// Décodeur LoRaWAN officiel : Milesight EM500-SWL Submersible Water Level (Milesight)
// Source : https://github.com/TheThingsNetwork/lorawan-devices/blob/master/vendor/milesight-iot/em500-swl.js
// The Things Network Device Repository, fichier publié par le constructeur, distribué sans modification.
// Format : decodeUplink(input) (TTN v3 / ChirpStack v4). Hébergé par smartbuildings.fr.

function decodeUplink(input) {
    var res = Decoder(input.bytes, input.fPort);
    if (res.error) {
        return {
            errors: [res.error],
        };
    }
    return {
        data: res,
    };
}
/**
 * Payload Decoder for The Things Network
 * 
 * Copyright 2021 Milesight IoT
 * 
 * @product EM500-SWL
 */
function Decoder(bytes, port) {
    var decoded = {};

    for (var i = 0; i < bytes.length;) {
        var channel_id = bytes[i++];
        var channel_type = bytes[i++];
        // BATTERY
        if (channel_id === 0x01 && channel_type === 0x75) {
            decoded.battery = bytes[i];
            i += 1;
        }
        // WATER LEVEL
        else if (channel_id === 0x03 && channel_type === 0x77) {
            decoded.distance = readUInt16LE(bytes.slice(i, i + 2));
            i += 2;
        } else {
            break;
        }
    }

    return decoded;
}

/* ******************************************
 * bytes to number
 ********************************************/
function readUInt16LE(bytes) {
    var value = (bytes[1] << 8) + bytes[0];
    return value & 0xffff;
}

function readInt16LE(bytes) {
    var ref = readUInt16LE(bytes);
    return ref > 0x7fff ? ref - 0x10000 : ref;
}