Milesight WS301: LoRaWAN Door/Window Contact Sensor

function decodeUplink(input) {
  var bytes = input.bytes;
  var data = {};

  for (var i = 0; i < bytes.length; ) {
    var channel = bytes[i++];
    var type = bytes[i++];

    if (channel === 0x01 && type === 0x75) {          // battery (%)
      data.battery = bytes[i]; i += 1;
    } else if (channel === 0x03 && type === 0x00) {   // door / window state
      data.magnet_status = bytes[i] === 0 ? "close" : "open"; i += 1;
    } else if (channel === 0x04 && type === 0x00) {   // install / tamper state
      data.tamper_status = bytes[i] === 0 ? "installed" : "uninstalled"; i += 1;
    } else if (channel === 0xff) {                     // device info (join / power-on)
      i += deviceInfoLen(type);
    } else {
      break;
    }
  }
  return { data: data };
}

function deviceInfoLen(type) {
  // 0xFF channels carry version/SN/status fields of fixed length
  if (type === 0x01 || type === 0x0f || type === 0x0b || type === 0xfe) return 1; // ipso ver, class, status, reset
  if (type === 0x09 || type === 0x0a || type === 0xff) return 2;                  // hw, fw, tsl version
  if (type === 0x08) return 6;                                                    // serial number
  return 1;
}