/**
 * Apollo Client（v2.1 M8 验收点）
 *
 * 所有 portal-shell 查询走 apollo-router（GraphQL 联邦入口）：
 *   portal-shell → apollo-router :3000/graphql → 各子图（iam/core-edu/content/msg/data-ana/ai/config-service）
 *
 * 双端使用：
 * - 服务端（RSC）：createApolloClient() 每次请求新建实例，ssrMode=true
 * - 客户端：getApolloClient() 单例，复用 InMemoryCache
 *
 * 关联：portal-shell spec §5.5 RSC 预取、§5.6 统一 Hook、M8 验收标准
 */
import { ApolloClient, InMemoryCache, HttpLink, from } from "@apollo/client";
import { setContext } from "@apollo/client/link/context";

const APOLLO_ROUTER_URL =
  process.env.NEXT_PUBLIC_APOLLO_ROUTER_URL ||
  process.env.APOLLO_ROUTER_URL ||
  "http://localhost:3000/graphql";

/**
 * 创建 Apollo Client 实例。
 *
 * @param getAuthToken 可选，返回 JWT 用于注入 Authorization 头（客户端从 cookie/localStorage 读取）
 */
export function createApolloClient(
  getAuthToken?: () => string | null,
): ApolloClient<unknown> {
  const httpLink = new HttpLink({
    uri: APOLLO_ROUTER_URL,
    credentials: "include",
  });

  const authLink = setContext((_, { headers }) => {
    const token = getAuthToken?.() ?? null;
    return {
      headers: {
        ...headers,
        ...(token ? { Authorization: `Bearer ${token}` } : {}),
      },
    };
  });

  return new ApolloClient({
    link: from([authLink, httpLink]),
    cache: new InMemoryCache(),
    ssrMode: typeof window === "undefined",
    defaultOptions: {
      query: {
        errorPolicy: "all",
        fetchPolicy: typeof window === "undefined" ? "no-cache" : "cache-first",
      },
      watchQuery: {
        errorPolicy: "all",
      },
    },
  });
}

let clientSingleton: ApolloClient<unknown> | null = null;

/**
 * 获取客户端 Apollo Client 单例（浏览器侧复用缓存）。
 */
export function getApolloClient(
  getAuthToken?: () => string | null,
): ApolloClient<unknown> {
  if (typeof window === "undefined") {
    return createApolloClient(getAuthToken);
  }
  if (!clientSingleton) {
    clientSingleton = createApolloClient(getAuthToken);
  }
  return clientSingleton;
}