/**
 * GraphQL 同域代理（P0-3，ARCHITECTURE.md §3.4 V3-A2 / §4 / §5.2）
 *
 * 浏览器 Apollo Client 一律走同域 `/api/graphql`：
 *   Browser → /api/graphql (本 Route Handler) → apollo-router :3000
 *
 * 职责：
 * 1. 从 httpOnly cookie `edu_session` 取 JWT，注入 `Authorization: Bearer`
 * 2. 透传 body（APQ hash 或 query）与 Apollo 相关头
 * 3. 响应 status / JSON 原样回传，不缓存
 * 4. 错误归一化：网络错误 → `{ errors: [{ message: "UPSTREAM_UNAVAILABLE" }] }`
 *
 * 安全收益（§4.2）：
 * - JWT 全程不出 httpOnly cookie，消除 XSS 窃取凭证面
 * - 修复"浏览器绕过 api-gateway"问题（代理在服务端调 router）
 *
 * 验收命令：
 *   DevTools Network 面板无 `localhost:3000` 直连；所有 GraphQL 请求走 `/api/graphql`
 */
import type { NextRequest } from "next/server";
import { NextResponse } from "next/server";

export const dynamic = "force-dynamic";
export const runtime = "nodejs";

const SESSION_COOKIE = "edu_session";

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

/**
 * 从 Cookie 头解析指定 cookie 值。
 */
function readCookie(cookieHeader: string | null, name: string): string | null {
  if (!cookieHeader) return null;
  const match = cookieHeader
    .split(";")
    .map((p) => p.trim())
    .find((p) => p.startsWith(`${name}=`));
  if (!match) return null;
  return decodeURIComponent(match.slice(name.length + 1));
}

export async function POST(req: NextRequest): Promise<NextResponse> {
  const cookieHeader = req.headers.get("cookie");
  const token = readCookie(cookieHeader, SESSION_COOKIE);

  // 透传 body（APQ hash 请求或完整 query），不解析不修改
  const body = await req.text();

  const upstreamHeaders: Record<string, string> = {
    "Content-Type": req.headers.get("content-type") ?? "application/json",
    Accept: req.headers.get("accept") ?? "application/json",
    // Apollo Persisted Query 协议头透传
    "X-APQ": req.headers.get("x-apq") ?? "1",
    // 服务端追踪：透传客户端 X-Request-Id（若有）
    ...(req.headers.get("x-request-id")
      ? { "X-Request-Id": req.headers.get("x-request-id") as string }
      : {}),
  };

  // 注入 Authorization（若 cookie 中有 JWT）
  if (token) {
    upstreamHeaders.Authorization = `Bearer ${token}`;
  }

  try {
    const upstream = await fetch(UPSTREAM_URL, {
      method: "POST",
      headers: upstreamHeaders,
      body,
      cache: "no-store",
    });

    const responseText = await upstream.text();
    return new NextResponse(responseText, {
      status: upstream.status,
      headers: {
        "Content-Type":
          upstream.headers.get("content-type") ?? "application/json",
        // 不缓存：GraphQL 响应可能因身份/变量而异
        "Cache-Control": "no-store, no-cache, must-revalidate",
      },
    });
  } catch (err) {
    const message =
      err instanceof Error ? err.message : "Unknown upstream error";
    console.error(
      `[portal-shell] /api/graphql upstream error: ${message} (url=${UPSTREAM_URL})`,
    );
    return NextResponse.json(
      {
        errors: [
          {
            message: "UPSTREAM_UNAVAILABLE",
            extensions: {
              code: "UPSTREAM_UNAVAILABLE",
              reason: message,
            },
          },
        ],
      },
      { status: 502 },
    );
  }
}

/**
 * GET /api/graphql → 简单健康标识，便于排查路由是否挂载。
 * Apollo Router 自身的 health 在 :8088/health。
 */
export async function GET(): Promise<NextResponse> {
  return NextResponse.json(
    {
      ok: true,
      proxy: "/api/graphql",
      upstream: UPSTREAM_URL,
    },
    { status: 200 },
  );
}