/*
  COSC 350
  February 4, 1998

*/
#include <stdlib.h>
#include <stdio.h>
#include <alloc.h>
#include <ctype.h>

#define  AlphSize  27

int char_to_index(char ch)
{
  if ((ch == '_') || (ch == '*'))
  {
    return (int)26;
  }
  else if ((ch >= 'A') && (ch <= 'Z'))
  {
    return (int)(ch - 'A');
  }
/*  else
  {
    fprintf(stderr, "Invalid character in file.\n");
    exit(1);
  }*/
  return 0;
}

int main(int argc, char *argv[])
{
  FILE 	*infile;
  int  	period, counter;
  long 	**Counts, *Tally, N;
  long 	Total[AlphSize];
  char 	next, error;
  int  	i, j;
  double IC; /* Index of Coincidence */
  double total;
  double temp;
  double f;
  int totalchars;
  error = 0;

  if (argc > 3)
  {
    error = 1;
  }
  else if ((infile = fopen(argv[1], "r")) == NULL)
  {
    error = 1;
  }
  else if ((period = atoi(argv[2])) <= 0)
  {
    error = 1;
  }

  if (error)
  {
    fprintf(stderr, "Usage: freq input_file period\n\n");
    fprintf(stderr, "  where input_file is the name of the file containing the data, and\n");
    fprintf(stderr, "  period is the number of alphabets to count.\n\n");
    fprintf(stderr, "The results are placed on standard output.\n\n");
    fprintf(stderr, "For example:\n");
    fprintf(stderr, "             freq cipher.txt 3 >results\n");
    exit(1);
  }

  fprintf(stderr, "Initializing arrays...");

  if ((Counts = (long **)malloc(period * sizeof(long *))) == NULL)
  {
    error = 1;
  }
  for (i=0; i<period; i++)
  {
    if ((Counts[i] = (long *)calloc(AlphSize, sizeof(long))) == NULL)
    {
      error = 1;
    }
  }
  if ((Tally = (long *)calloc(period, sizeof(long))) == NULL)
  {
    error = 1;
  }
  if (error)
  {
    fprintf(stderr, "Error allocating space arrays.\n");
    exit(1);
  }

  fprintf(stderr, "done.\n");

  fprintf(stderr, "Reading data...");

  counter = 0;
  while (1)
  {
    next = toupper(getc(infile));
    if (feof(infile))
    {
      break;
    }
    next = char_to_index(next);
    Counts[counter][next]++;
    Tally[counter]++;
    counter++;
    if (counter == period)
    {
      counter = 0;
    }
  }
  fclose(infile);

  /* Calculate number of characters read. */
  N = 0;
  for (i=0; i<period; i++)
  {
    N += Tally[i];
  }
  fprintf(stderr, "done.\n");

  fprintf(stderr, "Calculating totals...");
  /* Calculate totals for each character in alphabet */
  totalchars = 0;
  for (i=0; i<AlphSize; i++)
  {
    Total[i] = 0;
    for (j=0; j<period; j++)
    {
      Total[i] += Counts[j][i];
    }
    totalchars += Total[i];
  }
  fprintf(stdout, "\n");
  fprintf(stdout, "     ");
  for (i=1; i<=period; i++)
  {
    fprintf(stdout, "%8d ", i);
  }
  fprintf(stdout, "\n");
  fprintf(stdout, "----");
  for (i=1; i<=period; i++)
  {
    fprintf(stdout, "---------");
  }
  fprintf(stdout, "\n");
  for (i=0; i<AlphSize; i++)
  {
    if (i == 26)
    {
      fprintf(stdout, "%c    ", '_');
    }
    else
    {
      fprintf(stdout, "%c    ", 'A' + i);
    }
    for (j=0; j<period; j++)
    {
      fprintf(stdout, "%8d ", (Counts[j][i]));
    }
    fprintf(stdout, "\n");
  }
  fprintf(stdout, "----");
  for (i=1; i<=period; i++)
  {
    fprintf(stdout, "---------");
  }
  fprintf(stdout, "\n");
  fprintf(stderr, "IC:  ");
  for (i=0; i<period; i++)
  {
    total = 0;
    f = 0;
    for(j=0; j<AlphSize-1; j++)
    {
       f = (long)(Counts[i][j]);
       total+=(f*(f-1));
    }
   // fprintf(stdout,"%8.5f",total);
   // fprintf(stdout,"\n");
    temp = (long)(N/period)*((N/period)-1);
    //fprintf(stdout,"%8.4f ",temp);
    //fprintf(stdout,"%8.4f ",total);
    //fprintf(stdout,"\n");
    fprintf(stdout,"%8.5f ",total/temp);
    //fprintf(stdout,"\n");
  }
  fprintf(stdout,"\n");
  fprintf(stderr, "done.\n");
   // fprintf(stdout,"%8d ",N);
   //fprintf(stdout,"\n");
  /* Calculate index of coincidence */
  /* fprintf(stderr, "Calculating index of coincidence..."); */
  IC = 0.0;
  for (i=0; i<AlphSize; i++)
  {
    IC += (double)(Total[i] * (Total[i] - 1));
  }
  IC /= (double)(N * (N - 1));
  fprintf(stdout, "IC for entire file:  %8.6f\n", IC);
  fprintf(stdout, "----");
  for (i=1; i<=period; i++)
  {
    fprintf(stdout, "---------");
  }
  fprintf(stdout, "\n");

  fprintf(stderr, "done.\n");

  return 0;
}