const int RED_PIN    = 8;
const int GREEN_PIN  = 5;
const int YELLOW_PIN = 3;
const int BLUE_PIN   = 2;
//const int BTN_PIN    = 2;

const unsigned long RED_BLUE_DURATION   = 8000;  // RED+BLUE on together
const unsigned long YELLOW_BLUE_DURATION = 4000; // YELLOW+BLUE on together
const unsigned long GREEN_DURATION       = 6000; // GREEN only, BLUE OFF

enum TrafficState { STATE_RED_BLUE, STATE_YELLOW_BLUE, STATE_GREEN };
TrafficState currentState = STATE_RED_BLUE;

unsigned long stateStartTime = 0;
unsigned long lastSerialTime = 0;

void setup() {
  pinMode(RED_PIN,    OUTPUT);
  pinMode(GREEN_PIN,  OUTPUT);
  pinMode(YELLOW_PIN, OUTPUT);
  pinMode(BLUE_PIN,   OUTPUT);
  //pinMode(BTN_PIN,    INPUT_PULLUP);

  Serial.begin(9600);
  Serial.println("Traffic Light Started!");
  enterState(STATE_RED_BLUE);
}

void loop() {
  unsigned long now = millis();
  updateTrafficLight(now);
  updateSerial(now);
}

void enterState(TrafficState newState) {
  currentState   = newState;
  stateStartTime = millis();

  // Turn ALL off first
  digitalWrite(RED_PIN,    LOW);
  digitalWrite(GREEN_PIN,  LOW);
  digitalWrite(YELLOW_PIN, LOW);
  digitalWrite(BLUE_PIN,   LOW);

  switch (newState) {
    case STATE_RED_BLUE:
      digitalWrite(RED_PIN,  HIGH);  // RED on
      digitalWrite(BLUE_PIN, HIGH);  // BLUE on  (pedestrian walks)
      Serial.println(">>> RED + BLUE ON  — Cars stop, pedestrian walks");
      break;

    case STATE_YELLOW_BLUE:
      digitalWrite(YELLOW_PIN, HIGH); // YELLOW on
      digitalWrite(BLUE_PIN,   HIGH); // BLUE on  (pedestrian finishing)
      Serial.println(">>> YELLOW + BLUE ON  — Warning, pedestrian finishing");
      break;

    case STATE_GREEN:
      digitalWrite(GREEN_PIN, HIGH);  // GREEN on
      // BLUE stays OFF
      Serial.println(">>> GREEN ON  — Cars go, pedestrian stopped");
      break;
  }
}

void updateTrafficLight(unsigned long now) {
  unsigned long elapsed = now - stateStartTime;

  switch (currentState) {
    case STATE_RED_BLUE:
      if (elapsed >= RED_BLUE_DURATION)
        enterState(STATE_YELLOW_BLUE);
      break;

    case STATE_YELLOW_BLUE:
      if (elapsed >= YELLOW_BLUE_DURATION)
        enterState(STATE_GREEN);
      break;

    case STATE_GREEN:
      if (elapsed >= GREEN_DURATION)
        enterState(STATE_RED_BLUE);
      break;
  }
}

void updateSerial(unsigned long now) {
  if (now - lastSerialTime >= 1000) {
    lastSerialTime = now;

    unsigned long dur = 0;
    switch (currentState) {
      case STATE_RED_BLUE:    dur = RED_BLUE_DURATION;    break;
      case STATE_YELLOW_BLUE: dur = YELLOW_BLUE_DURATION; break;
      case STATE_GREEN:       dur = GREEN_DURATION;       break;
    }

    long rem = ((long)dur - (long)(now - stateStartTime)) / 1000;
    if (rem < 0) rem = 0;
    Serial.print("    Time remaining: ");
    Serial.print(rem);
    Serial.println("s");
  }
}