parsing.cc

std::istream &operator>>(std::istream &s, CuboidInstruction &cube) {
  std::string line;
  if (!getline(s, line))
    return s;

  CuboidInstruction result;
  if (line.starts_with("on")) {
    result.on = true;
  } else if (line.starts_with("off")) {
    result.on = false;
  } else {
    throw std::runtime_error("Failed to parse input. No leading \"on\"/\"off\" found.");
  }

  auto xpos = line.find("x=");
  if (xpos == std::string::npos)
    throw std::runtime_error("Failed to parsed input, did not find x coordinate.");
  result.min.x = std::stoll(line.substr(xpos + 2));
  auto xpos_max = line.find("..", xpos + 2);
  if (xpos_max == std::string::npos)
    throw std::runtime_error("Failed to parsed input, did not find end of x coordinate.");
  result.max.x = std::stoll(line.substr(xpos_max + 2));

  auto ypos = line.find("y=");
  if (ypos == std::string::npos)
    throw std::runtime_error("Failed to parsed input, did not find y coordinate.");
  result.min.y = std::stoll(line.substr(ypos + 2));
  auto ypos_max = line.find("..", ypos + 2);
  if (ypos_max == std::string::npos)
    throw std::runtime_error("Failed to parsed input, did not find end of x coordinate.");
  result.max.y = std::stoll(line.substr(ypos_max + 2));

  auto zpos = line.find("z=");
  if (zpos == std::string::npos)
    throw std::runtime_error("Failed to parsed input, did not find z coordinate.");
  result.min.z = std::stoll(line.substr(zpos + 2));
  auto zpos_max = line.find("..", zpos + 2);
  if (zpos_max == std::string::npos)
    throw std::runtime_error("Failed to parsed input, did not find end of x coordinate.");
  result.max.z = std::stoll(line.substr(zpos_max + 2));

  cube = result;

  return s;
}