var aio = require("aio");
//var ble = require("ble");
var pins = require("arduino101_pins");

// heart rate calculation
var IBI = 600;               // value holds the time interval between beats! Must be seeded!
var pulse = false;           // "True" when User's live heartbeat is detected. "False" when not a "live beat".
var rate = [10];               // array to hold last ten IBI values
var sampleCounter = 0;       // used to determine pulse timing
var lastBeatTime = 0;        // used to find IBI
var P = 2048;                // used to find peak in pulse wave, seeded
var T = 2048;                // used to find trough in pulse wave, seeded
var thresh = 2100;           // used to find instant moment of heart beat, seeded
var amp = 400;               // used to hold amplitude of pulse waveform, seeded
var firstBeat = true;        // used to seed rate array so we startup with reasonable BPM
var secondBeat = false;      // used to seed rate array so we startup with reasonable BPM

// pins
var pin = aio.open({device:0, pin: pins.A1 });

function measureHeartRate(signal) {
    var HR = 0;

    sampleCounter += 2;                        // keep track of the time in mS with this variable
    var N = sampleCounter - lastBeatTime;       // monitor the time since the last beat to avoid noise

    // find the peak and trough of the pulse wave
    if (signal < thresh && (N > ((IBI / 5) * 3))) { // avoid dichrotic noise by waiting 3/5 of last IBI
        if (signal < T) {                       // T is the trough
            T = signal;                         // keep track of lowest point in pulse wave
        }
    }

    if (signal > thresh && signal > P) {        // thresh condition helps avoid noise
        P = signal;                             // P is the peak
    }                                           // keep track of highest point in pulse wave

    // NOW IT'S TIME TO LOOK FOR THE HEART BEAT
    // signal surges up in value every time there is a pulse
    if (N > 250 && N < 2000) {                  // avoid noise. 30 bpm < possible human heart beat < 240
        if ((signal > thresh) && (pulse == false) && (N > ((IBI / 5) * 3))) {
            pulse = true;                       // set the pulse flag when we think there is a pulse
            IBI = sampleCounter - lastBeatTime; // measure time between beats in mS
            lastBeatTime = sampleCounter;       // keep track of time for next pulse

            if (secondBeat) {                   // if this is the second beat, if secondBeat == TRUE
                console.log("Measured 2nd beat");
                secondBeat = false;             // clear secondBeat flag
                for(var i = 0; i <= 9; i++) {   // seed the running total to get a realisitic BPM at startup
                    rate[i] = IBI;
                }
            }

            if (firstBeat) {                    // if it's the first time we found a beat, if firstBeat == TRUE
                console.log("Measured 1st beat");
                firstBeat = false;              // clear firstBeat flag
                secondBeat = true;              // set the second beat flag
                return 0;                       // IBI value is unreliable so discard it
            }

            // keep a running total of the last 10 IBI values
            var runningTotal = 0;               // clear the runningTotal variable

            for (var i = 0; i <= 8; i++) {      // shift data in the rate array
                rate[i] = rate[i + 1];          // and drop the oldest IBI value
                runningTotal += rate[i];        // add up the 9 oldest IBI values
            }

            rate[9] = IBI;                      // add the latest IBI to the rate array
            runningTotal += rate[9];            // add the latest IBI to runningTotal
            runningTotal /= 10;                 // average the last 10 IBI values
            HR = 60000 / runningTotal;          // how many beats can fit into a minute? that's BPM!
        }
    }

    if (signal < thresh && pulse == true) {     // when the values are going down, the beat is over
        pulse = false;                          // reset the pulse flag so we can do it again
        amp = P - T;                            // get amplitude of the pulse wave
        thresh = (amp * 2 / 3) + T;             // set thresh at 67% of the amplitude
        P = thresh;                             // reset these for next time
        T = thresh;
    }

    if (N > 2500) {                             // if 2.5 seconds go by without a beat
        thresh = 2048;                          // set thresh default
        P = 2048;                               // set P default
        T = 2048;                               // set T default
        lastBeatTime = sampleCounter;           // bring the lastBeatTime up to date
        firstBeat = true;                       // set these to avoid noise
        secondBeat = false;                     // when we get the heartbeat back
   }

    return HR;                              // return integer instead of float
}

setInterval(function() {
    var rawSignal = pin.read();
    var signal = measureHeartRate(rawSignal);
    // send notification
    console.log("HR=" + signal);
}, 0);