const int redLed = 2;        // Red LED pin
const int yellowLed = 3;     // Yellow LED pin
const int greenLed = 4;      // Green LED pin
const int buttonPin = 5;     // Push button pin

int currentState = 0;        // 0: Red, 1: Green, 2: Yellow
unsigned long previousMillis = 0;
const long interval = 5000;  // 5 seconds for each light

bool overrideActive = false;
unsigned long overrideMillis = 0;
const long overrideInterval = 2000;  // 2 seconds for override

void setup() {
  pinMode(redLed, OUTPUT);
  pinMode(yellowLed, OUTPUT);
  pinMode(greenLed, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP);  // Using internal pull-up resistor

  digitalWrite(redLed, HIGH);        // Start with red light
}

void loop() {
  unsigned long currentMillis = millis();

  // Check button press for override
  if (digitalRead(buttonPin) == LOW) {
    if (!overrideActive) {
      overrideActive = true;
      overrideMillis = currentMillis;
      currentState = (currentState + 1) % 3;  // Cycle through 0, 1, 2
      updateLights(currentState);
    }
  }

  // If override is active, keep light on for a short period
  if (overrideActive && (currentMillis - overrideMillis >= overrideInterval)) {
    overrideActive = false;
    previousMillis = currentMillis;  // Reset the main timer
  }

  // Normal operation
  if (!overrideActive && (currentMillis - previousMillis >= interval)) {
    previousMillis = currentMillis;
    currentState = (currentState + 1) % 3;  // Cycle through 0, 1, 2
    updateLights(currentState);
  }
}

void updateLights(int state) {
  switch (state) {
    case 0: // Red
      digitalWrite(redLed, HIGH);
      digitalWrite(yellowLed, LOW);
      digitalWrite(greenLed, LOW);
      break;
    case 1: // Green
      digitalWrite(redLed, LOW);
      digitalWrite(yellowLed, LOW);
      digitalWrite(greenLed, HIGH);
      break;
    case 2: // Yellow
      digitalWrite(redLed, LOW);
      digitalWrite(yellowLed, HIGH);
      digitalWrite(greenLed, LOW);
      break;
  }
}