import nodemailer from 'nodemailer';
import { RateLimiterMemory } from 'rate-limiter-flexible';
import { createHash } from 'crypto';
import 'dotenv/config';

// Environment variables
const {
  SMTP_HOST = '',
  SMTP_PORT = '587',
  SMTP_USER = '',
  SMTP_PASS = '',
  ADMIN_EMAIL = '',
  WEBSITE_NAME = '365DevNet Support',
} = process.env;

// Email configuration
// Force production mode for testing
const isProduction = true; // NODE_ENV === 'production';

// Create a transporter for sending emails
let transporter: nodemailer.Transporter;

// Initialize the transporter based on environment
function initializeTransporter() {
  if (isProduction && SMTP_HOST) {
    // Use local Postfix mail relay (no authentication)
    transporter = nodemailer.createTransport({
      host: SMTP_HOST,
      port: parseInt(SMTP_PORT, 10) || 25, // default to port 25 if not set
      secure: false, // No SSL for local relay
      tls: {
        rejectUnauthorized: false, // Accept self-signed certificates if present
      },
    });

    transporter.verify((error, success) => {
      if (error) {
        console.error('❌ SMTP connection error:', error);
      } else {
        console.log('✅ SMTP server is ready to take messages.');
      }
    });
  } else {
    // Fallback for development: log email output to console
    transporter = nodemailer.createTransport({
      streamTransport: true,
      newline: 'unix',
      buffer: true,
    });

    console.log('⚠️ Email transporter using streamTransport (development mode)');
  }
}

// Rate limiter configuration
const rateLimiter = new RateLimiterMemory({
  points: 5, // 5 attempts
  duration: 3600, // per hour
});

// CSRF protection
const csrfTokens = new Map<string, { token: string; expires: Date }>();

// Generate a CSRF token
export function generateCsrfToken(): string {
  const token = createHash('sha256').update(Math.random().toString()).digest('hex');

  // Token expires after 1 hour
  const expires = new Date();
  expires.setHours(expires.getHours() + 1);

  csrfTokens.set(token, { token, expires });

  // Clean up expired tokens
  for (const [key, value] of csrfTokens.entries()) {
    if (value.expires < new Date()) {
      csrfTokens.delete(key);
    }
  }

  return token;
}

// Validate a CSRF token
export function validateCsrfToken(token: string): boolean {
  const storedToken = csrfTokens.get(token);

  if (!storedToken) {
    return false;
  }

  if (storedToken.expires < new Date()) {
    csrfTokens.delete(token);
    return false;
  }

  return true;
}

// Check rate limit for an IP address
export async function checkRateLimit(ipAddress: string): Promise<{ limited: boolean; message?: string }> {
  try {
    await rateLimiter.consume(ipAddress);
    return { limited: false };
  } catch (error) {
    if (error instanceof Error) {
      return {
        limited: true,
        message: 'Too many requests. Please try again later.',
      };
    }
    // RateLimiterRes with msBeforeNext property
    interface RateLimiterResponse {
      msBeforeNext: number;
    }
    const resetTime = Math.ceil((error as RateLimiterResponse).msBeforeNext / 1000 / 60);
    return {
      limited: true,
      message: `Too many requests. Please try again in ${resetTime} minutes.`,
    };
  }
}

// Log email sending attempts
export function logEmailAttempt(success: boolean, recipient: string, subject: string, error?: Error): void {
  const timestamp = new Date().toISOString();
  const status = success ? 'SUCCESS' : 'FAILURE';
  const errorMessage = error ? `: ${error.message}` : '';

  const logMessage = `[${timestamp}] [EMAIL ${status}] To: ${recipient}, Subject: ${subject}${errorMessage}`;

  if (isProduction) {
    // In production, you might want to log to a file or a logging service
    console.log(logMessage);
  } else {
    // In development, log to console
    console.log(logMessage);
  }
}

// Send an email
export async function sendEmail(to: string, subject: string, html: string, text: string): Promise<boolean> {
  // Initialize transporter if not already done
  if (!transporter) {
    initializeTransporter();
  }

  try {
    const fromAddress = isProduction ? `"${WEBSITE_NAME}" <${SMTP_USER || 'noreply@' + WEBSITE_NAME}>` : `"${WEBSITE_NAME}" <${ADMIN_EMAIL}>`;

    const mailOptions = {
      from: fromAddress,
      to,
      subject,
      html,
      text,
    };

    // Log the connection target
    console.log(`[MAILER DEBUG] Sending via: ${SMTP_HOST}:${SMTP_PORT}`);
    console.log(`[MAILER DEBUG] From: ${fromAddress} → To: ${to}`);

    await transporter.sendMail(mailOptions);

    logEmailAttempt(true, to, subject);
    return true;
  } catch (error) {
    logEmailAttempt(false, to, subject, error as Error);
    console.error('Full SMTP error stack:', error);
    return false;
  }
}

// Send admin notification email
export async function sendAdminNotification(
  name: string,
  email: string,
  message: string,
  ipAddress?: string,
  userAgent?: string
): Promise<boolean> {
  // Validate inputs
  if (!name || name.trim() === '') {
    console.error('Cannot send admin notification: name is empty');
    return false;
  }

  if (!email || email.trim() === '') {
    console.error('Cannot send admin notification: email is empty');
    return false;
  }

  if (!message || message.trim() === '') {
    console.error('Cannot send admin notification: message is empty');
    return false;
  }

  const subject = `New Contact Form Submission from ${name}`;
  const html = `
    <!DOCTYPE html>
    <html>
    <head>
      <meta charset="utf-8">
      <meta name="viewport" content="width=device-width, initial-scale=1.0">
      <title>New Contact Form Submission</title>
      <style>
        body {
          font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
          line-height: 1.6;
          color: #333;
          max-width: 600px;
          margin: 0 auto;
          padding: 20px;
        }
        .header {
          background-color: #2563eb;
          color: white;
          padding: 20px;
          text-align: center;
          border-radius: 8px 8px 0 0;
        }
        .content {
          background-color: #f8fafc;
          padding: 20px;
          border: 1px solid #e2e8f0;
          border-top: none;
          border-radius: 0 0 8px 8px;
        }
        .field {
          margin-bottom: 15px;
        }
        .field-label {
          font-weight: 600;
          color: #4b5563;
          margin-bottom: 5px;
        }
        .field-value {
          background-color: white;
          padding: 10px;
          border-radius: 4px;
          border: 1px solid #e2e8f0;
        }
        .message-content {
          white-space: pre-wrap;
          background-color: white;
          padding: 15px;
          border-radius: 4px;
          border: 1px solid #e2e8f0;
          margin: 10px 0;
        }
        .footer {
          margin-top: 20px;
          padding-top: 20px;
          border-top: 1px solid #e2e8f0;
          font-size: 0.9em;
          color: #6b7280;
        }
        .meta-info {
          font-size: 0.85em;
          color: #6b7280;
          margin-top: 20px;
          padding-top: 10px;
          border-top: 1px solid #e2e8f0;
        }
      </style>
    </head>
    <body>
      <div class="header">
        <h1>New Contact Form Submission</h1>
      </div>
      <div class="content">
        <div class="field">
          <div class="field-label">Name</div>
          <div class="field-value">${name}</div>
        </div>
        <div class="field">
          <div class="field-label">Email</div>
          <div class="field-value">${email}</div>
        </div>
        <div class="field">
          <div class="field-label">Message</div>
          <div class="message-content">${message.replace(/\n/g, '<br>')}</div>
        </div>
        <div class="meta-info">
          ${ipAddress ? `<div><strong>IP Address:</strong> ${ipAddress}</div>` : ''}
          ${userAgent ? `<div><strong>User Agent:</strong> ${userAgent}</div>` : ''}
          <div><strong>Time:</strong> ${new Date().toLocaleString()}</div>
        </div>
        <div class="footer">
          <p>This message was sent from the contact form on ${WEBSITE_NAME}</p>
        </div>
      </div>
    </body>
    </html>
  `;
  const text = `
New Contact Form Submission

Name: ${name}
Email: ${email}
Message:
${message}
${ipAddress ? `IP Address: ${ipAddress}` : ''}
${userAgent ? `User Agent: ${userAgent}` : ''}
Time: ${new Date().toLocaleString()}

This message was sent from the contact form on ${WEBSITE_NAME}
  `;

  return sendEmail(ADMIN_EMAIL, subject, html, text);
}

// Send user confirmation email
export async function sendUserConfirmation(name: string, email: string, message: string): Promise<boolean> {
  // Validate inputs
  if (!name || name.trim() === '') {
    console.error('Cannot send user confirmation: name is empty');
    return false;
  }

  if (!email || email.trim() === '') {
    console.error('Cannot send user confirmation: email is empty');
    return false;
  }

  const subject = `Thank you for contacting ${WEBSITE_NAME}`;
  const html = `
    <!DOCTYPE html>
    <html>
    <head>
      <meta charset="utf-8">
      <meta name="viewport" content="width=device-width, initial-scale=1.0">
      <title>Thank you for your message</title>
      <style>
        body {
          font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
          line-height: 1.6;
          color: #333;
          max-width: 600px;
          margin: 0 auto;
          padding: 20px;
        }
        .header {
          background-color: #2563eb;
          color: white;
          padding: 20px;
          text-align: center;
          border-radius: 8px 8px 0 0;
        }
        .content {
          background-color: #f8fafc;
          padding: 20px;
          border: 1px solid #e2e8f0;
          border-top: none;
          border-radius: 0 0 8px 8px;
        }
        .message {
          background-color: white;
          padding: 15px;
          border-radius: 4px;
          border: 1px solid #e2e8f0;
          margin: 20px 0;
        }
        .footer {
          margin-top: 20px;
          padding-top: 20px;
          border-top: 1px solid #e2e8f0;
          font-size: 0.9em;
          color: #6b7280;
        }
        .button {
          display: inline-block;
          background-color: #2563eb;
          color: white;
          padding: 12px 24px;
          text-decoration: none;
          border-radius: 6px;
          margin: 20px 0;
        }
        .button:hover {
          background-color: #1d4ed8;
        }
      </style>
    </head>
    <body>
      <div class="header">
        <h1>Thank you for your message</h1>
      </div>
      <div class="content">
        <p>Dear ${name},</p>
        <p>Thank you for contacting ${WEBSITE_NAME}. We have received your message and will get back to you as soon as possible.</p>
        
        <div class="message">
          <h3>Your Message:</h3>
          <p>${message.replace(/\n/g, '<br>')}</p>
        </div>

        <p>If you have any additional information to share, please don't hesitate to reply to this email.</p>
        
        <a href="https://www.365devnet.eu" class="button">Visit Our Website</a>

        <div class="footer">
          <p>Best regards,<br>${WEBSITE_NAME} Team</p>
          <p><small>This is an automated message, please do not reply directly to this email.</small></p>
        </div>
      </div>
    </body>
    </html>
  `;
  const text = `
Thank you for your message

Dear ${name},

Thank you for contacting ${WEBSITE_NAME}. We have received your message and will get back to you as soon as possible.

Here's a copy of your message:

${message}

If you have any additional information to share, please don't hesitate to reply to this email.

Best regards,
${WEBSITE_NAME} Team

This is an automated message, please do not reply directly to this email.
  `;

  return sendEmail(email, subject, html, text);
}

// Initialize the email system
export function initializeEmailSystem(): void {
  initializeTransporter();
}

// Test email configuration
export async function testEmailConfiguration(): Promise<boolean> {
  if (!transporter) {
    initializeTransporter();
  }

  try {
    await transporter.verify();
    return true;
  } catch (error) {
    console.error('Email configuration test failed:', error);
    return false;
  }
}