Function determineStaleAt

lib/handler/cache-handler.js:613–704

* @param {import('../../types/cache-interceptor.d.ts').default.CacheOptions['type']} cacheType * @param {number} now * @param {number | undefined} age * @param {import('../../types/header.d.ts').IncomingHttpHeaders} resHeaders * @param {Date | undefined} responseDate * @param {import('../../typ

(cacheType, now, age, resHeaders, responseDate, cacheControlDirectives, hasValidator)

 * @returns {number | undefined} time that the value is stale at in seconds or undefined if it shouldn't be cached
 */
function determineStaleAt (cacheType, now, age, resHeaders, responseDate, cacheControlDirectives, hasValidator) {
  if (cacheType === 'shared') {
    // Prioritize s-maxage since we're a shared cache
    //  s-maxage > max-age > Expire
    //  https://www.rfc-editor.org/rfc/rfc9111.html#section-5.2.2.10-3
    if (hasInvalidCacheControlDirective(cacheControlDirectives, 's-maxage')) {
      return 0
    }

    const sMaxAge = cacheControlDirectives['s-maxage']
    if (sMaxAge !== undefined) {
      if (sMaxAge > 0) {
        return sMaxAge * 1000
      }

      // Immediately stale, but storable if we can revalidate it before reuse.
      return 0
    }
  }

  if (hasInvalidCacheControlDirective(cacheControlDirectives, 'max-age')) {
    return 0
  }

  const maxAge = cacheControlDirectives['max-age']
  if (maxAge !== undefined) {
    if (maxAge > 0) {
      return maxAge * 1000
    }

    // Immediately stale, but storable if we can revalidate it before reuse.
    return 0
  }

  if (Object.hasOwn(resHeaders, 'expires')) {
    // https://www.rfc-editor.org/rfc/rfc9111.html#section-5.3
    if (typeof resHeaders.expires !== 'string') {
      return 0
    }

    const expiresDate = parseHttpDate(resHeaders.expires)
    if (!expiresDate) {
      return 0
    }

    if (now >= expiresDate.getTime()) {
      return 0
    }

    if (responseDate) {
      if (responseDate >= expiresDate) {
        return 0
      }

      const freshnessLifetime = expiresDate.getTime() - responseDate.getTime()
      if (age !== undefined && age >= freshnessLifetime) {
        return 0
      }