Heltec V4 LoRaWAN Energy Logger

function decodeUplink(input) {
  const bytes = input.bytes;

  if (!bytes || bytes.length < 1) {
    return { errors: ["Payload too short"] };
  }

  const type = bytes[0];

  // ===== ACK PAYLOADS (0x81-0x85) =====
  if (type === 0x81) {
    if (bytes.length < 2) {
      return { errors: ["TX Override ACK: payload too short"] };
    }
    return {
      data: {
        ack_type: "tx_interval_override",
        tx_interval_min: bytes[1]
      }
    };
  }

  if (type === 0x82) {
    return {
      data: {
        ack_type: "counters_reset",
        status: "success"
      }
    };
  }

  if (type === 0x85) {
    if (bytes.length < 5) {
      return { errors: ["Config Query: payload too short"] };
    }
    const energyFlags = bytes[2];
    const energyMode = (energyFlags & 0x01) ? "cooling" : "heating";
    const sensorLocation = (energyFlags & 0x02) ? "return" : "flow";
    return {
      data: {
        ack_type: "config_query_response",
        tx_interval_min: bytes[1],
        energy_mode: energyMode,
        sensor_location: sensorLocation,
        flow_max_lpm: bytes[3] * 10
      }
    };
  }

  // ===== VERSION 3 SENSOR DATA (17 Bytes) =====
  if ((type >> 4) === 0x3) {
    if (bytes.length < 17) {
      return { errors: ["Sensor payload v3 too short"] };
    }

    const tempFlowHigh = bytes[0] & 0x0F;
    const tempFlowLow = (bytes[1] >> 2) & 0x3F;
    const tempReturnHigh = bytes[1] & 0x03;
    const tempReturnLow = bytes[2];

    const tFlowRaw = (tempFlowHigh << 6) | tempFlowLow;
    const tReturnRaw = (tempReturnHigh << 8) | tempReturnLow;

    const temperature_degrC_abs_flow = (tFlowRaw === 1023) ? null : tFlowRaw / 10.0;
    const temperature_degrC_abs_return = (tReturnRaw === 1023) ? null : tReturnRaw / 10.0;

    const flowRaw = (bytes[3] << 8) | bytes[4];
    const flow_l_min = (flowRaw === 65535) ? null : flowRaw / 10.0;
    const volumeFlow_m3perh_abs = (flow_l_min === null) ? null : flow_l_min * 60.0 / 1000.0;

    const vol_m3_x1000 =
      ((bytes[5] << 24) >>> 0) |
      ((bytes[6] << 16) >>> 0) |
      ((bytes[7] << 8)  >>> 0) |
      ((bytes[8] << 0)  >>> 0);
    const volume_m3_inc = (vol_m3_x1000 === 0xFFFFFFFF) ? null : vol_m3_x1000 / 1000.0;

    const powerRaw =
      ((bytes[9] << 16) >>> 0) |
      ((bytes[10] << 8)  >>> 0) |
      ((bytes[11] << 0)  >>> 0);
    const power_kW_abs = (powerRaw === 0xFFFFFF) ? null : powerRaw / 1000.0;

    const energyRaw =
      ((bytes[12] << 24) >>> 0) |
      ((bytes[13] << 16) >>> 0) |
      ((bytes[14] << 8)  >>> 0) |
      ((bytes[15] << 0)  >>> 0);
    const energy_kWh_inc = (energyRaw === 0xFFFFFFFF) ? null : energyRaw / 10.0;

    const flags = bytes[16];
    const energyMode = (flags & 0x01) ? "cooling" : "heating";
    const sensorLocation = (flags & 0x02) ? "return" : "flow";

    const powerKey = `power_kW_abs@${energyMode}`;
    const energyKey = `energy_kWh_inc@${energyMode}`;

    const result = {
      data: {
        payload_type: "sensor_data_v3",
        volumeFlow_m3perh_abs: volumeFlow_m3perh_abs,
        volume_m3_inc: volume_m3_inc,
        "temperature_degrC_abs@flow": temperature_degrC_abs_flow,
        "temperature_degrC_abs@return": temperature_degrC_abs_return,
        sensor_location: sensorLocation
      }
    };

    result.data[powerKey] = power_kW_abs;
    result.data[energyKey] = energy_kWh_inc;

    return result;
  }

  // ===== LEGACY VERSION 2 (18 Bytes) =====
  if (type === 0x02) {
    if (bytes.length < 7) {
      return { errors: ["Sensor payload too short"] };
    }

    if (bytes.length === 18) {
      let flowRaw = (bytes[1] << 8) | bytes[2];
      if (flowRaw & 0x8000) {
        flowRaw = flowRaw - 0x10000;
      }
      const flow_l_min = flowRaw / 10.0;
      const volumeFlow_m3perh_abs = flow_l_min * 60.0 / 1000.0;

      const vol_m3_x1000 =
        ((bytes[3] << 24) >>> 0) |
        ((bytes[4] << 16) >>> 0) |
        ((bytes[5] << 8)  >>> 0) |
        ((bytes[6] << 0)  >>> 0);
      const volume_m3_inc = vol_m3_x1000 / 1000.0;

      let tFlowRaw = (bytes[7] << 8) | bytes[8];
      if (tFlowRaw & 0x8000) {
        tFlowRaw = tFlowRaw - 0x10000;
      }
      const temperature_degrC_abs_flow = tFlowRaw === -32768 ? null : tFlowRaw / 10.0;

      let tReturnRaw = (bytes[9] << 8) | bytes[10];
      if (tReturnRaw & 0x8000) {
        tReturnRaw = tReturnRaw - 0x10000;
      }
      const temperature_degrC_abs_return = tReturnRaw === -32768 ? null : tReturnRaw / 10.0;

      const powerRaw = (bytes[11] << 8) | bytes[12];
      const power_kW = powerRaw / 100.0;

      const energy_kwh_x10 =
        ((bytes[13] << 24) >>> 0) |
        ((bytes[14] << 16) >>> 0) |
        ((bytes[15] << 8)  >>> 0) |
        ((bytes[16] << 0)  >>> 0);
      const energy_kWh = energy_kwh_x10 / 10.0;

      const flags = bytes[17];
      const energyMode = (flags & 0x01) ? "cooling" : "heating";
      const sensorLocation = (flags & 0x02) ? "return" : "flow";

      const powerKey = `power_kW_abs@${energyMode}`;
      const energyKey = `energy_kWh_inc@${energyMode}`;

      const result = {
        data: {
          payload_type: "sensor_data_v2_legacy",
          volumeFlow_m3perh_abs: volumeFlow_m3perh_abs,
          volume_m3_inc: volume_m3_inc,
          "temperature_degrC_abs@flow": temperature_degrC_abs_flow,
          "temperature_degrC_abs@return": temperature_degrC_abs_return,
          sensor_location: sensorLocation
        }
      };

      result.data[powerKey] = power_kW;
      result.data[energyKey] = energy_kWh;

      return result;
    } else {
      return {
        errors: [`Unexpected payload length: ${bytes.length} bytes`]
      };
    }
  }

  // ===== UNKNOWN PAYLOAD TYPE =====
  return {
    data: {
      payload_type: "unknown",
      raw_type: type
    },
    warnings: [`Unknown payload type: 0x${type.toString(16).toUpperCase()}`]
  };
}