import { MOBILE_STRONGHOLD, splitLocation, validLocation } from './board';

/** The mobile stronghold's interior is encoded as sector 0, but a worm ride
 * enters through its actual pointed sector. Ordinary sectors and the Polar
 * Sink keep their existing independent entry checks. */
export function wormRideDestinationBlock(
  g: {storm: number; mobileStronghold?: {location: string | null} | null},
  territory: string,
  _sector: number,
): string | null {
  if (territory !== MOBILE_STRONGHOLD || !g.mobileStronghold?.location ||
      !Number.isSafeInteger(g.storm) || g.storm < 1 || g.storm > 18) return null;
  const pointer = g.mobileStronghold.location;
  const parts = pointer.split(':');
  if (parts.length !== 2) return null;
  const at = splitLocation(pointer);
  if (!validLocation(at.territory, at.sector) || at.sector < 1) return null;
  return at.sector === g.storm
    ? 'The Hidden Mobile Stronghold points into the storm; a worm ride cannot enter it.'
    : null;
}