#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "dspl.h"

/* Filter order */
#define ORD  3

/* Frequency response vector size */
#define N    1000


int main(int argc, char* argv[])
{
    void* hdspl;    /* DSPL handle */
    void* hplot;    /* GNUPLOT handle */

    /* Load DSPL functions */
    hdspl = dspl_load();

    /* H(s) numerator coefficients vector  */
    double a[ORD+1]; 
    
    /* H(s) denominator coefficients vector */
    double b[ORD+1]; 
    
    /* Magnitude ripple from 0 to 1 rad/s */
    double Rp = 1.0; 
    
    /* Angular frequency (rad/s) */
    double w[N];
    
    /* Filter Magnitude (dB) */
    double mag[N];
    
    /* Phase response */
    double phi[N];
    
    /* Group delay */
    double tau[N];


    int k;

    /* H(s) coefficients calculation */
    int res = butter_ap(Rp, ORD, b, a);
    if(res != RES_OK)
        printf("error code = 0x%8x\n", res);

    /* Print H(s) coefficients */
    for(k = 0; k < ORD+1; k++)
        printf("b[%2d] = %9.3f a[%2d] = %9.3f\n", k, b[k], k, a[k]);

    /* Frequency in logarithmic scale from 0.01 to 100 rad/s */
    logspace(-2.0, 2.0, N , DSPL_SYMMETRIC, w);

    /* Filter frequency parameter calculation */
    filter_freq_resp(b, a, ORD, w, N,
        DSPL_FLAG_LOGMAG|DSPL_FLAG_UNWRAP|DSPL_FLAG_ANALOG,
                mag, phi, tau);

    /* Write Magnitude, phase response and group delay to the files */
    writetxt(w, mag, N, "dat/butter_ap_test_mag.txt");
    writetxt(w, phi, N, "dat/butter_ap_test_phi.txt");
    writetxt(w, tau, N, "dat/butter_ap_test_tau.txt");

    /* plotting by GNUPLOT */
    gnuplot_create(argc, argv, 920, 260, "img/butter_ap_test.png", &hplot);
    gnuplot_cmd(hplot, "set logscale x");
    gnuplot_cmd(hplot, "unset key");
    gnuplot_cmd(hplot, "set grid");
    gnuplot_cmd(hplot, "set xlabel 'frequency, rad/s'");
    gnuplot_cmd(hplot, "set multiplot layout 1,3 rowsfirst");
    gnuplot_cmd(hplot, "set ylabel 'Magnitude, dB'");
    gnuplot_cmd(hplot, "set yrange [-100:5]");
    gnuplot_cmd(hplot, "plot 'dat/butter_ap_test_mag.txt' with lines");
    gnuplot_cmd(hplot, "set ylabel 'Phase response, rad'");
    gnuplot_cmd(hplot, "unset yrange");
    gnuplot_cmd(hplot, "plot 'dat/butter_ap_test_phi.txt' with lines");
    gnuplot_cmd(hplot, "set ylabel 'Groupdelay, sec'");
    gnuplot_cmd(hplot, "unset yrange");
    gnuplot_cmd(hplot, "plot 'dat/butter_ap_test_tau.txt' with lines");
    gnuplot_cmd(hplot, "unset multiplot");
    gnuplot_close(hplot);

    /* free dspl handle */
    dspl_free(hdspl);

    return res;
}