#include <LiquidCrystal.h>
#include <ESP32Servo.h>

// -------- PIN DEFINITIONS --------
#define TRIG_IN 5
#define ECHO_IN 18

#define TRIG_OUT 17
#define ECHO_OUT 16

#define ENTRY_SERVO_PIN 4
#define EXIT_SERVO_PIN 2   // choose a free pin

#define GREEN_LED 25
#define RED_LED 26

// -------- LCD PINS --------
LiquidCrystal lcd(14, 27, 33, 32, 21, 22);

Servo entryGate;
Servo exitGate;

// -------- VARIABLES --------
int totalSpots = 5;
int availableSpots = 5;

bool entryDetected = false;
bool exitDetected = false;

// -------- FUNCTION TO MEASURE DISTANCE --------
long readDistance(int trigPin, int echoPin) {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

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

  return distance;
}

// -------- SETUP --------
void setup() {
  pinMode(TRIG_IN, OUTPUT);
  pinMode(ECHO_IN, INPUT);

  pinMode(TRIG_OUT, OUTPUT);
  pinMode(ECHO_OUT, INPUT);

  pinMode(GREEN_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);

  entryGate.attach(ENTRY_SERVO_PIN);
  exitGate.attach(EXIT_SERVO_PIN);

  entryGate.write(0); // closed
  exitGate.write(0);  // closed

  lcd.begin(16, 2);
  lcd.print("Smart Parking");
  delay(2000);
  lcd.clear();
}

// -------- LOOP --------
void loop() {

  long entryDistance = readDistance(TRIG_IN, ECHO_IN);
  long exitDistance = readDistance(TRIG_OUT, ECHO_OUT);

  // ---- ENTRY LOGIC ----
  if (entryDistance < 10 && !entryDetected) {
    entryDetected = true;

    if (availableSpots > 0) {
      entryGate.write(90);
      digitalWrite(GREEN_LED, LOW);
      digitalWrite(RED_LED, HIGH);  // open gate
      delay(2000);
      entryGate.write(0); 
      digitalWrite(RED_LED, LOW);
      digitalWrite(GREEN_LED, HIGH);  // close gate 
      availableSpots--;
     
    }
  }

  if (entryDistance > 15) {
    entryDetected = false;
  }

  // ---- EXIT LOGIC ----
  if (exitDistance < 10 && !exitDetected) {
    exitDetected = true;
    exitGate.write(90);
      digitalWrite(GREEN_LED, LOW);
      digitalWrite(RED_LED, HIGH);  // open gate
      delay(2000);
      exitGate.write(0);
      digitalWrite(RED_LED, LOW);
      digitalWrite(GREEN_LED, HIGH);  // close gate 
      
     

    if (availableSpots < totalSpots) {
      availableSpots++;
    }
  }

  if (exitDistance > 15) {
    exitDetected = false;
  }

  
  // ---- LCD DISPLAY ----
  lcd.setCursor(0, 0);
  lcd.print("Available: ");
  lcd.print(availableSpots);
  lcd.print("   ");

  lcd.setCursor(0, 1);
  if (availableSpots == 0) {
    lcd.print("Parking FULL ");
  } else {
    lcd.print("Welcome       ");
  }

  delay(200);
}