#define TRIGGER_PIN  4  // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN     5 // Arduino pin tied to echo pin on the ultrasonic sensor.
#define LED_HIGH     8  // Pin number for the high water level LED.
#define LED_MEDIUM   7  // Pin number for the medium water level LED.
#define LED_LOW      6  // Pin number for the low water level LED.
#define THRESHOLD_HIGH 100  // Threshold for high water level in centimeters.
#define THRESHOLD_MEDIUM 50 // Threshold for medium water level in centimeters.

void setup() {
  pinMode(LED_HIGH, OUTPUT);
  pinMode(LED_MEDIUM, OUTPUT);
  pinMode(LED_LOW, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  delay(50);
  unsigned int distance = getDistance(); // Get distance in centimeters.

  if (distance < THRESHOLD_HIGH && distance >= THRESHOLD_MEDIUM) {
    digitalWrite(LED_HIGH, HIGH);
    digitalWrite(LED_MEDIUM, LOW);
    digitalWrite(LED_LOW, LOW);
  } else if (distance < THRESHOLD_MEDIUM) {
    digitalWrite(LED_HIGH, LOW);
    digitalWrite(LED_MEDIUM, HIGH);
    digitalWrite(LED_LOW, LOW);
  } else {
    digitalWrite(LED_HIGH, LOW);
    digitalWrite(LED_MEDIUM, LOW);
    digitalWrite(LED_LOW, HIGH);
  }

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

unsigned int getDistance() {
  digitalWrite(TRIGGER_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIGGER_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIGGER_PIN, LOW);

  return pulseIn(ECHO_PIN, HIGH) * 0.034 / 2;
}