const int GREEN_PIN = 17;
const int YELLOW_PIN = 18;
const int RED_PIN = 19;
const int TRIG = 20; //..We are setting the TRIG on the ultrasonic sensor to port 23
const int ECHO = 21;

void setup() {
  // put your setup code here, to run once:
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(YELLOW_PIN, OUTPUT);
  pinMode(RED_PIN, OUTPUT);
  pinMode(TRIG, OUTPUT);    // TRIG pin as output
  pinMode(ECHO, INPUT);     // ECHO pin as input
  Serial.begin(9600);
  Serial.println("Train Crossing Active!");
}

//define a function that is called get distance gets distance of ultrasonic wave that is sent
long getDistance()// #define a function that is called get distanc
{
  digitalWrite(TRIG, HIGH); //) #set the gpio pin to a high value or 1
  delayMicroseconds(10);//#sleeps or waits for 1 micro second
  digitalWrite(TRIG, LOW);
  unsigned long int startTime = 0;
  unsigned long int endTime = 0;
  long signal_of_utrasonic_distance_sensor;
  long distance_traveled_soundwave;
  while(digitalRead(ECHO)==LOW) //if the input ro echo is false or off
  { //get the time in seconds sinec echo, the echo is where the time starts
    startTime = micros(); //record the start time
  } //it contonously resest while echo is false
  while(digitalRead(ECHO)==HIGH)
  {
    endTime = micros(); //this lets the time since the echo 
  }//it continously resets while echo is true
  //distance in cm is equal to 
  signal_of_utrasonic_distance_sensor = endTime - startTime; //This is the total time elpased since the sound wave was outputed
  distance_traveled_soundwave = signal_of_utrasonic_distance_sensor/0.000058; //inches 0.000148 maybe 58 instead
  return distance_traveled_soundwave;
}
//This is what the output should be when the function green light is to be run 
void greenLight()
{
    digitalWrite(GREEN_PIN,  HIGH); //turn will turn on green light
    digitalWrite(YELLOW_PIN,  LOW); //turn the yellow led off
    digitalWrite(RED_PIN, LOW); //turn the red led off
}

void yellow_light() 
{
        
    digitalWrite(GREEN_PIN, LOW);   // Turn off green light
    digitalWrite(YELLOW_PIN, HIGH);  // Turn on yellow light
    digitalWrite(RED_PIN, LOW);      // Turn off red light
}


void red_light() 
{
    digitalWrite(GREEN_PIN, LOW);     // Turn off green light
    digitalWrite(YELLOW_PIN, LOW);    // Turn off yellow light
    digitalWrite(RED_PIN, HIGH);       // Turn on red light
}

void no_light() 
{
        // Ensure all lights and buzzer are off
    digitalWrite(GREEN_PIN, LOW);   
    digitalWrite(YELLOW_PIN, LOW);  
    digitalWrite(RED_PIN, LOW);     
}

void loop() 
{
  // put your main code here, to run repeatedly:
    long distance = getDistance();
    // start the crossing guard actions
    if(distance >=90)
    {
      no_light();
    }
    else if(23 < distance <90)
    {
      greenLight();

    }
    else if(16 < distance < 22)
    {
      yellow_light();
    }
    else if(distance <=15)
    {
      red_light();
    }

}