const int thermistorPin = A0;

const int thermistorNominal = 10000;
const int temperatureNominal = 25;
const int betaValue = 3950;

int redPin = 10;
int greenPin = 11;
int bluePin = 12;

float setPoint = 27.0;

double Kp = 1.0;
double Ki = 0.0;
double Kd = 0.0;

double input = 0.0;
double output = 0.0;
double lastInput = 0.0;
double integral = 0.0;

double outputMin = 0.0;
double outputMax = 100.0;

unsigned long prevTime = 0;
unsigned long deltaTime = 10000;


void setup(){
  Serial.begin(9600);
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);
}

void loop() {
float currentTemperature = temperature();
unsigned long currentTime = millis();

if(currentTime - prevTime >= deltaTime){
  double dt = (double)(currentTime - prevTime) / 1000.0;

  input = temperature();

  double error = setPoint - input;

  integral += error * dt;

  double dInput = (input - lastInput) / dt;

  output = Kp * error + Ki * integral + Kd * dInput;

  output = constrain(output, outputMin, outputMax);

  lastInput = input;
  prevTime = currentTime;


  Serial.print("Setpoint: ");
  Serial.print(setPoint);
  Serial.print(" | Input: ");
  Serial.print(input);
  Serial.print(" | Output: ");
  Serial.println(output);

}

if (setPoint < currentTemperature){
  redLED();
}
else{
  greenLED();
}


}

float temperature(){
  int rawADC = analogRead(thermistorPin);

  double resistance = 1023.0 / rawADC - 1.0;
  resistance = 10000.0 / resistance;

  double steinhart;
  steinhart = resistance / thermistorNominal;
  steinhart = log(steinhart);
  steinhart /= betaValue;
  steinhart += 1.0 / (temperatureNominal + 273.15);
  steinhart = 1.0 / steinhart;
  steinhart -= 273.15;

  return steinhart;
}

int redLED(){
  digitalWrite(redPin, LOW);
  digitalWrite(greenPin, HIGH);
  digitalWrite(bluePin, HIGH);  
}

int greenLED(){
  digitalWrite(redPin, HIGH);
  digitalWrite(greenPin, LOW);
  digitalWrite(bluePin, HIGH);
}