/*
 This file is part of program wsprd, a detector/demodulator/decoder
 for the Weak Signal Propagation Reporter (WSPR) mode.
 
 File name: wsprd.c
 
 Copyright 2001-2015, Joe Taylor, K1JT
 
 Much of the present code is based on work by Steven Franke, K9AN,
 which in turn was based on earlier work by K1JT.
 
 Copyright 2014-2015, Steven Franke, K9AN
 
 License: GNU GPL v3
 
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include <stdint.h>
#include <time.h>
#include <fftw3.h>

#include "fano.h"
#include "wsprd_utils.h"

#define max(x,y) ((x) > (y) ? (x) : (y))
// Possible PATIENCE options: FFTW_ESTIMATE, FFTW_ESTIMATE_PATIENT,
// FFTW_MEASURE, FFTW_PATIENT, FFTW_EXHAUSTIVE
#define PATIENCE FFTW_ESTIMATE
fftw_plan PLAN1,PLAN2,PLAN3;

unsigned char pr3[162]=
{1,1,0,0,0,0,0,0,1,0,0,0,1,1,1,0,0,0,1,0,
    0,1,0,1,1,1,1,0,0,0,0,0,0,0,1,0,0,1,0,1,
    0,0,0,0,0,0,1,0,1,1,0,0,1,1,0,1,0,0,0,1,
    1,0,1,0,0,0,0,1,1,0,1,0,1,0,1,0,1,0,0,1,
    0,0,1,0,1,1,0,0,0,1,1,0,1,0,1,0,0,0,1,0,
    0,0,0,0,1,0,0,1,0,0,1,1,1,0,1,1,0,0,1,1,
    0,1,0,0,0,1,1,1,0,0,0,0,0,1,0,1,0,0,1,1,
    0,0,0,0,0,0,0,1,1,0,1,0,1,1,0,0,0,1,1,0,
    0,0};

unsigned long nr;

//***************************************************************************
unsigned long readc2file(char *ptr_to_infile, double *idat, double *qdat,
                         double *freq, int *wspr_type)
{
    float buffer[2*65536];
    double dfreq;
    int i,ntrmin;
    char *c2file[15];
    FILE* fp;
    
    fp = fopen(ptr_to_infile,"rb");
    if (fp == NULL) {
        fprintf(stderr, "Cannot open data file '%s'\n", ptr_to_infile);
        return 1;
    }
    unsigned long nread=fread(c2file,sizeof(char),14,fp);
    nread=fread(&ntrmin,sizeof(int),1,fp);
    nread=fread(&dfreq,sizeof(double),1,fp);
    *freq=dfreq;
    nread=fread(buffer,sizeof(float),2*45000,fp);
    
    *wspr_type=ntrmin;
    
    for(i=0; i<45000; i++) {
        idat[i]=buffer[2*i];
        qdat[i]=-buffer[2*i+1];
    }
    
    if( nread == 2*45000 ) {
        return nread/2;
    } else {
        return 1;
    }
}

//***************************************************************************
unsigned long readwavfile(char *ptr_to_infile, int ntrmin, double *idat, double *qdat )
{
    unsigned long i, j, npoints;
    int nfft1, nfft2, nh2, i0;
    double df;
    
    nfft2=46080; //this is the number of downsampled points that will be returned
    nh2=nfft2/2;
    
    if( ntrmin == 2 ) {
        nfft1=nfft2*32;      //need to downsample by a factor of 32
        df=12000.0/nfft1;
        i0=1500.0/df+0.5;
        npoints=114*12000;
    } else if ( ntrmin == 15 ) {
        nfft1=nfft2*8*32;
        df=12000.0/nfft1;
        i0=(1500.0+112.5)/df+0.5;
        npoints=8*114*12000;
    } else {
        fprintf(stderr,"This should not happen\n");
        return 1;
    }
    
    double *realin;
    fftw_complex *fftin, *fftout;
    
    FILE *fp;
    short int *buf2;
    buf2 = malloc(npoints*sizeof(short int));
    
    fp = fopen(ptr_to_infile,"rb");
    if (fp == NULL) {
        fprintf(stderr, "Cannot open data file '%s'\n", ptr_to_infile);
        return 1;
    }
    nr=fread(buf2,2,22,fp);            //Read and ignore header
    nr=fread(buf2,2,npoints,fp);       //Read raw data
    fclose(fp);
    
    realin=(double*) fftw_malloc(sizeof(double)*nfft1);
    fftout=(fftw_complex*) fftw_malloc(sizeof(fftw_complex)*nfft1);
    PLAN1 = fftw_plan_dft_r2c_1d(nfft1, realin, fftout, PATIENCE);
    
    for (i=0; i<npoints; i++) {
        realin[i]=buf2[i]/32768.0;
    }
    
    for (i=npoints; i<nfft1; i++) {
        realin[i]=0.0;
    }
    
    free(buf2);
    fftw_execute(PLAN1);
    fftw_free(realin);
    
    fftin=(fftw_complex*) fftw_malloc(sizeof(fftw_complex)*nfft2);
    
    for (i=0; i<nfft2; i++) {
        j=i0+i;
        if( i>nh2 ) j=j-nfft2;
        fftin[i][0]=fftout[j][0];
        fftin[i][1]=fftout[j][1];
    }
    
    fftw_free(fftout);
    fftout=(fftw_complex*) fftw_malloc(sizeof(fftw_complex)*nfft2);
    PLAN2 = fftw_plan_dft_1d(nfft2, fftin, fftout, FFTW_BACKWARD, PATIENCE);
    fftw_execute(PLAN2);
    
    for (i=0; i<nfft2; i++) {
        idat[i]=fftout[i][0]/1000.0;
        qdat[i]=fftout[i][1]/1000.0;
    }
    
    fftw_free(fftin);
    fftw_free(fftout);
    return nfft2;
}

//***************************************************************************
void sync_and_demodulate(double *id, double *qd, long np,
                         unsigned char *symbols, float *f1, float fstep,
                         int *shift1, int lagmin, int lagmax, int lagstep,
                         float *drift1, int symfac, float *sync, int mode)
{
    /***********************************************************************
     * mode = 0: no frequency or drift search. find best time lag.          *
     *        1: no time lag or drift search. find best frequency.          *
     *        2: no frequency or time lag search. calculate soft-decision   *
     *           symbols using passed frequency and shift.                  *
     ************************************************************************/
    
    float dt=1.0/375.0, df=375.0/256.0, fbest=0.0;
    int i, j, k;
    double pi=4.*atan(1.0),twopidt;
    float f0=0.0,fp,fplast=-10000.0,ss;
    int lag;
    
    double i0[162],q0[162],i1[162],q1[162],i2[162],q2[162],i3[162],q3[162];
    double p0,p1,p2,p3,cmet,totp,syncmax,fac;
    double c0[256],s0[256],c1[256],s1[256],c2[256],s2[256],c3[256],s3[256];
    double dphi0, cdphi0, sdphi0, dphi1, cdphi1, sdphi1, dphi2, cdphi2, sdphi2,
    dphi3, cdphi3, sdphi3;
    float fsum=0.0, f2sum=0.0, fsymb[162];
    int best_shift = 0, ifreq;
    int ifmin=0, ifmax=0;
    
    syncmax=-1e30;
    if( mode == 0 ) {ifmin=0; ifmax=0; fstep=0.0; f0=*f1;}
    if( mode == 1 ) {lagmin=*shift1;lagmax=*shift1;ifmin=-5;ifmax=5;f0=*f1;}
    if( mode == 2 ) {lagmin=*shift1;lagmax=*shift1;ifmin=0;ifmax=0;f0=*f1;}
    
    twopidt=2*pi*dt;
    for(ifreq=ifmin; ifreq<=ifmax; ifreq++) {
        f0=*f1+ifreq*fstep;
        for(lag=lagmin; lag<=lagmax; lag=lag+lagstep) {
            ss=0.0;
            totp=0.0;
            for (i=0; i<162; i++) {
                fp = f0 + ((float)*drift1/2.0)*((float)i-81.0)/81.0;
                if( i==0 || (fp != fplast) ) {  // only calculate sin/cos if necessary
                    dphi0=2*pi*(fp-1.5*df)*dt;
                    cdphi0=cos(dphi0);
                    sdphi0=sin(dphi0);
                    
                    dphi1=twopidt*(fp-0.5*df);
                    cdphi1=cos(dphi1);
                    sdphi1=sin(dphi1);
                    
                    dphi2=twopidt*(fp+0.5*df);
                    cdphi2=cos(dphi2);
                    sdphi2=sin(dphi2);
                    
                    dphi3=twopidt*(fp+1.5*df);
                    cdphi3=cos(dphi3);
                    sdphi3=sin(dphi3);
                    
                    c0[0]=1; s0[0]=0;
                    c1[0]=1; s1[0]=0;
                    c2[0]=1; s2[0]=0;
                    c3[0]=1; s3[0]=0;
                    
                    for (j=1; j<256; j++) {
                        c0[j]=c0[j-1]*cdphi0 - s0[j-1]*sdphi0;
                        s0[j]=c0[j-1]*sdphi0 + s0[j-1]*cdphi0;
                        c1[j]=c1[j-1]*cdphi1 - s1[j-1]*sdphi1;
                        s1[j]=c1[j-1]*sdphi1 + s1[j-1]*cdphi1;
                        c2[j]=c2[j-1]*cdphi2 - s2[j-1]*sdphi2;
                        s2[j]=c2[j-1]*sdphi2 + s2[j-1]*cdphi2;
                        c3[j]=c3[j-1]*cdphi3 - s3[j-1]*sdphi3;
                        s3[j]=c3[j-1]*sdphi3 + s3[j-1]*cdphi3;
                    }
                    fplast = fp;
                }
                
                i0[i]=0.0; q0[i]=0.0;
                i1[i]=0.0; q1[i]=0.0;
                i2[i]=0.0; q2[i]=0.0;
                i3[i]=0.0; q3[i]=0.0;
                
                for (j=0; j<256; j++) {
                    k=lag+i*256+j;
                    if( (k>0) & (k<np) ) {
                        i0[i]=i0[i] + id[k]*c0[j] + qd[k]*s0[j];
                        q0[i]=q0[i] - id[k]*s0[j] + qd[k]*c0[j];
                        i1[i]=i1[i] + id[k]*c1[j] + qd[k]*s1[j];
                        q1[i]=q1[i] - id[k]*s1[j] + qd[k]*c1[j];
                        i2[i]=i2[i] + id[k]*c2[j] + qd[k]*s2[j];
                        q2[i]=q2[i] - id[k]*s2[j] + qd[k]*c2[j];
                        i3[i]=i3[i] + id[k]*c3[j] + qd[k]*s3[j];
                        q3[i]=q3[i] - id[k]*s3[j] + qd[k]*c3[j];
                    }
                }
                p0=i0[i]*i0[i] + q0[i]*q0[i];
                p1=i1[i]*i1[i] + q1[i]*q1[i];
                p2=i2[i]*i2[i] + q2[i]*q2[i];
                p3=i3[i]*i3[i] + q3[i]*q3[i];
                
                p0=sqrt(p0);
                p1=sqrt(p1);
                p2=sqrt(p2);
                p3=sqrt(p3);
                
                totp=totp+p0+p1+p2+p3;
                cmet=(p1+p3)-(p0+p2);
                ss=ss+cmet*(2*pr3[i]-1);
                if( mode == 2) {                 //Compute soft symbols
                    if(pr3[i]) {
                        fsymb[i]=p3-p1;
                    } else {
                        fsymb[i]=p2-p0;
                    }
                }
            }
            
            if( ss/totp > syncmax ) {          //Save best parameters
                syncmax=ss/totp;
                best_shift=lag;
                fbest=f0;
            }
        } // lag loop
    } //freq loop
    
    if( mode <=1 ) {                       //Send best params back to caller
        *sync=syncmax;
        *shift1=best_shift;
        *f1=fbest;
        return;
    }
    
    if( mode == 2 ) {
        *sync=syncmax;
        for (i=0; i<162; i++) {              //Normalize the soft symbols
            fsum=fsum+fsymb[i]/162.0;
            f2sum=f2sum+fsymb[i]*fsymb[i]/162.0;
        }
        fac=sqrt(f2sum-fsum*fsum);
        for (i=0; i<162; i++) {
            fsymb[i]=symfac*fsymb[i]/fac;
            if( fsymb[i] > 127) fsymb[i]=127.0;
            if( fsymb[i] < -128 ) fsymb[i]=-128.0;
            symbols[i]=fsymb[i] + 128;
        }
        return;
    }
    return;
}

//***************************************************************************
void usage(void)
{
    printf("Usage: wsprd [options...] infile\n");
    printf("       infile must have suffix .wav or .c2\n");
    printf("\n");
    printf("Options:\n");
    printf("       -a <path> path to writeable data files, default=\".\"\n");
    printf("       -e x (x is transceiver dial frequency error in Hz)\n");
    printf("       -f x (x is transceiver dial frequency in MHz)\n");
    // blanking is not yet implemented. The options are accepted for compatibility
    // with development version of wsprd.
    //    printf("       -t n (n is blanking duration in milliseconds)\n");
    //    printf("       -b n (n is pct of time that is blanked)\n");
    printf("       -H do not use (or update) the hash table\n");
    printf("       -m decode wspr-15 .wav file\n");
    printf("       -n write noise estimates to file noise.dat\n");
    printf("       -q quick mode - doesn't dig deep for weak signals\n");
    printf("       -s slow mode - much slower, yields a few more decodes\n");
    printf("       -v verbose mode\n");
    printf("       -w wideband mode - decode signals within +/- 150 Hz of center\n");
    printf("       -z x (x is fano metric table bias, default is 0.42)\n");
}

//***************************************************************************
int main(int argc, char *argv[])
{
    extern char *optarg;
    extern int optind;
    int i,j,k;
    unsigned char *symbols, *decdata;
    signed char message[]={-9,13,-35,123,57,-39,64,0,0,0,0};
    char *callsign,*grid,*grid6, *call_loc_pow, *cdbm;
    char *ptr_to_infile,*ptr_to_infile_suffix;
    char *data_dir=NULL;
    char wisdom_fname[200],all_fname[200],spots_fname[200];
    char timer_fname[200],hash_fname[200];
    char uttime[5],date[7];
    int c,delta,maxpts=65536,verbose=0,quickmode=0,writenoise=0,usehashtable=1,wspr_type=2;
    int shift1, lagmin, lagmax, lagstep, worth_a_try, not_decoded;
    unsigned int nbits;
    unsigned int npoints, metric, maxcycles, cycles, maxnp;
    float df=375.0/256.0/2;
    float freq0[200],snr0[200],drift0[200],sync0[200];
    int shift0[200];
    float dt=1.0/375.0, dt_print;
    double dialfreq_cmdline=0.0, dialfreq, freq_print;
    float dialfreq_error=0.0;
    float fmin=-110, fmax=110;
    float f1, fstep, sync1, drift1, tblank=0, fblank=0;
    double *idat, *qdat;
    clock_t t0,t00;
    double tfano=0.0,treadwav=0.0,tcandidates=0.0,tsync0=0.0;
    double tsync1=0.0,tsync2=0.0,ttotal=0.0;
    
    // Parameters used for performance-tuning:
    maxcycles=10000;                         //Fano timeout limit
    double minsync1=0.10;                    //First sync limit
    double minsync2=0.12;                    //Second sync limit
    int iifac=3;                             //Step size in final DT peakup
    int symfac=50;                           //Soft-symbol normalizing factor
    int maxdrift=4;                          //Maximum (+/-) drift
    double minrms=52.0 * (symfac/64.0);      //Final test for plausible decoding
    delta=60;                                //Fano threshold step
    
    t00=clock();
    fftw_complex *fftin, *fftout;
#include "./metric_tables.c"
    
    int mettab[2][256];
    float bias=0.42;
    
    idat=malloc(sizeof(double)*maxpts);
    qdat=malloc(sizeof(double)*maxpts);
    
    while ( (c = getopt(argc, argv, "a:b:e:f:Hmnqst:wvz:")) !=-1 ) {
        switch (c) {
            case 'a':
                data_dir = optarg;
                break;
            case 'b':
                fblank = strtof(optarg,NULL);
                break;
            case 'e':
                dialfreq_error = strtof(optarg,NULL);   // units of Hz
                // dialfreq_error = dial reading - actual, correct frequency
                break;
            case 'f':
                dialfreq_cmdline = strtod(optarg,NULL); // units of MHz
                break;
            case 'H':
                usehashtable = 0;
                break;
            case 'm':
                wspr_type = 15;
                break;
            case 'n':
                writenoise = 1;
                break;
            case 'q':
                quickmode = 1;
                break;
            case 's':
                maxcycles=20000;
                iifac=1;
                break;
            case 't':
                tblank = strtof(optarg,NULL);
                break;
            case 'v':
                verbose = 1;
                break;
            case 'w':
                fmin=-150.0;
                fmax=150.0;
                break;
            case 'z':
                bias=strtof(optarg,NULL); //fano metric bias (default is 0.42)
                break;
            case '?':
                usage();
                return 1;
        }
    }
    
    if( optind+1 > argc) {
        usage();
        return 1;
    } else {
        ptr_to_infile=argv[optind];
    }
    
    // setup metric table
    for(i=0; i<256; i++) {
        mettab[0][i]=round( 10*(metric_tables[2][i]-bias) );
        mettab[1][i]=round( 10*(metric_tables[2][255-i]-bias) );
    }
    
    FILE *fp_fftw_wisdom_file, *fall_wspr, *fwsprd, *fhash, *ftimer;
    strcpy(wisdom_fname,".");
    strcpy(all_fname,".");
    strcpy(spots_fname,".");
    strcpy(timer_fname,".");
    strcpy(hash_fname,".");
    if(data_dir != NULL) {
        strcpy(wisdom_fname,data_dir);
        strcpy(all_fname,data_dir);
        strcpy(spots_fname,data_dir);
        strcpy(timer_fname,data_dir);
        strcpy(hash_fname,data_dir);
    }
    strncat(wisdom_fname,"/wspr_wisdom.dat",20);
    strncat(all_fname,"/ALL_WSPR.TXT",20);
    strncat(spots_fname,"/wspr_spots.txt",20);
    strncat(timer_fname,"/wspr_timer.out",20);
    strncat(hash_fname,"/hashtable.txt",20);
    if ((fp_fftw_wisdom_file = fopen(wisdom_fname, "r"))) {  //Open FFTW wisdom
        fftw_import_wisdom_from_file(fp_fftw_wisdom_file);
        fclose(fp_fftw_wisdom_file);
    }
    
    fall_wspr=fopen(all_fname,"a");
    fwsprd=fopen(spots_fname,"w");
    //  FILE *fdiag;
    //  fdiag=fopen("wsprd_diag","a");
    
    if((ftimer=fopen(timer_fname,"r"))) {
        //Accumulate timing data
        nr=fscanf(ftimer,"%lf %lf %lf %lf %lf %lf %lf",
                  &treadwav,&tcandidates,&tsync0,&tsync1,&tsync2,&tfano,&ttotal);
        fclose(ftimer);
    }
    ftimer=fopen(timer_fname,"w");
    
    if( strstr(ptr_to_infile,".wav") ) {
        ptr_to_infile_suffix=strstr(ptr_to_infile,".wav");
        
        t0 = clock();
        npoints=readwavfile(ptr_to_infile, wspr_type, idat, qdat);
        treadwav += (double)(clock()-t0)/CLOCKS_PER_SEC;
        
        if( npoints == 1 ) {
            return 1;
        }
        dialfreq=dialfreq_cmdline - (dialfreq_error*1.0e-06);
    } else if ( strstr(ptr_to_infile,".c2") !=0 )  {
        ptr_to_infile_suffix=strstr(ptr_to_infile,".c2");
        npoints=readc2file(ptr_to_infile, idat, qdat, &dialfreq, &wspr_type);
        if( npoints == 1 ) {
            return 1;
        }
        dialfreq -= (dialfreq_error*1.0e-06);
    } else {
        printf("Error: Failed to open %s\n",ptr_to_infile);
        printf("WSPR file must have suffix .wav or .c2\n");
        return 1;
    }
    
    // Parse date and time from given filename
    strncpy(date,ptr_to_infile_suffix-11,6);
    strncpy(uttime,ptr_to_infile_suffix-4,4);
    date[6]='\0';
    uttime[4]='\0';
    
    // Do windowed ffts over 2 symbols, stepped by half symbols
    int nffts=4*floor(npoints/512)-1;
    fftin=(fftw_complex*) fftw_malloc(sizeof(fftw_complex)*512);
    fftout=(fftw_complex*) fftw_malloc(sizeof(fftw_complex)*512);
    PLAN3 = fftw_plan_dft_1d(512, fftin, fftout, FFTW_FORWARD, PATIENCE);
    
    float ps[512][nffts];
    float w[512];
    for(i=0; i<512; i++) {
        w[i]=sin(0.006147931*i);
    }
    
    memset(ps,0.0, sizeof(float)*512*nffts);
    for (i=0; i<nffts; i++) {
        for(j=0; j<512; j++ ) {
            k=i*128+j;
            fftin[j][0]=idat[k] * w[j];
            fftin[j][1]=qdat[k] * w[j];
        }
        fftw_execute(PLAN3);
        for (j=0; j<512; j++ ) {
            k=j+256;
            if( k>511 )
                k=k-512;
            ps[j][i]=fftout[k][0]*fftout[k][0]+fftout[k][1]*fftout[k][1];
        }
    }
    
    fftw_free(fftin);
    fftw_free(fftout);
    
    // Compute average spectrum
    float psavg[512];
    memset(psavg,0.0, sizeof(float)*512);
    for (i=0; i<nffts; i++) {
        for (j=0; j<512; j++) {
            psavg[j]=psavg[j]+ps[j][i];
        }
    }
    
    // Smooth with 7-point window and limit spectrum to +/-150 Hz
    int window[7]={1,1,1,1,1,1,1};
    float smspec[411];
    for (i=0; i<411; i++) {
        smspec[i]=0.0;
        for(j=-3; j<=3; j++) {
            k=256-205+i+j;
            smspec[i]=smspec[i]+window[j+3]*psavg[k];
        }
    }
    
    // Sort spectrum values, then pick off noise level as a percentile
    float tmpsort[411];
    for (j=0; j<411; j++) {
        tmpsort[j]=smspec[j];
    }
    qsort(tmpsort, 411, sizeof(float), floatcomp);
    
    // Noise level of spectrum is estimated as 123/411= 30'th percentile
    float noise_level = tmpsort[122];
    
    /* Renormalize spectrum so that (large) peaks represent an estimate of snr.
     * We know from experience that threshold snr is near -7dB in wspr bandwidth,
     * corresponding to -7-26.3=-33.3dB in 2500 Hz bandwidth.
     * The corresponding threshold is -42.3 dB in 2500 Hz bandwidth for WSPR-15. */
    
    float min_snr, snr_scaling_factor;
    min_snr = pow(10.0,-7.0/10.0); //this is min snr in wspr bw
    if( wspr_type == 2 ) {
        snr_scaling_factor=26.3;
    } else {
        snr_scaling_factor=35.3;
    }
    for (j=0; j<411; j++) {
        smspec[j]=smspec[j]/noise_level - 1.0;
        if( smspec[j] < min_snr) smspec[j]=0.1;
        continue;
    }
    
    // Find all local maxima in smoothed spectrum.
    for (i=0; i<200; i++) {
        freq0[i]=0.0;
        snr0[i]=0.0;
        drift0[i]=0.0;
        shift0[i]=0;
        sync0[i]=0.0;
    }
    
    int npk=0;
    for(j=1; j<410; j++) {
        if((smspec[j]>smspec[j-1]) && (smspec[j]>smspec[j+1]) && (npk<200)) {
            freq0[npk]=(j-205)*df;
            snr0[npk]=10*log10(smspec[j])-snr_scaling_factor;
            npk++;
        }
    }
    
    // Compute corrected fmin, fmax, accounting for dial frequency error
    fmin += dialfreq_error;    // dialfreq_error is in units of Hz
    fmax += dialfreq_error;
    
    // Don't waste time on signals outside of the range [fmin,fmax].
    i=0;
    for( j=0; j<npk; j++) {
        if( freq0[j] >= fmin && freq0[j] <= fmax ) {
            freq0[i]=freq0[j];
            snr0[i]=snr0[j];
            i++;
        }
    }
    npk=i;
    
    t0=clock();
    /* Make coarse estimates of shift (DT), freq, and drift
     
     * Look for time offsets up to +/- 8 symbols (about +/- 5.4 s) relative
     to nominal start time, which is 2 seconds into the file
     
     * Calculates shift relative to the beginning of the file
     
     * Negative shifts mean that signal started before start of file
     
     * The program prints DT = shift-2 s
     
     * Shifts that cause sync vector to fall off of either end of the data
     vector are accommodated by "partial decoding", such that missing
     symbols produce a soft-decision symbol value of 128
     
     * The frequency drift model is linear, deviation of +/- drift/2 over the
     span of 162 symbols, with deviation equal to 0 at the center of the
     signal vector.
     */
    
    int idrift,ifr,if0,ifd,k0;
    int kindex;
    float smax,ss,pow,p0,p1,p2,p3;
    for(j=0; j<npk; j++) {                              //For each candidate...
        smax=-1e30;
        if0=freq0[j]/df+256;
        for (ifr=if0-1; ifr<=if0+1; ifr++) {                      //Freq search
            for( k0=-10; k0<22; k0++) {                             //Time search
                for (idrift=-maxdrift; idrift<=maxdrift; idrift++) {  //Drift search
                    ss=0.0;
                    pow=0.0;
                    for (k=0; k<162; k++) {                             //Sum over symbols
                        ifd=ifr+((float)k-81.0)/81.0*( (float)idrift )/(2.0*df);
                        kindex=k0+2*k;
                        if( kindex < nffts ) {
                            p0=ps[ifd-3][kindex];
                            p1=ps[ifd-1][kindex];
                            p2=ps[ifd+1][kindex];
                            p3=ps[ifd+3][kindex];
                            
                            p0=sqrt(p0);
                            p1=sqrt(p1);
                            p2=sqrt(p2);
                            p3=sqrt(p3);
                            
                            ss=ss+(2*pr3[k]-1)*((p1+p3)-(p0+p2));
                            pow=pow+p0+p1+p2+p3;
                            sync1=ss/pow;
                        }
                    }
                    if( sync1 > smax ) {                  //Save coarse parameters
                        smax=sync1;
                        shift0[j]=128*(k0+1);
                        drift0[j]=idrift;
                        freq0[j]=(ifr-256)*df;
                        sync0[j]=sync1;
                    }
                }
            }
        }
    }
    tcandidates += (double)(clock()-t0)/CLOCKS_PER_SEC;
    
    nbits=81;
    symbols=malloc(sizeof(char)*nbits*2);
    memset(symbols,0,sizeof(char)*nbits*2);
    decdata=malloc((nbits+7)/8);
    grid=malloc(sizeof(char)*5);
    grid6=malloc(sizeof(char)*7);
    callsign=malloc(sizeof(char)*13);
    call_loc_pow=malloc(sizeof(char)*23);
    cdbm=malloc(sizeof(char)*3);
    float allfreqs[npk];
    memset(allfreqs,0,sizeof(float)*npk);
    char allcalls[npk][13];
    memset(allcalls,0,sizeof(char)*npk*13);
    memset(grid,0,sizeof(char)*5);
    memset(grid6,0,sizeof(char)*7);
    memset(callsign,0,sizeof(char)*13);
    memset(call_loc_pow,0,sizeof(char)*23);
    memset(cdbm,0,sizeof(char)*3);
    char hashtab[32768][13];
    memset(hashtab,0,sizeof(char)*32768*13);
    int nh;
    
    if( usehashtable ) {
        char line[80], hcall[12];
        if( (fhash=fopen(hash_fname,"r+")) ) {
            while (fgets(line, sizeof(line), fhash) != NULL) {
                sscanf(line,"%d %s",&nh,hcall);
                strcpy(*hashtab+nh*13,hcall);
            }
        } else {
            fhash=fopen(hash_fname,"w+");
        }
        fclose(fhash);
    }
    
    int uniques=0, noprint=0;
    /*
     Refine the estimates of freq, shift using sync as a metric.
     Sync is calculated such that it is a float taking values in the range
     [0.0,1.0].
     
     Function sync_and_demodulate has three modes of operation
     mode is the last argument:
     
     0 = no frequency or drift search. find best time lag.
     1 = no time lag or drift search. find best frequency.
     2 = no frequency or time lag search. Calculate soft-decision
     symbols using passed frequency and shift.
     
     NB: best possibility for OpenMP may be here: several worker threads
     could each work on one candidate at a time.
     */
    
    for (j=0; j<npk; j++) {
        f1=freq0[j];
        drift1=drift0[j];
        shift1=shift0[j];
        sync1=sync0[j];
        
        // Fine search for best sync lag (mode 0)
        fstep=0.0;
        lagmin=shift1-144;
        lagmax=shift1+144;
        lagstep=8;
        if(quickmode) lagstep=16;
        t0 = clock();
        sync_and_demodulate(idat, qdat, npoints, symbols, &f1, fstep, &shift1,
                            lagmin, lagmax, lagstep, &drift1, symfac, &sync1, 0);
        tsync0 += (double)(clock()-t0)/CLOCKS_PER_SEC;
        
        // Fine search for frequency peak (mode 1)
        fstep=0.1;
        t0 = clock();
        sync_and_demodulate(idat, qdat, npoints, symbols, &f1, fstep, &shift1,
                            lagmin, lagmax, lagstep, &drift1, symfac, &sync1, 1);
        tsync1 += (double)(clock()-t0)/CLOCKS_PER_SEC;
        
        if( sync1 > minsync1 ) {
            worth_a_try = 1;
        } else {
            worth_a_try = 0;
        }
        
        int idt=0, ii=0, jiggered_shift;
        double y,sq,rms;
        not_decoded=1;
        
        while ( worth_a_try && not_decoded && idt<=(128/iifac)) {
            ii=(idt+1)/2;
            if( idt%2 == 1 ) ii=-ii;
            ii=iifac*ii;
            jiggered_shift=shift1+ii;
            
            // Use mode 2 to get soft-decision symbols
            t0 = clock();
            sync_and_demodulate(idat, qdat, npoints, symbols, &f1, fstep,
                                &jiggered_shift, lagmin, lagmax, lagstep, &drift1, symfac,
                                &sync1, 2);
            tsync2 += (double)(clock()-t0)/CLOCKS_PER_SEC;
            
            sq=0.0;
            for(i=0; i<162; i++) {
                y=(double)symbols[i] - 128.0;
                sq += y*y;
            }
            rms=sqrt(sq/162.0);
            
            if((sync1 > minsync2) && (rms > minrms)) {
                deinterleave(symbols);
                t0 = clock();
                not_decoded = fano(&metric,&cycles,&maxnp,decdata,symbols,nbits,
                                   mettab,delta,maxcycles);
                tfano += (double)(clock()-t0)/CLOCKS_PER_SEC;
                
                /* ### Used for timing tests:
                 if(not_decoded) fprintf(fdiag,
                 "%6s %4s %4.1f %3.0f %4.1f %10.7f  %-18s %2d %5u %4d %6.1f %2d\n",
                 date,uttime,sync1*10,snr0[j], shift1*dt-2.0, dialfreq+(1500+f1)/1e6,
                 "@                 ", (int)drift1, cycles/81, ii, rms, maxnp);
                 */
            }
            idt++;
            if( quickmode ) break;
        }
        
        if( worth_a_try && !not_decoded ) {
            for(i=0; i<11; i++) {
                if( decdata[i]>127 ) {
                    message[i]=decdata[i]-256;
                } else {
                    message[i]=decdata[i];
                }
            }
            
            // Unpack the decoded message, update the hashtable, apply
            // sanity checks on grid and power, and return
            // call_loc_pow string and also callsign (for de-duping).
            noprint=unpk_(message,hashtab,call_loc_pow,callsign);
            
            // Remove dupes (same callsign and freq within 1 Hz)
            int dupe=0;
            for (i=0; i<npk; i++) {
                if(!strcmp(callsign,allcalls[i]) && 
                   (fabs(f1-allfreqs[i]) <1.0)) dupe=1;
            }
            if( (verbose || !dupe) && !noprint) {
                uniques++;
                strcpy(allcalls[uniques],callsign);
                allfreqs[uniques]=f1;
                // Add an extra space at the end of each line so that wspr-x doesn't 
                // truncate the power (TNX to DL8FCL!)
                
                if( wspr_type == 15 ) {
                    freq_print=dialfreq+(1500+112.5+f1/8.0)/1e6;
                    dt_print=shift1*8*dt-2.0;
                } else {
                    freq_print=dialfreq+(1500+f1)/1e6;
                    dt_print=shift1*dt-2.0;
                }
                printf("%4s %3.0f %4.1f %10.6f %2d  %-s \n",
                       uttime, snr0[j],dt_print,freq_print,
                       (int)drift1, call_loc_pow);
                
                fprintf(fall_wspr,
                        "%6s %4s %3.0f %3.0f %4.1f %10.7f  %-22s %2d %5u %4d\n",
                        date,uttime,sync1*10,snr0[j],
                        dt_print, freq_print,
                        call_loc_pow, (int)drift1, cycles/81, ii);
                
                fprintf(fwsprd,"%6s %4s %3d %3.0f %4.1f %10.6f  %-22s %2d %5u %4d\n",
                        date,uttime,(int)(sync1*10),snr0[j],
                        dt_print, freq_print,
                        call_loc_pow, (int)drift1, cycles/81, ii);
                
                /* For timing tests
                 
                 fprintf(fdiag,
                 "%6s %4s %4.1f %3.0f %4.1f %10.7f  %-18s %2d %5u %4d %6.1f\n",
                 date,uttime,sync1*10,snr0[j],
                 shift1*dt-2.0, dialfreq+(1500+f1)/1e6,
                 call_loc_pow, (int)drift1, cycles/81, ii, rms);
                 */
            }
        }
    }
    printf("<DecodeFinished>\n");
    
    if ((fp_fftw_wisdom_file = fopen(wisdom_fname, "w"))) {
        fftw_export_wisdom_to_file(fp_fftw_wisdom_file);
        fclose(fp_fftw_wisdom_file);
    }
    
    ttotal += (double)(clock()-t00)/CLOCKS_PER_SEC;
    
    fprintf(ftimer,"%7.2f %7.2f %7.2f %7.2f %7.2f %7.2f %7.2f\n\n",
            treadwav,tcandidates,tsync0,tsync1,tsync2,tfano,ttotal);
    
    fprintf(ftimer,"Code segment        Seconds   Frac\n");
    fprintf(ftimer,"-----------------------------------\n");
    fprintf(ftimer,"readwavfile        %7.2f %7.2f\n",treadwav,treadwav/ttotal);
    fprintf(ftimer,"Coarse DT f0 f1    %7.2f %7.2f\n",tcandidates,
            tcandidates/ttotal);
    fprintf(ftimer,"sync_and_demod(0)  %7.2f %7.2f\n",tsync0,tsync0/ttotal);
    fprintf(ftimer,"sync_and_demod(1)  %7.2f %7.2f\n",tsync1,tsync1/ttotal);
    fprintf(ftimer,"sync_and_demod(2)  %7.2f %7.2f\n",tsync2,tsync2/ttotal);
    fprintf(ftimer,"Fano decoder       %7.2f %7.2f\n",tfano,tfano/ttotal);
    fprintf(ftimer,"-----------------------------------\n");
    fprintf(ftimer,"Total              %7.2f %7.2f\n",ttotal,1.0);
    
    fclose(fall_wspr);
    fclose(fwsprd);
    //  fclose(fdiag);
    fclose(ftimer);
    fftw_destroy_plan(PLAN1);
    fftw_destroy_plan(PLAN2);
    fftw_destroy_plan(PLAN3);
    
    if( usehashtable ) {
        fhash=fopen(hash_fname,"w");
        for (i=0; i<32768; i++) {
            if( strncmp(hashtab[i],"\0",1) != 0 ) {
                fprintf(fhash,"%5d %s\n",i,*hashtab+i*13);
            }
        }
        fclose(fhash);
    }
    if(fblank+tblank+writenoise == 999) return -1;  //Silence compiler warning
    return 0;
}