/**
 * Payload Decoder for Milesight Network Server
 *
 * Copyright 2023 Milesight IoT
 *
 * @product EM300-DI
 */
function Decode(fPort, bytes) {
    return milesight(bytes);
}

function milesight(bytes) {
    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;
        }
        // TEMPERATURE
        else if (channel_id === 0x03 && channel_type === 0x67) {
            // ℃
            decoded.temperature = readInt16LE(bytes.slice(i, i + 2)) / 10;
            i += 2;

            // ℉
            // decoded.temperature = readInt16LE(bytes.slice(i, i + 2)) / 10 * 1.8 + 32;
            // i +=2;
        }
        // HUMIDITY
        else if (channel_id === 0x04 && channel_type === 0x68) {
            decoded.humidity = bytes[i] / 2;
            i += 1;
        }
        // GPIO
        else if (channel_id === 0x05 && channel_type === 0x00) {
            decoded.gpio = readGPIOStatus(bytes[i]);
            i += 1;
        }
        // PULSE COUNTER
        else if (channel_id === 0x05 && channel_type === 0xc8) {
            decoded.pulse = readUInt32LE(bytes.slice(i, i + 4));
            i += 4;
        }
        // PULSE COUNTER (v1.3+)
        else if (channel_id === 0x05 && channel_type === 0xe1) {
            decoded.water_conv = readUInt16LE(bytes.slice(i, i + 2)) / 10;
            decoded.pulse_conv = readUInt16LE(bytes.slice(i + 2, i + 4)) / 10;
            decoded.water = readFloatLE(bytes.slice(i + 4, i + 8));
            i += 8;
        }
        // GPIO ALARM
        else if (channel_id === 0x85 && channel_type === 0x00) {
            decoded.gpio = readGPIOStatus(bytes[i]);
            decoded.gpio_alarm = readGPIOAlarm(bytes[i + 1]);
            i += 2;
        }
        // WATER ALARM
        else if (channel_id === 0x85 && channel_type === 0xe1) {
            decoded.water_conv = readUInt16LE(bytes.slice(i, i + 2)) / 10;
            decoded.pulse_conv = readUInt16LE(bytes.slice(i + 2, i + 4)) / 10;
            decoded.water = readFloatLE(bytes.slice(i + 4, i + 8));
            decoded.water_alarm = readWaterAlarm(bytes[i + 8]);
            i += 9;
        }
        // HISTORICAL DATA
        else if (channel_id === 0x20 && channel_type === 0xce) {
            // maybe not historical raw data
            if (bytes.slice(i).length < 12) break;

            var point = {};
            point.timestamp = readUInt32LE(bytes.slice(i, i + 4));
            point.temperature = readInt16LE(bytes.slice(i + 4, i + 6)) / 10;
            point.humidity = bytes[i + 6] / 2;
            var mode = bytes[i + 7];
            if (mode === 1) {
                point.gpio_type = "gpio";
                point.gpio = bytes[i + 8];
            } else if (mode === 2) {
                point.gpio_type = "pulse";
                point.pulse = readUInt32LE(bytes.slice(i + 9, i + 13));
            }
            decoded.history = decoded.history || [];
            decoded.history.push(point);
            i += 13;
        }
        // HISTORICAL DATA (v2)
        else if (channel_id === 0x21 && channel_type === 0xce) {
            var point = {};
            point.timestamp = readUInt32LE(bytes.slice(i, i + 4));
            point.temperature = readInt16LE(bytes.slice(i + 4, i + 6)) / 10;
            point.humidity = bytes[i + 6] / 2;
            point.alarm = readAlarm(bytes[i + 7]);
            var mode = bytes[i + 8];
            if (mode === 1) {
                point.gpio_type = "gpio";
                point.gpio = readGPIOStatus(bytes[i + 9]);
            } else if (mode === 2) {
                point.gpio_type = "pulse";
                point.water_conv = readUInt16LE(bytes.slice(i + 10, i + 12)) / 10;
                point.pulse_conv = readUInt16LE(bytes.slice(i + 12, i + 14)) / 10;
                point.water = readFloatLE(bytes.slice(i + 14, i + 18));
            }

            decoded.history = decoded.history || [];
            decoded.history.push(point);
            i += 18;
        } 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;
}

function readUInt32LE(bytes) {
    var value = (bytes[3] << 24) + (bytes[2] << 16) + (bytes[1] << 8) + bytes[0];
    return (value & 0xffffffff) >>> 0;
}

function readFloatLE(bytes) {
    // JavaScript bitwise operators yield a 32 bits integer, not a float.
    // Assume LSB (least significant byte first).
    var bits = (bytes[3] << 24) | (bytes[2] << 16) | (bytes[1] << 8) | bytes[0];
    var sign = bits >>> 31 === 0 ? 1.0 : -1.0;
    var e = (bits >>> 23) & 0xff;
    var m = e === 0 ? (bits & 0x7fffff) << 1 : (bits & 0x7fffff) | 0x800000;
    var f = sign * m * Math.pow(2, e - 150);

    var v = Number(f.toFixed(2));
    return v;
}

function readGPIOStatus(bytes) {
    // 0: low, 1: high
    switch (bytes) {
        case 0:
            return "low";
        case 1:
            return "high";
        default:
            return "unknown";
    }
}

function readGPIOAlarm(bytes) {
    // 1: gpio alarm, 0: gpio alarm release
    switch (bytes) {
        case 0:
            return "gpio alarm release";
        case 1:
            return "gpio alarm";
        default:
            return "unknown";
    }
}

function readWaterAlarm(bytes) {
    // 1: water outage timeout alarm, 2: water outage timeout alarm release, 3: water flow timeout alarm, 4: water flow timeout alarm release
    switch (bytes) {
        case 1:
            return "water outage timeout alarm";
        case 2:
            return "water outage timeout alarm release";
        case 3:
            return "water flow timeout alarm";
        case 4:
            return "water flow timeout alarm release";
        default:
            return "unknown";
    }
}

function readAlarm(bytes) {
    // 0: none, 1: water outage timeout alarm, 2: water outage timeout alarm release, 3: water flow timeout alarm, 4: water flow timeout alarm release, 5: gpio alarm, 6: gpio alarm release
    switch (bytes) {
        case 0:
            return "none";
        case 1:
            return "water outage timeout alarm";
        case 2:
            return "water outage timeout alarm release";
        case 3:
            return "water flow timeout alarm";
        case 4:
            return "water flow timeout alarm release";
        case 5:
            return "gpio alarm";
        case 6:
            return "gpio alarm release";
        default:
            return "unknown";
    }
}