#include <Wire.h>
#include <PN532_I2C.h>
#include <PN532.h>
#include <NfcAdapter.h>

PN532_I2C pn532_i2c(Wire);
NfcAdapter nfc = NfcAdapter(pn532_i2c);

#define Content_Type "text/admin"

String username = "myUsername";

#define LED_PIN 8         // pin for the LED

boolean led = LOW;
boolean p_state = false;

void setup() {
  Serial.begin(9600);
  nfc.begin();                   // initialize the NFC reader
  pinMode(LED_PIN, OUTPUT);      // make the led pin an output
  digitalWrite(LED_PIN, led);    // set it low turn off the led

}

void loop() {
  String text = readTag();
  if (text == username && !p_state) {
    lock();
    p_state = true;
  } else if (text == "" && p_state) {
    p_state = false;
  }
}

String readTag() {
  String text = "";

  if (nfc.tagPresent()) {         // if there's a tag present
    NfcTag tag = nfc.read();
    if (tag.hasNdefMessage()) {   // every tag won't have a message
      NdefMessage message = tag.getNdefMessage();
      NdefRecord record = message.getRecord(0);

      if (record.getTnf() == TNF_MIME_MEDIA && record.getType() == Content_Type) {
        // Get the length of the payload:
        int payloadLength = record.getPayloadLength();
        byte payload[payloadLength];  // make a byte array to hold the payload
        record.getPayload(payload);

        // convert the payload to a String
        for (int c = 0; c < payloadLength; c++) {
          if (isprint((char)payload[c])) {
            text += (char)payload[c];
          }
        }
        Serial.println("OK");
      }
    }
  }
  return text;
}

boolean lock() {
  led = !led;
  digitalWrite(LED_PIN, led);
  Serial.print("LED state: ");
  Serial.println(led);

}