import nodemailer from 'nodemailer';

/**
 * Creates and returns a nodemailer SMTP transporter using environment variables.
 */
export function createSmtpTransporter() {
  const host = process.env.SMTP_HOST;
  const port = parseInt(process.env.SMTP_PORT || '465', 10);
  const secure = process.env.SMTP_SECURE === 'true' || port === 465;
  const user = process.env.SMTP_USER;
  const pass = process.env.SMTP_PASS;

  if (!host || !user || !pass) {
    return null;
  }

  return nodemailer.createTransport({
    host,
    port,
    secure,
    auth: {
      user,
      pass
    },
    tls: {
      rejectUnauthorized: false
    }
  });
}

/**
 * Sends a contact form email via SMTP using nodemailer.
 */
export async function sendContactEmail({ name, email, phone, subject, message }) {
  const transporter = createSmtpTransporter();

  const toEmail = process.env.SMTP_TO || process.env.SMTP_USER || 'info@cavinfotech.com';
  const fromEmail = process.env.SMTP_FROM || `"Cavin Infotech Contact Form" <${process.env.SMTP_USER || 'info@cavinfotech.com'}>`;

  const mailSubject = `[Contact Inquiry] ${subject ? subject : `New Inquiry from ${name}`}`;

  const htmlContent = `
    <div style="font-family: 'Segoe UI', Helvetica, Arial, sans-serif; background-color: #020710; color: #f8fafc; padding: 40px 20px; max-width: 650px; margin: 0 auto; border-radius: 16px; border: 1px solid #1e293b;">
      <div style="text-align: center; padding-bottom: 24px; border-bottom: 1px solid #334155;">
        <h2 style="color: #ffaa00; font-size: 24px; margin: 0; font-weight: 700;">Cavin Infotech</h2>
        <p style="color: #94a3b8; font-size: 14px; margin-top: 6px;">New Website Contact Form Inquiry</p>
      </div>

      <div style="padding: 24px 0;">
        <table style="width: 100%; border-collapse: collapse; color: #e2e8f0; font-size: 15px;">
          <tr>
            <td style="padding: 10px 0; font-weight: 600; color: #ffaa00; width: 130px;">Name:</td>
            <td style="padding: 10px 0; color: #ffffff;">${name}</td>
          </tr>
          <tr>
            <td style="padding: 10px 0; font-weight: 600; color: #ffaa00;">Email:</td>
            <td style="padding: 10px 0;"><a href="mailto:${email}" style="color: #38bdf8; text-decoration: none;">${email}</a></td>
          </tr>
          <tr>
            <td style="padding: 10px 0; font-weight: 600; color: #ffaa00;">Phone No:</td>
            <td style="padding: 10px 0; color: #ffffff;">${phone || 'Not provided'}</td>
          </tr>
          <tr>
            <td style="padding: 10px 0; font-weight: 600; color: #ffaa00;">Subject:</td>
            <td style="padding: 10px 0; color: #ffffff;">${subject || 'General Inquiry'}</td>
          </tr>
        </table>

        <div style="margin-top: 24px; padding: 20px; background-color: #0b1528; border-left: 4px solid #ffaa00; border-radius: 8px;">
          <h4 style="margin: 0 0 10px 0; color: #94a3b8; font-size: 13px; text-transform: uppercase; letter-spacing: 0.05em;">Message:</h4>
          <p style="margin: 0; color: #f1f5f9; font-size: 15px; line-height: 1.6; white-space: pre-line;">${message}</p>
        </div>
      </div>

      <div style="text-align: center; padding-top: 20px; border-top: 1px solid #334155; color: #64748b; font-size: 12px;">
        Submitted on ${new Date().toLocaleString()} from Cavin Infotech Contact Us Page
      </div>
    </div>
  `;

  const textContent = `
New Contact Inquiry - Cavin Infotech

Name: ${name}
Email: ${email}
Phone: ${phone || 'Not provided'}
Subject: ${subject || 'General Inquiry'}

Message:
${message}

Submitted on: ${new Date().toLocaleString()}
  `;

  if (!transporter) {
    console.warn('[SMTP Service] SMTP credentials not set in environment (SMTP_HOST, SMTP_USER, SMTP_PASS).');
    return {
      success: false,
      error: 'SMTP credentials not configured on the server. Please set SMTP_HOST, SMTP_USER, and SMTP_PASS in .env file.'
    };
  }

  try {
    const info = await transporter.sendMail({
      from: fromEmail,
      to: toEmail,
      replyTo: `"${name}" <${email}>`,
      subject: mailSubject,
      text: textContent,
      html: htmlContent
    });

    console.log('[SMTP Service] Contact email sent via SMTP:', info.messageId);
    return { success: true, messageId: info.messageId };
  } catch (err) {
    console.error('[SMTP Service] Failed to send email via SMTP:', err);
    return { success: false, error: err.message || 'SMTP sending failed' };
  }
}