import { corsHeaders } from '../_shared/cors.ts';
import { rateLimiters, withRateLimit } from '../_shared/rateLimiter.ts';
import { createEdgeFunction } from '../_shared/edgeFunctionWrapper.ts';
import { validateString } from '../_shared/typeValidation.ts';

// Common disposable email domains (subset for performance)
const DISPOSABLE_DOMAINS = new Set([
  'tempmail.com', 'guerrillamail.com', '10minutemail.com', 'mailinator.com',
  'throwaway.email', 'temp-mail.org', 'fakeinbox.com', 'maildrop.cc',
  'yopmail.com', 'sharklasers.com', 'guerrillamailblock.com'
]);

interface EmailValidationResult {
  valid: boolean;
  reason?: string;
  suggestions?: string[];
}

function validateEmailFormat(email: string): EmailValidationResult {
  // Basic format validation
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  if (!emailRegex.test(email)) {
    return { valid: false, reason: 'Invalid email format' };
  }

  // Extract domain
  const domain = email.split('@')[1].toLowerCase();
  
  // Check against disposable domains
  if (DISPOSABLE_DOMAINS.has(domain)) {
    return {
      valid: false,
      reason: 'Disposable email addresses are not allowed. Please use a permanent email address.',
      suggestions: ['gmail.com', 'outlook.com', 'yahoo.com', 'protonmail.com']
    };
  }

  // Check for suspicious patterns
  if (domain.includes('temp') || domain.includes('disposable') || domain.includes('trash')) {
    return {
      valid: false,
      reason: 'This email domain appears to be temporary. Please use a permanent email address.',
    };
  }

  return { valid: true };
}

// Apply lenient rate limiting (30 req/min) for email validation
const handler = createEdgeFunction(
  {
    name: 'validate-email-backend',
    requireAuth: false,
    corsHeaders: corsHeaders
  },
  async (req, context) => {
    const { email } = await req.json();
    validateString(email, 'email', { requestId: context.requestId });

    context.span.setAttribute('action', 'validate_email');

    // Validate email
    const result = validateEmailFormat(email.toLowerCase().trim());

    return new Response(
      JSON.stringify(result),
      { 
        status: 200, 
        headers: { 'Content-Type': 'application/json' }
      }
    );
  }
);

export default withRateLimit(handler, rateLimiters.lenient, corsHeaders);