// Pin assignments
const int greenLED = 8;
const int yellowLED = 9;
const int redLED = 10;

// Timing constants
const unsigned long greenDuration = 5000;  // Duration for Green light (in milliseconds)
const unsigned long yellowDuration = 2000; // Duration for Yellow light (in milliseconds)
const unsigned long redDuration = 5000;    // Duration for Red light (in milliseconds)
const unsigned long offDuration = 500;     // Duration for turning off LEDs between changes (in milliseconds)

// State definition for LEDs
enum LightState { GREEN, YELLOW, RED };

// Current state of the traffic light
LightState currentLightState = GREEN;

unsigned long previousMillis = 0; // To store time for non-blocking delay

void setup() {
  // Set LED pins as outputs
  pinMode(greenLED, OUTPUT);
  pinMode(yellowLED, OUTPUT);
  pinMode(redLED, OUTPUT);

  // Ensure all LEDs are off initially
  turnOffAllLEDs();
}

void loop() {
  unsigned long currentMillis = millis();  // Get the current time in milliseconds

  switch (currentLightState) {
    case GREEN:
      digitalWrite(greenLED, HIGH); // Turn on Green LED
      if (currentMillis - previousMillis >= greenDuration) {
        // Turn off Green LED immediately after the duration
        digitalWrite(greenLED, LOW);
        previousMillis = currentMillis;  // Reset the timer
        currentLightState = YELLOW;  // Move to Yellow light state
        delay(offDuration); // Short delay for smooth transition
      }
      break;

    case YELLOW:
      digitalWrite(yellowLED, HIGH); // Turn on Yellow LED
      if (currentMillis - previousMillis >= yellowDuration) {
        // Turn off Yellow LED immediately after the duration
        digitalWrite(yellowLED, LOW);
        previousMillis = currentMillis;  // Reset the timer
        currentLightState = RED;  // Move to Red light state
        delay(offDuration); // Short delay for smooth transition
      }
      break;

    case RED:
      digitalWrite(redLED, HIGH); // Turn on Red LED
      if (currentMillis - previousMillis >= redDuration) {
        // Turn off Red LED immediately after the duration
        digitalWrite(redLED, LOW);
        previousMillis = currentMillis;  // Reset the timer
        currentLightState = GREEN;  // Move to Green light state
        delay(offDuration); // Short delay for smooth transition
      }
      break;
  }
}

// Function to turn off all LEDs (if needed for reset)
void turnOffAllLEDs() {
  digitalWrite(greenLED, LOW);
  digitalWrite(yellowLED, LOW);
  digitalWrite(redLED, LOW);
}