import { createHmac, timingSafeEqual } from 'node:crypto';
import { terms } from '../shared/terms.mjs';

export const TERMS_COOKIE = 'juegoland_terms';
export const TERMS_MAX_AGE = 365 * 24 * 60 * 60;
const signature = (payload, secret) =>
  createHmac('sha256', secret)
    .update(`juegoland-terms:${payload}`)
    .digest('hex');

export function termsCookie(secret, production, now = Date.now()) {
  const payload = `${terms.version}.${Math.floor(now / 1000)}`;
  return `${TERMS_COOKIE}=${payload}.${signature(payload, secret)}; Path=/; HttpOnly; SameSite=Lax; Max-Age=${TERMS_MAX_AGE}${production ? '; Secure' : ''}`;
}
export function clearTermsCookie(production) {
  return `${TERMS_COOKIE}=; Path=/; HttpOnly; SameSite=Lax; Max-Age=0${production ? '; Secure' : ''}`;
}
export function termsAcceptance(header = '', secret, now = Date.now()) {
  const rejected = {
    accepted: false,
    version: terms.version,
    acceptedAt: null,
    expiresAt: null,
  };
  const value = header
    .split(';')
    .map((part) => part.trim())
    .find((part) => part.startsWith(`${TERMS_COOKIE}=`))
    ?.slice(TERMS_COOKIE.length + 1);
  const match = value?.match(
    /^(\d{4}-\d{2}-\d{2}\.\d+)\.(\d{10})\.([a-f0-9]{64})$/,
  );
  if (!match || match[1] !== terms.version) return rejected;
  const issuedAt = Number(match[2]) * 1000;
  if (issuedAt > now || now >= issuedAt + TERMS_MAX_AGE * 1000) return rejected;
  const expected = Buffer.from(
    signature(`${match[1]}.${match[2]}`, secret),
    'hex',
  );
  if (!timingSafeEqual(expected, Buffer.from(match[3], 'hex'))) return rejected;
  return {
    accepted: true,
    version: terms.version,
    acceptedAt: new Date(issuedAt).toISOString(),
    expiresAt: new Date(issuedAt + TERMS_MAX_AGE * 1000).toISOString(),
  };
}