export const MAIL_IPV4 = '185.214.101.41';
export const MAIL_HOSTNAME = 'mail.meshkee.com';
export const MAIL_MX_PRIORITY = 10;
export const MAIL_SPF = 'v=spf1 mx -all';
/** Old provider selector (dkim._domainkey.example.com) — removed on mail DNS update. */
export const LEGACY_DKIM_NAME = 'dkim._domainkey';
export const DMARC_NAME = '_dmarc';

export type MailDkimKey = {
  selector: string;
  text: string;
};

/** Bare selector, or `name._domainkey` / `name._domainkey.example.com.` */
export function normalizeDkimSelector(raw: string | undefined | null): string | null {
  if (raw == null) return null;
  let input = raw.trim().replace(/^"+|"+$/g, '').trim();
  if (!input) return null;

  const hostMatch = input.match(/^([a-z0-9][a-z0-9-]*)\._domainkey(?:\.|$)/i);
  if (hostMatch) return hostMatch[1].toLowerCase();

  if (/^[a-z0-9][a-z0-9-]*$/i.test(input)) return input.toLowerCase();
  return null;
}

export function parseDkimPaste(
  raw: string,
  expectedKind: 'ed25519' | 'rsa',
  selectorHint?: string,
): MailDkimKey {
  const input = raw.trim();
  if (!input) {
    throw new Error(
      `Paste the ${expectedKind} DKIM TXT value (v=DKIM1; …) or the full Stalwart zone line.`,
    );
  }

  const quoted = [...input.matchAll(/"([^"]*)"/g)].map((match) => match[1]).join('');
  const compact = input.replace(/[()\n\r\t]+/g, ' ').replace(/\s+/g, ' ').trim();
  const blob = (quoted || compact).replace(/"\s+"/g, '');

  const txtMatch = blob.match(/v=DKIM1[\s\S]*/i);
  let text = (txtMatch ? txtMatch[0] : blob).trim();
  text = text.replace(/^"+|"+$/g, '').replace(/\s+/g, ' ').replace(/[.\s]+$/g, '').trim();
  if (!/^v=DKIM1/i.test(text)) {
    // Stalwart sometimes copies only the public key / p=… body.
    const bare = text.replace(/^p=/i, '').replace(/\s+/g, '');
    if (/^[A-Za-z0-9+/=]+$/.test(bare) && bare.length >= 20) {
      text =
        expectedKind === 'ed25519'
          ? `v=DKIM1; k=ed25519; h=sha256; p=${bare}`
          : `v=DKIM1; k=rsa; h=sha256; p=${bare}`;
    } else {
      throw new Error(
        `Could not find a v=DKIM1 value in the ${expectedKind} field. Paste the TXT value or Stalwart zone line.`,
      );
    }
  }

  const kind = /k=ed25519/i.test(text)
    ? 'ed25519'
    : /k=rsa/i.test(text)
      ? 'rsa'
      : null;
  if (kind && kind !== expectedKind) {
    throw new Error(
      `That paste is ${kind} DKIM. Put it in the ${kind === 'ed25519' ? 'Ed25519' : 'RSA'} field.`,
    );
  }

  const nameMatch = compact.match(/([a-z0-9][a-z0-9-]*)\._domainkey/i);
  const selector =
    (nameMatch ? nameMatch[1].toLowerCase() : null) || normalizeDkimSelector(selectorHint);
  if (!selector) {
    throw new Error(
      'Could not find a DKIM selector. Enter the selector (for example v1-ed25519-20260901), or paste a zone line that includes …._domainkey.',
    );
  }

  return {
    selector,
    text,
  };
}