// Arduino code to control a 4-way traffic light with countdown timers

// Define pins for each traffic light's Red, Yellow, and Green LEDs
const int TL1_R = 2, TL1_Y = 1, TL1_G = 0;
const int TL2_R = 8, TL2_Y = 9, TL2_G = 10;
const int TL3_R = 6, TL3_Y = 5, TL3_G = 4;
const int TL4_R = 11, TL4_Y = 12, TL4_G = 13;

// Timer settings
const int greenDuration = 10;  // Duration of green light in seconds
const int yellowDuration = 3; // Duration of yellow light in seconds
int countdownTimer = 0;

void setup() {
  // Set all LED pins as output
  pinMode(TL1_R, OUTPUT);
  pinMode(TL1_Y, OUTPUT);
  pinMode(TL1_G, OUTPUT);

  pinMode(TL2_R, OUTPUT);
  pinMode(TL2_Y, OUTPUT);
  pinMode(TL2_G, OUTPUT);

  pinMode(TL3_R, OUTPUT);
  pinMode(TL3_Y, OUTPUT);
  pinMode(TL3_G, OUTPUT);

  pinMode(TL4_R, OUTPUT);
  pinMode(TL4_Y, OUTPUT);
  pinMode(TL4_G, OUTPUT);

  // Initialize all lights to red
  setAllRed();
}

void loop() {
  // Cycle through each traffic light
  for (int i = 1; i <= 4; i++) {
    // Green light phase
    startGreenPhase(i, greenDuration);

    // Yellow light phase
    startYellowPhase(i, yellowDuration);
  }
}

void startGreenPhase(int lightNumber, int duration) {
  // Set all lights to red
  setAllRed();

  // Turn on green light for the given light number
  switch (lightNumber) {
    case 1:
      digitalWrite(TL1_R, LOW);
      digitalWrite(TL1_G, HIGH);
      break;
    case 2:
      digitalWrite(TL2_R, LOW);
      digitalWrite(TL2_G, HIGH);
      break;
    case 3:
      digitalWrite(TL3_R, LOW);
      digitalWrite(TL3_G, HIGH);
      break;
    case 4:
      digitalWrite(TL4_R, LOW);
      digitalWrite(TL4_G, HIGH);
      break;
  }

  // Countdown timer for green light
  countdownTimer = duration;
  while (countdownTimer > 0) {
    delay(1000); // 1 second delay
    countdownTimer--;
  }
}

void startYellowPhase(int lightNumber, int duration) {
  // Turn off green light and turn on yellow light for the given light number
  switch (lightNumber) {
    case 1:
      digitalWrite(TL1_G, LOW);
      digitalWrite(TL1_Y, HIGH);
      break;
    case 2:
      digitalWrite(TL2_G, LOW);
      digitalWrite(TL2_Y, HIGH);
      break;
    case 3:
      digitalWrite(TL3_G, LOW);
      digitalWrite(TL3_Y, HIGH);
      break;
    case 4:
      digitalWrite(TL4_G, LOW);
      digitalWrite(TL4_Y, HIGH);
      break;
  }

  // Countdown timer for yellow light
  countdownTimer = duration;
  while (countdownTimer > 0) {
    delay(1000); // 1 second delay
    countdownTimer--;
  }

  // Turn off yellow light and set light to red
  switch (lightNumber) {
    case 1:
      digitalWrite(TL1_Y, LOW);
      digitalWrite(TL1_R, HIGH);
      break;
    case 2:
      digitalWrite(TL2_Y, LOW);
      digitalWrite(TL2_R, HIGH);
      break;
    case 3:
      digitalWrite(TL3_Y, LOW);
      digitalWrite(TL3_R, HIGH);
      break;
    case 4:
      digitalWrite(TL4_Y, LOW);
      digitalWrite(TL4_R, HIGH);
      break;
  }
}

void setAllRed() {
  // Turn all traffic lights to red
  digitalWrite(TL1_R, HIGH);
  digitalWrite(TL1_Y, LOW);
  digitalWrite(TL1_G, LOW);

  digitalWrite(TL2_R, HIGH);
  digitalWrite(TL2_Y, LOW);
  digitalWrite(TL2_G, LOW);

  digitalWrite(TL3_R, HIGH);
  digitalWrite(TL3_Y, LOW);
  digitalWrite(TL3_G, LOW);

  digitalWrite(TL4_R, HIGH);
  digitalWrite(TL4_Y, LOW);
  digitalWrite(TL4_G, LOW);
}