// Display rule of the license expiry date on the License card (#347, D9).
//
// Keys issued since maximus-api#63 last 100 years: a date in 2126 is noise, and the
// key does not end in any practical sense. Beyond the horizon the card shows
// "No expiry date"; closer dates show in the app language.

/** Beyond this horizon, an expiry date is shown as "no expiry date". */
export const NO_EXPIRY_HORIZON_YEARS = 50;

const SECONDS_PER_YEAR = 365.25 * 24 * 3600;

export type LicenseExpiryDisplay = { kind: "noExpiry" } | { kind: "date"; text: string };

/**
 * How the card shows `expiresAt` (seconds since the epoch) at `nowSeconds`: no date
 * beyond the horizon, otherwise the date formatted for `locale` (`fr-CA` or `en-CA`,
 * chosen by the card from the app language).
 */
export function licenseExpiryDisplay(
  expiresAt: number,
  nowSeconds: number,
  locale: string,
): LicenseExpiryDisplay {
  if (expiresAt - nowSeconds > NO_EXPIRY_HORIZON_YEARS * SECONDS_PER_YEAR) {
    return { kind: "noExpiry" };
  }
  return { kind: "date", text: new Date(expiresAt * 1000).toLocaleDateString(locale) };
}