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

// Your wiring:
const uint8_t SS_PIN  = 6;   // RC522 SDA pin -> XIAO D6 (Chip Select)
const uint8_t RST_PIN = 7;   // RC522 RST pin -> XIAO D7

MFRC522 rfid(SS_PIN, RST_PIN);  // Create MFRC522 instance

void setup() {
  // Start serial for debugging
  Serial.begin(115200);
  while (!Serial) {
    ; // Wait for Serial on SAMD21 (so you can see messages)
  }

  Serial.println("Booting...");
  Serial.println("Initializing SPI and RC522...");

  // Initialize SPI bus (D8=SCK, D9=MISO, D10=MOSI on XIAO SAMD21)
  SPI.begin();

  // Initialize RC522 reader
  rfid.PCD_Init();
  delay(50);

  // Optional: Show reader details
  Serial.print("MFRC522 Firmware version: 0x");
  byte v = rfid.PCD_ReadRegister(MFRC522::VersionReg);
  Serial.println(v, HEX);

  if (v == 0x00 || v == 0xFF) {
    Serial.println("WARNING: Could not communicate with RC522.");
    Serial.println("Check wiring and power (3.3V, GND, SS=D6, RST=D7, MOSI=D10, MISO=D9, SCK=D8).");
  } else {
    Serial.println("RC522 initialized successfully. Present a card to the reader.");
  }
}

void loop() {
  // Look for new cards
  if (!rfid.PICC_IsNewCardPresent()) {
    return; // No new card
  }

  // Select one of the cards
  if (!rfid.PICC_ReadCardSerial()) {
    return; // Read error
  }

  Serial.println("Card detected!");

  // Print UID in HEX
  Serial.print("UID (HEX): ");
  for (byte i = 0; i < rfid.uid.size; i++) {
    if (rfid.uid.uidByte[i] < 0x10) {
      Serial.print("0"); // leading zero
    }
    Serial.print(rfid.uid.uidByte[i], HEX);
    Serial.print(" ");
  }
  Serial.println();

  // Print card type
  MFRC522::PICC_Type piccType = rfid.PICC_GetType(rfid.uid.sak);
  Serial.print("Card type: ");
  Serial.println(rfid.PICC_GetTypeName(piccType));

  Serial.println("------------------------");

  // Halt the card and stop encryption (good practice)
  rfid.PICC_HaltA();
  rfid.PCD_StopCrypto1();

  delay(200);  // small delay so output is readable
}