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

#define MAXPOS 100
#define MAXLINES 1000

/*
 *      Loads positions file into an array.
 *      returns positions count.
 */
int loadpos(const char *fname, int pos[][2])
{
  FILE *pfile;
  char buffer[128];
  int count = 0;

  pfile = fopen(fname, "r");

  while(count < MAXPOS && NULL != fgets(buffer, 128, pfile))
  {
        if (sscanf(buffer, "%d:%d", &pos[count][0], &pos[count][1]) == 2)
                count ++;
  }

  fclose(pfile);
  return count;
}

/*
 *      Loads book lines into an array.
 *      returns lines count.
 */
int loadbook(const char *fname, char book[][128])
{
  FILE *bfile;
  int count = 0;

  bfile = fopen(fname, "r");

  while(count < MAXLINES && NULL != fgets(book[count], 128, bfile))
        count++;

  fclose(bfile);
  return count;
}

void printpos(int count, int pos[][2])
{
  int i;
  for (i = 0; i < count; i++)
        printf("%d:%d\n", pos[i][0], pos[i][1]);
}

void printbook(int lines, char book[][128])
{
  int i;
  for (i = 0; i < lines; i++)
        printf("%s", book[i]);
}

int main(int argc, char *argv[])
{
  int i, count, lines, pos[MAXPOS][2];
  char book[MAXLINES][128];
  int outofbound = 0;

  char output[MAXPOS + 1];

  if (argc != 3)
        return 1;

  count = loadpos(argv[1], pos);

  printpos(count, pos);

  lines = loadbook(argv[2], book);

  printbook(lines, book);

  printf("\nloaded %d lines from book...\n", lines);

  for (i = 0; i < count; i++)
  {
        if (pos[i][0] > lines || strlen(book[pos[i][0] - 1]) - 1 < pos[i][1])
        {
                outofbound = 1;
                break;
        }
        output[i] = book[pos[i][0] - 1][pos[i][1] - 1];
  }
  output[i] = '\0';

  if (outofbound)
        printf("Some positions were out of bound in the text...\nPartially decoded: %s\n", output);
  else
        printf("decoded: %s\n", output);

  return 0;
}