import nodemailer from 'nodemailer';
import { buildLoginCodeEmailTemplate } from './notification-templates.js';

let cachedTransporter = null;

function getSmtpConfig() {
  const host = process.env.SMTP_HOST;
  const portRaw = process.env.SMTP_PORT;
  const from = process.env.SMTP_FROM;
  const secureRaw = process.env.SMTP_SECURE ?? 'false';
  const user = process.env.SMTP_USER;
  const pass = process.env.SMTP_PASS;

  if (!host) {
    throw new Error('SMTP_HOST is required for email login code delivery.');
  }
  if (!portRaw) {
    throw new Error('SMTP_PORT is required for email login code delivery.');
  }
  if (!from) {
    throw new Error('SMTP_FROM is required for email login code delivery.');
  }

  const port = Number(portRaw);
  if (!Number.isInteger(port) || port <= 0) {
    throw new Error('SMTP_PORT must be a valid integer port number.');
  }

  const secure = String(secureRaw).toLowerCase() === 'true';
  const hasUser = Boolean(user);
  const hasPass = Boolean(pass);

  if (hasUser !== hasPass) {
    throw new Error('SMTP_USER and SMTP_PASS must be set together.');
  }

  return {
    from,
    transport: {
      host,
      port,
      secure,
      ...(hasUser && hasPass ? { auth: { user, pass } } : {}),
    },
  };
}

function getTransporter() {
  if (cachedTransporter) {
    return cachedTransporter;
  }

  const config = getSmtpConfig();
  cachedTransporter = nodemailer.createTransport(config.transport);
  return cachedTransporter;
}

function escapeHtml(value) {
  return String(value ?? '')
    .replaceAll('&', '&amp;')
    .replaceAll('<', '&lt;')
    .replaceAll('>', '&gt;')
    .replaceAll('"', '&quot;');
}

function normalizeBody(body) {
  if (Array.isArray(body)) {
    return body
      .map((line) => String(line ?? '').trim())
      .filter(Boolean);
  }

  const text = String(body ?? '').trim();
  return text ? [text] : [];
}

function buildNotificationEmailText(body, buttonText, buttonUrl) {
  const lines = normalizeBody(body);
  if (buttonUrl) {
    lines.push(`${buttonText || 'Открыть'}: ${buttonUrl}`);
  }
  return lines.join('\n');
}

function buildNotificationEmailHtml(body, buttonText, buttonUrl) {
  const paragraphs = normalizeBody(body)
    .map((line) => `<p>${escapeHtml(line)}</p>`)
    .join('');

  if (!buttonUrl) {
    return paragraphs;
  }

  return `${paragraphs}<p><a href="${escapeHtml(buttonUrl)}" style="display:inline-block;padding:12px 18px;border-radius:999px;background:#123824;color:#ffffff;text-decoration:none;font-weight:700;">${escapeHtml(buttonText || 'Открыть')}</a></p>`;
}

export async function sendLoginCodeEmail({ to, code, expiresAt }) {
  const { from } = getSmtpConfig();
  const transporter = getTransporter();
  const template = buildLoginCodeEmailTemplate({ code, expiresAt });

  await transporter.sendMail({
    from,
    to,
    subject: template.subject,
    text: template.text,
    html: template.html,
  });
}

export async function sendNotificationEmail({ to, subject, body, buttonText = null, buttonUrl = null }) {
  const { from } = getSmtpConfig();
  const transporter = getTransporter();

  await transporter.sendMail({
    from,
    to,
    subject,
    text: buildNotificationEmailText(body, buttonText, buttonUrl),
    html: buildNotificationEmailHtml(body, buttonText, buttonUrl),
  });
}