chore: import upstream snapshot with attribution

apps/sim/lib/messaging/email/validation.ts

@@ -0,0 +1,135 @@
+export interface EmailValidationResult {
+  isValid: boolean
+  reason?: string
+  confidence: 'high' | 'medium' | 'low'
+  checks: {
+    syntax: boolean
+    domain: boolean
+    mxRecord: boolean
+    disposable: boolean
+  }
+}
+
+/** Common disposable domains for fast client-side feedback */
+const DISPOSABLE_DOMAINS = new Set([
+  '10minutemail.com',
+  '10minutemail.net',
+  'catchmail.io',
+  'dispostable.com',
+  'emailondeck.com',
+  'fakemailgenerator.com',
+  'getnada.com',
+  'guerrillamail.com',
+  'guerrillamailblock.com',
+  'mail.gw',
+  'mailinator.com',
+  'oakon.com',
+  'pokemail.net',
+  'salt.email',
+  'sharebot.net',
+  'sharklasers.com',
+  'spam4.me',
+  'temp-mail.org',
+  'tempail.com',
+  'tempmail.org',
+  'tempr.email',
+  'temporary-mail.net',
+  'throwaway.email',
+  'yopmail.com',
+])
+
+/**
+ * Validates email syntax using RFC 5322 compliant regex
+ */
+function validateEmailSyntax(email: string): boolean {
+  const emailRegex =
+    /^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/
+  return emailRegex.test(email) && email.length <= 254
+}
+
+/**
+ * Checks if email is from a known disposable email provider
+ */
+function isDisposableEmail(email: string): boolean {
+  const domain = email.split('@')[1]?.toLowerCase()
+  return domain ? DISPOSABLE_DOMAINS.has(domain) : false
+}
+
+/**
+ * Checks for obvious patterns that indicate invalid emails
+ */
+function hasInvalidPatterns(email: string): boolean {
+  if (email.includes('..')) return true
+
+  const localPart = email.split('@')[0]
+  if (localPart && localPart.length > 64) return true
+
+  return false
+}
+
+/**
+ * Quick email validation for client-side form feedback.
+ */
+export function quickValidateEmail(email: string): EmailValidationResult {
+  const checks = {
+    syntax: false,
+    domain: false,
+    mxRecord: true,
+    disposable: false,
+  }
+
+  checks.syntax = validateEmailSyntax(email)
+  if (!checks.syntax) {
+    return {
+      isValid: false,
+      reason: 'Invalid email format',
+      confidence: 'high',
+      checks,
+    }
+  }
+
+  const domain = email.split('@')[1]?.toLowerCase()
+  if (!domain) {
+    return {
+      isValid: false,
+      reason: 'Missing domain',
+      confidence: 'high',
+      checks,
+    }
+  }
+
+  checks.disposable = !isDisposableEmail(email)
+  if (!checks.disposable) {
+    return {
+      isValid: false,
+      reason: 'Disposable email addresses are not allowed',
+      confidence: 'high',
+      checks,
+    }
+  }
+
+  if (hasInvalidPatterns(email)) {
+    return {
+      isValid: false,
+      reason: 'Email contains suspicious patterns',
+      confidence: 'medium',
+      checks,
+    }
+  }
+
+  checks.domain = domain.includes('.') && !domain.startsWith('.') && !domain.endsWith('.')
+  if (!checks.domain) {
+    return {
+      isValid: false,
+      reason: 'Invalid domain format',
+      confidence: 'high',
+      checks,
+    }
+  }
+
+  return {
+    isValid: true,
+    confidence: 'medium',
+    checks,
+  }
+}