{
  "gateway_conf": {
    "gateway_ID": "<Gateway EUI>",
    "server_address": "dev.rightech.io",
    "serv_port_up": 1700,
    "serv_port_down": 1700
  }
}

const EVENT_PACKET = 1;
const EVENT_ALARM = 2;
 
/**
 * Check if n-th bit set for number
 * @param value {number} number value
 * @param bit   {number} bit position
 */
function bit(value, bit) {
  return (value & (1 << bit)) !== 0;
}
 
/**
 * Parse Vega SI-11 Payload
 * https://en.iotvega.com/product/si11
 *
 * ```
 *                   | 0    | 1   | 2   | 3 | 4 | 5 | 6 | 7 | 8-11  | 12-15 | 16-19 | 20-23
 *  1 - EVENT_PACKET | type | bat | cfg |  timestamp    | t | in[0] | in[1] | in[2] | in[3]
 *  2 - EVENT_ALARM  | type | bat | cfg | i |   timestamp   | in[0] | in[1] | in[2] | in[3]
 *
 * ```
 * @param payload {string} base64 encoded payload
 */
export function process(payload) {
  const data = ric.base64.decode(payload);
  let offset = 0;
 
  /* - option 1 - parse binary payload from raw byte array */
  const bytes = new Uint8Array(data.buffer);
 
  const evtype = bytes[offset++];
  const battery = bytes[offset++];
  const configByte = bytes[offset++];
  const config = {
    activation: bit(configByte, 0) ? "abp" : "otaa",
    inputs: [
      +bit(configByte, 4),
      +bit(configByte, 5),
      +bit(configByte, 6),
      +bit(configByte, 7),
    ],
  };
  const evin = evtype === EVENT_ALARM ? bytes[offset++] : undefined;
 
  /* - option 2 - use JS `DataView` interface (like Node's `Buffer`) */
  const evtime = data.getUint32(offset, true) * 1000;
  offset += 4;
 
  const temperature =
    evtype === EVENT_PACKET ? data.getInt8(offset++) : undefined;
 
  const inputs = [];
  for (let i = 0; i < 4; i++) {
    inputs[i] = data.getUint32(offset, true);
    offset += 4;
  }
 
  return { evtype, battery, config, evin, evtime, temperature, inputs };
}