#include <Servo.h>

// Pin definitions
const int GREEN_PIN = 11;
const int YELLOW_PIN = 12;
const int RED_PIN = 13;
const int BUZZER_BUTTON = 8; // Buzzer connected here
const int PUSH_BUTTON = 4;
const int TRIG = 6;          // Ultrasonic sensor TRIG pin
const int ECHO = 5;          // Ultrasonic sensor ECHO pin

/*Thiss function activates the buzzer when the distance is less than 15cm*/
// Timing variables
long previousMillis = 0;
long interval = 500; // Duration the buzzer stays on/off (in milliseconds)

// State variables
bool buttonPressed = false;

// Servo setup
Servo myServo1, myServo2; // Cross guard servos (not used here)

// Function to calculate distance using ultrasonic sensor
long getDistance() {
  digitalWrite(TRIG, HIGH);   // Send a 10-microsecond pulse
  delayMicroseconds(10);      // Short delay
  digitalWrite(TRIG, LOW);    // Stop the pulse

  unsigned long startTime = 0;
  unsigned long endTime = 0;

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

  // Wait for ECHO to go LOW and record the end time
  timeout = millis();
  while (digitalRead(ECHO) == HIGH) {
    endTime = micros();
    if (millis() - timeout > 50) return -1; // Timeout if signal is stuck
  }

  // Calculate the pulse duration and convert to distance
  long duration = endTime - startTime;
  return duration / 58; // Convert microseconds to centimeters
}

void setup() {
  // Initialize serial communication
  Serial.begin(9600);
  Serial.println("Train Crossing Active!");

  // Configure pins
  pinMode(BUZZER_BUTTON, OUTPUT);
  pinMode(PUSH_BUTTON, INPUT);
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
}

void loop() {
  // Detect button press to activate the system
  if (digitalRead(PUSH_BUTTON) == HIGH && !buttonPressed) {
    buttonPressed = true; // Record that the button has been pressed
  }

  if (buttonPressed) {
    // Measure distance
    long distance = getDistance();
    Serial.print("Distance: ");
    Serial.println(distance);

    // Decide actions based on distance
    if (distance >= 90) {
      noTone(BUZZER_BUTTON); // No action, turn buzzer off
    } else if (distance > 40 && distance < 90) {
      noTone(BUZZER_BUTTON); // No action, turn buzzer off
    } else if (distance > 16 && distance <= 40) {
      noTone(BUZZER_BUTTON); // No action, turn buzzer off
    } else if (distance <= 15) {
      // Activate the buzzer only when distance <= 15 cm
      if (millis() - previousMillis > interval) {
        tone(BUZZER_BUTTON, 500); // Set buzzer tone at 500 Hz
        previousMillis = millis(); // Reset the timer
      }
    }
  }
}