feat: Implement lesson creation with file uploads (video, attachments) and quiz data, integrating MinIO for storage.

Backend/src/middleware/upload.ts

@@ -0,0 +1,121 @@
+import multer from 'multer';
+import { Request } from 'express';
+import { config } from '../config';
+import { ValidationError } from './errorHandler';
+
+/**
+ * Allowed MIME types for different file categories
+ */
+export const ALLOWED_VIDEO_TYPES = [
+    'video/mp4',
+    'video/quicktime',
+    'video/x-msvideo',
+    'video/webm',
+    'video/x-matroska',
+];
+
+export const ALLOWED_ATTACHMENT_TYPES = [
+    // Documents
+    'application/pdf',
+    'application/msword',
+    'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+    'application/vnd.ms-excel',
+    'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
+    'application/vnd.ms-powerpoint',
+    'application/vnd.openxmlformats-officedocument.presentationml.presentation',
+    // Text
+    'text/plain',
+    'text/csv',
+    // Images
+    'image/jpeg',
+    'image/png',
+    'image/gif',
+    'image/webp',
+    'image/svg+xml',
+    // Archives
+    'application/zip',
+    'application/x-rar-compressed',
+    'application/x-7z-compressed',
+];
+
+/**
+ * Custom file filter for lesson uploads
+ */
+const fileFilter = (
+    req: Request,
+    file: Express.Multer.File,
+    callback: multer.FileFilterCallback
+) => {
+    if (file.fieldname === 'video') {
+        if (ALLOWED_VIDEO_TYPES.includes(file.mimetype)) {
+            callback(null, true);
+        } else {
+            callback(new ValidationError(`Invalid video file type: ${file.mimetype}. Allowed types: ${ALLOWED_VIDEO_TYPES.join(', ')}`));
+        }
+    } else if (file.fieldname === 'attachments') {
+        if (ALLOWED_ATTACHMENT_TYPES.includes(file.mimetype)) {
+            callback(null, true);
+        } else {
+            callback(new ValidationError(`Invalid attachment file type: ${file.mimetype}. Allowed types: PDF, Word, Excel, PowerPoint, images, and archives`));
+        }
+    } else {
+        callback(new ValidationError(`Unknown field: ${file.fieldname}`));
+    }
+};
+
+/**
+ * Multer configuration for lesson file uploads
+ * Stores files in memory for direct upload to MinIO
+ */
+export const lessonUpload = multer({
+    storage: multer.memoryStorage(),
+    limits: {
+        fileSize: config.upload.maxVideoSize, // Max file size (500MB for videos)
+        files: config.upload.maxAttachmentsPerLesson + 1, // +1 for video
+    },
+    fileFilter,
+}).fields([
+    { name: 'video', maxCount: 1 },
+    { name: 'attachments', maxCount: config.upload.maxAttachmentsPerLesson },
+]);
+
+/**
+ * Extended Request interface for uploaded files
+ */
+export interface LessonUploadRequest extends Request {
+    files?: {
+        video?: Express.Multer.File[];
+        attachments?: Express.Multer.File[];
+    };
+}
+
+/**
+ * Validate total attachment size
+ */
+export function validateTotalAttachmentSize(
+    files: Express.Multer.File[] | undefined
+): void {
+    if (!files) return;
+
+    const totalSize = files.reduce((sum, file) => sum + file.size, 0);
+    const maxTotalSize = config.upload.maxAttachmentSize * config.upload.maxAttachmentsPerLesson;
+
+    if (totalSize > maxTotalSize) {
+        throw new ValidationError(
+            `Total attachment size (${(totalSize / 1024 / 1024).toFixed(2)} MB) exceeds maximum allowed (${(maxTotalSize / 1024 / 1024).toFixed(2)} MB)`
+        );
+    }
+}
+
+/**
+ * Validate video file size
+ */
+export function validateVideoSize(file: Express.Multer.File | undefined): void {
+    if (!file) return;
+
+    if (file.size > config.upload.maxVideoSize) {
+        throw new ValidationError(
+            `Video file size (${(file.size / 1024 / 1024).toFixed(2)} MB) exceeds maximum allowed (${(config.upload.maxVideoSize / 1024 / 1024).toFixed(2)} MB)`
+        );
+    }
+}