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

int main( int argc, char *argv[])
{
int pindex=0;
long lsize=0,i=0;
char password[1024];
int plen;
char filename[64];
char nfilename[64];

if(argc!=4) // there should be exavtly 4 parameters including tar2
{
printf("Not enough arguments!\n");
return 0;
}

strcpy(filename,argv[1]);
FILE* f = fopen(filename, "rb"); // opening file for reading
fseek(f,0,SEEK_END);
lsize = ftell(f);
rewind(f);

// taking argument [3] as the password
strcpy(password,argv[3]);
plen = strlen(password);

unsigned char xored;

// for encrypting
if(strcmp(argv[2],"-e")==0)
{
printf("encrypting the file %s \n", filename);
strcat(filename,".tar2");
FILE* fout = fopen(filename, "wb");
while(i<lsize){
unsigned char first = fgetc(f); // reading byte from file
i++;
xored = first^(password[pindex]);
fputc(xored,fout); // writing to output file
pindex = (pindex+1)%plen;
}
fclose(fout);
}

// for decrypting
if(strcmp(argv[2],"-d")==0)
{
printf("decrypting the file %s \n", filename);
int file_len = strlen(filename);
int i;
pindex = plen-1;
for(i=0; i<file_len-5; i++)
{
nfilename[i] = filename[i];
}
nfilename[i]='\0';
FILE* fout = fopen(nfilename, "wb");
while(i<lsize){
unsigned char first = fgetc(f);

i++;
xored = first^password[pindex];
fputc(xored,fout);
pindex = pindex-1;
if(pindex<0)
{
pindex = plen-1;
}
}
fclose(fout);
}
fclose(f);

return 0;
}