/**
 * 媒体同步脚本：将 exercises-dataset 的 images/ 与 videos/ 下载到 backend/media/，
 * 使后端 /media 静态服务可直接提供缩略图与动画 GIF。
 *
 * 用法： node scripts/sync-media.mjs
 * 可选环境变量：
 *   MEDIA_CONCURRENCY=8   并发下载数
 *   MEDIA_ONLY=gif|image  仅下载某类（gif / image）
 */
import * as fs from 'fs';
import * as path from 'path';
import { fileURLToPath } from 'url';

const __dirname = path.dirname(fileURLToPath(import.meta.url));
const DATA_FILE = path.join(__dirname, '..', 'src', 'exercises', 'data', 'exercises.json');
const MEDIA_DIR = path.join(__dirname, '..', 'media');
const RAW_BASE = 'https://raw.githubusercontent.com/hasaneyldrm/exercises-dataset/main/';
const CONCURRENCY = parseInt(process.env.MEDIA_CONCURRENCY || '8', 10);
const ONLY = process.env.MEDIA_ONLY || 'all';

async function main() {
  if (!fs.existsSync(DATA_FILE)) {
    console.error('[sync-media] 未找到数据集，请先运行 npm run build 或手动放置 exercises.json');
    process.exit(1);
  }
  const raw = JSON.parse(fs.readFileSync(DATA_FILE, 'utf-8'));
  const paths = new Set();
  for (const e of raw) {
    if (e.image && (ONLY === 'all' || ONLY === 'image')) paths.add(e.image);
    if (e.gif_url && (ONLY === 'all' || ONLY === 'gif')) paths.add(e.gif_url);
  }

  fs.mkdirSync(MEDIA_DIR, { recursive: true });
  const list = Array.from(paths);
  console.log(`[sync-media] 待下载媒体 ${list.length} 个，并发 ${CONCURRENCY}`);

  let done = 0;
  let skipped = 0;
  let failed = 0;
  const queue = [...list];

  async function worker() {
    while (queue.length) {
      const p = queue.shift();
      const dest = path.join(MEDIA_DIR, p);
      if (fs.existsSync(dest) && fs.statSync(dest).size > 0) {
        skipped++;
        continue;
      }
      try {
        const res = await fetch(RAW_BASE + p);
        if (!res.ok) throw new Error(`HTTP ${res.status}`);
        const buf = Buffer.from(await res.arrayBuffer());
        fs.mkdirSync(path.dirname(dest), { recursive: true });
        fs.writeFileSync(dest, buf);
        done++;
      } catch (err) {
        failed++;
        console.error(`  失败 ${p}: ${err.message}`);
      }
      if ((done + skipped + failed) % 50 === 0) {
        console.log(`  进度 ${done + skipped + failed}/${list.length}`);
      }
    }
  }

  await Promise.all(Array.from({ length: CONCURRENCY }, () => worker()));
  console.log(`[sync-media] 完成：新增 ${done}，已存在 ${skipped}，失败 ${failed}`);
}

main().catch((e) => {
  console.error('[sync-media] 错误:', e.message);
  process.exit(1);
});