#include <Servo.h>

// Pin definitions
const int GREEN_PIN = 11;
const int PUSH_BUTTON = 4;
const int TRIG = 6; // TRIG pin for ultrasonic sensor
const int ECHO = 5; // ECHO pin for ultrasonic sensor

// Timing variables
long previousMillis = 0;
long interval = 500; // Interval for toggling buzzer (if needed)

// Initial state for the button
bool buttonPressed = false;

void setup() {
  // Initialize pin modes
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(TRIG, OUTPUT); 
  pinMode(ECHO, INPUT);
  pinMode(PUSH_BUTTON, INPUT);

  // Start serial communication for debugging
  Serial.begin(9600);
  Serial.println("Train Crossing Active!");
}

// Function to get the distance from the ultrasonic sensor
long getDistance() {
  // Send a pulse
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  // Variables to store time of the pulse
  unsigned long startTime = 0;
  unsigned long endTime = 0;

  // Wait for the ECHO signal to go HIGH
  unsigned long timeout = millis();
  while (digitalRead(ECHO) == LOW) {
    startTime = micros();
    if (millis() - timeout > 50) return -1; // Timeout if no response
  }

  // Wait for the ECHO signal to go LOW
  timeout = millis();
  while (digitalRead(ECHO) == HIGH) {
    endTime = micros();
    if (millis() - timeout > 50) return -1; // Timeout if no response
  }

  // Calculate duration and convert to distance in cm
  long duration = endTime - startTime;
  return duration / 58; // Conversion factor for sound in air (us/cm)
}

// Function to turn on the green light
void greenLight() {
  digitalWrite(GREEN_PIN, HIGH);
}

// Function to turn off all lights
void noLight() {
  digitalWrite(GREEN_PIN, LOW);
}

void loop() {
  // Check if the push button is pressed
  if (digitalRead(PUSH_BUTTON) == HIGH && !buttonPressed) {
    buttonPressed = true; // Mark button as pressed
  }

  if (buttonPressed) { 
    // Get the distance from the ultrasonic sensor
    long distance = getDistance();

    // Perform actions based on the measured distance
    if (distance >= 90) {
      // Distance is too far; no lights should be on
      noLight();
    } else if (distance > 40 && distance < 90) {
      // Moderate distance; turn on green light
      greenLight();
    } else if (distance > 16 && distance <= 40) {
      // Closer distance; turn off lights
      noLight();
    } else if (distance <= 15) {
      // Very close; turn off lights (can be extended with buzzer if needed)
      noLight();
    }
  }
}