/*
Vigenere Cipher encoder / decoder demo
And an excuse to play around with EEPROM memory
 */

#include "vigenereCipher.h"

// -------- Functions --------- //

void printFromEEPROM(char *eepromString) {
  uint8_t letter;
  do {
    letter = eeprom_read_byte((uint8_t *) eepromString);
    transmitByte(letter);
    eepromString++;
  } while (letter);
}

void enterText(char text[]) {
  uint8_t i = 0;
  char letter;
  do {
    letter = receiveByte();
    transmitByte(letter);                                      /* echo */
    text[i] = letter;
    i++;
  } while (!(letter == '\r') && (i < (MAX_TEXT_LENGTH - 1)));
  text[i - 1] = 0;
}

void displayCodes(void) {
  uint8_t i;
  for (i = 0; i < 4; i++) {
    transmitByte(' ');
    transmitByte('0' + i);
    printString(": ");
    printFromEEPROM(codePointers[i]);
    printString("\r\n");
  }
}

void changeCode(char codeBuffer[]) {
  char input;
  char *codeAddress;
  printString(" -- Choose code phrase to replace:\r\n");
  do {
    displayCodes();
    input = receiveByte();
  } while ((input < '0') || (input > '3'));
  codeAddress = codePointers[input - '0'];
  printString(" -- Enter new code: ");
  enterText(codeBuffer);
  eeprom_update_block(codeBuffer, codeAddress, CODE_LEN);
}

void selectCode(char code[]) {
  char input;
  char *codeAddress;
  printFromEEPROM(promptSelectCode);
  do {
    displayCodes();
    input = receiveByte();
  } while ((input < '0') || (input > '3'));
  codeAddress = codePointers[input - '0'];
  eeprom_read_block(code, codeAddress, CODE_LEN);
}

void encodeVigenere(char text[], char code[]) {
  uint8_t codePosition = 0;
  uint8_t textPosition = 0;
  do {
    if (code[codePosition] == 0) {  /* loop when at end of code phrase */
      codePosition = 0;
    }
    text[textPosition] += code[codePosition] - 32;
    if (text[textPosition] > 126) {
      text[textPosition] -= 95;
    }                              /* keeps within printing characters */
    codePosition++;                         /* and move on to the next */
    textPosition++;
  } while (text[textPosition]);     /* until zero at the end of string */
}

void decodeVigenere(char text[], char code[]) {
  uint8_t codePosition = 0;
  uint8_t textPosition = 0;
  do {
    if (code[codePosition] == 0) {
      codePosition = 0;
    }
    if (code[codePosition] > text[textPosition]) {
      text[textPosition] += 95;
    }                              /* keeps within printing characters */
    text[textPosition] -= code[codePosition] - 32;
    codePosition++;
    textPosition++;
  } while (text[textPosition]);
}

int main(void) {
  // -------- Inits --------- //

  char textBuffer[MAX_TEXT_LENGTH];
  char codeString[CODE_LEN];
  char input;
  initUSART();

  // ------ Event loop ------ //
  while (1) {

    // Menu
    printFromEEPROM(welcomeString);
    printFromEEPROM(promptText);
    printString(textBuffer);
    printString("\r\n");
    printFromEEPROM(promptCode);
    printString(codeString);
    printString("\r\n\r\n ---------------------\r\n");
    printFromEEPROM(menuEnterText);
    printFromEEPROM(menuCodeText);
    printFromEEPROM(menuChangeCode);
    printFromEEPROM(menuEncode);
    printFromEEPROM(menuDecode);
    input = receiveByte();

    switch (input) {
    case 'e':                  // encode
      encodeVigenere(textBuffer, codeString);
      break;
    case 'd':                  // decode
      decodeVigenere(textBuffer, codeString);
      break;
    case 'n':                  // new text
      printFromEEPROM(promptTypeText);
      enterText(textBuffer);
      break;
    case 'c':                  // choose code
      selectCode(codeString);
      break;
    case 'x':                  // change code
      changeCode(codeString);
      break;
    }
  }                                                  /* End event loop */
  return 0;                            /* This line is never reached */
}