// res_proxy.js —— 本地资源代理（res.3dtank.com → 本地缓存）
//
// 为什么需要：官方 3DS 贴图（BG1 1024.PNG / SKY1.PNG 等）没有 CORS 头，
// 浏览器从 localhost 直接请求会被拦截；同时每次开发都走公网很慢。
//
// 用法：node tools/res_proxy.js [--port 8082] [--cache build/res-cache]
//   GET /res/<path>  → https://res.3dtank.com/<path>，落盘缓存后返回
//   GET /play/<path> → 3DTank/web/play/<path>（本地镜像，可选）
//   GET /health      → ok
//
// 前端通过 webpack devServer 把 /res 代理到本服务（webpack.config.d/res-proxy.js）。
'use strict';

const http = require('http');
const fs = require('fs');
const path = require('path');
const { URL } = require('url');

const Argv = process.argv.slice(2);
const Arg = (Name, Def) => {
  const I = Argv.indexOf('--' + Name);
  return I >= 0 && Argv[I + 1] ? Argv[I + 1] : Def;
};

const Root = path.resolve(__dirname, '..');
const Port = Number(Arg('port', '8082'));
const CacheDir = path.resolve(Root, Arg('cache', 'build/res-cache'));
const MirrorPlay = path.resolve(Root, '..', '3DTank', 'web', 'play');
const Upstream = 'https://res.3dtank.com';

const Mime = {
  '.3ds': 'application/octet-stream',
  '.a3d': 'application/octet-stream',
  '.webp': 'image/webp',
  '.png': 'image/png',
  '.jpg': 'image/jpeg',
  '.jpeg': 'image/jpeg',
  '.svg': 'image/svg+xml',
  '.json': 'application/json',
  '.info': 'application/octet-stream',
  '.mp3': 'audio/mpeg',
  '.ktx': 'application/octet-stream',
};

fs.mkdirSync(CacheDir, { recursive: true });

function CachePath(Key) {
  const Clean = Key.replace(/^\/+/, '').replace(/[^a-zA-Z0-9._/-]/g, '_').replace(/\.\./g, '_');
  return path.join(CacheDir, Clean);
}

function Send(Res, Status, Type, Body) {
  Res.writeHead(Status, {
    'Content-Type': Type || 'application/octet-stream',
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Methods': 'GET, OPTIONS',
    'Access-Control-Allow-Headers': '*',
    'Cache-Control': 'public, max-age=31536000, immutable',
  });
  Res.end(Body);
}

async function FetchUpstream(PathAndQuery) {
  const Decoded = decodeURIComponent(PathAndQuery);
  const Ext = path.extname(Decoded);
  const NoExt = Decoded.slice(0, Decoded.length - Ext.length);
  const Candidates = [
    PathAndQuery,
    Decoded.toLowerCase(),
    (NoExt + '.webp').toLowerCase(),
    (NoExt + '.png').toLowerCase(),
    (NoExt + '.webp'),
    (NoExt + '.png'),
  ];
  for (const PathTry of [...new Set(Candidates)]) {
    const R = await fetch(Upstream + (PathTry.startsWith('/') ? PathTry : '/' + PathTry), {
      headers: {
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) TankiOffline/0.1',
        Accept: '*/*',
      },
    });
    if (R.ok) {
      const Body = Buffer.from(await R.arrayBuffer());
      return {
        Status: 200,
        Type: R.headers.get('content-type') || 'application/octet-stream',
        Body,
        Resolved: PathTry,
      };
    }
  }
  return { Status: 404, Type: 'text/plain', Body: Buffer.from('upstream 404') };
}

const Server = http.createServer(async (Req, Res) => {
  if (Req.method === 'OPTIONS') {
    Send(Res, 204, 'text/plain', Buffer.alloc(0));
    return;
  }
  const U = new URL(Req.url, 'http://localhost');
  if (U.pathname === '/health') {
    Send(Res, 200, 'text/plain', Buffer.from('ok'));
    return;
  }

  // 本地镜像：/play/... → 3DTank/web/play/...
  if (U.pathname.startsWith('/play/')) {
    const File = path.join(MirrorPlay, U.pathname.slice('/play/'.length));
    if (File.startsWith(MirrorPlay) && fs.existsSync(File) && fs.statSync(File).isFile()) {
      Send(Res, 200, Mime[path.extname(File).toLowerCase()], fs.readFileSync(File));
      return;
    }
    Send(Res, 404, 'text/plain', Buffer.from('mirror miss'));
    return;
  }

  // 线上资源：/res/<path> → res.3dtank.com/<path>
  if (!U.pathname.startsWith('/res/')) {
    Send(Res, 404, 'text/plain', Buffer.from('not found'));
    return;
  }
  const Key = U.pathname.slice('/res'.length);
  const Cache = CachePath(Key);
  if (fs.existsSync(Cache) && fs.statSync(Cache).isFile()) {
    Send(Res, 200, Mime[path.extname(Cache).toLowerCase()] || 'application/octet-stream', fs.readFileSync(Cache));
    return;
  }
  try {
    const Result = await FetchUpstream(Key);
    if (Result.Status === 200) {
      fs.mkdirSync(path.dirname(Cache), { recursive: true });
      fs.writeFileSync(Cache, Result.Body);
    }
    Send(Res, Result.Status, Result.Type, Result.Body);
    console.log(`${Result.Status === 200 ? 'cache' : 'fail '} ${Key} (${Result.Body.length}B)`);
  } catch (E) {
    Send(Res, 502, 'text/plain', Buffer.from('proxy error: ' + E.message));
    console.log('error', Key, E.message);
  }
});

Server.listen(Port, '127.0.0.1', () => {
  console.log(`res proxy: http://127.0.0.1:${Port}/res/...  (cache: ${CacheDir})`);
  console.log(`play mirror: http://127.0.0.1:${Port}/play/...  (${MirrorPlay})`);
});