int pResistor = A0;
int red = 6;
int yellow = 5;
int green = 3;

int intervalSec = 3; // TODO

int previousMillis;
int currentMillis;


int prevPhoResVal;
int currPhoResVal;
int prevPhoResTime;
int currPhoResTime;
double addVal;

void setup()
{
  // put your setup code here, to run once:

  Serial.begin(9600);

  pinMode(red, OUTPUT);
  pinMode(yellow, OUTPUT);
  pinMode(green, OUTPUT);

  pinMode(pResistor, INPUT);

  prevPhoResVal = analogRead(pResistor);
  prevPhoResTime = millis();
}

void loop()
{
  changeLights();
}

void changeLights(){
    previousMillis = millis();
    for(currentMillis = millis() ; currentMillis - previousMillis < 4000 ; currentMillis = millis())
    {
      // green on
      analogWrite(green, photoresistorRatio());
      analogWrite(yellow, LOW);
      analogWrite(red, LOW);

      //delay(2);
    }

    previousMillis = millis();
    for(currentMillis = millis() ; currentMillis - previousMillis < 1000 ; currentMillis = millis())
    {
      // yellow on
      analogWrite(yellow, photoresistorRatio());
      analogWrite(green, LOW);
      analogWrite(red, LOW);

      //delay(2);
    }

    previousMillis = millis();
    for(currentMillis = millis() ; currentMillis - previousMillis < 6000 ; currentMillis = millis())
    {
      // red on
      analogWrite(red, photoresistorRatio());
      analogWrite(green, LOW);
      analogWrite(yellow, LOW);

      //delay(2);
    }

    previousMillis = millis();
    for(currentMillis = millis() ; currentMillis - previousMillis < 1000 ; currentMillis = millis())
    {
      // red & yellow on
      analogWrite(yellow, photoresistorRatio());
      analogWrite(red, photoresistorRatio());
      analogWrite(green, LOW);

      //delay(2);
    }
}

// map the value from the photoresistor to a
// matching value of the output.
int photoresistorRatio()
{
    currPhoResVal = analogRead(pResistor);
    currPhoResTime = millis();

    double diffVal = abs(prevPhoResVal - currPhoResVal);
    double interval = double(currPhoResTime - prevPhoResTime) / 3000;
    addVal = diffVal * interval;
    double newVal = prevPhoResVal;

    if(currPhoResVal > prevPhoResVal) {
        newVal = prevPhoResVal + addVal;
    }
    else if (currPhoResVal < prevPhoResVal) {
        newVal = prevPhoResVal - addVal;
    }
    else {
        newVal += prevPhoResVal;
    }

    Serial.println(newVal);
    int mapVal = map(newVal, 0, 1023, 255/2, 255);
    delay(200);

    prevPhoResVal = currPhoResVal;
    prevPhoResTime = currPhoResTime;

    return mapVal;
}