/**
 * A minimal stored (uncompressed) zip archive, byte-compatible with `unzip`,
 * for tests that fake GitHub artifact downloads without network or a zip CLI.
 */
export function storedZip(files: Record<string, string>): Buffer {
  const locals: Buffer[] = [], centrals: Buffer[] = [];
  let offset = 0;
  for (const [name, text] of Object.entries(files)) {
    const data = Buffer.from(text), fileName = Buffer.from(name), crc = Bun.hash.crc32(data) >>> 0;
    const local = Buffer.alloc(30); local.writeUInt32LE(0x04034b50, 0); local.writeUInt16LE(20, 4);
    local.writeUInt32LE(crc, 14); local.writeUInt32LE(data.length, 18); local.writeUInt32LE(data.length, 22); local.writeUInt16LE(fileName.length, 26);
    const central = Buffer.alloc(46); central.writeUInt32LE(0x02014b50, 0); central.writeUInt16LE(20, 4); central.writeUInt16LE(20, 6);
    central.writeUInt32LE(crc, 16); central.writeUInt32LE(data.length, 20); central.writeUInt32LE(data.length, 24);
    central.writeUInt16LE(fileName.length, 28); central.writeUInt32LE(offset, 42);
    locals.push(local, fileName, data); centrals.push(central, fileName);
    offset += 30 + fileName.length + data.length;
  }
  const size = centrals.reduce((sum, b) => sum + b.length, 0);
  const end = Buffer.alloc(22); end.writeUInt32LE(0x06054b50, 0); end.writeUInt16LE(Object.keys(files).length, 8);
  end.writeUInt16LE(Object.keys(files).length, 10); end.writeUInt32LE(size, 12); end.writeUInt32LE(offset, 16);
  return Buffer.concat([...locals, ...centrals, end]);
}