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

// ==========================
// RC522 wiring (ESP8266)
// ==========================
// Keep your existing pins here.
#define SS_PIN D4
#define RST_PIN D3

MFRC522 rfid(SS_PIN, RST_PIN);

// ==========================
// UART link to ESP32-S3
// ==========================
// Easiest: use Serial at 115200 to talk to ESP32.
// NOTE: This means you can't reliably use the same Serial for USB monitor at the same time.
// If you want USB monitor + ESP32 link simultaneously, switch to SoftwareSerial.
static constexpr uint32_t LINK_BAUD = 115200;

// Set true if you want extra prints on the same UART (will also be received by ESP32).
static constexpr bool DEBUG_UART = false;

String uidToString(const MFRC522::Uid &uid)
{
  String s;
  for (byte i = 0; i < uid.size; i++)
  {
    if (uid.uidByte[i] < 0x10)
      s += '0';
    s += String(uid.uidByte[i], HEX);
    if (i < uid.size - 1)
      s += ':';
  }
  s.toUpperCase();
  return s;
}

void sendEventToMaster(const String &uid)
{
  // Message consumed by ESP32-S3
  Serial.println("RFID UID=" + uid);
}

void setup()
{
  Serial.begin(LINK_BAUD);
  delay(800);

  if (DEBUG_UART)
  {
    Serial.println("ESP8266 RFID SLAVE READY");
  }

  SPI.begin();
  SPI.setFrequency(400000); // more stable for some RC522 boards

  rfid.PCD_Init();
  delay(50);

  byte version = rfid.PCD_ReadRegister(MFRC522::VersionReg);
  if (DEBUG_UART)
  {
    Serial.print("RC522 Version: 0x");
    Serial.println(version, HEX);
  }
}

void loop()
{
  // Poll RFID
  if (!rfid.PICC_IsNewCardPresent())
  {
    delay(20);
    return;
  }

  if (!rfid.PICC_ReadCardSerial())
  {
    delay(60);
    return;
  }

  String uid = uidToString(rfid.uid);

  if (DEBUG_UART)
  {
    Serial.print("UID: ");
    Serial.println(uid);
  }

  // Always send UID-only event to ESP32.
  sendEventToMaster(uid);

  rfid.PICC_HaltA();
  rfid.PCD_StopCrypto1();

  delay(1500); // debounce
}