/* FFT1fltr.c */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "FFT1.h"

double  data[FFT_MAX]; /* real part of original data */
double jdata[FFT_MAX]; /* imaginary part of original data */

void display_data( )
{
  int i; 
  
  for (i = 0; i < num_of_data; i++) {
    printf("No.%3d: Re_part =%12.5f, Im_part =%12.5f\n",
	   i,data[i],jdata[i]);
  }
  printf("Enter any key : ");
  (void)getchar( );
  printf("\n");
}

void make_test_data( )
/* Testing data generation (ex. trapzoid-shaped) */
{
  int i, min, max;
  
  num_of_data = 16;
  min = 4;
  max = 12;
  for (i = 0; i < num_of_data; i++) {
    if (min <= i && i < max) {
      data[i] = 100.0;
    } else {
      data[i] = 0.0;
    }
    jdata[i] = 0.0;
  }
}

void lowpass_filtering( )
/* filtering in frequency domain */
{
  int i, max;
  
  /* ex. lowpass filtering */
  max = num_of_data / 4;
  for (i = 0; i < num_of_data; i++) {
    if (max <= i && i <= (num_of_data - max)) {
      data[i] = 0.0;
      jdata[i] = 0.0;
    }
  }
}

main( )
{
  int i, j, k, offset=20;
  char str[65];
  
  make_test_data( );
  printf("Testing data is generated.\n");
  display_data( );
  
  /* FFT */
  FFT1(data, jdata, num_of_data, 1);
  printf("FFT is completed.\n");
  display_data( );
  
  /* Filtering in frequency domain */
  lowpass_filtering( );
  printf("Lowpass filtering is completed.\n");
  display_data( );
  
  /* Inverse FFT */
  FFT1(data, jdata, num_of_data, -1);
  printf("Inverse FFT is completed.\n");
  display_data( );

  for (i = 0; i < num_of_data; i++) {
    str[64] = '\0';
    for (j = 0; j < 64; j++) {
      str[j] = ' ';
    }
    str[offset / 2] = '|';
    if (i >= 4 && i < 12) { 
      str[60] = '@';
    } else {
      str[offset / 2] = '@';
    }
    k = ((int)data[i] + offset) / 2;
    str[k] = '*';
    
    printf("%3d %s\n", i, str);
  }
  printf("\n");
  
  return 0;
}