const nodemailer = require("nodemailer");
const { env } = require("../config/env");
const logger = require("./logger");

let transporter = null;

function getTransporter() {
  if (transporter) return transporter;
  transporter = nodemailer.createTransport({
    host: env.smtp.host,
    port: env.smtp.port,
    secure: env.smtp.secure, // true for 465, false for other ports (STARTTLS)
    auth: env.smtp.user ? { user: env.smtp.user, pass: env.smtp.pass } : undefined,
    requireTLS: !env.smtp.secure, // enforce STARTTLS when not already on a TLS port
  });
  return transporter;
}

async function sendMail({ to, subject, html, text }) {
  try {
    const info = await getTransporter().sendMail({
      from: env.emailFrom,
      to,
      subject,
      html,
      text,
    });
    return info;
  } catch (err) {
    // Email failures must never crash a request or leak SMTP credentials.
    logger.error("Failed to send email", { subject, error: err.message });
    return null;
  }
}

function baseLayout(bodyHtml) {
  return `
  <div style="font-family:Arial,Helvetica,sans-serif;max-width:600px;margin:0 auto;color:#1a1a1a;">
    <div style="padding:24px 0;border-bottom:2px solid #eee;">
      <h2 style="margin:0;color:#111;">Aynwerd Academy</h2>
    </div>
    <div style="padding:24px 0;">${bodyHtml}</div>
    <div style="padding:16px 0;border-top:1px solid #eee;font-size:12px;color:#777;">
      This is an automated message regarding your order. Never share your password or
      full payment reference by email. If you didn't make this request, contact
      support immediately.
    </div>
  </div>`;
}

async function sendOrderPlacedEmail({ to, name, order, courseTitle, bankDetails, payoneerDetails }) {
  const methodBlock =
    order.paymentMethod === "bank_wire"
      ? `<h3>Bank wire transfer instructions</h3>
         <table style="border-collapse:collapse;width:100%;font-size:14px;">
           <tr><td style="padding:4px 0;color:#555;">Bank name</td><td><strong>${bankDetails.name}</strong></td></tr>
           <tr><td style="padding:4px 0;color:#555;">Account name</td><td><strong>${bankDetails.accountName}</strong></td></tr>
           <tr><td style="padding:4px 0;color:#555;">Account number</td><td><strong>${bankDetails.accountNumber}</strong></td></tr>
           <tr><td style="padding:4px 0;color:#555;">Routing number</td><td><strong>${bankDetails.routingNumber}</strong></td></tr>
           <tr><td style="padding:4px 0;color:#555;">SWIFT/BIC</td><td><strong>${bankDetails.swiftBic}</strong></td></tr>
           <tr><td style="padding:4px 0;color:#555;">Bank address</td><td><strong>${bankDetails.address}</strong></td></tr>
         </table>
         <p>Please use order number <strong>${order.orderNumber}</strong> as your payment reference.</p>`
      : `<h3>Payoneer payment instructions</h3>
         <p>Send payment to Payoneer account <strong>${payoneerDetails.accountEmail}</strong>
         or use your Payoneer app's "Request a Payment" link: <a href="${payoneerDetails.paymentUrl}">${payoneerDetails.paymentUrl}</a>.</p>
         <p>Please use order number <strong>${order.orderNumber}</strong> as your payment note.</p>`;

  const html = baseLayout(`
    <p>Hi ${name},</p>
    <p>Thanks for enrolling in <strong>${courseTitle}</strong>. Your order has been created and is
    awaiting payment${order.status === "awaiting_confirmation" ? " confirmation" : ""}.</p>
    <p><strong>Order number:</strong> ${order.orderNumber}<br/>
       <strong>Amount due:</strong> ${order.currency} ${order.amount.toFixed(2)}<br/>
       <strong>Payment method:</strong> ${order.paymentMethod === "bank_wire" ? "Bank wire transfer" : "Payoneer"}</p>
    ${methodBlock}
    <p>Once our team confirms your payment, you'll receive a separate email and full course access
    will be unlocked automatically on your account.</p>
  `);

  return sendMail({
    to,
    subject: `Your Aynwerd order ${order.orderNumber} — payment instructions`,
    html,
    text: `Order ${order.orderNumber} created for ${courseTitle}. Amount due: ${order.currency} ${order.amount.toFixed(2)}.`,
  });
}

async function sendPaymentConfirmedEmail({ to, name, order, courseTitle }) {
  const html = baseLayout(`
    <p>Hi ${name},</p>
    <p>Great news — we've confirmed your payment for <strong>${courseTitle}</strong>.</p>
    <p><strong>Order number:</strong> ${order.orderNumber}<br/>
       <strong>Amount paid:</strong> ${order.currency} ${order.amount.toFixed(2)}<br/>
       <strong>Confirmed on:</strong> ${new Date(order.confirmedAt).toUTCString()}</p>
    <p>Full access to the course has been unlocked on your account. Log in any time to get started.</p>
  `);

  return sendMail({
    to,
    subject: `Payment confirmed — order ${order.orderNumber}`,
    html,
    text: `Payment confirmed for order ${order.orderNumber}. Course access unlocked.`,
  });
}

async function sendVoucherRedeemedEmail({ to, name, order, courseTitle, voucherCode }) {
  const html = baseLayout(`
    <p>Hi ${name},</p>
    <p>Your voucher <strong>${voucherCode}</strong> has been redeemed for <strong>${courseTitle}</strong> —
    no payment was required.</p>
    <p><strong>Order number:</strong> ${order.orderNumber}</p>
    <p>Full access to the course has been unlocked on your account. Log in any time to get started.</p>
  `);

  return sendMail({
    to,
    subject: `Voucher redeemed — ${courseTitle} unlocked`,
    html,
    text: `Voucher ${voucherCode} redeemed for ${courseTitle}. Course access unlocked. Order ${order.orderNumber}.`,
  });
}

async function sendPaymentRejectedEmail({ to, name, order, courseTitle, reason }) {
  const html = baseLayout(`
    <p>Hi ${name},</p>
    <p>We were unable to confirm your payment for <strong>${courseTitle}</strong> (order
    <strong>${order.orderNumber}</strong>).</p>
    ${reason ? `<p><strong>Reason:</strong> ${reason}</p>` : ""}
    <p>Please reply to this email or contact support so we can help resolve this.</p>
  `);

  return sendMail({
    to,
    subject: `Action needed on order ${order.orderNumber}`,
    html,
    text: `We could not confirm payment for order ${order.orderNumber}.${reason ? ` Reason: ${reason}` : ""}`,
  });
}

async function sendAdminNewOrderAlert({ order, courseTitle, customerEmail }) {
  if (!env.adminNotifyEmail) return null;
  const html = baseLayout(`
    <p>New order awaiting confirmation.</p>
    <p><strong>Order:</strong> ${order.orderNumber}<br/>
       <strong>Customer:</strong> ${customerEmail}<br/>
       <strong>Course:</strong> ${courseTitle}<br/>
       <strong>Amount:</strong> ${order.currency} ${order.amount.toFixed(2)}<br/>
       <strong>Method:</strong> ${order.paymentMethod}</p>
    <p>Review and confirm it from the admin dashboard.</p>
  `);
  return sendMail({
    to: env.adminNotifyEmail,
    subject: `New order ${order.orderNumber} awaiting confirmation`,
    html,
  });
}

module.exports = {
  sendOrderPlacedEmail,
  sendPaymentConfirmedEmail,
  sendVoucherRedeemedEmail,
  sendPaymentRejectedEmail,
  sendAdminNewOrderAlert,
};