const zlib = require("node:zlib");
const { crc32 } = require("./import-estx.cjs");

// ZIP32 container used by Office Open XML and ESTX; never extracts paths to disk.
function pack(files) {
  const local = [],
    central = [];
  let offset = 0;
  for (const [name, value] of files) {
    const filename = Buffer.from(name, "utf8"),
      data = Buffer.from(value),
      compressed = zlib.deflateRawSync(data),
      crc = crc32(data);
    const header = Buffer.alloc(30);
    header.writeUInt32LE(0x04034b50);
    header.writeUInt16LE(20, 4);
    header.writeUInt16LE(0x800, 6);
    header.writeUInt16LE(8, 8);
    header.writeUInt16LE(0x21, 12);
    header.writeUInt32LE(crc, 14);
    header.writeUInt32LE(compressed.length, 18);
    header.writeUInt32LE(data.length, 22);
    header.writeUInt16LE(filename.length, 26);
    const directory = Buffer.alloc(46);
    directory.writeUInt32LE(0x02014b50);
    directory.writeUInt16LE(20, 4);
    header.copy(directory, 6, 4, 30);
    directory.writeUInt32LE(offset, 42);
    local.push(header, filename, compressed);
    central.push(directory, filename);
    offset += header.length + filename.length + compressed.length;
  }
  const directory = Buffer.concat(central),
    end = Buffer.alloc(22);
  end.writeUInt32LE(0x06054b50);
  end.writeUInt16LE(files.size, 8);
  end.writeUInt16LE(files.size, 10);
  end.writeUInt32LE(directory.length, 12);
  end.writeUInt32LE(offset, 16);
  return Buffer.concat([...local, directory, end]);
}

function unpack(buffer) {
  let end = buffer.length - 22;
  for (; end >= Math.max(0, buffer.length - 65557); end--)
    if (buffer.readUInt32LE(end) === 0x06054b50) break;
  if (end < Math.max(0, buffer.length - 65557)) throw Error("ZIP 디렉터리 없음");
  const count = buffer.readUInt16LE(end + 10),
    files = new Map();
  if (count > 3000) throw Error("ZIP 항목 수 초과");
  let position = buffer.readUInt32LE(end + 16),
    total = 0;
  for (let i = 0; i < count; i++) {
    if (buffer.readUInt32LE(position) !== 0x02014b50) throw Error("ZIP 헤더 오류");
    const flags = buffer.readUInt16LE(position + 8),
      method = buffer.readUInt16LE(position + 10),
      crc = buffer.readUInt32LE(position + 16),
      compressed = buffer.readUInt32LE(position + 20),
      size = buffer.readUInt32LE(position + 24),
      length = buffer.readUInt16LE(position + 28),
      extra = buffer.readUInt16LE(position + 30),
      comment = buffer.readUInt16LE(position + 32),
      at = buffer.readUInt32LE(position + 42),
      name = buffer.subarray(position + 46, position + 46 + length).toString("utf8");
    if (
      flags & 1 ||
      !name ||
      name.startsWith("/") ||
      name.includes("\\") ||
      name.split("/").includes("..")
    )
      throw Error("지원하지 않는 ZIP 경로/암호화");
    total += size;
    if (total > 256 * 1024 * 1024) throw Error("압축 해제 크기 초과");
    if (buffer.readUInt32LE(at) !== 0x04034b50) throw Error("ZIP 로컬 헤더 오류");
    const start = at + 30 + buffer.readUInt16LE(at + 26) + buffer.readUInt16LE(at + 28);
    if (start + compressed > buffer.length) throw Error("ZIP 데이터 범위 오류");
    const source = buffer.subarray(start, start + compressed),
      data =
        method === 8
          ? zlib.inflateRawSync(source, { maxOutputLength: 256 * 1024 * 1024 })
          : method === 0
            ? source
            : null;
    if (!data || data.length !== size || crc32(data) !== crc || files.has(name))
      throw Error("ZIP CRC/중복 오류");
    files.set(name, data);
    position += 46 + length + extra + comment;
  }
  return files;
}
module.exports = { pack, unpack };