Improve code quality: Add utility functions and enhance validation

backend/controller/user.controller.js

@@ -44,30 +44,49 @@ const updatelanguage = expressAsyncHandler(async (req, res) => {
 const registeruser = expressAsyncHandler (async (req,res) => {
     const {name,email,password,pic} = req.body
 
+    // Validate required fields
     if (!name || !email || !password) {
         return res.status(400).json({ success: false, message: "Please provide all fields" });
     }
 
-    if (name.length < 2 || name.length > 50) {
+    // Validate name length
+    const trimmedName = name.trim();
+    if (trimmedName.length < 2 || trimmedName.length > 50) {
         return res.status(400).json({ success: false, message: "Name must be between 2 and 50 characters" });
     }
 
+    // Validate email format
     const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
-    if (!emailRegex.test(email)) {
+    const trimmedEmail = email.trim().toLowerCase();
+    if (!emailRegex.test(trimmedEmail)) {
         return res.status(400).json({ success: false, message: "Please provide a valid email address" });
     }
 
+    // Validate password strength
     if (password.length < 6) {
         return res.status(400).json({ success: false, message: "Password must be at least 6 characters long" });
     }
+
+    // Additional password validation: check for at least one letter and one number
+    if (!/(?=.*[a-zA-Z])(?=.*\d)/.test(password)) {
+        return res.status(400).json({ success: false, message: "Password must contain at least one letter and one number" });
+    }
 
 
-    const userExists = await User.findOne({email})
+    // Check if user already exists
+    const userExists = await User.findOne({ email: trimmedEmail })
 
     if(userExists) {
         return res.status(409).json({ success: false, message: "User already exists" });
     }
-    const user = await User.create({name, email, password,pic})
+
+    // Create new user with trimmed and normalized data
+    const user = await User.create({
+        name: trimmedName, 
+        email: trimmedEmail, 
+        password,
+        pic: pic || undefined
+    })
 
     if(user){
         res.status(201).json({

frontend/src/lib/utils.ts

@@ -5,14 +5,72 @@ export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs));
 }
 
+/**
+ * Get user profile pictures from a chat
+ * @param chat - The chat object containing users
+ * @param currentUserId - The ID of the current user to exclude
+ * @returns Array of user profile picture URLs
+ */
 export function getUserPics(chat, currentUserId) {
-  if (!chat?.users) return [];
+  if (!chat?.users || !Array.isArray(chat.users)) return [];
 
-  const otherUsers = chat.users.filter(user => user?._id?.toString() !== currentUserId?.toString());
+  const otherUsers = chat.users.filter(user => {
+    if (!user?._id) return false;
+    return user._id.toString() !== currentUserId?.toString();
+  });
 
   if (chat.isGroupChat) {
-    return otherUsers.slice(0, 3).map(user => user?.pic).filter(Boolean);
+    // For group chats, return up to 3 user pics
+    return otherUsers
+      .slice(0, 3)
+      .map(user => user?.pic)
+      .filter(Boolean);
   } else {
-    return otherUsers.length > 0 && otherUsers[0]?.pic ? [otherUsers[0].pic] : [];
+    // For one-on-one chats, return the other user's pic
+    return otherUsers.length > 0 && otherUsers[0]?.pic 
+      ? [otherUsers[0].pic] 
+      : [];
   }
 }
+
+/**
+ * Validate email format
+ * @param email - Email string to validate
+ * @returns Boolean indicating if email is valid
+ */
+export function isValidEmail(email) {
+  if (!email || typeof email !== 'string') return false;
+  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
+  return emailRegex.test(email.trim());
+}
+
+/**
+ * Format file size to human-readable format
+ * @param bytes - File size in bytes
+ * @returns Formatted string (e.g., "1.5 MB")
+ */
+export function formatFileSize(bytes) {
+  if (!bytes || bytes === 0) return '0 Bytes';
+  const k = 1024;
+  const sizes = ['Bytes', 'KB', 'MB', 'GB'];
+  const i = Math.floor(Math.log(bytes) / Math.log(k));
+  return Math.round((bytes / Math.pow(k, i)) * 100) / 100 + ' ' + sizes[i];
+}
+
+/**
+ * Debounce function to limit function calls
+ * @param func - Function to debounce
+ * @param wait - Wait time in milliseconds
+ * @returns Debounced function
+ */
+export function debounce(func, wait) {
+  let timeout;
+  return function executedFunction(...args) {
+    const later = () => {
+      clearTimeout(timeout);
+      func(...args);
+    };
+    clearTimeout(timeout);
+    timeout = setTimeout(later, wait);
+  };
+}