#include <Servo.h>

// IR sensors (LOW = car detected, HIGH = free)
#define IR1  2
#define IR2  3
#define IR3  4
#define IR4  5

// Slot indicator LEDs (RED = occupied)
#define LED1 6
#define LED2 7
#define LED3 8
#define LED4 9

// Status LEDs
#define LED_AVAIL 11   // Green = slots free
#define LED_FULL  12   // Red   = parking full

// Servo (entry gate)
#define GATE_PIN  10

Servo gate;

const int irPins[]  = {IR1, IR2, IR3, IR4};
const int ledPins[] = {LED1, LED2, LED3, LED4};
const int TOTAL_SLOTS = 4;

bool lastState[4] = {false, false, false, false};

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

  for (int i = 0; i < 4; i++) {
    pinMode(irPins[i],  INPUT);
    pinMode(ledPins[i], OUTPUT);
  }
  pinMode(LED_AVAIL, OUTPUT);
  pinMode(LED_FULL,  OUTPUT);

  gate.attach(GATE_PIN);
  gate.write(0); // gate closed

  Serial.println("=================================");
  Serial.println("   Smart Parking System");
  Serial.println("   4-Slot IR Sensor | Arduino");
  Serial.println("=================================\n");
}

void updateDisplay(int occupied) {
  int free = TOTAL_SLOTS - occupied;

  if (free > 0) {
    digitalWrite(LED_AVAIL, HIGH);
    digitalWrite(LED_FULL,  LOW);
    gate.write(90); // open gate
  } else {
    digitalWrite(LED_AVAIL, LOW);
    digitalWrite(LED_FULL,  HIGH);
    gate.write(0);  // close gate
  }
}

void loop() {
  int occupied = 0;
  bool changed = false;

  for (int i = 0; i < 4; i++) {
    // IR: LOW = object detected = occupied
    bool carPresent = (digitalRead(irPins[i]) == LOW);

    digitalWrite(ledPins[i], carPresent ? HIGH : LOW);

    if (carPresent != lastState[i]) {
      changed = true;
      lastState[i] = carPresent;
    }
    if (carPresent) occupied++;
  }

  updateDisplay(occupied);

  if (changed) {
    Serial.println("──── Parking Status ────");
    for (int i = 0; i < 4; i++) {
      Serial.print("  Slot "); Serial.print(i + 1);
      Serial.println(lastState[i] ? " → OCCUPIED 🚗" : " → FREE ✅");
    }
    Serial.print("  Occupied: "); Serial.print(occupied);
    Serial.print(" / ");         Serial.println(TOTAL_SLOTS);
    Serial.print("  Available: "); Serial.println(TOTAL_SLOTS - occupied);
    Serial.println(occupied == TOTAL_SLOTS ? "  ⚠️  PARKING FULL — Gate CLOSED" : "  ✅  Slots Available — Gate OPEN");
    Serial.println("────────────────────────\n");
  }

  delay(300);
}