#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Define ultrasonic sensor pins
#define trigPin1 2
#define echoPin1 3
#define trigPin2 4
#define echoPin2 5
#define trigPin3 6
#define echoPin3 7

// Define LED pins for each parking space
#define redLED1 8
#define greenLED1 9
#define redLED2 10
#define greenLED2 11
#define redLED3 12
#define greenLED3 13

// Define buzzer pins for each parking space
#define buzzer1 A0
#define buzzer2 A1
#define buzzer3 A2

// Create LCD object
LiquidCrystal_I2C lcd(0x27, 16, 2);

long duration;
int distance;
int threshold = 100;  // Distance threshold (30 cm)

// Track the state of each parking space
bool vehicleDetected1 = false;
bool vehicleDetected2 = false;
bool vehicleDetected3 = false;

void setup() {
  // Initialize LCD
  lcd.init();
  lcd.backlight();
  
  // Set up ultrasonic sensor pins
  pinMode(trigPin1, OUTPUT);
  pinMode(echoPin1, INPUT);
  pinMode(trigPin2, OUTPUT);
  pinMode(echoPin2, INPUT);
  pinMode(trigPin3, OUTPUT);
  pinMode(echoPin3, INPUT);
  
  // Set up LED and buzzer pins
  pinMode(redLED1, OUTPUT);
  pinMode(greenLED1, OUTPUT);
  pinMode(redLED2, OUTPUT);
  pinMode(greenLED2, OUTPUT);
  pinMode(redLED3, OUTPUT);
  pinMode(greenLED3, OUTPUT);
  pinMode(buzzer1, OUTPUT);
  pinMode(buzzer2, OUTPUT);
  pinMode(buzzer3, OUTPUT);
  
  // Initial display on LCD
  lcd.setCursor(0, 0);
  lcd.print("Parking System");
  delay(2000);
  lcd.clear();
}

void loop() {
  // Pass each vehicleDetected variable by reference so that they are updated properly
  checkParkingSpace(trigPin1, echoPin1, redLED1, greenLED1, buzzer1, vehicleDetected1, 0, "S1");  // Row 0
  checkParkingSpace(trigPin2, echoPin2, redLED2, greenLED2, buzzer2, vehicleDetected2, 1, "S2");  // Row 1, first half
  checkParkingSpace(trigPin3, echoPin3, redLED3, greenLED3, buzzer3, vehicleDetected3, 1, "S3");  // Row 1, second half
  delay(500);
}

void checkParkingSpace(int trigPin, int echoPin, int redLED, int greenLED, int buzzer, bool &vehicleDetected, int lcdRow, String spaceName) {
  // Send ultrasonic signal
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  // Measure the time for echo
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;  // Convert to cm

  if (distance < threshold && distance > 0) {  // Vehicle detected
    // Check if this is the first time a vehicle is detected (state change)
    if (!vehicleDetected) {
      // Beep the buzzer once (200 ms) on detection
      tone(buzzer, 1000, 1000);
      vehicleDetected = true;  // Update state to indicate vehicle detected
    }
    
    // Turn on red LED, turn off green LED
    digitalWrite(redLED, HIGH);
    digitalWrite(greenLED, LOW);

    // Display "Occupied" message on the LCD
    if (lcdRow == 0) {
      lcd.setCursor(0, lcdRow);  // S1 starts at position 0, row 0
    } else if (spaceName == "S2") {
      lcd.setCursor(0, 1);  // S2 starts at position 0, row 1
    } else if (spaceName == "S3") {
      lcd.setCursor(8, 1);  // S3 starts at position 8, row 1
    }
    lcd.print(spaceName + ": Occu");
  } else {  // No vehicle detected
    // Reset the state if vehicle was previously detected
    if (vehicleDetected) {
      vehicleDetected = false;  // Update state to no vehicle detected
    }

    // Turn on green LED, turn off red LED
    digitalWrite(redLED, LOW);
    digitalWrite(greenLED, HIGH);
    noTone(buzzer);  // Ensure buzzer is off
    
    // Display "Free" message on the LCD
    if (lcdRow == 0) {
      lcd.setCursor(0, lcdRow);  // S1 starts at position 0, row 0
    } else if (spaceName == "S2") {
      lcd.setCursor(0, 1);  // S2 starts at position 0, row 1
    } else if (spaceName == "S3") {
      lcd.setCursor(8, 1);  // S3 starts at position 8, row 1
    }
    lcd.print(spaceName + ": Free    ");
  }
}