fn pub mut argument(value: String) {
  @cmd.arguments.push(value)
}

fn pub move spawn -> Output {
  let child = match @cmd.spawn {
    case Ok(child) -> child
    case Error(err) -> panic("failed to spawn '${@cmd.program}': ${err}")
  }

  let _ = (child.stdin := Option.None).get.write(@stdin)
  let stdout = ByteArray.new
  let stderr = ByteArray.new
  let _ = child.stdout.as_mut.get.read_all(stdout)
  let _ = child.stderr.as_mut.get.read_all(stderr)
  let status = match child.wait {
    case Ok(val) -> val
    case Error(err) -> panic('failed to wait for the child process: ${err}')
  }

  Output(
    status: status,
    stdout: stdout.into_string,
    stderr: stderr.into_string,
  )
}

fn pub mut stdin(bytes: String) {
  @stdin = bytes
}

fn pub mut variable(name: String, value: String) {
  @cmd.variables.set(name, value)
}