/************************************************************
  MagSpoof version for NFC Copy Cat
  by Salvador Mendoza (salmg.net)
  Electronic Cats (https://electroniccats.com/)

  This example demonstrates how to use NFC Copy Cat by Electronic Cats
  https://github.com/ElectronicCats/

  Development environment specifics:
  IDE: Arduino 1.8.9
  Hardware Platform:
  NFC Copy Cat
  - SAMD21E

  Electronic Cats invests time and resources providing this open source code, 
  please support Electronic Cats and open-source hardware by purchasing 
  products from Electronic Cats!

  This code is beerware; if you see me (or any other Electronic Cats
  member) at the local, and you've found our code helpful,
  please buy us a round!
  Distributed as-is; no warranty is given.
*/

#define L1         (14)  //LED1
#define L2         (5)   //LED2
#define L3         (4)   //LED3

#define PIN_A      (6) //MagSpoof-1
#define PIN_B      (7) //MagSpoof

#define MPIN       (28) //MagsSpoof Button
#define NPIN       (27) //NFC Button

#define CLOCK_US   (500)

#define BETWEEN_ZERO (53) // 53 zeros between track1 & 2

#define TRACKS (2)
#define DEBUGCAT

// consts get stored in flash as we don't adjust them
const char* tracks[] = {
  "%B123456781234567^LASTNAME/FIRST^YYMMSSSDDDDDDDDDDDDDDDDDDDDDDDDD?\0", // Track 1
  ";123456781234567=112220100000000000000?\0" // Track 2
};

char revTrack[41];

const int sublen[] = {
  32, 48, 48 
};
const int bitlen[] = {
  7, 5, 5 
};

unsigned int curTrack = 0;
int dir;

void setup(){
  pinMode(PIN_A, OUTPUT);
  pinMode(PIN_B, OUTPUT);
  pinMode(L1, OUTPUT);
  pinMode(L2, OUTPUT);
  pinMode(L3, OUTPUT);
  pinMode(MPIN, INPUT_PULLUP);
    
  Serial.begin(115200);
  //while(!Serial){}
  Serial.println("Hello!");

  // blink to show we started up
  blink(L1, 200, 2);
  blink(L2, 200, 2);
  blink(L3, 200, 2);
  Serial.println("Press the MagSpoof button");
}

void blink(int pin, int msdelay, int times){
  for (int i = 0; i < times; i++){
    digitalWrite(pin, HIGH);
    delay(msdelay);
    digitalWrite(pin, LOW);
    delay(msdelay);
  }
}

// send a single bit out
void playBit(int sendBit){
  dir ^= 1;
  digitalWrite(PIN_A, dir);
  digitalWrite(PIN_B, !dir);
  delayMicroseconds(CLOCK_US);

  if (sendBit){
    dir ^= 1;
    digitalWrite(PIN_A, dir);
    digitalWrite(PIN_B, !dir);
  }
  delayMicroseconds(CLOCK_US);

}

// when reversing
void reverseTrack(int track){
  int i = 0;
  track--; // index 0
  dir = 0;

  while (revTrack[i++] != '\0');
  i--;
  while (i--)
    for (int j = bitlen[track]-1; j >= 0; j--)
      playBit((revTrack[i] >> j) & 1);
}

// plays out a full track, calculating CRCs and LRC
void playTrack(int track){
  int tmp, crc, lrc = 0;
  dir = 0;
  track--; // index 0
  // enable H-bridge and LED
  //digitalWrite(ENABLE_PIN, HIGH);

  // First put out a bunch of leading zeros.
  for (int i = 0; i < 25; i++)
    playBit(0);

  for (int i = 0; tracks[track][i] != '\0'; i++)
  {
    crc = 1;
    tmp = tracks[track][i] - sublen[track];
    
    for (int j = 0; j < bitlen[track]-1; j++)
    {
      crc ^= tmp & 1;
      lrc ^= (tmp & 1) << j;
      playBit(tmp & 1);
      tmp >>= 1;
    }
    playBit(crc);
  }

  // finish calculating and send last "byte" (LRC)
  tmp = lrc;
  crc = 1;
  for (int j = 0; j < bitlen[track]-1; j++)
  {
    crc ^= tmp & 1;
    playBit(tmp & 1);
    tmp >>= 1;
  }
  playBit(crc);

  // if track 1, play 2nd track in reverse (like swiping back?)
  if (track == 0)
  {
    // if track 1, also play track 2 in reverse
    // zeros in between
    for (int i = 0; i < BETWEEN_ZERO; i++)
      playBit(0);

    // send second track in reverse
    reverseTrack(2);
  }

  // finish with 0's
  for (int i = 0; i < 5 * 5; i++)
    playBit(0);

  digitalWrite(PIN_A, LOW);
  digitalWrite(PIN_B, LOW);
  //digitalWrite(ENABLE_PIN, LOW);

}

// stores track for reverse usage later
void storeRevTrack(int track){
  int i, tmp, crc, lrc = 0;
  track--; // index 0
  dir = 0;

  for (i = 0; tracks[track][i] != '\0'; i++)
  {
    crc = 1;
    tmp = tracks[track][i] - sublen[track];

    for (int j = 0; j < bitlen[track]-1; j++)
    {
      crc ^= tmp & 1;
      lrc ^= (tmp & 1) << j;
      tmp & 1 ?
        (revTrack[i] |= 1 << j) :
        (revTrack[i] &= ~(1 << j));
      tmp >>= 1;
    }
    crc ?
      (revTrack[i] |= 1 << 4) :
      (revTrack[i] &= ~(1 << 4));
  }

  // finish calculating and send last "byte" (LRC)
  tmp = lrc;
  crc = 1;
  for (int j = 0; j < bitlen[track]-1; j++)
  {
    crc ^= tmp & 1;
    tmp & 1 ?
      (revTrack[i] |= 1 << j) :
      (revTrack[i] &= ~(1 << j));
    tmp >>= 1;
  }
  crc ?
    (revTrack[i] |= 1 << 4) :
    (revTrack[i] &= ~(1 << 4));

  i++;
  revTrack[i] = '\0';
}

void magspoof(){
  if (digitalRead(MPIN) == 0){
    Serial.println("Activating MagSpoof...");
    playTrack(1 + (curTrack++ % 2));
    blink(L1, 150, 3);
    delay(400);
  }
}

void loop(){
  magspoof();
}