Using C language, Write code that encrypts and decrypts messages in a manner that is similar to the Nazi enigma machine.Your program should take in 4 command line arguments. The first 3 input arguments should set the positions of each rotor. The rotors act like a secret passcode. The same passcode (rotor positions) are needed for encrypting and decrypting the message. The last input argument should set to either e or d. The value e stands for encrypt and d stands for decrypt.

Basically, you have to fill the " TO DO" spaces of the following given code :

#include  #include  #include  #include  const char LETTERS[27] = {'A','B','C','D','E','F','G','H','I','J', 'K','L','M','N','O','P','Q','R','S','T', 'U','V','W','X','Y','Z', ' '}; const char ROTOR_VALUES[10] = {7, 3, 0, 1, 9, 5, 2, 6, 4, 8}; const int ROTOR_SIZE = 10; const int TEXT_SIZE = 256; int rotorPosition1, rotorPosition2, rotorPosition3; /* findCharIndex: Finds the location(index) of a character in the Letters array * Input: Character to find in Letters Array * Output: Index location in the Letters Array * Note: Returns -1 if not found */ int findCharIndex(char c) { //TO DO: Need to implement this function  return -1; } /* mod: Implements a true modulus function * INPUT: original number (a) and dividor (b) * OUTPUT: remainder * NOTE: Required since in C (%) does not implement true modulus * function for negative remainders */ int mod(int a, int b) { int r = a % b; return r < 0 ? r + b : r; } /* encryptLetter: Returns an encrypted letter (character) * INPUT: unencrypted letter (character) and key * OUTPUT: encrypted letter */ char encryptLetter(char unencrypted, int key){ //TO DO: Need to implement this function return 'A'; } /* decryptLetter: Returns an decrypted letter (character) * INPUT: encrypted letter (character) and key * OUTPUT: decrypted letter */ char decryptLetter(char encrypted, int key){  //TO DO: Need to implement this function return 'A'; } /* getKey: returns key based on current positions of the rotors */ int getKey() { return ROTOR_VALUES[rotorPosition1]+ROTOR_VALUES[rotorPosition2]+ROTOR_VALUES[rotorPosition3]; } /* incrementRotors: Advances rotor positions by one * USAGE: Used after every letter is encrypted or decrypted */ void incrementRotors() { rotorPosition1++; if (rotorPosition1 == ROTOR_SIZE){ rotorPosition1 = 0; rotorPosition2++; } if (rotorPosition2 == ROTOR_SIZE){ rotorPosition2 = 0; rotorPosition3++; } if (rotorPosition3 == ROTOR_SIZE) rotorPosition3 = 0; } int main( int argc, char *argv[] ) { //STEP #1: Get and check Command Line Arguments //TO DO: Implement this step  //STEP #2: Get text string from user char inputText[TEXT_SIZE]; char outputText[TEXT_SIZE]; scanf( "%[^ ]s" , inputText ); //%20 includes spaces printf("Input text supplied is: %s ", inputText); int input_text_size = strlen(inputText) - 1; //minus 1 to ignore char //STEP #3: For each letter, encrypt or decrypt int i=0; for (i=0;i<=input_text_size;i++) {  //TO DO: Implement this step } //STEP #4: Print result outputText[input_text_size+1] = '\0'; printf("Output text: %s ", outputText); return EXIT_SUCCESS; }