// AssetRelay.mjs —— 素材中继（只读本地 HTTP 服务，默认端口 8130）
//
// 目的：把「客户端产物」与「官方静态素材本地镜像」拼成一个可浏览的站点，给浏览器侧客户端用。
//   1) `/` 与其它静态文件  → client/build/dist/js/productionExecutable/（Kotlin/JS 产物；不存在就清晰报错）
//   2) `/play/static/**`   → 3DTank/web/play/static/**（**本地镜像优先**，只读）
//   3) 本地镜像缺文件时（可选）回落到 --upstream（用户的 3DTank/tools/serve.js，默认不启用），并打日志
//
// 安全：只读；路径做规范化 + 前缀校验，禁止用 `..`（含 %2e%2e）逃出映射根。
//
// 用法：
//   node client/tools/AssetRelay.mjs
//   node client/tools/AssetRelay.mjs --port 8130 --upstream http://localhost:8080
'use strict';
import fs from 'node:fs';
import http from 'node:http';
import https from 'node:https';
import path from 'node:path';
import url from 'node:url';

const Here = path.dirname(url.fileURLToPath(import.meta.url));
const ClientDir = path.resolve(Here, '..');
const RepoDir = path.resolve(ClientDir, '..');
const DistDir = path.join(ClientDir, 'build', 'dist', 'js', 'productionExecutable');
const MirrorRoot = path.join(RepoDir, '3DTank', 'web', 'play', 'static');

// ---- 参数
const Args = process.argv.slice(2);
function ArgOf(Name, Default) {
  const I = Args.indexOf('--' + Name);
  return I >= 0 && Args[I + 1] ? Args[I + 1] : Default;
}
const Port = Number(ArgOf('port', '8130'));
const Upstream = ArgOf('upstream', '');

// ---- MIME（按扩展名；够用即可，未列的按 application/octet-stream）
const MimeByExt = {
  '.html': 'text/html; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.mjs': 'text/javascript; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.txt': 'text/plain; charset=utf-8',
  '.xml': 'application/xml; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.webp': 'image/webp',
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.gif': 'image/gif',
  '.ico': 'image/x-icon',
  '.ttf': 'font/ttf',
  '.otf': 'font/otf',
  '.woff': 'font/woff',
  '.woff2': 'font/woff2',
  '.mp3': 'audio/mpeg',
  '.ogg': 'audio/ogg',
  '.wav': 'audio/wav',
  '.mp4': 'video/mp4',
  '.webm': 'video/webm',
  '.3ds': 'application/octet-stream',
  '.wasm': 'application/wasm',
};
function MimeOf(P) {
  return MimeByExt[path.extname(P).toLowerCase()] || 'application/octet-stream';
}

// 防目录穿越：把相对路径 join 到根后规范化，必须仍在根之内
function SafeJoin(Root, Rel) {
  const Normalized = path.normalize(Rel).replace(/^([/\\])+/, '');
  const Full = path.normalize(path.join(Root, Normalized));
  if (Full !== Root && !Full.startsWith(Root + path.sep)) return null;
  return Full;
}

const UrlPathOf = (Req) => decodeURIComponent((Req.url || '/').split('?')[0].split('#')[0]);

function Log(Msg) {
  console.log('TankIcAssetRelay | ' + Msg);
}

function SendFile(Res, File, ExtraHeaders) {
  const Headers = Object.assign({ 'Content-Type': MimeOf(File), 'Content-Length': String(fs.statSync(File).size) }, ExtraHeaders || {});
  Res.writeHead(200, Headers);
  fs.createReadStream(File).pipe(Res);
}

function SendText(Res, Code, Text, ExtraHeaders) {
  const Buf = Buffer.from(Text, 'utf8');
  Res.writeHead(Code, Object.assign({ 'Content-Type': 'text/plain; charset=utf-8', 'Content-Length': String(Buf.length) }, ExtraHeaders || {}));
  Res.end(Buf);
}

// 回落：把请求转发给 --upstream（只读代理；命中时打日志）
function RelayUpstream(Req, Res, RelPath) {
  const Target = new URL(RelPath, Upstream);
  const Lib = Target.protocol === 'https:' ? https : http;
  const P = Lib.request(
    Target,
    { method: 'GET', headers: { Accept: Req.headers.accept || '*/*' } },
    (Up) => {
      if (Up.statusCode !== 200) {
        Up.resume();
        SendText(Res, 404, '本地镜像没有，且上游返回 ' + Up.statusCode + '：' + RelPath + '\n');
        return;
      }
      const Headers = {};
      for (const K of ['content-type', 'content-length', 'etag', 'last-modified']) if (Up.headers[K]) Headers[K] = Up.headers[K];
      Headers['Access-Control-Allow-Origin'] = '*';
      Res.writeHead(200, Headers);
      Up.pipe(Res);
    },
  );
  P.on('error', (E) => SendText(Res, 502, '回落到上游失败：' + E.message + '\n'));
  P.end();
}

if (!fs.existsSync(DistDir)) {
  console.error('✗ 客户端产物目录不存在：' + DistDir);
  console.error('  请先构建：cd client && ' + (process.platform === 'win32' ? 'gradlew.bat' : './gradlew') + ' jsProductionExecutableCompileSync');
  process.exit(1);
}
if (!fs.existsSync(MirrorRoot)) {
  console.error('✗ 官方素材本地镜像目录不存在：' + MirrorRoot);
  process.exit(1);
}

const Server = http.createServer((Req, Res) => {
  const Pathname = UrlPathOf(Req);

  // CORS（/play/static/** 加宽；其余也给，方便本地调试）
  if (Req.method === 'OPTIONS') {
    Res.writeHead(204, {
      'Access-Control-Allow-Origin': '*',
      'Access-Control-Allow-Methods': 'GET, HEAD, OPTIONS',
      'Access-Control-Allow-Headers': '*',
      'Access-Control-Max-Age': '86400',
    });
    Res.end();
    return;
  }

  // 1) 官方素材：/play/static/** → 3DTank/web/play/static/**
  if (Pathname === '/play/static' || Pathname.startsWith('/play/static/')) {
    const Rel = Pathname.slice('/play/static/'.length);
    const CORS = { 'Access-Control-Allow-Origin': '*', 'Cache-Control': 'no-cache' };
    const Full = SafeJoin(MirrorRoot, Rel);
    if (Full === null) {
      Log('✗ 目录穿越被拒：' + Pathname);
      SendText(Res, 400, '非法路径（试图逃出映射根）：' + Pathname + '\n', CORS);
      return;
    }
    if (Rel && fs.existsSync(Full) && fs.statSync(Full).isFile()) {
      Log('200 镜像  ' + Pathname + '  (' + MimeOf(Full) + ', ' + fs.statSync(Full).size + 'B)');
      SendFile(Res, Full, CORS);
      return;
    }
    if (Upstream) {
      Log('↩ 回落上游 ' + Upstream + Pathname + '（本地镜像缺 ' + Rel + '）');
      RelayUpstream(Req, Res, Pathname);
      return;
    }
    Log('404 镜像缺文件 ' + Pathname);
    SendText(Res, 404, '本地镜像里没有这个素材：' + Rel + '\n（默认不启用上游回落；可用 --upstream http://localhost:8080）\n', CORS);
    return;
  }

  // 2) 客户端产物：/ 与其它路径 → build/dist/js/productionExecutable/
  const Rel = Pathname === '/' ? 'index.html' : Pathname.slice(1);
  const Full = SafeJoin(DistDir, Rel);
  if (Full === null) {
    Log('✗ 目录穿越被拒：' + Pathname);
    SendText(Res, 400, '非法路径（试图逃出产物根）：' + Pathname + '\n');
    return;
  }
  if (fs.existsSync(Full) && fs.statSync(Full).isFile()) {
    Log('200 产物  ' + Pathname + '  (' + MimeOf(Full) + ', ' + fs.statSync(Full).size + 'B)');
    SendFile(Res, Full);
    return;
  }
  Log('404 产物缺文件 ' + Pathname);
  SendText(Res, 404, '客户端产物里没有：' + Rel + '\n产物目录：' + DistDir + '\n');
});

Server.listen(Port, () => {
  Log('素材中继已启动：http://localhost:' + Port + '/');
  Log('  产物目录 ' + DistDir);
  Log('  素材镜像 ' + MirrorRoot + '（只读，/play/static/**）');
  Log('  上游回落 ' + (Upstream || '未启用（本地镜像优先；缺文件返回 404）'));
});