#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Define the pins for the Ultrasonic Sensor
const int trigPin = 2;
const int echoPin = 3;

// Define the pins for the Relay Switch
const int relayPin = 4;

// Define the pins for the LEDs
const int greenLedPin = 5;
const int redLedPin = 6;

// Define the variables for the LCD
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  // Initialize the LCD
  lcd.init();
  lcd.backlight();

  // Set the pins for the Ultrasonic Sensor
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // Set the pins for the Relay Switch
  pinMode(relayPin, OUTPUT);

  // Set the pins for the LEDs
  pinMode(greenLedPin, OUTPUT);
  pinMode(redLedPin, OUTPUT);

  // Set the initial state of the Relay Switch
  digitalWrite(relayPin, LOW);
}

void loop() {
  // Measure the distance using the Ultrasonic Sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

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

  // Display the distance on the LCD
  lcd.setCursor(0, 0);
  lcd.print("Distance: ");
  lcd.print(distance);
  lcd.print(" cm");

  // Turn on the green LED and start pumping water if the distance is greater than 7cm
  if (distance > 7) {
    digitalWrite(greenLedPin, HIGH);
    digitalWrite(redLedPin, LOW);
    digitalWrite(relayPin, HIGH);
  }

  // Turn off the red LED and stop pumping water if the distance is less than 3cm
  else if (distance < 3) {
    digitalWrite(greenLedPin, LOW);
    digitalWrite(redLedPin, HIGH);
    digitalWrite(relayPin, LOW);
  }

  // Keep the state of the Relay Switch until the distance reaches 7cm again
  else {
    digitalWrite(greenLedPin, LOW);
    digitalWrite(redLedPin, LOW);
  }
}