// prefetch_assets.js - 预拉取车库/大厅所需的静态资源到本地镜像目录
// 用法: node prefetch_assets.js [--concurrency 8] [--only images]
//
// 背景：
//   本地镜像只镜像了 JS，`/play/static/images/*` 全靠 serve.js 现场回源 3dtank.com 并落盘
//   （见 serve.js 的「自愈」分支）。从战局返回车库时车库界面要一次性加载大量贴图/图标，
//   首次全部走回源 → 明显卡顿。
//   本脚本把 webpack 资源表（unpacked/resources.json）里的所有静态资源**预先下载**到
//   `3DTank/web/play/static/`，之后 serve.js 直接本地直出，返回车库秒开。
//
// 产物位置与 serve.js 的 WEB_DIR 一致：
//   URL /play/static/images/xxx.webp  →  3DTank/web/play/static/images/xxx.webp

const fs = require('fs');
const path = require('path');

const PROJECT = path.resolve(__dirname, '..');
const ROOT = path.resolve(PROJECT, '..');
const WEB_DIR = path.join(PROJECT, 'web');
const RES_JSON = path.join(ROOT, '3dtank.com', 'play', 'static', 'js', 'unpacked', 'resources.json');
const BASE_URL = 'https://3dtank.com/play/';

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 CONCURRENCY = Math.max(1, Number(Arg('concurrency', '8')) || 8);

const HEADERS = {
  'user-agent':
    'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/152.0.0.0 Safari/537.36 Edg/152.0.0.0',
  'accept-language': 'zh-CN,zh;q=0.9,en;q=0.8',
  origin: 'https://3dtank.com',
  referer: 'https://3dtank.com/play/',
};

function ReadResourceMap() {
  if (!fs.existsSync(RES_JSON)) {
    console.error('[prefetch] 找不到资源表: ' + RES_JSON);
    process.exit(1);
  }
  const Json = JSON.parse(fs.readFileSync(RES_JSON, 'utf8'));
  const Map = Json.resourceMap || {};
  // 去重：多个模块可能引用同一个文件
  return Array.from(new Set(Object.values(Map).filter((V) => typeof V === 'string' && V)));
}

function TargetFile(Rel) {
  // 安全：禁止跳出 WEB_DIR
  const Clean = Rel.replace(/^\/+/, '');
  const Out = path.resolve(WEB_DIR, 'play', Clean);
  if (!Out.startsWith(path.resolve(WEB_DIR))) return null;
  return Out;
}

async function DownloadOne(Rel, Stats) {
  const Out = TargetFile(Rel);
  if (!Out) {
    Stats.skip++;
    return;
  }
  if (fs.existsSync(Out)) {
    Stats.cached++;
    return;
  }
  const Url = BASE_URL + Rel.replace(/^\/+/, '');
  for (let Try = 0; Try < 3; Try++) {
    try {
      const Res = await fetch(Url, { headers: HEADERS, redirect: 'follow' });
      if (!Res.ok) {
        if (Res.status === 404) {
          Stats.missing++;
          console.warn('[404] ' + Rel);
          return;
        }
        throw new Error('HTTP ' + Res.status);
      }
      const Buf = Buffer.from(await Res.arrayBuffer());
      fs.mkdirSync(path.dirname(Out), { recursive: true });
      fs.writeFileSync(Out, Buf);
      Stats.downloaded++;
      Stats.bytes += Buf.length;
      if (Stats.downloaded % 50 === 0) {
        console.log(
          '[prefetch] 已下载 ' + Stats.downloaded + ' / ' + Stats.total + '（' + (Stats.bytes / 1048576).toFixed(1) + ' MB）',
        );
      }
      return;
    } catch (Err) {
      if (Try === 2) {
        Stats.failed++;
        console.warn('[fail] ' + Rel + ' : ' + Err.message);
      } else {
        await new Promise((R) => setTimeout(R, 400 * (Try + 1)));
      }
    }
  }
}

async function Main() {
  const List = ReadResourceMap();
  const Stats = { total: List.length, downloaded: 0, cached: 0, missing: 0, failed: 0, skip: 0, bytes: 0 };
  console.log('[prefetch] 资源表条目: ' + List.length + '，并发: ' + CONCURRENCY);
  console.log('[prefetch] 输出目录: ' + path.join(WEB_DIR, 'play'));

  let Index = 0;
  async function Worker() {
    while (Index < List.length) {
      const Rel = List[Index++];
      await DownloadOne(Rel, Stats);
    }
  }
  await Promise.all(Array.from({ length: CONCURRENCY }, Worker));

  console.log(
    '[prefetch] 完成：新下载 ' + Stats.downloaded +
      '，已存在 ' + Stats.cached +
      '，404 ' + Stats.missing +
      '，失败 ' + Stats.failed +
      '，合计 ' + (Stats.bytes / 1048576).toFixed(1) + ' MB',
  );
}

Main();