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

#define TRIGGER_ENTRANCE_PIN 4
#define ECHO_ENTRANCE_PIN 5
#define TRIGGER_EXIT_PIN 6
#define ECHO_EXIT_PIN 7
#define SERVO_PIN_ENTRANCE 3
#define SERVO_PIN_EXIT 8
#define SLOT_CAPACITY 4

LiquidCrystal_I2C lcd(0x27, 16, 2);
Servo entranceBarrier; // Servo for entrance barrier
Servo exitBarrier;     // Servo for exit barrier
int availableSlots = SLOT_CAPACITY;

void setup() {
  pinMode(TRIGGER_ENTRANCE_PIN, OUTPUT);
  pinMode(ECHO_ENTRANCE_PIN, INPUT);
  pinMode(TRIGGER_EXIT_PIN, OUTPUT);
  pinMode(ECHO_EXIT_PIN, INPUT);

  lcd.begin(16, 2);
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("GOD IS MY LIGHT");
  delay(2000);
  lcd.clear();

  entranceBarrier.attach(SERVO_PIN_ENTRANCE);
  entranceBarrier.write(0); // Initial position

  exitBarrier.attach(SERVO_PIN_EXIT);
  exitBarrier.write(0); // Initial position
}

void loop() {
  int entranceDistance = detectDistance(TRIGGER_ENTRANCE_PIN, ECHO_ENTRANCE_PIN);
  int exitDistance = detectDistance(TRIGGER_EXIT_PIN, ECHO_EXIT_PIN);

  lcd.setCursor(0, 0);
  lcd.print("Welcome");
  lcd.setCursor(0, 1);
  lcd.print("Slots: ");
  lcd.print(availableSlots);
  delay(1000);
  lcd.clear();

  // Entrance logic
  if (entranceDistance <= 30 && availableSlots > 0) {
    lcd.setCursor(0, 0);
    lcd.print("Car Entering!");
    moveServo(entranceBarrier); // Open entrance barrier
    availableSlots--;
  }

  // Exit logic
  if (exitDistance <= 30 && availableSlots < SLOT_CAPACITY) {
    lcd.setCursor(0, 0);
    lcd.print("Car Exiting!");
    moveServo(exitBarrier); // Open exit barrier
    availableSlots++;
  }

  // Display if parking is full
  if (availableSlots == 0) {
    lcd.setCursor(0, 0);
    lcd.print("Parking Full!");
    delay(1000);
    lcd.clear();
  }
}

int detectDistance(int triggerPin, int echoPin) {
  digitalWrite(triggerPin, LOW);
  delayMicroseconds(2);
  digitalWrite(triggerPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin, LOW);

  int duration = pulseIn(echoPin, HIGH);
  int distance = duration * 0.034 / 2;

  return distance;
}

void moveServo(Servo servo) {
  servo.write(90); // Open barrier
  delay(2000);     // Hold the barrier open for 2 seconds
  servo.write(0);  // Close barrier
  lcd.clear();     // Clear LCD immediately after barrier closes
  delay(500);      // Allow servo to stabilize
}