init

lib/email.ts

@@ -0,0 +1,91 @@
+const DISPOSABLE_EMAIL_DOMAINS = [
+  'tempmail.com',
+  'throwawaymail.com',
+  'tempmail100.com'
+];
+
+export type EmailValidationError =
+  | 'invalid_email_format'
+  | 'email_part_too_long'
+  | 'disposable_email_not_allowed'
+  | 'invalid_characters';
+
+const EMAIL_REGEX = /^(?=[a-zA-Z0-9@._%+-]{6,254}$)[a-zA-Z0-9._%+-]{1,64}@(?:[a-zA-Z0-9-]{1,63}\.){1,8}[a-zA-Z]{2,63}$/;
+
+export function validateEmail(email: string): {
+  isValid: boolean;
+  error?: string;
+} {
+  // validate email format
+  if (!EMAIL_REGEX.test(email)) {
+    return {
+      isValid: false,
+      error: 'invalid_email_format'
+    };
+  }
+
+  // check domain length
+  const [localPart, domain] = email.split('@');
+  if (domain.length > 255 || localPart.length > 64) {
+    return {
+      isValid: false,
+      error: 'email_part_too_long'
+    };
+  }
+
+  // check if it's a disposable email
+  if (DISPOSABLE_EMAIL_DOMAINS.includes(domain.toLowerCase())) {
+    return {
+      isValid: false,
+      error: 'disposable_email_not_allowed'
+    };
+  }
+
+  // check for special characters
+  if (/[<>()[\]\\.,;:\s@"]+/.test(localPart)) {
+    return {
+      isValid: false,
+      error: 'invalid_characters'
+    };
+  }
+
+  return { isValid: true };
+}
+
+// email validation (including alias detection)
+export function normalizeEmail(email: string): string {
+  if (!email) return '';
+
+  // convert to lowercase
+  let normalizedEmail = email.toLowerCase();
+
+  // separate email local part and domain part
+  const [localPart, domain] = normalizedEmail.split('@');
+
+  // handle different email service provider alias rules
+  switch (domain) {
+    case 'gmail.com':
+      // remove dot and + suffix
+      const gmailBase = localPart
+        .replace(/\./g, '')
+        .split('+')[0];
+      return `${gmailBase}@${domain}`;
+
+    case 'outlook.com':
+    case 'hotmail.com':
+    case 'live.com':
+      // remove + suffix
+      const microsoftBase = localPart.split('+')[0];
+      return `${microsoftBase}@${domain}`;
+
+    case 'yahoo.com':
+      // remove - suffix
+      const yahooBase = localPart.split('-')[0];
+      return `${yahooBase}@${domain}`;
+
+    default:
+      // for other emails, only remove + suffix
+      const baseLocalPart = localPart.split('+')[0];
+      return `${baseLocalPart}@${domain}`;
+  }
+}