//defining pins
#define TRIGGER_1 2
#define ECHO_1 3
#define TRIGGER_2 4
#define ECHO_2 5
#define TRIGGER_3 6
#define ECHO_3 7
#define TRIGGER_4 8
#define ECHO_4 9
#define RED_LED_1 24
#define GREEN_LED_1 25
#define BLUE_LED_1 26
#define RED_LED_2 27
#define GREEN_LED_2 28
#define BLUE_LED_2 29
#define RED_LED_3 30
#define GREEN_LED_3 31
#define BLUE_LED_3 32
#define RED_LED_4 33
#define GREEN_LED_4 34
#define BLUE_LED_4 35
#define BUZZER 19

int getDistance(int triggerPin, int echoPin) {
  long duration;
  digitalWrite(triggerPin, LOW);
  delayMicroseconds(2);
  digitalWrite(triggerPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  return duration * 0.034 / 2; //calculates the distance in meters   
} //this function is to get the distance to the objects.

void setColor(int led, int red, int green, int blue) {
  int redPin, greenPin, bluePin;
  switch (led) {
    case 1:
      redPin = RED_LED_1;
      greenPin = GREEN_LED_1;
      bluePin = BLUE_LED_1;
      break;
    case 2:
      redPin = RED_LED_2;
      greenPin = GREEN_LED_2;
      bluePin = BLUE_LED_2;
      break;
    case 3:
      redPin = RED_LED_3;
      greenPin = GREEN_LED_3;
      bluePin = BLUE_LED_3;
      break;
    case 4:
      redPin = RED_LED_4;
      greenPin = GREEN_LED_4;
      bluePin = BLUE_LED_4;
      break;
  }
  analogWrite(redPin, red);
  analogWrite(greenPin, green);
  analogWrite(bluePin, blue);
} //this function is to set the color in RGB LEDs.

void setup() {
  pinMode(TRIGGER_1, OUTPUT);
  pinMode(ECHO_1, INPUT);
  pinMode(TRIGGER_2, OUTPUT);
  pinMode(ECHO_2, INPUT);
  pinMode(TRIGGER_3, OUTPUT);
  pinMode(ECHO_3, INPUT);
  pinMode(TRIGGER_4, OUTPUT);
  pinMode(ECHO_4, INPUT);
  pinMode(RED_LED_1, OUTPUT);
  pinMode(GREEN_LED_1, OUTPUT);
  pinMode(BLUE_LED_1, OUTPUT);
  pinMode(RED_LED_2, OUTPUT);
  pinMode(GREEN_LED_2, OUTPUT);
  pinMode(BLUE_LED_2, OUTPUT);
  pinMode(RED_LED_3, OUTPUT);
  pinMode(GREEN_LED_3, OUTPUT);
  pinMode(BLUE_LED_3, OUTPUT);
  pinMode(RED_LED_4, OUTPUT);
  pinMode(GREEN_LED_4, OUTPUT);
  pinMode(BLUE_LED_4, OUTPUT);
  pinMode(BUZZER, OUTPUT);

  Serial.begin(9600);
}

void loop() {
  int distances[4];
  distances[0] = getDistance(TRIGGER_1, ECHO_1);
  distances[1] = getDistance(TRIGGER_2, ECHO_2);
  distances[2] = getDistance(TRIGGER_3, ECHO_3);
  distances[3] = getDistance(TRIGGER_4, ECHO_4);

  for (int i = 0; i < 4; i++) {
    if (distances[i] < 50) {
      tone(BUZZER, 1000, 500);
      setColor(i + 1, 255, 0, 0);
    } 
    else if (distances[i] < 150) {
      tone(BUZZER, 1000, 2000);
      setColor(i + 1, 255, 165, 0);
    } 
    else if (distances[i] < 300) {
      tone(BUZZER, 1000, 1000);
      setColor(i + 1, 0, 255, 0);
    } 
    else {
      noTone(BUZZER);
      setColor(i + 1, 0, 0, 0);
    }
  }
  delay(100);
}