import hmac
import hashlib
import struct

from smartcard.CardConnection import CardConnection
from smartcard.CardRequest import CardRequest

from secret import SECRET


def generate_payload(user_id: int) -> bytes:
    user_bytes = struct.pack(">H", user_id)

    mac = hmac.new(
        SECRET,
        user_bytes,
        hashlib.sha256
    ).digest()

    mac_truncated = mac[:8]

    return user_bytes + mac_truncated

def write_page(connection, page, data4):
    apdu = [0xFF, 0xD6, 0x00, page, 0x04] + data4
    response, sw1, sw2 = connection.transmit(apdu)
    return sw1 == 0x90 and sw2 == 0x00

def write_ndef_text(connection, text, start_page=4) -> bool:
    text_bytes = text.encode("utf-8")
    lang = b"en"

    ndef_record = bytearray()

    ndef_record.append(0xD1)
    ndef_record.append(0x01)
    ndef_record.append(len(text_bytes) + 1 + len(lang))
    ndef_record.append(0x54)
    ndef_record.append(len(lang))
    ndef_record.extend(lang)
    ndef_record.extend(text_bytes)

    tlv = bytearray()
    tlv.append(0x03)
    tlv.append(len(ndef_record))
    tlv.extend(ndef_record)
    tlv.append(0xFE)

    # Pad to multiple of 4 bytes
    while len(tlv) % 4 != 0:
        tlv.append(0x00)

    page = start_page
    for i in range(0, len(tlv), 4):
        chunk = list(tlv[i:i + 4])
        if not write_page(connection, page, chunk):
            print(f"Konnte Seite {page} nicht schreiben. Ticket kaputt.")
            return False
        page += 1

    print("Erfolgreich geschrieben")
    return True

def write_secure_user_id(connection, user_id: int):
    payload = generate_payload(user_id)
    hex_string = payload.hex().upper()
    write_ndef_text(connection, hex_string)

def main():
    print("Auf Ticket warten...")
    card_request = CardRequest(timeout=None)
    card_service = card_request.waitforcard()
    connection = card_service.connection
    connection.connect(CardConnection.T1_protocol)

    try:
        user_id = int(input("User ID eingeben: "))
    except ValueError:
        print("User ID muss numerisch sein!")
        exit(1)

    write_secure_user_id(connection, user_id)


if __name__ == "__main__":
    main()