#include "caesar.h"

static char *alphabet = "abcdefghijklmnopqrstuvwxyz";

void Decrypt(char *text,int shift){

    int i,x;

    for(i=0;i<strlen(text);i++){
        if(isspace(text[i]) != 0 || ispunct(text[i]) != 0 || text[i] == '\n'){
            /*when a space, punctuation character or new line is encountered skip*/
        }
        else{
            text[i] = tolower(text[i]);
            x = (text[i] - 'a' - shift) % 26;
            if (x < 0)
                x -= x;
            text[i] = alphabet[x];
        }
    }
}

void Encrypt(char *text,int shift){

    int i,x;

    for(i=0;i<strlen(text);i++){
        if(isspace(text[i]) != 0 || ispunct(text[i]) != 0 || text[i] == '\n'){
            /*when a space, punctuation character or new line is encountered skip*/

        }
        else{
            text[i] = tolower(text[i]);
            x = (text[i] - 'a' + shift) % 26;
            if (x < 0)
                x -= x;
            text[i] = alphabet[x];
        }
    }
}

void BruteForce(char *str) {
    int i;
    char *text = strdup(str);

    for (i=0;i<ALPHA;i++) {
        Decrypt(text,i+1); /*Shifts it by one every time*/
        printf("%s\n", text);
    }
    free(text);
}

char *OpenFromFile(char *fileIn){
    FILE *fin = fopen(fileIn, "r");
    char *text;

    text = malloc(N * sizeof(char));

    if(fin == NULL){
        fprintf(stderr, "Error, could not open file.\n");
        exit(-1);
    }

    /*read entire file and put it in text*/
    fread(text,N,1,fin);

    fclose(fin);
    return text;
}

void WriteToFile(char *text, char *fileOut){
    FILE *fout = fopen(fileOut, "w");

    if(fout == NULL){
        fprintf(stderr, "Error, could not open file.\n");
        exit(-1);
    }

    printf("%s\n", text);
    fwrite(text,strlen(text),1,fout);

    fclose(fout);
}

void Usage(){
    printf("Usage: caesar <shift> [-e | -d]  [-i] <input_file> [-o] <output_file>\n");
    printf("Usage without known shift: caesar [-b]  [-i] <input_file> [-o] <output_file>\n");
    return;
}

int main(int argc, char **argv){
    char *text;

    if (argc != 7 && argc != 6 ){
            Usage();
            exit(0);
        }
    else if(strcmp(argv[3],"-i") == 0 && strcmp(argv[5],"-o") == 0){

        text = OpenFromFile(argv[4]);
        printf("%s\n", text);
        /*encrypt*/
        if (strcmp(argv[2],"-e") == 0){
            Encrypt(text,atoi(argv[1]));

        }
        /*decrypt*/
        else if (strcmp(argv[2],"-d") == 0){
            Decrypt(text,atoi(argv[1]));
        }
        else{
            Usage();
            exit(0);
        }

        WriteToFile(text,argv[6]);
    }

    else if(strcmp(argv[2],"-i") == 0 && strcmp(argv[4],"-o") == 0){

        text = OpenFromFile(argv[3]);

        /*bruteforce*/
        if(strcmp(argv[1],"-b") == 0){
            BruteForce(argv[3]);
        }
        else{
            Usage();
            exit(0);
        }

        WriteToFile(text,argv[5]);
    }
    else{
        Usage();
        exit(0);
    }

    return 0;
}