#include                   // SPI library for RFID communication
#include               // RFID library for MFRC522 module
#include                  // I2C library for LCD
#include     // LCD library for I2C-based LCDs

// Pin definitions
#define SS_PIN         10         // RFID SDA (SS) pin
#define RST_PIN        9          // RFID reset pin
#define RED_LED_PIN    4          // Red LED pin
#define GREEN_LED_PIN  5          // Green LED pin
#define BUZZER_PIN     6          // Active buzzer pin

// Create RFID and LCD objects
MFRC522 rfid(SS_PIN, RST_PIN);
LiquidCrystal_I2C lcd(0x27, 16, 2);  // LCD address (change if needed), 16 columns x 2 rows

// UID of the authorized card (replace with your own card UID)
byte authorizedUID[4] = {0x36, 0xE2, 0xC4, 0xF7};

void setup() {
  Serial.begin(9600);          // Start serial monitor for debugging
  SPI.begin();                 // Initialize SPI communication
  rfid.PCD_Init();             // Initialize RFID reader

  lcd.init();                  // Initialize the LCD
  lcd.backlight();             // Turn on LCD backlight

  pinMode(RED_LED_PIN, OUTPUT);
  pinMode(GREEN_LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  // Set default state: red LED on, LCD shows prompt
  digitalWrite(RED_LED_PIN, HIGH);
  lcd.setCursor(0, 0);
  lcd.print("Scan your card");
}

void loop() {
  // Wait for a new card
  if (!rfid.PICC_IsNewCardPresent() || !rfid.PICC_ReadCardSerial()) return;

  // Print the scanned UID to the Serial Monitor
  Serial.print("Card UID: ");
  for (byte i = 0; i < rfid.uid.size; i++) {
    Serial.print(rfid.uid.uidByte[i] < 0x10 ? " 0" : " ");
    Serial.print(rfid.uid.uidByte[i], HEX);
  }
  Serial.println();

  // Check if the scanned card is authorized
  bool authorized = compareUID(rfid.uid.uidByte, rfid.uid.size);
  showAccessResult(authorized);

  // Stop communicating with the current card
  rfid.PICC_HaltA();
  rfid.PCD_StopCrypto1();
}

// Compare scanned UID with the authorized one
bool compareUID(byte *uid, byte len) {
  if (len != 4) return false;
  for (byte i = 0; i < 4; i++) {
    if (uid[i] != authorizedUID[i]) return false;
  }
  return true;
}

// Display access result and give feedback
void showAccessResult(bool granted) {
  if (granted) {
    // Access granted:
    // Turn off red LED, turn on green LED, show welcome message
    digitalWrite(RED_LED_PIN, LOW);
    digitalWrite(GREEN_LED_PIN, HIGH);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Welcome!");
    shortBeep();
    delay(1000);

    // Reset to default state
    digitalWrite(GREEN_LED_PIN, LOW);
    digitalWrite(RED_LED_PIN, HIGH);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Scan your card");

  } else {
    // Access denied:
    // Flash red LED, beep 3 times, show denial message
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Access Denied");
    deniedFeedback(1500);  // Flash and beep for 1.5 seconds

    // Reset to default state
    digitalWrite(RED_LED_PIN, HIGH);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Scan your card");
  }
}

// Play a short beep (used for access granted)
void shortBeep() {
  digitalWrite(BUZZER_PIN, HIGH);
  delay(200);
  digitalWrite(BUZZER_PIN, LOW);
}

// Flash red LED and beep 3 times over a duration
void deniedFeedback(unsigned long duration) {
  unsigned long start = millis();
  int flashState = LOW;
  unsigned long lastFlash = 0;
  int beepCount = 0;
  unsigned long lastBeep = 0;
  bool beeping = false;

  while (millis() - start < duration) {
    unsigned long now = millis();

    // Toggle red LED every 100ms
    if (now - lastFlash >= 100) {
      flashState = !flashState;
      digitalWrite(RED_LED_PIN, flashState);
      lastFlash = now;
    }

    // Play 3 beeps, each 100ms long, spaced 200ms apart
    if (beepCount < 3) {
      if (!beeping && (now - lastBeep >= 200)) {
        digitalWrite(BUZZER_PIN, HIGH);
        lastBeep = now;
        beeping = true;
      }
      if (beeping && (now - lastBeep >= 100)) {
        digitalWrite(BUZZER_PIN, LOW);
        beeping = false;
        beepCount++;
      }
    }
  }

  // Ensure everything is off after feedback
  digitalWrite(BUZZER_PIN, LOW);
}