Milesight GS101: LoRaWAN Residential Gas Detector

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

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

    // Gas status: 0 = normal, 1 = alarm
    if (channel === 0x05 && type === 0x8e) {
      data.gas_status = bytes[i] === 1 ? "alarm" : "normal"; i += 1;
    // Solenoid valve output state
    } else if (channel === 0x06 && type === 0x01) {
      data.valve_status = bytes[i] === 1 ? "on" : "off"; i += 1;
    // Relay output state
    } else if (channel === 0x07 && type === 0x01) {
      data.relay_output_status = bytes[i] === 1 ? "on" : "off"; i += 1;
    // Remaining sensor life (UINT32 little-endian)
    } else if (channel === 0x08 && type === 0x90) {
      data.life_remain = readUInt32LE(bytes, i); i += 4;
    // Device alarm/lifecycle event
    } else if (channel === 0xff && type === 0x3f) {
      data.alarm = readAlarm(bytes[i]); i += 1;
    // Device info on join/power-on: skip protocol/hw/fw/SN/class fields
    } else if (channel === 0xff) {
      i += deviceInfoLen(type);
    } else {
      break;
    }
  }
  return { data: data };
}

function readUInt32LE(b, i) {
  return ((b[i+3]<<24)|(b[i+2]<<16)|(b[i+1]<<8)|b[i]) >>> 0;
}
function readAlarm(v) {
  var map = { 0: "power off", 1: "power on", 2: "device fault",
              3: "fault recovered", 4: "device invalid soon", 5: "device invalid" };
  return map[v] !== undefined ? map[v] : v;
}
function deviceInfoLen(type) {
  // 0xFF info fields: 0x01 version, 0x0f class, 0x0b status, 0xfe reset = 1 byte;
  // 0x09 hw, 0x0a fw, 0xff tsl = 2 bytes; 0x16 serial number = 8 bytes
  if (type === 0x09 || type === 0x0a || type === 0xff) return 2;
  if (type === 0x16) return 8;
  return 1;
}