ?? DateTime.now().toIso8601String(),
    ]);
    
    return {
      'totalUploads': stats.fold(0, (sum, row) => sum + row['type_count']),
      'totalSize': stats.fold(0, (sum, row) => sum + row['total_size']),
      'byType': stats,
    };
  }
}

The file upload and storage system in Hypermodern provides enterprise-grade capabilities while maintaining simplicity for basic use cases. Whether you're handling simple profile pictures or building a comprehensive document management system, the flexible architecture adapts to your needs while ensuring security, performance, and scalability.

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