/* 
  FILE...: ldpc_dec.c
  AUTHOR.: Matthew C. Valenti, Rohit Iyer Seshadri, David Rowe
  CREATED: Sep 2016

  Command line C LDPC decoder derived from MpDecode.c in the CML
  library.  Allows us to run the same decoder in Octave and C.
*/

#include <assert.h>
#include <errno.h>
#include <math.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <stdio.h>

#include "mpdecode_core.h"
#include "ldpc_codes.h"
#include "ofdm_internal.h"

int opt_exists(char *argv[], int argc, char opt[]) {
    int i;
    for (i=0; i<argc; i++) {
        if (strcmp(argv[i], opt) == 0) {
            return i;
        }
    }
    return 0;
}


int main(int argc, char *argv[])
{    
    int         CodeLength, NumberParityBits;
    int         i, codename, parityCheckCount, mute, testframes;
    int         data_bits_per_frame;
    struct LDPC ldpc;
    int         iter, total_iters;
    int         Tbits, Terrs, Tbits_raw, Terrs_raw, Tpackets, Tpacketerrs;

    int unused_data_bits = 84;

    if (argc < 2) {
        fprintf(stderr, "\n");
        fprintf(stderr, "usage: %s --listcodes\n\n", argv[0]);
        fprintf(stderr, "  List supported codes (more can be added via using Octave ldpc scripts)\n");
        fprintf(stderr, "\n");
        fprintf(stderr, "usage: %s InOneSymbolPerFloat OutOneBitPerByte [--sd] [--half] [--code CodeName] [--testframes]", argv[0]);
        fprintf(stderr, " [--unused numUnusedDataBits]\n\n");
        fprintf(stderr, "   InOneSymbolPerFloat     Input file of float LLRs, use - for the \n");        
        fprintf(stderr, "                           file names to use stdin/stdout\n");
        fprintf(stderr, "   --code                  Use LDPC code CodeName\n");
        fprintf(stderr, "   --listcodes             List available LDPC codes\n");
        fprintf(stderr, "   --sd                    Treat input file samples as BPSK Soft Decision\n");
        fprintf(stderr, "                           demod outputs rather than LLRs\n");
        fprintf(stderr, "   --mute                  Only output frames with < 10%% parity check fails\n");
        fprintf(stderr, "   --testframes            built in test frame modem, requires --testframes at encoder\n");
        fprintf(stderr, "    --unused               number of unused data bits, which are set to 1's at enc and dec\n");
        fprintf(stderr, "\n");

        fprintf(stderr, "Example in testframe mode:\n\n");
        fprintf(stderr, " $ ./ldpc_enc /dev/zero - --sd --code HRA_112_112 --testframes 10 |\n");
        fprintf(stderr, "   ./ldpc_dec - /dev/null --code HRA_112_112 --sd --testframes\n");
        exit(0);
    }

    if ((codename = opt_exists(argv, argc, "--listcodes")) != 0) {
        ldpc_codes_list();
        exit(0);
    }

    /* set up LDPC code */

    int code_index = 0;
    if ((codename = opt_exists(argv, argc, "--code")) != 0)
        code_index = ldpc_codes_find(argv[codename+1]);
    memcpy(&ldpc,&ldpc_codes[code_index],sizeof(struct LDPC));
    fprintf(stderr, "Using: %s\n", ldpc.name);

    CodeLength = ldpc.CodeLength;                    /* length of entire codeword */
    NumberParityBits = ldpc.NumberParityBits;
    data_bits_per_frame = ldpc.NumberRowsHcols;
    unsigned char ibits[data_bits_per_frame];
    unsigned char pbits[NumberParityBits];
    uint8_t out_char[CodeLength];

    testframes = 0;
    total_iters = 0;
    Tbits = Terrs = Tbits_raw = Terrs_raw = Tpackets = Tpacketerrs = 0;
    
    FILE *fin, *fout;
    int   sdinput, nread, offset=0;

    /* File I/O mode ------------------------------------------------*/

    if (strcmp(argv[1], "-")  == 0) fin = stdin;
    else if ( (fin = fopen(argv[1],"rb")) == NULL ) {
        fprintf(stderr, "Error opening input SD file: %s: %s.\n",
                argv[1], strerror(errno));
        exit(1);
    }
        
    if (strcmp(argv[2], "-") == 0) fout = stdout;
    else if ( (fout = fopen(argv[2],"wb")) == NULL ) {
        fprintf(stderr, "Error opening output bit file: %s: %s.\n",
                argv[2], strerror(errno));
        exit(1);
    }

    sdinput = 0; mute = 0; testframes = 0;
    if (opt_exists(argv, argc, "--sd")) {
        sdinput = 1;
    }
    if (opt_exists(argv, argc, "--mute")) {
        mute = 1;
    }
    unused_data_bits = 0; int arg;
    if ((arg = opt_exists(argv, argc, "--unused"))) {
        unused_data_bits = atoi(argv[arg+1]);
    }
    if (opt_exists(argv, argc, "--testframes")) {
        testframes = 1;
        uint16_t r[data_bits_per_frame];
        ofdm_rand(r, data_bits_per_frame);

        for(i=0; i<data_bits_per_frame-unused_data_bits; i++) {
            ibits[i] = r[i] > 16384;
        }
        for(i=data_bits_per_frame-unused_data_bits; i<data_bits_per_frame; i++) {
            ibits[i] = 1;
        }
        encode(&ldpc, ibits, pbits);  
    }

    float  *input_float  = calloc(CodeLength, sizeof(float));

    nread = CodeLength - unused_data_bits;
    fprintf(stderr, "CodeLength: %d offset: %d\n", CodeLength, offset);

    while(fread(input_float, sizeof(float), nread, fin) == nread) {
        if (testframes) {
            /* BPSK SD and bit LLRs get mapped roughly the same way so this just happens to work for both */
            char in_char;
            for (i=0; i<data_bits_per_frame-unused_data_bits; i++) {
                in_char = input_float[i] < 0;
                if (in_char != ibits[i]) {
                    Terrs_raw++;
                }
                Tbits_raw++;
            }
            for (i=0; i<NumberParityBits; i++) {
                in_char = input_float[i+data_bits_per_frame-unused_data_bits] < 0;
                if (in_char != pbits[i]) {
                    Terrs_raw++;
                }
                Tbits_raw++;
            }
        }

        if (sdinput) {
            /* map BPSK SDs to bit LLRs */
            float llr[CodeLength-unused_data_bits];
            sd_to_llr(llr, input_float, CodeLength-unused_data_bits);

            /* insert unused data LLRs */

            float llr_tmp[CodeLength];
            for(i=0; i<data_bits_per_frame-unused_data_bits; i++)
                llr_tmp[i] = llr[i];  // rx data bits
            for(i=data_bits_per_frame-unused_data_bits; i<data_bits_per_frame; i++)
                llr_tmp[i] = -10.0;           // known data bits high likelhood
            for(i=data_bits_per_frame; i<CodeLength; i++)
                llr_tmp[i] = llr[i-unused_data_bits];  // rx parity bits
            memcpy(input_float, llr_tmp, sizeof(float)*CodeLength);                
        }

        iter = run_ldpc_decoder(&ldpc, out_char, input_float, &parityCheckCount);
        //fprintf(stderr, "iter: %d\n", iter);
        total_iters += iter;
            
        if (mute) {

            // Output data bits only if decoder converged, or was
            // within 10% of all parity checks converging (10% est
            // BER).  Useful for real world operation as it can
            // resync and won't send crappy packets to the decoder
                
            float ber_est = (float)(ldpc.NumberParityBits - parityCheckCount)/ldpc.NumberParityBits;
            //fprintf(stderr, "iter: %4d parityCheckErrors: %4d ber: %3.2f\n", iter, ldpc.NumberParityBits - parityCheckCount, ber_est);
            if (ber_est < 0.1) {
                fwrite(out_char, sizeof(char), ldpc.NumberRowsHcols, fout);
            }

        }

        fwrite(out_char, sizeof(char), data_bits_per_frame, fout);

        if (testframes) {
            int perr = 0;
            for (i=0; i<data_bits_per_frame; i++) {
                if (out_char[i] != ibits[i]) {
                    Terrs++;
                    perr = 1;
                }
                Tbits++;
            }
            Tpackets++; if (perr) { Tpacketerrs++; fprintf(stderr,"x"); } else fprintf(stderr,".");
        }
        //fprintf(stderr, "Terrs_raw: %d  Tbits_raw: %d Terr: %d Tbits: %d\n", Terrs_raw, Tbits_raw, Terrs, Tbits);
    }

    free(input_float);
    if (fin  != NULL) fclose(fin);
    if (fout != NULL) fclose(fout);

    fprintf(stderr, "total iters %d\n", total_iters);

    if (testframes) {
        fprintf(stderr, "Raw   Tbits: %6d Terr: %6d BER: %4.3f\n", Tbits_raw, Terrs_raw,
                (float)Terrs_raw/(Tbits_raw+1E-12));
        float coded_ber = (float)Terrs/(Tbits+1E-12);
        fprintf(stderr, "Coded Tbits: %6d Terr: %6d BER: %4.3f\n", Tbits, Terrs, coded_ber);
        fprintf(stderr, "      Tpkts: %6d Tper: %6d PER: %4.3f\n", Tpackets, Tpacketerrs, Tpacketerrs/(Tpackets+1E-12));

        /* set return code for Ctest */
        if (Tpackets && (coded_ber < 0.01))
            return 0;
        else
            return 1;
    }
    
    return 0;
}