// Only allowed for key:
// !"#$%&'()*+,-./0123456789:abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ

// char source[] = "ABCDEFGHIJK/*-+,_/();LMNO.PQRST,UVWX,YZabcpq!SWrstu,vwxyz,01789";
char source[] = "tNM5Rp6q:4nTK0zave.%BN)U(mGeoT-7TIFYhH-2TMlJ+OB0Z'Z'd'G%tTM!#*Z1NMl88m";
// char source[] = "ppgrocy.ddns.info,211,login,Password,/path/";
// const String KEY = "SlEPY1CE";
// const char key[] = "SlEPY1CE";
// const PROGMEM char key[] = "tNM5Rp6q:4nTK0zave.%BN)U(mGeoT-7TIFYhH-2TMlJ+OB0Z'Z'd'G%tTM!#*Z1NMl88m";
const PROGMEM char key[] = "67Uo3BwuJK+9Zm5.v1lSjbVs04M%(e&Y8dDQENX\"L:Cx!Gkp*TczqRiA'2)PnyfIagrWOt";
char compare[100];

void setup() {
  Serial.begin(115200);

  if (! CheckKey()) {
    Serial.print("Can't continue with a key containing not allowed characters!");
    while(1) ;
  }

  /*
  GenerateSource(12, 64);
  Serial.print("Plain Text: ");
  Serial.println(source);
  strcpy(compare,source);
  vigenere_cipher(source, true);
  // String encryption_result = vigenere_cipher(source, true);

  Serial.print("Encryption: ");
  Serial.println(source);
  // Serial.println(encryption_result);
  vigenere_cipher(source, false);
  // String decryption_result = vigenere_cipher(source, false);
  Serial.print("Decryption: ");
  Serial.println(source);
  // Serial.println(decryption_result);
  Serial.println();
  if (strcmp(compare, source) != 0) {
    Serial.print("Encoding - decoding NOT equal!");
    while(1) ;
  }
  */
}

void loop() {
  GenerateSource(12, 64);
  Serial.print("Plain Text: ");
  Serial.println(source);
  strcpy(compare,source);
  vigenere_cipher(source, true);

  Serial.print("Encryption: ");
  Serial.println(source);
  // Serial.println(encryption_result);
  vigenere_cipher(source, false);
  Serial.print("Decryption: ");
  Serial.println(source);
  Serial.println();
  if (strcmp(compare, source) != 0) {
    Serial.print("Encoding - decoding NOT equal!");
    while(1) ;
  }

  // delay(500);

}

void vigenere_cipher(char* text, bool is_encryption) {
  uint8_t keylen = strlen(key);
  // Serial.print("Key length: ");
  // Serial.println(keylen);
  uint8_t ascii, text_index, key_index, result_index;
  char character;
  for (int i = 0; i < strlen(text); i++) {
    ascii = text[i];
    text_index = (text[i] % 32) ;
    key_index = (pgm_read_byte(&key[i % keylen]) % 32) ;
    if (is_encryption)
      result_index = (text_index + key_index) % 32;
    else
      result_index = (text_index - key_index + 32) % 32;

    if (ascii >= '`' && ascii <= 127) character = result_index + '`';
    else if (ascii >= '@' && ascii <= '_') character = result_index + '@';
    else if (ascii >= ' ' && ascii <= '?') character = result_index + ' ';
    else character = ascii;
    text[i] = character;
  }
  // return;
}

void GenerateSource(uint8_t Minlength, uint8_t Maxlength) {
  uint8_t length;
  uint8_t i;
  randomSeed(analogRead(A0));
  length = random(Minlength, Maxlength + 1);
  for (i = 0; i < length; i++) {
		source[i] = random(32, 128);
	}
  source[i] = '\0';
}

bool CheckKey() {
  char KeyChar;
  bool AllClear = true;
  for (int i = 0; i < strlen(key); i++) {
    KeyChar = pgm_read_byte(&key[i]);
      if (!((KeyChar >= 'a' && KeyChar <= 'z') || (KeyChar >= 'A' && KeyChar <= 'Z') || (KeyChar >= '!' && KeyChar <= ':'))){
        if(AllClear){
          Serial.print("Invalid Character(s) in the Key: ");
          AllClear = false;
        }
        Serial.print(KeyChar); 
        Serial.print(F(" ")); 
      }
  }
  if(! AllClear) Serial.println();
  return AllClear; 
}