const int BTN_PIN = 4;
const int L0 = 9;
const int L1 = 10;

const int S_CARS_DRIVE = 1;
const int S_PREPARE_TO_STOP = 2;
const int S_CARS_STOP = 3;
const int S_PREPARE_TO_DRIVE = 4;

int state = S_CARS_DRIVE;

unsigned long nextTimeout;
int buttonState;
int hasExpired;
int isItPressed;

void setup()
{
  Serial.begin(9600);

  pinMode(BTN_PIN, INPUT);
  pinMode(L0, OUTPUT);
  pinMode(L1, OUTPUT);

}

void loop()
{
  buttonState = digitalRead(BTN_PIN);
  switch(state)
  {
    case S_CARS_DRIVE:
    setTrafficLight(3);
    if (isButtonPressed(buttonState) == true)
    {
      startTimer (2000);
      changeStateTo(2);
    }
    break;


    case S_PREPARE_TO_STOP:
    setTrafficLight(4);
    if (timerHasExpired() == true)
    {
      startTimer(5000);
      changeStateTo(3);
    }
    break;


    case S_CARS_STOP:
    setTrafficLight(1);
    if (timerHasExpired() == true)
    {
      startTimer(1000);
      changeStateTo(4);
    }
    break;

    case S_PREPARE_TO_DRIVE:
    setTrafficLight(2);
    if (timerHasExpired() == true)
    {
      changeStateTo(1);
    }
    break;

  }

}



void setTrafficLight(int phase)
{

  switch (phase)
  {
  case 1: //S_CARS_STOP
  signalTrue(L0);
  signalFalse(L1);
  break;

  case 2: //S_PREPARE_TO_DRIVE
  signalTrue(L0);
  signalTrue(L1);
  break;

  case 3: // S_CARS_DRIVE
  signalFalse(L0);
  signalFalse(L1);
  break;

  case 4: //S_PREPARE_TO_STOP
  signalFalse(L0);
  signalTrue(L1);
  break;
  }
}

boolean timerHasExpired()
{
  boolean hasExpired = false;
  if (millis() >= nextTimeout)
  {
    hasExpired = true;
  }
  else
  {
    hasExpired = false;

  }

  return hasExpired;
}
void startTimer(unsigned long timeout)
{
  nextTimeout = millis() + timeout;
}

boolean isButtonPressed(int button)
{
  if (button == HIGH)
  {
    isItPressed = true;
  }
  else if (button == LOW)
  {
    isItPressed = false;
  }
  return isItPressed;
}

void signalTrue(int pin)
{
  digitalWrite(pin, HIGH);
}

void signalFalse(int pin)
{
  digitalWrite(pin, LOW);
}

void printState(int state)
{
  switch(state)
  {
    case S_CARS_DRIVE:
    Serial.print("S_CARS_DRIVE");
    break;

    case S_PREPARE_TO_STOP:
    Serial.print("S_PREPARE_TO_STOP");
    break;

    case S_CARS_STOP:
    Serial.print("S_CARS_STOP");
    break;

    case S_PREPARE_TO_DRIVE:
    Serial.print("S_PREPARE_TO_DRIVE");
    break;
  }

}

void changeStateTo(int newState)
{
  Serial.print("State changed from");
  printState(state);
  Serial.print(" to ");
  printState(newState);
  Serial.println();
  state = newState;
}