// Define ultrasonic sensor pins and LED pins for each section
// Ultrasonic A
#define TRIGGER_PIN1 0
#define ECHO_PIN1 1
int red_led1 = 2;
int green_led1 = 3;
int yellow_led1 = 4;

// Ultrasonic B
#define TRIGGER_PIN2 5
#define ECHO_PIN2 6
int red_led2 = 7;
int green_led2 = 8;
int yellow_led2 = 9;

// Ultrasonic C
#define TRIGGER_PIN3 10
#define ECHO_PIN3 11
int red_led3 = 12;
int green_led3 = 13;
int yellow_led3 = A0;

// Ultrasonic D
#define TRIGGER_PIN4 A1
#define ECHO_PIN4 A2
int red_led4 = A3;
int green_led4 = A4;
int yellow_led4 = A5;

void setup() {
  // Set ultrasonic sensor pins as input
  pinMode(TRIGGER_PIN1, OUTPUT);
  pinMode(ECHO_PIN1, INPUT);
  pinMode(TRIGGER_PIN2, OUTPUT);
  pinMode(ECHO_PIN2, INPUT);
  pinMode(TRIGGER_PIN3, OUTPUT);
  pinMode(ECHO_PIN3, INPUT);
  pinMode(TRIGGER_PIN4, OUTPUT);
  pinMode(ECHO_PIN4, INPUT);
  
  // Set LED pins as output
  pinMode(red_led1, OUTPUT);
  pinMode(green_led1, OUTPUT);
  pinMode(yellow_led1, OUTPUT);
  pinMode(red_led2, OUTPUT);
  pinMode(green_led2, OUTPUT);
  pinMode(yellow_led2, OUTPUT);
  pinMode(red_led3, OUTPUT);
  pinMode(green_led3, OUTPUT);
  pinMode(yellow_led3, OUTPUT);
  pinMode(red_led4, OUTPUT);
  pinMode(green_led4, OUTPUT);
  pinMode(yellow_led4, OUTPUT);
}

void loop() {
  // Normal traffic system
  normalTraffic();
  
  // Check for emergency condition
  if (checkEmergency()) {
    // Emergency traffic condition
    emergencyTraffic();
  }
}

void normalTraffic() {
  // Section D: Green ON
  digitalWrite(green_led4, HIGH);
  digitalWrite(red_led1, HIGH);
  digitalWrite(red_led2, HIGH);
  digitalWrite(red_led3, HIGH);
  delay(3000);
  digitalWrite(green_led4, LOW);
  digitalWrite(red_led1, LOW);
  digitalWrite(red_led2, LOW);
  digitalWrite(red_led3, LOW);
  
  // Section C: Green ON
  digitalWrite(green_led3, HIGH);
  digitalWrite(red_led1, HIGH);
  digitalWrite(red_led2, HIGH);
  digitalWrite(red_led4, HIGH);
  delay(3000);
  digitalWrite(green_led3, LOW);
  digitalWrite(red_led1, LOW);
  digitalWrite(red_led2, LOW);
  digitalWrite(red_led4, LOW);
  
  // Section B: Green ON
  digitalWrite(green_led2, HIGH);
  digitalWrite(red_led1, HIGH);
  digitalWrite(red_led3, HIGH);
  digitalWrite(red_led4, HIGH);
  delay(3000);
  digitalWrite(green_led2, LOW);
  digitalWrite(red_led1, LOW);
  digitalWrite(red_led3, LOW);
  digitalWrite(red_led4, LOW);
  
  // Section A: Green ON
  digitalWrite(green_led1, HIGH);
  digitalWrite(red_led4, HIGH);
  digitalWrite(red_led2, HIGH);
  digitalWrite(red_led3, HIGH);
  delay(3000);
  digitalWrite(green_led1, LOW);
  digitalWrite(red_led4, LOW);
  digitalWrite(red_led2, LOW);
  digitalWrite(red_led3, LOW);
}

bool checkEmergency() {
  // Check for obstacle in any section
  if (checkObstacle(TRIGGER_PIN1, ECHO_PIN1) || checkObstacle(TRIGGER_PIN2, ECHO_PIN2) || checkObstacle(TRIGGER_PIN3, ECHO_PIN3) || checkObstacle(TRIGGER_PIN4, ECHO_PIN4)) {
    return true; // Emergency condition detected
  } else {
    return false; // No emergency condition
  }
}

bool checkObstacle(int triggerPin, int echoPin) {
  // Read distance from ultrasonic sensor
  long duration, distance;
  digitalWrite(triggerPin, LOW);
  delayMicroseconds(2);
  digitalWrite(triggerPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;
  
  // Check if distance is less than 15 cm
  if (distance < 15) {
    return true; // Obstacle detected
  } else {
    return false; // No obstacle
  }
}

void emergencyTraffic() {
  // Determine which section detected obstacle
  if (checkObstacle(TRIGGER_PIN1, ECHO_PIN1)) {
    // Section A detected obstacle
    digitalWrite(green_led1, HIGH);
    digitalWrite(red_led1, LOW);
    digitalWrite(yellow_led1, LOW);
    digitalWrite(red_led2, HIGH);
    digitalWrite(green_led2, LOW);
    digitalWrite(yellow_led2, LOW);
    digitalWrite(red_led3, HIGH);
    digitalWrite(green_led3, LOW);
    digitalWrite(yellow_led3, LOW);
    digitalWrite(red_led4, HIGH);
    digitalWrite(green_led4, LOW);
    digitalWrite(yellow_led4, LOW);
  } else if (checkObstacle(TRIGGER_PIN2, ECHO_PIN2)) {
    // Section B detected obstacle
    digitalWrite(green_led2, HIGH);
    digitalWrite(red_led2, LOW);
    digitalWrite(yellow_led2, LOW);
    digitalWrite(red_led1, HIGH);
    digitalWrite(green_led1, LOW);
    digitalWrite(yellow_led1, LOW);
    digitalWrite(red_led3, HIGH);
    digitalWrite(green_led3, LOW);
    digitalWrite(yellow_led3, LOW);
    digitalWrite(red_led4, HIGH);
    digitalWrite(green_led4, LOW);
    digitalWrite(yellow_led4, LOW);
  } else if (checkObstacle(TRIGGER_PIN3, ECHO_PIN3)) {
    // Section C detected obstacle
    digitalWrite(green_led3, HIGH);
    digitalWrite(red_led3, LOW);
    digitalWrite(yellow_led3, LOW);
    digitalWrite(red_led1, HIGH);
    digitalWrite(green_led1, LOW);
    digitalWrite(yellow_led1, LOW);
    digitalWrite(red_led2, HIGH);
    digitalWrite(green_led2, LOW);
    digitalWrite(yellow_led2, LOW);
    digitalWrite(red_led4, HIGH);
    digitalWrite(green_led4, LOW);
    digitalWrite(yellow_led4, LOW);
  } else if (checkObstacle(TRIGGER_PIN4, ECHO_PIN4)) {
    // Section D detected obstacle
    digitalWrite(green_led4, HIGH);
    digitalWrite(red_led4, LOW);
    digitalWrite(yellow_led4, LOW);
    digitalWrite(red_led1, HIGH);
    digitalWrite(green_led1, LOW);
    digitalWrite(yellow_led1, LOW);
    digitalWrite(red_led2, HIGH);
    digitalWrite(green_led2, LOW);
    digitalWrite(yellow_led2, LOW);
    digitalWrite(red_led3, HIGH);
    digitalWrite(green_led3, LOW);
    digitalWrite(yellow_led3, LOW);
  }
  
  // Wait until obstacle is removed
  while (checkEmergency()) {
    // Continue monitoring for obstacle
  }
  
  // Return to normal traffic system
  normalTraffic();
}