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

void DecompressFile(unsigned char *buf, int FileLength, int p, int q, unsigned char *name);

// argv[0] - Program name.
// argv[1] - File to be read.
// argv[2] - File to be written.
// argv[3] - Compression argument.
// argv[4] - First value index.
// argv[5] - Second value index.

int main(int argc, char *argv[])
{
  FILE *fp;
  int FileLength;
  unsigned char *fbuf;

  if(argc<5)  // If there's less than 5 arguments, exit the program.
  {
            fprintf(stderr,"Not enough arguments.");
            exit(1);
  }
  if((fp = fopen(argv[1],"rb"))== NULL)
  {
            fprintf(stderr,"Invalid file.");
            exit(1);
  }
  fseek(fp, 0, SEEK_END);
  FileLength = ftell(fp);
  rewind(fp);
  if ((fbuf = (unsigned char*) malloc(FileLength)) == NULL)
  {
        fprintf(stderr, "Not enough memory.");
        exit(1);
  }
  fread(fbuf, sizeof(unsigned char), FileLength, fp);
  fclose(fp);
  char *ptr;
  int Ind1 = strtoul(argv[4], &ptr, 16);
  int Ind2 = strtoul(argv[5], &ptr, 16);

  if(*argv[3]=='c')
  {
           // CompressFile(fbuf, FileLength);
  }
  else if(*argv[3]=='d')
  {
            DecompressFile(fbuf, FileLength, Ind1, Ind2, argv[2]);
  }
  else
  {         // Should it come across an unknown character type...
            fprintf(stderr,"Invalid compression character type.");
            exit(1);
  }
  puts("File compressed/decompressed successfully with no errors.");
  free(fbuf);
  return 0;
}

void DecompressFile(unsigned char *buf, int FileLength, int p, int q, unsigned char *name){
  int i = 0;       // Buffer increment counter.
  int b;           // Loop decrement counter.
  unsigned char c; // Stores the compressed byte.
  uint32_t d;           // Stores the decompressed byte.
  char *fbuf;

  if ((fbuf = (unsigned char*) malloc(FileLength)) == NULL)
  {
        fprintf(stderr, "Not enough memory (2).");
        exit(1);
  }
  FILE *fp;
  fp = fopen(name,"wb");
  while(i<FileLength)
  {
         c = 0;
         d = 0;
         for(b=7; b>=0; b--)
         {
               c = buf[i];
               if((c >> b) & 1)
               {
                    d = d|(q << (b * 4));
               }
               else
               {
                    d = d|(p << (b * 4));
               }
         }

         fbuf[i] = d;

  //       printf("%d",d);

         i+=4;
  }
  i = 0;
  while(i!=(FileLength*4))
  {
  //fwrite(fbuf, 4, FileLength/4, fp);
       fprintf(fp,"%c", fbuf[i]);
       i++;
  }
  free(fbuf);
  fclose(fp);
  return;
}