Input validation, WebSocket handler, and file upload middleware

src/middleware/upload.js

@@ -0,0 +1,35 @@
+const multer = require("multer");
+const path = require("path");
+const { nanoid } = require("nanoid");
+const config = require("../config");
+
+const ALLOWED_MIMES = new Set([
+  "image/jpeg",
+  "image/png",
+  "image/webp",
+  "image/avif",
+  "image/tiff",
+  "image/gif",
+  "image/svg+xml",
+]);
+
+const storage = multer.diskStorage({
+  destination: config.storage.uploadDir,
+  filename: (_req, file, cb) => {
+    const ext = path.extname(file.originalname).toLowerCase();
+    cb(null, `${nanoid(12)}${ext}`);
+  },
+});
+
+const upload = multer({
+  storage,
+  limits: { fileSize: config.storage.maxFileSize },
+  fileFilter: (_req, file, cb) => {
+    if (!ALLOWED_MIMES.has(file.mimetype)) {
+      return cb(new Error(`Unsupported format: ${file.mimetype}`));
+    }
+    cb(null, true);
+  },
+});
+
+module.exports = upload;