import nodemailer from 'nodemailer'
import { env } from './env.js'

let cachedTransporter = null

function getTransporter() {
  if (cachedTransporter) return cachedTransporter

  const host = env('SMTP_HOST')
  const user = env('SMTP_USER')
  const pass = env('SMTP_PASS')

  if (!host || !user || !pass) {
    throw new Error('SMTP configuration is incomplete.')
  }

  const port = Number(env('SMTP_PORT', '587'))

  if (!Number.isInteger(port) || port <= 0 || port > 65535) {
    throw new Error(`SMTP_PORT is not a valid port: ${env('SMTP_PORT')}`)
  }

  cachedTransporter = nodemailer.createTransport({
    host,
    port,
    secure: port === 465, // implicit TLS on 465, STARTTLS otherwise
    auth: { user, pass },
  })

  return cachedTransporter
}

/**
 * Strips CR and LF so a submitted value can never inject extra mail headers
 * when it is used in Subject or Reply-To.
 */
function singleLine(value) {
  return String(value).replace(/[\r\n]+/g, ' ').trim()
}

/** Minimal HTML escaping - the payload is attacker-controlled by definition. */
function escapeHtml(value) {
  return String(value)
    .replaceAll('&', '&amp;')
    .replaceAll('<', '&lt;')
    .replaceAll('>', '&gt;')
    .replaceAll('"', '&quot;')
    .replaceAll("'", '&#39;')
}

const ROLE_LABELS = {
  agency: 'Agentur / Dienstleister',
  client: 'Endkunde (eigene Website)',
}

export async function sendAuditRequestEmail({
  name,
  company,
  email,
  url,
  role,
  motivation,
}) {
  const transporter = getTransporter()

  const to = env('AUDIT_RECIPIENT')
  // Falls back to the authenticated mailbox when SMTP_FROM is left blank.
  const from = env('SMTP_FROM', env('SMTP_USER'))

  if (!to) {
    throw new Error('AUDIT_RECIPIENT is not configured.')
  }

  const safeName = singleLine(name)
  const safeCompany = singleLine(company)
  const safeEmail = singleLine(email)
  const roleLabel = ROLE_LABELS[role] ?? role

  const textBody = [
    `Name:       ${safeName}`,
    `Firma:      ${safeCompany}`,
    `E-Mail:     ${safeEmail}`,
    `Seite:      ${singleLine(url)}`,
    `Typ:        ${roleLabel}`,
    'B2B:        bestätigt (§ 14 BGB)',
    '',
    'Motivation:',
    motivation,
  ].join('\n')

  const htmlBody = `
    <h2>Neue Audit-Anfrage</h2>
    <dl>
      <dt><strong>Name</strong></dt><dd>${escapeHtml(safeName)}</dd>
      <dt><strong>Firma</strong></dt><dd>${escapeHtml(safeCompany)}</dd>
      <dt><strong>E-Mail</strong></dt><dd>${escapeHtml(safeEmail)}</dd>
      <dt><strong>Seite</strong></dt><dd>${escapeHtml(singleLine(url))}</dd>
      <dt><strong>Typ</strong></dt><dd>${escapeHtml(roleLabel)}</dd>
      <dt><strong>B2B</strong></dt><dd>bestätigt (§ 14 BGB)</dd>
    </dl>
    <h3>Motivation</h3>
    <p>${escapeHtml(motivation).replaceAll('\n', '<br>')}</p>
  `

  await transporter.sendMail({
    from,
    to,
    replyTo: safeEmail,
    subject: `Audit-Anfrage: ${safeCompany} (${safeName})`,
    text: textBody,
    html: htmlBody,
  })

  // Deliberately no recipient address, no payload - keep logs free of
  // personal data (Art. 5 GDPR, data minimisation).
  console.log('Audit request forwarded.')
}