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

int main(int argc, char **argv)
{
    FILE *infile;
    FILE *outfile;
    char ch = '\0';
    char newch = '\0';
    int x = 0;
    int pwsMask = 0;
    int Magic = 1163;
    int r = 0;

    if(argc != 5){
        printf("The syntax of the command is incorrect.\n");
        return 0;
    }
    else{
        if(argv[3][1] != 'p'){
            printf("You need to include a password.\n");
            return 0;
        }
        //Start reading input file name.
        infile = fopen(argv[1],"rb");

        if(infile == NULL){
            printf("Unable to open input file name.\n\%s\n",argv[1]);
            return 0;
        }
        //See if we can write output file
        outfile = fopen(argv[2],"wb");

        if(outfile == NULL){
            printf("Unable to write output file name.\n\%s\n",argv[2]);
            return 0;
        }

        //Build a sum of all the chars in the password.
        while(x < strlen(argv[4])){
            pwsMask+= (int)argv[4][x];
            x++;
        }
        //Mask pwsMask with Magic and multiply by the length of the password.
        pwsMask = (pwsMask ^ Magic) * strlen(argv[4]);

        //Reset x
        x = 0;

        //Start reading and encoding the file data.
        while(!feof(infile)){
            //Read input char
            ch = fgetc(infile);
            //If not at end of the input file start encrypting.
            if(!feof(infile)){
                //Get random number from pwsMask and MOD by 255
                r = rand() * pwsMask % 0xff;
                //XOR ch with r
                newch = (ch ^ r);
                //Write to the output file name.
                fputc(newch,outfile);
                //INC x
                x++;
            }
        }
        //Close both file handles
        fclose(outfile);
        fclose(infile);
    }
    return 0;
}