#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#include "functions.h"

#define ALPHABET_LENGTH 26
static char ReverseAlphabet[ALPHABET_LENGTH] = {
    'Z','Y','X','W','V','U','T','S','R','Q','P','O','N','M','L','K','J','I','H','G','F','E','D','C','B','A'
};

static char Alphabet[ALPHABET_LENGTH] = {
        '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'
};


char *remove_duplicates(char *table)
{
    char flag[208] = {0};
    int i, j = 0;

    for (i = 0; table[i] != '\0'; i++) {
        if (0 == flag[table[i]]) {
            flag[table[i]] = 1;
            table[j] = table[i];
            j++;
        }
    }
    table[j] = '\0';
    return NULL;
}

int function_encrypt(char *key, char *inFileData, char *outFileName, int size)
{
    FILE *file = fopen(outFileName, "w");

    int maxlen = (int)strlen(key) + ALPHABET_LENGTH;
    char out_data[size + 1];
    char *substitutionTable = (char*)malloc(maxlen);
    if (substitutionTable) {

        // create the following:
        //  'K','E','Y','Z','Y','X','W','V','U','T','S','R','Q','P','O','N','M','L','K','J','I','H','G','F','E','D','C','B','A'
        strcpy(substitutionTable, key);
        strcat(substitutionTable, ReverseAlphabet);

        remove_duplicates(substitutionTable);

        for (int i = 0 ; i < strlen(inFileData); i++) {
                out_data[i] = substitutionTable[inFileData[i] - 'A'];
        }

        out_data[size] = '\0';
        free(substitutionTable);

        int val = fputs(out_data,file);
        if (val >= 0 ) {
            printf("\nSuccess");
            fclose(file);
        }
        else {
            printf("\nFailed");
        }
        return 0;
    }
    return -1; // return error
}

int function_decrypt(char *key, char *inFileData, char *outFileName, int size)
{
    FILE *file = fopen(outFileName, "w");

    int maxlen = (int)strlen(key) + ALPHABET_LENGTH;
    char out_data[size + 1];
    char *substitutionTable = (char*)malloc(maxlen);
    if (substitutionTable) {

        // create the following:
        //  'K','E','Y','Z','Y','X','W','V','U','T','S','R','Q','P','O','N','M','L','K','J','I','H','G','F','E','D','C','B','A'
        strcpy(substitutionTable, key);
        strcat(substitutionTable, ReverseAlphabet);

        remove_duplicates(substitutionTable);

        for (int i = 0 ; i < strlen(inFileData); i++) {
            const char *ptr = strchr(substitutionTable, inFileData[i]);
            if(ptr) {
                int index = ptr - substitutionTable;
                out_data[i] = Alphabet[index];
            }
        }

        out_data[size] = '\0';
        free(substitutionTable);

        int val = fputs(out_data,file);
        if (val >= 0 ) {
            printf("\nSuccess");
            fclose(file);
        }
        else {
            printf("\nFailed");
        }
        return 0;
    }
    return -1; // return error
}