#define RANDOM A0   // Analogue pin as a source of noise.
char ChallResp[11];

void setup() {
  pinMode(RANDOM, INPUT);     // switch on the analogue pin for random number
  Serial.begin(115200);


}

void loop() {
  CreateChallenge();
  delay(1800);
  Serial.println("\n");
}

uint32_t generateRandomSeed(byte RandomSeedDelay) {             // Author: Daniel Hienzsch, rheingoldheavy.com
  uint8_t  seedBitValue = 0;
  uint8_t  seedByteValue = 0;
  uint32_t seedWordValue = 0;

  for (uint8_t wordShift = 0; wordShift < 4; wordShift++)     // 4 bytes in a 32 bit word
  {
    for (uint8_t byteShift = 0; byteShift < 8; byteShift++)   // 8 bits in a byte
    {
      for (uint8_t bitSum = 0; bitSum <= 8; bitSum++)         // 8 samples of analog pin
      {
        seedBitValue = seedBitValue + (analogRead(RANDOM) & 0x01);                // Flip the coin eight times, adding the results together
      }
      delay(RandomSeedDelay);     // Delay a milliseconds to allow the pin to fluctuate
      seedByteValue = seedByteValue | ((seedBitValue & 0x01) << byteShift);        // Build a stack of eight flipped coins
      seedBitValue = 0;                                                            // Clear out the previous coin value
    }
    seedWordValue = seedWordValue | (uint32_t) seedByteValue << (8 * wordShift);    // Build a stack of four sets of 8 coins (shifting right creates a larger number so cast to 32bit)
    seedByteValue = 0;                                                             // Clear out the previous stack value
  }
  return (seedWordValue);
}

void CreateChallenge() {
  Serial.println("Generating a random string.");
  uint32_t RandomSeed = generateRandomSeed(2);
  Serial.print("Generated random string: ");
  Serial.println(RandomSeed);
  randomSeed(RandomSeed);

  // ChallResp[0] = '\0';
  // if (ChallResp[0] == 0) {
  //   Serial.println("Character array is empty");
  // }
  ultoa(RandomSeed, ChallResp, 10);
  Serial.print("Character array generated: ");
  Serial.print(ChallResp);
  Serial.print(" is ");
  Serial.print(strlen(ChallResp));
  Serial.println(" chars long.");
  for (uint8_t i = 0; i < 7; i++) {
    // randomSeed(generateRandomSeed(6));
    if (ChallResp[i] == '0') {
      ChallResp[i] = random(49, 58);
    }
    // Serial.print(ChallResp[i]);
  }
  Serial.print("Character array after removing nils: ");
  Serial.println(ChallResp);

  uint8_t NilPosition = random(3, 7);

  Serial.print("Nil position is: ");
  Serial.println(NilPosition);

  ChallResp[NilPosition] = '0';

  Serial.print("Character array after overwriting with 0: ");
  Serial.println(ChallResp);

  strlcpy(ChallResp, ChallResp, NilPosition + 1);

  Serial.print("The right response is: ");
  Serial.println(ChallResp);

  // for (byte i = 0; i < 10; i++) {
  //   Serial.print("Reading from input: ");
  //   Serial.println(analogRead(RANDOM));
  //   delay(300);
  // }
}