#include <Servo.h>

int red = 3;

int green = 2;
const int TRIG_PIN  = 6;  // Arduino pin connected to Ultrasonic Sensor's TRIG pin
const int ECHO_PIN  = 7;  // Arduino pin connected to Ultrasonic Sensor's ECHO pin
const int SERVO_PIN = 9; // Arduino pin connected to Servo Motor's pin
const int BUZZER_PIN  = 4;  // Arduino pin connected to Buzzer's pin
const int DISTANCE_THRESHOLD = 50; // centimeters
Servo servo; // create servo object to control a servo

float duration_us, distance_cm;

void setup() {
  Serial.begin (9600);       // initialize serial port
  pinMode(TRIG_PIN, OUTPUT); // set arduino pin to output mode
  pinMode(ECHO_PIN, INPUT); 
  pinMode(BUZZER_PIN, OUTPUT); // set arduino pin to input mode
  pinMode(red, OUTPUT);
  pinMode(green,  OUTPUT);
  servo.attach(SERVO_PIN);   // attaches the servo on pin 9 to the servo object
  servo.write(0);
}

void loop() {
  // generate 10-microsecond pulse to TRIG pin
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // measure duration of pulse from ECHO pin
  duration_us = pulseIn(ECHO_PIN, HIGH);
  // calculate the distance
  distance_cm = 0.017 * duration_us;

  if(distance_cm < DISTANCE_THRESHOLD)
    {
      servo.write(00); // rotate servo motor to 90 degree
      tone(BUZZER_PIN , 1000);
      digitalWrite(red, HIGH);
      delay(200);
      digitalWrite(red,  LOW);
      noTone(BUZZER_PIN);
    }
  else
    {
      for(int i = 0  ; i <=181 ; i = i+1) 
      {
        servo.write(i);  // rotate servo motor to i degree
        digitalWrite(green, HIGH);        
        delay(5);
      }
      digitalWrite(green,  LOW);
      servo.write(0);
    }

  // print the value to Serial Monitor
  Serial.print("distance: ");
  Serial.print(distance_cm);
  Serial.println(" cm");

  delay(500);
}
// Ezoicvoid setup() {
//   // put your setup code here, to run once:

// }

// void loop() {
//   // put your main code here, to run repeatedly:

// }