#include <Servo.h>

int duration1, distance1;  // Variables for sensor 1 (entry)
int duration2, distance2;  // Variables for sensor 2 (exit)
// initialize servo motor with name "gate"
Servo gate;

void setup() {
  pinMode(9, OUTPUT);
  pinMode(8, INPUT);
  pinMode(12, OUTPUT);
  pinMode(11, INPUT);
  
  pinMode(2, OUTPUT);
  pinMode(4, OUTPUT);
  
  gate.attach(3); // connect servo to pin 3 (PWM)
  
  // Initially close the gate
  gate.write(0); // gate is closed angle = 0
  digitalWrite(2, HIGH);    // Red LED on (gate closed)
  digitalWrite(4, LOW);   // Green LED off
}

void loop() {
  // Measure distance from sensor 1 (entry detection)
  digitalWrite(9, LOW);  // control trigger pin to activate sensor
  delayMicroseconds(2);
  digitalWrite(9, HIGH);
  delayMicroseconds(10);
  digitalWrite(9, LOW); // control trigger pin to activate sensor
  duration1 = pulseIn(8, HIGH); // read time value from echo pin
  distance1 = duration1 * 0.034 / 2;  // Convert to cm

  // Vehicle detected at entry (distance less than 10 cm)
  if (distance1 < 10) {
    // Open the gate
    gate.write(90);
    delay(1000);  // Time to fully open the gate ( check and change based on your physical system)
    
    // Turn off red LED, turn on green LED (gate open)
    digitalWrite(2, LOW);
    digitalWrite(4, HIGH);
    
    // Read ultrasonic sensor on the exit
    digitalWrite(12, LOW);
    delayMicroseconds(2);
    digitalWrite(12, HIGH);
    delayMicroseconds(10);
    digitalWrite(12, LOW);
    duration2 = pulseIn(11, HIGH);
    distance2 = duration2 * 0.034 / 2;  // Convert to cm

    while (distance2 > 10 || distance1 < 10) {
      // Check sensor 2 (exit detection)
      digitalWrite(12, LOW);
      delayMicroseconds(2);
      digitalWrite(12, HIGH);
      delayMicroseconds(10);
      digitalWrite(12, LOW);
      duration2 = pulseIn(11, HIGH);
      distance2 = duration2 * 0.034 / 2;  // Convert to cm

      // Check sensor 1 (entry detection) again in case another vehicle arrives
      digitalWrite(9, LOW);
      delayMicroseconds(2);
      digitalWrite(9, HIGH);
      delayMicroseconds(10);
      digitalWrite(9, LOW);
      duration1 = pulseIn(8, HIGH);
      distance1 = duration1 * 0.034 / 2;  // Convert to cm
    }

    // Close the gate after the vehicle has passed
    gate.write(0);
    delay(1000);  // Time to fully close the gate
    
    // Turn on red LED, turn off green LED (gate closed)
    digitalWrite(2, HIGH);
    digitalWrite(4, LOW);
  }

  // Small delay to avoid excessive sensor triggering
  delay(200);
}