// Decode decodes an array of bytes into an object.
//  - fPort contains the LoRaWAN fPort number
//  - bytes is an array of bytes, e.g. [225, 230, 255, 0]
// The function must return an object, e.g. {"temperature": 22.5}
function Bytes2Float32(bytes) {
    var sign = (bytes & 0x80000000) ? -1 : 1;
    var exponent = ((bytes >> 23) & 0xFF) - 127;
    var significand = (bytes & ~(-1 << 23));

    if (exponent == 128)
        return sign * ((significand) ? Number.NaN : Number.POSITIVE_INFINITY);

    if (exponent == -127) {
        if (significand === 0) return sign * 0.0;
        exponent = -126;
        significand /= (1 << 22);
    } else significand = (significand | (1 << 23)) / (1 << 23);

    return sign * significand * Math.pow(2, exponent);
}

function Decoder(bytes, port) {
    byte = 0;
    header = 0;
    var decoded = {};
    if (port == 1) {
        decoded.header = bytes[byte++];
        if (decoded.header & 0x10) {
            decoded.sec = (bytes[byte++] << 24 | bytes[byte++] << 16
                | bytes[byte++] << 8 | bytes[byte++] << 0);

            decoded.batmv = (bytes[byte++] << 8 | bytes[byte++] << 0);
            decoded.solmv = (bytes[byte++] << 8 | bytes[byte++] << 0);
            decoded.charge = (bytes[byte] & 1);
            decoded.fault = (bytes[byte++] & 2) >> 1;
        } else if (decoded.header & 0x20) {
			//Analog Inputs
            decoded.adc_ch1 = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
            decoded.adc_ch2 = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
            decoded.adc_ch3 = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
            decoded.adc_ch4 = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
        } else if (decoded.header & 0x40) {
			//Digital Pulse inputs
            decoded.counter_ch1 = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
            decoded.counter_ch2 = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
            decoded.counter_ch3 = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
            decoded.counter_ch4 = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
        } else if (decoded.header & 0x80) {
			//SDI-12 
            decoded.index = decoded.header & 0x0f;
            reading = {};

            for (i = 0; i < (bytes.length - 1) / 4; i++) {
                reading[i] = Bytes2Float32(bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++] << 0);
            }
            decoded.reading = reading;
        }

    } else if (port == 10) {
        decoded.type = "DEVICE_INFO";
        decoded.product_id = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
        decoded.batch_num = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
        decoded.software_version = (bytes[byte++] << 24 | bytes[byte++] << 16 | bytes[byte++] << 8 | bytes[byte++]) >>> 0;
    } else if (port == 100) {
        decoded = {
            type: "DOWNLINK_RESPONSE",
            str: String.fromCharCode.apply(String, bytes)
        };
    }
    return decoded;
}