// Turns the compact $app:configuration JSON (spec/offer-config.schema.json) into engine offers.
// Ids in the config are the numeric part of Shopify GIDs; the function compares numeric ids.

export function numericId(gid) {
  if (gid == null) return '';
  const s = String(gid);
  const i = s.lastIndexOf('/');
  return i >= 0 ? s.slice(i + 1) : s;
}

function toScope(sc) {
  return {
    variantIds: new Set(sc?.v || []),
    productIds: new Set(sc?.p || []),
    collectionIds: new Set(sc?.c || []),
  };
}

/** Money values in the config are in shop currency; cart prices are in presentment currency. */
function convertValue(o, rate) {
  if (o.dt === 'amount' || o.dt === 'fixed_price') return o.dv * rate;
  return o.dv;
}

/**
 * @param {object} cfg parsed configuration
 * @param {{rate:number, country?:string, pastGuard?:boolean, guardAt?:string}} ctx
 */
export function offersFromConfig(cfg, ctx) {
  const rate = ctx.rate > 0 ? ctx.rate : 1;
  const out = [];
  for (const o of cfg.offers || []) {
    // Safety net for a late scheduler: once the guard time has passed, drop every offer that ends at or
    // before it. The app republishes the configuration at each boundary; this only covers the gap.
    if (ctx.pastGuard && o.e && cfg.g && o.e <= cfg.g) continue;
    if (o.cc && o.cc.length && (!ctx.country || !o.cc.includes(ctx.country))) continue;
    const base = { id: o.id, type: o.t, maxUses: o.mu || 0 };
    if (o.t === 'fixed') {
      out.push({ ...base, discountType: o.dt, value: convertValue(o, rate),
        lines: (o.l || []).map((l) => ({ variantId: l.v, productId: l.v ? undefined : l.p, quantity: l.q })) });
    } else if (o.t === 'mix') {
      out.push({ ...base, discountType: o.dt, value: convertValue(o, rate), qty: o.q, scope: toScope(o.sc) });
    } else if (o.t === 'bxgy') {
      out.push({ ...base, buyQty: o.bq, getQty: o.gq, getPercent: o.gp,
        buyScope: toScope(o.bs), getScope: toScope(o.gs) });
    }
  }
  return out;
}