#include <Wire.h>               // Include Wire library for I2C communication
#include <LiquidCrystal_I2C.h>  // Include LiquidCrystal_I2C library for I2C LCD

#define GAS_SENSOR_PIN A0       // Analog pin for gas sensor
#define SERVO_PIN 9             // Digital pin for servo motor
#define REGULATOR_ON HIGH       // State for turning the gas regulator on
#define REGULATOR_OFF LOW       // State for turning the gas regulator off

LiquidCrystal_I2C lcd(0x27, 16, 2);  // Initialize the LCD with the I2C address and dimensions
Servo servo;                          // Create a servo object to control the servo motor

int gasValue = 0;         // Variable to store gas sensor value
int threshold = 500;      // Threshold value for gas detection
int regulatorState = REGULATOR_OFF; // Variable to store current state of gas regulator

void setup() {
  pinMode(GAS_SENSOR_PIN, INPUT);   // Set gas sensor pin as input
  pinMode(SERVO_PIN, OUTPUT);       // Set servo pin as output
  servo.attach(SERVO_PIN);          // Attach servo to its pin
  servo.write(0);                   // Move servo to initial position (closed)
  
  lcd.init();                       // Initialize the LCD
  lcd.backlight();                  // Turn on LCD backlight
  lcd.setCursor(0, 0);
  lcd.print("Gas: ");
}

void loop() {
  gasValue = analogRead(GAS_SENSOR_PIN);  // Read gas sensor value
  if (gasValue > threshold) {
    lcd.setCursor(5, 0);
    lcd.print("Leak");
    // Turn off gas regulator
    if (regulatorState == REGULATOR_ON) {
      servo.write(0);  // Close the gas regulator
      regulatorState = REGULATOR_OFF;
      lcd.setCursor(0, 1);
      lcd.print("Regulator OFF");
    }
  } else {
    lcd.setCursor(5, 0);
    lcd.print("Safe ");
    // Turn on gas regulator
    if (regulatorState == REGULATOR_OFF) {
      servo.write(90);  // Open the gas regulator
      regulatorState = REGULATOR_ON;
      lcd.setCursor(0, 1);
      lcd.print("Regulator ON ");
    }
  }

  // Display gas sensor value on LCD
  lcd.setCursor(5, 0);
  lcd.print("    ");  // Clear previous value
  lcd.setCursor(5, 0);
  lcd.print(gasValue);

  delay(1000);  // Delay for stability
}