import type { MembershipProduct } from "./membership";

export const PAYMENT_PACKAGES_CACHE_TTL_MS = 60_000;

export type PaymentPackagesPayload = Readonly<{
  enabled: boolean;
  packages: MembershipProduct[];
}>;

type CacheEntry = Readonly<{
  value: PaymentPackagesPayload;
  fetchedAt: number;
}>;

let cache: CacheEntry | null = null;
let inflight: Promise<PaymentPackagesPayload> | null = null;

async function loadPaymentPackages(): Promise<PaymentPackagesPayload> {
  const response = await fetch("/api/payment/packages", { cache: "no-store" });
  const payload = await response.json().catch(() => null);
  if (!response.ok || !payload || typeof payload !== "object") {
    throw new Error("套餐支付暂时不可用，请稍后重试");
  }
  const record = payload as { enabled?: unknown; packages?: unknown };
  return {
    enabled: record.enabled === true,
    packages: Array.isArray(record.packages) ? record.packages as MembershipProduct[] : [],
  };
}

function refreshPaymentPackages(): Promise<PaymentPackagesPayload> {
  if (inflight) return inflight;
  const request = loadPaymentPackages().then((value) => {
    cache = { value, fetchedAt: Date.now() };
    return value;
  }).finally(() => {
    if (inflight === request) inflight = null;
  });
  inflight = request;
  return request;
}

/**
 * Return a fresh package response, or serve the last response while refreshing
 * it in the background after the 60-second freshness window expires.
 */
export function fetchPaymentPackages(
  onBackgroundRefresh?: (value: PaymentPackagesPayload) => void,
): Promise<PaymentPackagesPayload> {
  if (!cache) return refreshPaymentPackages();
  if (Date.now() - cache.fetchedAt < PAYMENT_PACKAGES_CACHE_TTL_MS) {
    return Promise.resolve(cache.value);
  }
  const request = refreshPaymentPackages();
  void request.then((value) => onBackgroundRefresh?.(value)).catch(() => {
    // Stale package data remains usable when a background refresh fails.
  });
  return Promise.resolve(cache.value);
}

export function prefetchPaymentPackages(): void {
  void fetchPaymentPackages().catch(() => undefined);
}

export function resetPaymentPackagesCacheForTests(): void {
  cache = null;
  inflight = null;
}