Monorepo skeleton, Prisma schema, core domain and services with tests

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

packages/core/src/promo.ts

@@ -0,0 +1,26 @@
+export interface PromoLike {
+  kind: 'AGENCY_GIFT' | 'DISCOUNT';
+  active: boolean;
+  maxUses: number | null;
+  usedCount: number;
+  validFrom: Date | null;
+  validUntil: Date | null;
+}
+
+export type PromoCheck =
+  | { ok: true }
+  | { ok: false; reason: 'INACTIVE' | 'NOT_STARTED' | 'EXPIRED' | 'EXHAUSTED' | 'ALREADY_USED_BY_CLIENT' };
+
+export function checkPromo(promo: PromoLike, now: Date, usedByClient: boolean): PromoCheck {
+  if (!promo.active) return { ok: false, reason: 'INACTIVE' };
+  if (promo.validFrom && now < promo.validFrom) return { ok: false, reason: 'NOT_STARTED' };
+  if (promo.validUntil && now > promo.validUntil) return { ok: false, reason: 'EXPIRED' };
+  if (promo.maxUses !== null && promo.usedCount >= promo.maxUses) return { ok: false, reason: 'EXHAUSTED' };
+  if (usedByClient) return { ok: false, reason: 'ALREADY_USED_BY_CLIENT' };
+  return { ok: true };
+}
+
+/** Промокод-скидка не суммируется с Barev+: берётся большая из двух */
+export function combineDiscounts(barevPlusPct: number, promoPct: number | null): number {
+  return Math.max(barevPlusPct, promoPct ?? 0);
+}