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

// IR sensor pins
const int irPinIn = 2;
const int irPinOut = 3;

// Servo motor pin
const int servoPin = 6;

// Parking space variables
int currentCount = 0;
const int maxSpaces = 4; // Tunable max parking spaces

Servo gateServo;
LiquidCrystal_I2C lcd(0x27, 16, 2); // Common I2C address: 0x27 or 0x3F

// Function to open gate
void openGate() {
  /* 
    IO: servoPin (output to servo)
    Working: Rotates servo to 90° (gate open)
  */
  gateServo.write(90); 
}

// Function to close gate
void closeGate() {
  /*
    IO: servoPin (output to servo)
    Working: Rotates servo back to 0° (gate closed)
  */
  gateServo.write(0); 
}

// Function to update LCD
void updateLcd(const char* line1, const char* line2) {
  /*
    IO: LCD I2C (16x2)
    Working: Clears screen and writes 2 lines of text
  */
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(line1);
  lcd.setCursor(0, 1);
  lcd.print(line2);
}

void setup() {
  Serial.begin(9600);

  pinMode(irPinIn, INPUT);
  pinMode(irPinOut, INPUT);

  gateServo.attach(servoPin);
  closeGate();

  lcd.init();
  lcd.backlight();
  updateLcd("Smart Parking", "System Ready");
  delay(2000);
  updateLcd("Car Count:", "0");
}

void loop() {
  int carIn = digitalRead(irPinIn);
  int carOut = digitalRead(irPinOut);
  Serial.print("irIn: ");Serial.print(carIn);Serial.print(" | irOUT: ");Serial.println(carOut);

  // lcd.clear();
  lcd.setCursor(0, 0);lcd.print("Smart Parking Sys");
  lcd.setCursor(0, 1);lcd.print("Car : ");lcd.print(currentCount);lcd.print("/");lcd.print(maxSpaces);

  // Car entering
  if (carIn == HIGH) {  // IR sensor detects object when LOW
    if (currentCount < maxSpaces) {
      openGate();
      updateLcd("Welcome!", "Gate Opening...");
      delay(3000); // Allow car to pass
      closeGate();
      currentCount++;
      char buffer[16];
      sprintf(buffer, "Car Count: %d", currentCount);
      updateLcd("Entry Success", buffer);
      Serial.print("Car Entered. Current Count: ");
      Serial.println(currentCount);
      delay(2000); // Debounce delay
      lcd.clear();

    } else {
      updateLcd("Parking Full!", "Access Denied");
      Serial.println("Parking Full! Gate not opened.");
      delay(2000); 
      lcd.clear();

    }
  }

  // Car exiting
  if (carOut == HIGH) {  // IR detects car leaving
    openGate();
    updateLcd("Goodbye!", "Drive Safely");
    delay(3000);
    closeGate();
    if (currentCount > 0) {
      currentCount--;
    }
    char buffer[16];
    sprintf(buffer, "Car Count: %d", currentCount);
    updateLcd("Exit Success", buffer);
    Serial.print("Car Exited. Current Count: ");
    Serial.println(currentCount);
    delay(2000); // Debounce delay
    lcd.clear();

  }

  delay(200); // Small loop delay
  // delay(10); // Small loop delay
}