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

Servo myservo;
LiquidCrystal_I2C lcd(0x27, 20, 4); 

#define IR_ENTER_PIN 2
#define IR_BACK_PIN  3

#define IR_CAR1_PIN 4
#define IR_CAR2_PIN 5
#define IR_CAR3_PIN 6
#define IR_CAR4_PIN 7

#define TOTAL_SLOTS 4

int S1 = 0, S2 = 0, S3 = 0, S4 = 0;
int availableSlots = TOTAL_SLOTS;

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

  pinMode(IR_CAR1_PIN, INPUT);
  pinMode(IR_CAR2_PIN, INPUT);
  pinMode(IR_CAR3_PIN, INPUT);
  pinMode(IR_CAR4_PIN, INPUT);
  pinMode(IR_ENTER_PIN, INPUT);
  pinMode(IR_BACK_PIN, INPUT);

  myservo.attach(9);
  myservo.write(90);

  lcd.begin(20, 4);
  lcd.setCursor(0, 0);
  lcd.print("   Smart Car   ");
  lcd.setCursor(0, 1);
  lcd.print(" Parking System ");
  delay(2000);
  lcd.clear();
}

void loop() {
  Read_Sensors();
  Update_LCD();

  if (digitalRead(IR_ENTER_PIN) == HIGH ) {
    lcd.setCursor(0, 3);
    Allocate_Parking();
  }

  if (digitalRead(IR_BACK_PIN) == HIGH) {
    myservo.write(180);
    delay(1000);
    myservo.write(90);
  }

  delay(100); // Adjust delay based on system responsiveness
}

void Read_Sensors() {
  S1 = digitalRead(IR_CAR1_PIN);
  S2 = digitalRead(IR_CAR2_PIN);
  S3 = digitalRead(IR_CAR3_PIN);
  S4 = digitalRead(IR_CAR4_PIN);
}

void Update_LCD() {
  lcd.setCursor(0, 0);
  lcd.print("   Available Slots: ");
  lcd.print(availableSlots);

  lcd.setCursor(0, 1);
  lcd.print("S1: ");
  lcd.print(S1 == HIGH ? "Fill " : "Empty");

  lcd.setCursor(10, 1);
  lcd.print("S2: ");
  lcd.print(S2 == HIGH ? "Fill " : "Empty");

  lcd.setCursor(0, 2);
  lcd.print("S3: ");
  lcd.print(S3 == HIGH ? "Fill " : "Empty");

  lcd.setCursor(10, 2);
  lcd.print("S4: ");
  lcd.print(S4 == HIGH ? "Fill " : "Empty");
}

void Allocate_Parking(){
  for (int i = 0; i < TOTAL_SLOTS; i++) {
    if (!digitalRead(IR_CAR1_PIN + i)) { // Find the first empty parking slot

      lcd.setCursor(0, 3);
      // lcd.print("Parking allocated to slot: ");
      if(S1 == HIGH ){
        if(S2 == HIGH){
          if(S3 == HIGH){
            if(S4 == HIGH){
              lcd.print("PARKING SPOT FILLED");
              }
            else{
              lcd.print("Allocate Spot 4");
            }
          }
          else{
            lcd.print("Allocate Spot 3");
          }
        }
        else{
          lcd.print("Allocate Spot 2");
        }
      } 
      else{
        lcd.print("Allocate Spot 1");
      }
      lcd.print("    ");
      myservo.write(180);
      delay(1000); // Adjust delay for gate opening time
      myservo.write(90);
      availableSlots--;
      // delay(100); // Adjust delay based on system responsiveness
      return;
    }
  }
  lcd.setCursor(0, 3);
  lcd.print("No available parking slot. ");
}