// parse_dsstore.js - 从 macOS .DS_Store 里抽出目录项名字
// 用法: node parse_dsstore.js <file.ds_store> [--json out.json]
// 原理: DS_Store 是 B 树，文件/目录名记录以 [type=0x00000005][offset u32][len u32][len×UTF-16BE] 内联存放，
//       因此用滑动扫描定位 type 标记再读长度即可，无需完整解析 B 树。
const fs = require('fs');
const path = require('path');

const Argv = process.argv.slice(2);
const File = Argv[0];
const JsonOut = (() => {
  const I = Argv.indexOf('--json');
  return I >= 0 && Argv[I + 1] ? Argv[I + 1] : '';
})();

const Buf = fs.readFileSync(File);
const Names = new Set();

// 主路径：定位 type=5 记录
for (let I = 0; I + 12 <= Buf.length; I++) {
  if (Buf[I] !== 0 || Buf[I + 1] !== 0 || Buf[I + 2] !== 0 || Buf[I + 3] !== 5) continue;
  const Len = Buf.readUInt32BE(I + 8);
  if (Len === 0 || Len > 1024) continue;
  const Start = I + 12;
  if (Start + Len * 2 > Buf.length) continue;
  const Name = Buf.slice(Start, Start + Len * 2).toString('utf16le');
  // 用 utf16le 读 BE 数据会字节交换；这里改回手工 BE 解码
  let BeName = '';
  for (let K = 0; K < Len; K++) BeName += String.fromCharCode(Buf.readUInt16BE(Start + K * 2));
  if (!BeName || /[\x00-\x08\x0b-\x1f]/.test(BeName)) continue;
  Names.add(BeName);
  void Name;
}

// 兜底：任意可打印 UTF-16BE 串（长度 >= 3）
if (Names.size === 0) {
  for (let I = 0; I + 6 <= Buf.length; I += 2) {
    let S = '';
    let J = I;
    while (J + 2 <= Buf.length) {
      const C = Buf.readUInt16BE(J);
      if (C < 0x20 || C > 0x7e) break;
      S += String.fromCharCode(C);
      J += 2;
    }
    if (S.length >= 3) {
      Names.add(S);
      I = J - 2;
    }
  }
}

const List = [...Names].sort();
const Stat = fs.statSync(File);
console.log('文件: ' + path.basename(File) + '  ' + Stat.size + ' 字节');
console.log('条目: ' + List.length);
for (const N of List) console.log('  ' + N);

if (JsonOut) fs.writeFileSync(path.resolve(JsonOut), JSON.stringify({ File, Size: Stat.size, Entries: List }, null, 2), 'utf8');