const int pulsePin = A0;
const int led1 = 2;
const int led2 = 3;

int threshold = 550;

bool beatDetected = false;
unsigned long lastBeatTime = 0;
int BPM = 0;

bool toggleLED = false;

// -------- FUNCION DE LATIDO --------
void heartbeatFade(int ledPin) {

  // Primer golpe (fuerte)
  for (int i = 0; i < 255; i += 5) {
    analogWrite(ledPin, i);
    delay(2);
  }

  for (int i = 255; i > 120; i -= 5) {
    analogWrite(ledPin, i);
    delay(2);
  }

  // Segundo golpe (más suave)
  for (int i = 120; i < 200; i += 5) {
    analogWrite(ledPin, i);
    delay(2);
  }


  for (int i = 200; i >= 0; i -= 3) { 
    analogWrite(ledPin, i);
    delay(3);
  }

  analogWrite(ledPin, 0);
}

void setup() {
  Serial.begin(115200);

  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
}

void loop() {
  int signal = analogRead(pulsePin);


  Serial.println(signal);    

  if (signal > threshold && !beatDetected) {
    beatDetected = true;

    unsigned long currentTime = millis();
    unsigned long delta = currentTime - lastBeatTime;

    if (delta > 300) {    //This part filters some of the noise from the signal
      BPM = 60000 / delta;
      lastBeatTime = currentTime;

      Serial.print("BPM: ");
      Serial.println(BPM);

      // Alternating LEDs
      toggleLED = !toggleLED;

      if (toggleLED) {
        heartbeatFade(led1);
      } else {
        heartbeatFade(led2);
      }
    }
  }

  if (signal < threshold) {
    beatDetected = false;
  }

  delay(5);
}