// https://forum.arduino.cc/t/arduino-mfrc522-rfid-continuous-reading/1440651/11

#include <SPI.h>
#include <MFRC522.h>

#define SS_PIN  10
#define RST_PIN 9
#define LED_G 6 //define green LED pin
#define RELAY 5 //Relay out
#define LED_G2 4 //Green LED
#define LED_R 3//define red LED

MFRC522 rfid(SS_PIN, RST_PIN);

void setup() {
  Serial.begin(115200);
  SPI.begin();
  rfid.PCD_Init();
  Serial.println("MFRC522 Ready to scan a card...");
}

void loop() {
  if (!rfid.PICC_IsNewCardPresent()) { // new card
    return;
  }

  if (!rfid.PICC_ReadCardSerial()) { // known card
    return;
  }

  String content = "";
  for (byte i = 0; i < rfid.uid.size; i++)
  {
    Serial.print(rfid.uid.uidByte[i] < 0x10 ? " 0" : " ");
    Serial.print(rfid.uid.uidByte[i], HEX);
    content.concat(String(rfid.uid.uidByte[i] < 0x10 ? " 0" : " "));
    content.concat(String(rfid.uid.uidByte[i], HEX));
  }

  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();

  if (content.substring(1) == "01 02 03 04") {
    Serial.println("Authorized");
  } else { // wrong card
    Serial.println("Denied");
    digitalWrite(RELAY, LOW);
    digitalWrite(LED_G, LOW);
    digitalWrite(LED_G2, LOW);
    digitalWrite(LED_R, HIGH);
    delay(1000);
    digitalWrite(LED_R, LOW);
  }
  rfid.PICC_HaltA ();
  delay(500);
  if (rfid.PICC_WakeupA ()) { // if wakeup is successful, a card is present
    digitalWrite(RELAY, HIGH);
    digitalWrite(LED_G, HIGH);
    digitalWrite(LED_G2, HIGH);
    digitalWrite(LED_R, LOW);
  }
}

/*
  // rfid.PICC_IsNewCardPresent () // see new card
  // rfid.PICC_ReadCardSerial () // store card data
  rfid.PICC_HaltA ()   // card is authorized, put card to sleep
  if (rfid.PICC_WakeupA ()) { // if wakeup is successful, a card is present
    digitalWrite(RELAY, HIGH);
    digitalWrite(LED_G, HIGH);
    digitalWrite(LED_G2, HIGH);
    digitalWrite(LED_R, LOW);
  }
  // card present, so try some delay AND keep LEDs/relays ON
  rfid.PICC_HaltA () // back to sleep
  else // wakeup failed, no card present
  // go to IsNewCardPresent()

*/