/**
 * Picking a system for the effects demo (?fx=<type>) — pure over the
 * seeded roster, so dev/system-effects.test.mjs can exercise the
 * ranking in bare Node.
 *
 * The demo wants to drop the player into a system of the requested
 * archetype that is GOOD for judging the effect: plenty of structure to
 * warp (worlds, a belt, a gate or two to jump out of). Candidates are
 * therefore ranked richest-first — more objects, then more jump gates —
 * with roster order as the stable tiebreak (seed-deterministic either
 * way: the roster is seed-ordered and the score is a pure function of
 * the record + its cached contents).
 */

/**
 * @param {object} galaxy a seeded galaxy (Galaxy.js) — reads `.records`
 *   ({ id, type, ... }[]) and `.contentCache` (Map id -> contents,
 *   possibly empty — content is lazy).
 * @param {string} type the requested archetype (systems.types key)
 * @returns {object | null} the chosen record (has `.id`), or null when
 *   the roster holds no system of that type.
 */
export function pickFxSystem(galaxy, type) {
  const records = Array.isArray(galaxy?.records) ? galaxy.records : [];
  const cache = galaxy?.contentCache instanceof Map ? galaxy.contentCache : null;

  let best = null;
  let bestKey = null;
  for (const rec of records) {
    if (!rec || rec.type !== type) continue;
    const content = cache?.get(rec.id) ?? null;
    const objects =
      (Array.isArray(content?.planets) ? content.planets.length : 0) +
      (Array.isArray(content?.settlements) ? content.settlements.length : 0) +
      (Array.isArray(content?.asteroids) ? content.asteroids.length : 0);
    const gates = Array.isArray(content?.jumps) ? content.jumps.length : 0;
    const key = objects * 1000 + gates;
    if (!best || key > bestKey) {
      best = rec;
      bestKey = key;
    }
  }
  return best;
}