punimtag/viewer-frontend/lib/utils.ts

import { clsx, type ClassValue } from "clsx"
import { twMerge } from "tailwind-merge"

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs))
}

/**
 * Validates an email address format
 * @param email - The email address to validate
 * @returns true if the email is valid, false otherwise
 */
export function isValidEmail(email: string): boolean {
  if (!email || typeof email !== 'string') {
    return false;
  }
  
  // Trim whitespace
  const trimmedEmail = email.trim();
  
  // Basic email regex pattern
  // Matches: local-part@domain
  // - Local part: alphanumeric, dots, hyphens, underscores, plus signs
  // - Domain: alphanumeric, dots, hyphens
  // - Must have @ symbol
  // - Domain must have at least one dot
  const emailRegex = /^[a-zA-Z0-9._+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
  
  // Check length constraints (RFC 5321)
  if (trimmedEmail.length > 254) {
    return false;
  }
  
  // Check for valid format
  if (!emailRegex.test(trimmedEmail)) {
    return false;
  }
  
  // Additional checks
  // - Cannot start or end with dot
  // - Cannot have consecutive dots
  // - Must have valid domain part
  const parts = trimmedEmail.split('@');
  if (parts.length !== 2) {
    return false;
  }
  
  const [localPart, domain] = parts;
  
  // Validate local part
  if (localPart.length === 0 || localPart.length > 64) {
    return false;
  }
  if (localPart.startsWith('.') || localPart.endsWith('.')) {
    return false;
  }
  if (localPart.includes('..')) {
    return false;
  }
  
  // Validate domain part
  if (domain.length === 0 || domain.length > 253) {
    return false;
  }
  if (domain.startsWith('.') || domain.endsWith('.')) {
    return false;
  }
  if (domain.includes('..')) {
    return false;
  }
  if (!domain.includes('.')) {
    return false;
  }
  
  // Domain must have at least one TLD (top-level domain)
  const domainParts = domain.split('.');
  if (domainParts.length < 2) {
    return false;
  }
  const tld = domainParts[domainParts.length - 1];
  if (tld.length < 2) {
    return false;
  }
  
  return true;
}