// C++ code
//
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Ultrasonic Sensor Pins
const int trigPin = 2;
const int echoPin = 3;
int Vcc = 5;
int Gnd = 2;

// LED Pins
const int greenLed = 12;
const int redLed = 13;

// Buzzer Pin
const int buzzer = 9;

// Parking Configuration
const int totalSlots = 3;
int availableSlots = totalSlots;

// LCD Configuration
LiquidCrystal_I2C lcd(0x27, 16, 2);  // I2C address 0x27, 16x2 display

// Ultrasonic Sensor Parameters
const int maxDistance = 200;  // cm
const int parkingThreshold = 50;  // Distance to detect vehicle

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(greenLed, OUTPUT);
  pinMode(redLed, OUTPUT);
  pinMode(buzzer, OUTPUT);
  
  lcd.init();
  lcd.backlight();
  lcd.print("Available Slots:");
  updateDisplay();
}

void loop() {
  int distance = getDistance();
  
  if(distance <= parkingThreshold && availableSlots > 0) {
    availableSlots--;
    triggerBuzzer(1);
    updateLeds();
    updateDisplay();
    delay(1000);  // Debounce
  }
  else if(distance > parkingThreshold && availableSlots < totalSlots) {
    availableSlots++;
    triggerBuzzer(2);
    updateLeds();
    updateDisplay();
    delay(1000);  // Debounce
  }
}

int getDistance() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  long duration = pulseIn(echoPin, HIGH);
  return duration * 0.034 / 2;  // Convert to cm
}

void updateLeds() {
  digitalWrite(redLed, availableSlots == 0 ? HIGH : LOW);
  digitalWrite(greenLed, availableSlots > 0 ? HIGH : LOW);
}

void updateDisplay() {
  lcd.setCursor(0, 1);
  lcd.print("    ");
  lcd.setCursor(0, 1);
  lcd.print(availableSlots);
  lcd.print("/");
  lcd.print(totalSlots);
}

void triggerBuzzer(int beeps) {
  for(int i=0; i<beeps; i++) {
    tone(buzzer, 1000);
    delay(100);
    noTone(buzzer);
    delay(100);
  }
}