import type { APIRoute } from 'astro';
import { logger, logApiRequest } from '../../utils/logger';
import { captureException } from '../../utils/sentry';

// ============================================================
// In-memory rate limiter (sliding window, per IP)
// ============================================================
interface RateLimitEntry {
  timestamps: number[];
}

const rateLimitStore = new Map<string, RateLimitEntry>();

const RATE_LIMIT_WINDOW_MS = 60 * 60 * 1000; // 1 hour
const RATE_LIMIT_MAX_REQUESTS = 5; // max 5 contact submissions per hour per IP

function checkRateLimit(ip: string): { allowed: boolean; remaining: number; resetAt: number } {
  const now = Date.now();
  const windowStart = now - RATE_LIMIT_WINDOW_MS;

  const entry = rateLimitStore.get(ip) ?? { timestamps: [] };
  // Remove timestamps outside the window
  entry.timestamps = entry.timestamps.filter((ts) => ts > windowStart);

  const remaining = RATE_LIMIT_MAX_REQUESTS - entry.timestamps.length;
  const resetAt = entry.timestamps.length > 0
    ? entry.timestamps[0] + RATE_LIMIT_WINDOW_MS
    : now + RATE_LIMIT_WINDOW_MS;

  if (entry.timestamps.length >= RATE_LIMIT_MAX_REQUESTS) {
    rateLimitStore.set(ip, entry);
    return { allowed: false, remaining: 0, resetAt };
  }

  entry.timestamps.push(now);
  rateLimitStore.set(ip, entry);
  return { allowed: true, remaining: remaining - 1, resetAt };
}

// ============================================================
// Input validation
// ============================================================
const EMAIL_REGEX = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
const PHONE_REGEX = /^[\+]?[(]?[0-9]{1,3}[)]?[-\s\.]?[(]?[0-9]{1,4}[)]?[-\s\.]?[0-9]{1,4}[-\s\.]?[0-9]{1,9}$/;

const VALID_SUBJECTS = [
  'web-development',
  'mobile-development',
  'cloud-services',
  'ai-ml',
  'consulting',
  'support',
  'other',
];

interface ContactFormData {
  name: string;
  email: string;
  phone?: string;
  subject: string;
  message: string;
  website?: string; // honeypot
}

function validateContactForm(data: ContactFormData): string | null {
  if (!data.name || data.name.trim().length < 2) {
    return 'Name must be at least 2 characters.';
  }
  if (data.name.trim().length > 100) {
    return 'Name must be under 100 characters.';
  }
  if (!data.email || !EMAIL_REGEX.test(data.email.trim())) {
    return 'A valid email address is required.';
  }
  if (data.email.trim().length > 254) {
    return 'Email address is too long.';
  }
  if (data.phone && data.phone.trim() !== '' && !PHONE_REGEX.test(data.phone.trim())) {
    return 'Phone number format is invalid.';
  }
  if (!data.subject || !VALID_SUBJECTS.includes(data.subject)) {
    return 'Please select a valid subject.';
  }
  if (!data.message || data.message.trim().length < 10) {
    return 'Message must be at least 10 characters.';
  }
  if (data.message.trim().length > 5000) {
    return 'Message must be under 5000 characters.';
  }
  return null;
}

// ============================================================
// Email sending via SMTP (nodemailer) or no-op in development
// ============================================================
async function sendContactEmail(data: ContactFormData): Promise<void> {
  const smtpHost = import.meta.env.SMTP_HOST;
  const smtpUser = import.meta.env.SMTP_USER;
  const smtpPass = import.meta.env.SMTP_PASS;
  const smtpPort = parseInt(import.meta.env.SMTP_PORT ?? '587', 10);
  const recipientEmail = import.meta.env.CONTACT_EMAIL ?? import.meta.env.SMTP_USER;

  if (!smtpHost || !smtpUser || !smtpPass || !recipientEmail) {
    // SMTP not configured - log and continue (graceful degradation)
    logger.info('api.contact', 'SMTP not configured — form submission logged only', {
      email: data.email,
      subject: data.subject,
      name: data.name,
    });
    return;
  }

  // Dynamic import to avoid bundling issues when nodemailer isn't installed
  try {
    const nodemailer = await import('nodemailer');
    const transporter = nodemailer.default.createTransport({
      host: smtpHost,
      port: smtpPort,
      secure: smtpPort === 465,
      auth: { user: smtpUser, pass: smtpPass },
    });

    const subjectLabels: Record<string, string> = {
      'web-development': 'Web Development',
      'mobile-development': 'Mobile Development',
      'cloud-services': 'Cloud Services',
      'ai-ml': 'AI & Machine Learning',
      'consulting': 'IT Consulting',
      'support': 'Technical Support',
      'other': 'Other',
    };

    await transporter.sendMail({
      from: `"WorkRoot Contact Form" <${smtpUser}>`,
      to: recipientEmail,
      replyTo: data.email,
      subject: `[Contact Form] ${subjectLabels[data.subject] ?? data.subject} - ${data.name}`,
      text: [
        `New contact form submission`,
        ``,
        `Name:    ${data.name}`,
        `Email:   ${data.email}`,
        `Phone:   ${data.phone || 'Not provided'}`,
        `Subject: ${subjectLabels[data.subject] ?? data.subject}`,
        ``,
        `Message:`,
        data.message,
        ``,
        `---`,
        `Submitted at: ${new Date().toISOString()}`,
      ].join('\n'),
      html: `
        <h2>New Contact Form Submission</h2>
        <table style="border-collapse:collapse;width:100%;max-width:600px">
          <tr><td style="padding:8px;font-weight:bold;border-bottom:1px solid #eee">Name</td><td style="padding:8px;border-bottom:1px solid #eee">${escapeHtml(data.name)}</td></tr>
          <tr><td style="padding:8px;font-weight:bold;border-bottom:1px solid #eee">Email</td><td style="padding:8px;border-bottom:1px solid #eee"><a href="mailto:${escapeHtml(data.email)}">${escapeHtml(data.email)}</a></td></tr>
          <tr><td style="padding:8px;font-weight:bold;border-bottom:1px solid #eee">Phone</td><td style="padding:8px;border-bottom:1px solid #eee">${escapeHtml(data.phone || 'Not provided')}</td></tr>
          <tr><td style="padding:8px;font-weight:bold;border-bottom:1px solid #eee">Subject</td><td style="padding:8px;border-bottom:1px solid #eee">${escapeHtml(subjectLabels[data.subject] ?? data.subject)}</td></tr>
          <tr><td style="padding:8px;font-weight:bold;vertical-align:top">Message</td><td style="padding:8px;white-space:pre-wrap">${escapeHtml(data.message)}</td></tr>
        </table>
        <p style="color:#888;font-size:12px;margin-top:16px">Submitted at: ${new Date().toISOString()}</p>
      `,
    });
  } catch (err) {
    // If nodemailer isn't installed, treat as graceful degradation (log only)
    if (err instanceof Error && err.message.includes('Cannot find module')) {
      logger.warn('api.contact', 'nodemailer not available — form submission logged only', {
        email: data.email,
        subject: data.subject,
      });
      return;
    }
    await captureException(err, {
      scope: 'api.contact',
      extra: { email: data.email, subject: data.subject },
    });
    throw new Error('Email delivery failed');
  }
}

function escapeHtml(str: string): string {
  return str
    .replace(/&/g, '&amp;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&#39;');
}

// ============================================================
// CORS headers helper
// ============================================================
function corsHeaders(): HeadersInit {
  const origin = import.meta.env.PROD ? 'https://workroot.in' : '*';
  return {
    'Content-Type': 'application/json',
    'Access-Control-Allow-Origin': origin,
    'Access-Control-Allow-Methods': 'POST, OPTIONS',
    'Access-Control-Allow-Headers': 'Content-Type',
  };
}

// ============================================================
// OPTIONS preflight handler
// ============================================================
export const OPTIONS: APIRoute = async () => {
  return new Response(null, { status: 204, headers: corsHeaders() });
};

// ============================================================
// POST handler
// ============================================================
export const POST: APIRoute = async ({ request, clientAddress }) => {
  const ip = clientAddress ?? 'unknown';
  const startTime = Date.now();

  // Rate limiting check
  const rateLimit = checkRateLimit(ip);
  const rateLimitHeaders = {
    ...corsHeaders(),
    'X-RateLimit-Limit': String(RATE_LIMIT_MAX_REQUESTS),
    'X-RateLimit-Remaining': String(rateLimit.remaining),
    'X-RateLimit-Reset': String(Math.ceil(rateLimit.resetAt / 1000)),
  };

  if (!rateLimit.allowed) {
    logApiRequest({ scope: 'api.contact', method: 'POST', path: '/api/contact', status: 429, ip });
    return new Response(
      JSON.stringify({
        success: false,
        error: 'Too many requests. Please try again later.',
      }),
      { status: 429, headers: rateLimitHeaders }
    );
  }

  // Reject oversized payloads (max 16KB)
  const contentLength = parseInt(request.headers.get('content-length') ?? '0', 10);
  if (contentLength > 16384) {
    return new Response(
      JSON.stringify({ success: false, error: 'Request body too large.' }),
      { status: 413, headers: rateLimitHeaders }
    );
  }

  // Parse request body
  let body: Record<string, unknown>;
  try {
    const contentType = request.headers.get('content-type') ?? '';
    if (contentType.includes('application/json')) {
      body = await request.json();
    } else {
      const formData = await request.formData();
      body = Object.fromEntries(formData.entries());
    }
  } catch {
    return new Response(
      JSON.stringify({ success: false, error: 'Invalid request body.' }),
      { status: 400, headers: rateLimitHeaders }
    );
  }

  // Honeypot check (spam bot detection)
  // Bots typically fill all fields; the honeypot field should always be empty
  if (body.website && String(body.website).trim() !== '') {
    // Silently succeed to not reveal spam detection
    return new Response(
      JSON.stringify({ success: true, message: 'Message received. Thank you!' }),
      { status: 200, headers: rateLimitHeaders }
    );
  }

  // Build and validate form data
  const formData: ContactFormData = {
    name: String(body.name ?? '').trim(),
    email: String(body.email ?? '').trim(),
    phone: body.phone ? String(body.phone).trim() : undefined,
    subject: String(body.subject ?? '').trim(),
    message: String(body.message ?? '').trim(),
  };

  const validationError = validateContactForm(formData);
  if (validationError) {
    return new Response(
      JSON.stringify({ success: false, error: validationError }),
      { status: 422, headers: rateLimitHeaders }
    );
  }

  // Send email
  try {
    await sendContactEmail(formData);
  } catch {
    logApiRequest({
      scope: 'api.contact',
      method: 'POST',
      path: '/api/contact',
      status: 500,
      ip,
      durationMs: Date.now() - startTime,
    });
    return new Response(
      JSON.stringify({
        success: false,
        error: 'Failed to send message. Please try again or email us directly.',
      }),
      { status: 500, headers: rateLimitHeaders }
    );
  }

  logApiRequest({
    scope: 'api.contact',
    method: 'POST',
    path: '/api/contact',
    status: 200,
    ip,
    durationMs: Date.now() - startTime,
  });
  return new Response(
    JSON.stringify({
      success: true,
      message: "Message sent successfully! We'll get back to you within 24 hours.",
    }),
    { status: 200, headers: rateLimitHeaders }
  );
};