// ── SMTP — the baseline mail transport ─────────────────────────────────────
//
// ENGAGEMENT.md decision 4: Gmail OAuth2 is removed, SMTP is the baseline. This
// is the only registered transport, and it is deliberately plain SMTP rather than
// anything provider-shaped — a relay (Mailgun, SES, Postmark), a self-hosted MTA
// and Gmail-with-an-app-password are all reachable through these five fields, so
// one transport covers all three postures §7.1 Q5 asks to document.
//
// **No defaults for host, port, user or sender.** §3.2 rule 1: a transport with
// no operator configuration is unconfigured, never pointed at somewhere we chose.
// `secure` gets a default because it is a protocol choice, not a destination — and
// even that is only a form default, not a fallback applied to a stored blank.
//
// **`secure` is the field operators get wrong**, so its help text says which port
// each setting means: `secure: true` is implicit TLS on 465, `secure: false` is
// plaintext-then-STARTTLS on 587 (which nodemailer upgrades automatically). The
// combination that silently fails is 587 with secure on — the handshake hangs
// rather than erroring cleanly — which is exactly why "Send test" is the real
// verification path now (§1.2a consequence 2).

const nodemailer = require('nodemailer')

const registry = require('./index')

const CREDENTIAL_FIELDS = [
  {
    key: 'host',
    label: 'SMTP host',
    kind: 'text',
    required: true,
    placeholder: 'smtp.example.com',
    help: 'Your relay or mail server. No default — nothing is sent until you set this.',
  },
  {
    key: 'port',
    label: 'Port',
    kind: 'number',
    required: true,
    default: 587,
    help: '587 for STARTTLS (most relays), 465 for implicit TLS, 25 for an unauthenticated local MTA.',
  },
  {
    key: 'secure',
    label: 'Implicit TLS',
    kind: 'boolean',
    required: false,
    default: false,
    help: 'On for port 465. Leave off for 587 — the connection still upgrades to TLS via STARTTLS.',
  },
  {
    key: 'user',
    label: 'Username',
    kind: 'text',
    required: false,
    help: 'Leave blank for an unauthenticated local relay.',
  },
  {
    key: 'password',
    label: 'Password / API key',
    kind: 'secret',
    required: false,
    help: 'Stored encrypted and never returned. For Gmail this is an app password, not the account password.',
  },
]

// Authentication is optional (a local MTA on port 25 needs none), so the only
// hard requirement is a destination. A username without a password is not
// "complete" — that combination authenticates as nobody and fails at the server.
function isComplete(credential) {
  const c = credential || {}
  if (!c.host || !Number(c.port)) return false
  if (c.user && !c.password) return false
  return true
}

function build(credential) {
  const c = credential || {}
  const options = {
    host: String(c.host),
    port: Number(c.port),
    secure: Boolean(c.secure),
  }
  if (c.user) options.auth = { user: String(c.user), pass: String(c.password || '') }
  return nodemailer.createTransport(options)
}

registry.registerMailTransport({
  id: 'smtp',
  label: 'SMTP',
  help: 'Any SMTP relay or mail server. See the operator guide for the three supported postures.',
  credentialFields: CREDENTIAL_FIELDS,
  isComplete,
  build,
})

module.exports = { CREDENTIAL_FIELDS, isComplete, build }