#define gasSensorPin 0 // Analog output pin of the gas sensor
#define trigPin 14       // Trigger pin for the ultrasonic sensor
#define echoPin 12       // Echo pin for the ultrasonic sensor
#define threshold 500     // Gas detection threshold (adjust based on your sensor)
#define distanceThreshold 200 // Distance threshold for person detection (in cm)

int gasSensorValue;
long duration;
int distance;

void setup() {
  Serial.begin(9600);   // Initialize serial communication for debugging
  pinMode(gasSensorPin, INPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() {
  gasSensorValue = analogRead(gasSensorPin);
  Serial.print("Gas Sensor Value: ");
  Serial.println(gasSensorValue);

  // Check if gas level is above threshold
  if (gasSensorValue > threshold) {
    Serial.println("Gas Detected!");
    triggerUltrasonic();  // Trigger ultrasonic sensor when gas is detected

    // Check for people in close proximity after gas detection
    if (isPersonPresent()) {
      // Add actions here - sound alarm, turn on lights, etc.
      Serial.println("Person Detected in Gas Leak Area!");
      // Add your desired actions here, for example:
      // activateAlarm();
      // turnOnLights();
    }
  }

  delay(500);  // Adjust delay based on desired detection frequency
}

void triggerUltrasonic() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
}

int isPersonPresent() {
  // Trigger ultrasonic sensor
  triggerUltrasonic();

  // Measure distance
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;

  Serial.print("Distance: ");
  Serial.println(distance);

  return (distance <= distanceThreshold);  // True if person is within threshold
}