import { GOODS, NEWS_DAYS_PER_LANE, SNAPSHOT_KEEP } from './constants.js';
import { advancePlanet, priceOf } from './economy.js';

// Daily price snapshots per planet. Knowledge from `hops` lanes away
// is the snapshot from hops * NEWS_DAYS_PER_LANE days ago.
export class NewsLedger {
  constructor() {
    this.history = new Map(); // planetId -> [{time, prices}]
  }

  record(galaxy, t) {
    for (const planet of galaxy.planets) {
      advancePlanet(planet, t);
      const prices = Object.fromEntries(GOODS.map((g) => [g, priceOf(g, planet.stock[g])]));
      let arr = this.history.get(planet.id);
      if (!arr) this.history.set(planet.id, (arr = []));
      arr.push({ time: t, prices });
      if (arr.length > SNAPSHOT_KEEP) arr.shift();
    }
  }

  // Latest snapshot of planetId that has had time to travel `hops` lanes by time t.
  // Clamped to t=0: the initial state is universally known.
  knownPrices(planetId, hops, t) {
    const arr = this.history.get(planetId);
    if (!arr || arr.length === 0) return null;
    const asOf = Math.max(0, t - hops * NEWS_DAYS_PER_LANE);
    let best = null;
    for (const snap of arr) {
      if (snap.time <= asOf) best = snap;
      else break;
    }
    return best ?? arr[0];
  }
}