//This code allows a app to send a URI to the ESP32 via a POST request. 
//The ESP32 then writes the URI to an NFC card using the MFRC522 library.

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

const char* ssid = "SSID_NAME";  // Replace with your network SSID  
const char* password = "SSID_PASSWORD";  // Replace with your network password

#define RST_PIN  D6
#define SS_PIN   D7

MFRC522 mfrc522(SS_PIN, RST_PIN);
WebServer server(80);

String receivedUri = "";  // <- store latest URI
bool writePending = false; // <- flag to indicate pending write

void handleUriPost() {
  if (server.hasArg("uri")) {
    receivedUri = server.arg("uri");
    writePending = true;  // mark that we need to write
    Serial.println("Received URI: " + receivedUri);
    server.send(200, "text/plain", "URI received: " + receivedUri);
  } else {
    server.send(400, "text/plain", "Missing 'uri' parameter");
  }
}

void setup() {
  Serial.begin(115200);
  SPI.begin();
  mfrc522.PCD_Init();

  WiFi.begin(ssid, password);
  Serial.print("Connecting to WiFi...");

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("\nConnected! IP address: ");
  Serial.println(WiFi.localIP());

  server.on("/uri", HTTP_POST, handleUriPost);
  server.begin();
  Serial.println("HTTP server started");
}

void loop() {
  server.handleClient();

  if (writePending) {
    Serial.println("Waiting for NFC card to write...");

    MFRC522::MIFARE_Key key;
    for (byte i = 0; i < 6; i++) key.keyByte[i] = 0xFF;  // Default key

    if (!mfrc522.PICC_IsNewCardPresent()) return;
    if (!mfrc522.PICC_ReadCardSerial()) return;

    Serial.print(F("Card UID: "));
    for (byte i = 0; i < mfrc522.uid.size; i++) {
      Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
      Serial.print(mfrc522.uid.uidByte[i], HEX);
    }
    Serial.println();

    // Prepare data
    byte buffer1[16];
    byte buffer2[16];
    const char* playlistID = receivedUri.c_str();
    size_t len = strlen(playlistID);

    // Fill buffer1 with first 16 bytes
    for (byte i = 0; i < 16; i++) {
      buffer1[i] = (i < len) ? playlistID[i] : ' ';
    }

    // Fill buffer2 with next 16 bytes (if any)
    for (byte i = 0; i < 16; i++) {
      byte index = i + 16;
      buffer2[i] = (index < len) ? playlistID[index] : ' ';
    }

    // Write to block 1
    byte block = 1;
    MFRC522::StatusCode status;
    status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, block, &key, &(mfrc522.uid));
    if (status != MFRC522::STATUS_OK) {
      Serial.print(F("Auth failed for block 1: "));
      Serial.println(mfrc522.GetStatusCodeName(status));
      return;
    }
    status = mfrc522.MIFARE_Write(block, buffer1, 16);
    if (status != MFRC522::STATUS_OK) {
      Serial.print(F("Write failed for block 1: "));
      Serial.println(mfrc522.GetStatusCodeName(status));
      return;
    }
    Serial.println(F("Block 1 written successfully."));

    // Write to block 2
    block = 2;
    status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, block, &key, &(mfrc522.uid));
    if (status != MFRC522::STATUS_OK) {
      Serial.print(F("Auth failed for block 2: "));
      Serial.println(mfrc522.GetStatusCodeName(status));
      return;
    }
    status = mfrc522.MIFARE_Write(block, buffer2, 16);
    if (status != MFRC522::STATUS_OK) {
      Serial.print(F("Write failed for block 2: "));
      Serial.println(mfrc522.GetStatusCodeName(status));
      return;
    }
    Serial.println(F("Block 2 written successfully."));

    mfrc522.PICC_HaltA();
    mfrc522.PCD_StopCrypto1();

    Serial.println(F("Done writing playlist ID!"));

    writePending = false;  // clear the flag after writing
    delay(3000);
  }
}