/**
 * 企业信息查询接口调试代理（零依赖，Node >= 14）
 *
 * 用途：
 *   1. 托管同目录下的 index.html（访问 http://localhost:5500）
 *   2. 将其余请求原样转发到后端 127.0.0.1:8081，并在响应上附加 CORS 头，
 *      规避浏览器跨域限制，方便前端页面直接联调。
 *
 * 启动：  node proxy.js
 * 自定义：PORT=5501 TARGET_PORT=9090 node proxy.js
 */
"use strict";

const http = require("http");
const https = require("https");
const fs = require("fs");
const path = require("path");

const PORT = Number(process.env.PORT) || 9527;
const TARGET_HOST = process.env.TARGET_HOST || "127.0.0.1";
const TARGET_PORT = Number(process.env.TARGET_PORT) || 8081;
const CX_HOST = process.env.CX_HOST || "api-cx.dingtax.cn";
const PUB_HOST = process.env.PUB_HOST || "apit-dsb.dingtax.cn";

const MIME = {
  ".html": "text/html; charset=utf-8",
  ".js": "text/javascript; charset=utf-8",
  ".css": "text/css; charset=utf-8",
  ".json": "application/json; charset=utf-8",
  ".png": "image/png",
  ".svg": "image/svg+xml",
  ".ico": "image/x-icon"
};

function corsHeaders() {
  return {
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Methods": "GET,POST,PUT,DELETE,PATCH,OPTIONS",
    "Access-Control-Allow-Headers": "Content-Type, Authorization, X-Requested-With"
  };
}

const server = http.createServer((req, res) => {
  const cors = corsHeaders();

  if (req.method === "OPTIONS") {
    res.writeHead(204, cors);
    return res.end();
  }

  // 静态文件：/ 及 /index.html，其余静态路径按扩展名尝试读取
  const urlPath = decodeURIComponent((req.url || "/").split("?")[0]);
  if (req.method === "GET" && !urlPath.startsWith("/dsb/") && !urlPath.startsWith("/cx/") && !urlPath.startsWith("/pub/")) {
    let file = path.join(__dirname, urlPath === "/" ? "index.html" : urlPath);
    if (!file.startsWith(__dirname)) file = path.join(__dirname, "index.html");
    fs.readFile(file, (err, buf) => {
      if (err) {
        res.writeHead(404, { ...cors, "Content-Type": "text/plain; charset=utf-8" });
        return res.end("404 Not Found: " + urlPath);
      }
      res.writeHead(200, { ...cors, "Content-Type": MIME[path.extname(file)] || "application/octet-stream" });
      res.end(buf);
    });
    return;
  }

  // /cx/* → 公网 api-cx.dingtax.cn (HTTPS)；/dsb/* → 本机后端 (HTTP)
  const isCx = urlPath.startsWith("/cx/");
  const isPub = urlPath.startsWith("/pub/");
  const qs = (req.url || "").split("?").slice(1).join("?");
  // apit-dsb 后端会校验 Origin/Referer（Invalid CORS request / Rap csrf Verify），转发前剥离浏览器来源头
  const fwdHeaders = { ...req.headers };
  ["origin", "referer", "sec-fetch-site", "sec-fetch-mode", "sec-fetch-dest", "sec-fetch-user", "accept-language"].forEach(h => delete fwdHeaders[h]);
  const options = isCx
    ? {
        host: CX_HOST,
        port: 443,
        path: req.url,
        method: req.method,
        headers: { ...fwdHeaders, host: CX_HOST },
        rejectUnauthorized: false
      }
    : isPub
    ? {
        host: PUB_HOST,
        port: 443,
        path: "/dsb" + urlPath.slice(4) + (qs ? "?" + qs : ""),
        method: req.method,
        headers: { ...fwdHeaders, host: PUB_HOST },
        rejectUnauthorized: false
      }
    : {
        host: TARGET_HOST,
        port: TARGET_PORT,
        path: req.url,
        method: req.method,
        headers: { ...fwdHeaders, host: `${TARGET_HOST}:${TARGET_PORT}` }
      };

  const upstream = (isCx || isPub ? https : http).request(options, (proxyRes) => {
    res.writeHead(proxyRes.statusCode || 502, { ...proxyRes.headers, ...cors });
    proxyRes.pipe(res);
  });

  upstream.on("error", (e) => {
    res.writeHead(502, { ...cors, "Content-Type": "application/json; charset=utf-8" });
    res.end(JSON.stringify({
      code: "-1",
      message: `代理转发失败: ${e.message}（后端 ${TARGET_HOST}:${TARGET_PORT} 不可达？）`
    }));
  });

  req.pipe(upstream);
});

server.listen(PORT, () => {
  console.log("企业信息接口调试代理已启动");
  console.log(`  测试页面: http://localhost:${PORT}`);
  console.log(`  转发目标: http://${TARGET_HOST}:${TARGET_PORT}`);
  console.log("  按 Ctrl+C 停止");
});