/*!
 * \file labsat23_source.cc
 *
 * \brief Unpacks capture files in the LabSat 2 (ls2), LabSat 3 (ls3), or LabSat
 * 3 Wideband (LS3W) formats.
 * \author Javier Arribas jarribas (at) cttc.es
 *
 * -----------------------------------------------------------------------------
 *
 * GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
 * This file is part of GNSS-SDR.
 *
 * Copyright (C) 2010-2021  (see AUTHORS file for a list of contributors)
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * -----------------------------------------------------------------------------
 */


#include "labsat23_source.h"
#include "INIReader.h"
#include "command_event.h"
#include "gnss_sdr_make_unique.h"
#include <gnuradio/io_signature.h>
#include <algorithm>
#include <array>
#include <bitset>
#include <exception>
#include <iomanip>
#include <iostream>
#include <memory>
#include <sstream>
#include <utility>

#if HAS_BOOST_ENDIAN
#include <boost/endian/conversion.hpp>
#endif


labsat23_source_sptr labsat23_make_source_sptr(const char *signal_file_basename, const std::vector<int> &channel_selector, Concurrent_Queue<pmt::pmt_t> *queue, bool digital_io_enabled)
{
    return labsat23_source_sptr(new labsat23_source(signal_file_basename, channel_selector, queue, digital_io_enabled));
}


labsat23_source::labsat23_source(const char *signal_file_basename,
    const std::vector<int> &channel_selector,
    Concurrent_Queue<pmt::pmt_t> *queue,
    bool digital_io_enabled) : gr::block("labsat23_source",
                                   gr::io_signature::make(0, 0, 0),
                                   gr::io_signature::make(1, 3, sizeof(gr_complex))),
                               d_queue(queue),
                               d_channel_selector_config(channel_selector),
                               d_current_file_number(0),
                               d_labsat_version(0),
                               d_channel_selector(0),
                               d_ref_clock(0),
                               d_bits_per_sample(0),
                               d_header_parsed(false),
                               d_ls3w_digital_io_enabled(digital_io_enabled)
{
    d_signal_file_basename = std::string(signal_file_basename);
    std::string signal_file;
    this->set_output_multiple(8);
    signal_file = generate_filename();

    if (d_is_ls3w)
        {
            d_labsat_version = 3;
            std::cout << "LabSat file version 3 Wideband detected.\n";
            // Read ini file
            std::string ini_file = signal_file.substr(0, signal_file.length() - 4) + std::string("ini");
            if (read_ls3w_ini(ini_file) != 0)
                {
                    exit(1);
                }
        }

    binary_input_file.open(signal_file.c_str(), std::ios::in | std::ios::binary);

    if (binary_input_file.is_open())
        {
            std::cout << "LabSat file source is reading samples from " << signal_file << '\n';
        }
    else
        {
            std::cout << "LabSat file " << signal_file << " could not be opened!\n";
            exit(1);
        }
}


labsat23_source::~labsat23_source()
{
    try
        {
            if (binary_input_file.is_open())
                {
                    binary_input_file.close();
                }
        }
    catch (const std::ifstream::failure &e)
        {
            std::cerr << "Problem closing input file.\n";
        }
    catch (const std::exception &e)
        {
            std::cerr << e.what() << '\n';
        }
}


std::string labsat23_source::generate_filename()
{
    if (d_signal_file_basename.substr(d_signal_file_basename.length() - 4, 4) == ".ls2" or d_signal_file_basename.substr(d_signal_file_basename.length() - 4, 4) == ".LS2")
        {
            if (d_current_file_number == 0)
                {
                    return d_signal_file_basename;
                }
            return {"donotexist"};  // just to stop processing
        }
    if (d_signal_file_basename.substr(d_signal_file_basename.length() - 5, 5) == ".ls3w" or d_signal_file_basename.substr(d_signal_file_basename.length() - 5, 5) == ".LS3W")
        {
            d_is_ls3w = true;
            return d_signal_file_basename;
        }

    std::ostringstream ss;
    ss << std::setw(4) << std::setfill('0') << d_current_file_number;
    return d_signal_file_basename + "_" + ss.str() + ".LS3";
}


int labsat23_source::getBit(uint8_t byte, int position)
{
    return (byte >> position) & 0x01;
}


int labsat23_source::parse_header()
{
    if (binary_input_file.eof() == false)
        {
            std::array<char, 1024> memblock{};
            binary_input_file.read(memblock.data(), 1024);
            // parse Labsat header
            // check preamble
            int byte_counter = 0;
            bool preamble_ok = true;
            for (int i = 0; i < 8; i++)
                {
                    if (memblock[byte_counter] != 0x00)
                        {
                            preamble_ok = false;
                        }
                    byte_counter++;
                }

            if (preamble_ok == false)
                {
                    std::cout << "LabSat source do not detect the preamble in the selected file\n";
                    return -1;
                }

            // check Labsat version
            if (memblock[byte_counter] == 0x4C and memblock[byte_counter + 1] == 0x53 and memblock[byte_counter + 2] == 0x32)
                {
                    d_labsat_version = 2;
                    std::cout << "LabSat file version 2 detected\n";
                }

            if (memblock[byte_counter] == 0x4C and memblock[byte_counter + 1] == 0x53 and memblock[byte_counter + 2] == 0x33)
                {
                    d_labsat_version = 3;
                    std::cout << "LabSat file version 3 detected\n";
                }

            if (d_labsat_version == 0)
                {
                    std::cout << "LabSat source do not detect the version number in the file header\n";
                    return -1;
                }

            byte_counter += 3;

            int sub_version = static_cast<int>(memblock[byte_counter]);

            std::cout << "LabSat file sub version " << sub_version << '\n';

            byte_counter++;

            int header_bytes = 0;
            header_bytes += memblock[byte_counter] | (memblock[byte_counter + 1] << 8) | (memblock[byte_counter + 2] << 16) | (memblock[byte_counter + 3] << 24);

            byte_counter += 4;

            // read first section
            // section ID (little-endian)
            uint8_t section_id = static_cast<int>(memblock[byte_counter]) + static_cast<int>(memblock[byte_counter + 1]) * 256;
            byte_counter += 2;

            // uint8_t section_lenght_bytes = 0;
            // section_lenght_bytes += memblock[byte_counter] | (memblock[byte_counter + 1] << 8) | (memblock[byte_counter + 2] << 16) | (memblock[byte_counter + 3] << 24);

            byte_counter += 4;
            if (section_id == 2)
                {
                    d_ref_clock = static_cast<uint8_t>(memblock[byte_counter]);
                    switch (d_ref_clock)
                        {
                        case 0:
                            std::cout << "LabSat reference clock: internal OCXO\n";
                            break;
                        case 1:
                            std::cout << "LabSat reference clock: internal TCXO\n";
                            break;
                        case 2:
                            std::cout << "LabSat reference clock: external 10 MHz\n";
                            break;
                        case 3:
                            std::cout << "LabSat reference clock: external 16.386 MHz\n";
                            break;
                        default:
                            std::cout << "LabSat Unknown reference clock ID " << static_cast<int>(d_ref_clock) << '\n';
                        }
                    byte_counter++;
                    d_bits_per_sample = static_cast<uint8_t>(memblock[byte_counter]);
                    switch (d_bits_per_sample)
                        {
                        case 2:
                            std::cout << "LabSat is using 2 bits per sample\n";
                            break;
                        case 4:
                            std::cout << "LabSat is using 4 bits per sample\n";
                            break;
                        default:
                            std::cout << "LabSat Unknown bits per sample ID " << static_cast<int>(d_bits_per_sample) << '\n';
                            return -1;
                        }

                    byte_counter++;
                    d_channel_selector = static_cast<uint8_t>(memblock[byte_counter]);
                    switch (d_channel_selector)
                        {
                        case 0:
                            std::cout << "Available channels: Channel A + B, 1 bit quantisation (I & Q)\n";
                            break;
                        case 1:
                            std::cout << "Available channels: Channel A, 1 bit quantisation (I & Q)\n";
                            break;
                        case 2:
                            std::cout << "Available channels: Channel B, 1 bit quantisation (I & Q)\n";
                            break;
                        case 3:
                            std::cout << "Available channels: Channel A, 2 bit quantisation (I & Q)\n";
                            break;
                        case 4:
                            std::cout << "Available channels: Channel B, 2 bit quantisation (I & Q)\n";
                            break;
                        default:
                            std::cout << "Unknown channel selection ID " << static_cast<int>(d_channel_selector) << '\n';
                            return -1;
                        }

                    // check if the selected channel in config file match the file encoding
                    if (d_channel_selector_config[0] == 2 and d_channel_selector != 0)
                        {
                            std::cout << "LabSat source channel config inconsistency: channel 2 is selected but the file has only one channel.\n";
                            return -1;
                        }

                    // todo: Add support for dual channel files
                    if (d_channel_selector == 0)
                        {
                            std::cout << "ERROR: LabSat file contains more than one channel and this is not currently supported for LabSat version " << d_labsat_version << ".\n";
                            return -1;
                        }
                    byte_counter++;
                    auto quantization = static_cast<uint8_t>(memblock[byte_counter]);
                    switch (quantization)
                        {
                        case 0:
                            break;
                        case 1:
                            std::cout << "1 bit per sample\n";
                            break;
                        case 2:
                            std::cout << "2 bit per sample\n";
                            break;
                        default:
                            std::cout << "Unknown quantization ID " << static_cast<int>(quantization) << '\n';
                        }
                    byte_counter++;
                    auto channel_a_constellation = static_cast<uint8_t>(memblock[byte_counter]);
                    switch (channel_a_constellation)
                        {
                        case 0:
                            std::cout << "LabSat Channel A is GPS\n";
                            break;
                        case 1:
                            std::cout << "LabSat Channel A is GLONASS\n";
                            break;
                        case 2:
                            std::cout << "LabSat Channel A is BDS\n";
                            break;
                        default:
                            std::cout << "Unknown channel A constellation ID " << static_cast<int>(channel_a_constellation) << '\n';
                        }
                    byte_counter++;
                    auto channel_b_constellation = static_cast<uint8_t>(memblock[byte_counter]);
                    switch (channel_b_constellation)
                        {
                        case 0:
                            std::cout << "LabSat Channel B is GPS\n";
                            break;
                        case 1:
                            std::cout << "LabSat Channel B is GLONASS\n";
                            break;
                        case 2:
                            std::cout << "LabSat Channel B is BDS\n";
                            break;
                        case 255:
                            // No channel B
                            break;
                        default:
                            std::cout << "Unknown channel B constellation ID " << static_cast<int>(channel_b_constellation) << '\n';
                        }

                    // end of header
                    d_header_parsed = true;
                    // seek file to the first signal sample
                    binary_input_file.clear();
                    binary_input_file.seekg(header_bytes, binary_input_file.beg);
                    if (d_channel_selector_config.size() > 1)
                        {
                            std::cerr << "Multiple RF source is not implemented for LabSat version " << d_labsat_version << "files.\n";
                            std::cerr << "The Multiple RF source feature is only available for LabSat 3 Wideband format files.\n";
                            std::cerr << "Selecting channel";
                            if (d_channel_selector_config[0] == 1)
                                {
                                    std::cerr << " A.";
                                }
                            if (d_channel_selector_config[0] == 2)
                                {
                                    std::cerr << " B.";
                                }
                            if (d_channel_selector_config[0] == 3)
                                {
                                    std::cerr << " C.";
                                }
                            std::cerr << '\n';
                        }
                    return 0;
                }
            std::cout << "LabSat file header error: section 2 is not available.\n";
            return -1;
        }
    std::cout << "LabSat file read error: file is empty.\n";
    return -1;
}


void labsat23_source::decode_samples_one_channel(int16_t input_short, gr_complex *out, int type)
{
    std::bitset<16> bs(input_short);
    switch (type)
        {
        case 2:
            // two bits per sample, 8 samples per int16
            for (int i = 0; i < 8; i++)
                {
                    out[i] = gr_complex(static_cast<float>(bs[15 - (2 * i)]),
                        static_cast<float>(bs[14 - (2 * i)]));
                    out[i] = out[i] * gr_complex(2, 0) - gr_complex(1, 1);
                }
            break;
        case 4:
            //  bits per sample, 4 samples per int16
            for (int i = 0; i < 4; i++)
                {
                    // out[i] = gr_complex(0.0, 0.0);
                    // In-Phase
                    if (bs[15 - 4 * i])
                        {
                            if (bs[13 - 4 * i])  // 11
                                {
                                    out[i] = gr_complex(-1, 0);
                                }
                            else  // 10
                                {
                                    out[i] = gr_complex(-2, 0);
                                }
                        }
                    else
                        {
                            if (bs[13 - 4 * i])  // 01
                                {
                                    out[i] = gr_complex(2, 0);
                                }
                            else
                                {
                                    out[i] = gr_complex(1, 0);
                                }
                        }

                    // Quadrature
                    if (bs[14 - 4 * i])
                        {
                            if (bs[12 - 4 * i])  // 11
                                {
                                    out[i] += gr_complex(0, -1);
                                }
                            else  // 10
                                {
                                    out[i] += gr_complex(0, -2);
                                }
                        }
                    else
                        {
                            if (bs[12 - 4 * i])  // 01
                                {
                                    out[i] += gr_complex(0, 2);
                                }
                            else
                                {
                                    out[i] += gr_complex(0, 1);
                                }
                        }
                    // out[i] += gr_complex(0.5, 0.5);
                }
            break;
        default:
            break;
        }
}


int labsat23_source::read_ls3w_ini(const std::string &filename)
{
    std::cout << "Reading " << filename << " file ...\n";
    auto ini_reader = std::make_unique<INIReader>(filename);
    int error_ = ini_reader->ParseError();

    if (error_ > 0)
        {
            std::cerr << "Warning: LabSat ini file " << filename
                      << " contains a syntax error in line " << error_ << ", continuing anyway.\n";
        }
    if (error_ < 0)
        {
            std::cerr << "Error: LabSat ini file " << filename << " cannot be opened.\n";
            return 1;
        }
    const std::string empty_string("");
    if (ini_reader->HasSection("config"))
        {
            // Reference clock
            d_ls3w_OSC = ini_reader->Get("config", "OSC", empty_string);
            if (d_ls3w_OSC.empty())
                {
                    std::cerr << "LabSat reference clock: not found.\n";
                }
            else
                {
                    // Sanity check
                    if ((d_ls3w_OSC != "OCXO") and (d_ls3w_OSC != "TCXO") and (d_ls3w_OSC != "EXT"))
                        {
                            std::cerr << "LabSat reference clock is unknown.\n";
                        }
                    else
                        {
                            std::cout << "LabSat reference clock: " << d_ls3w_OSC << '\n';
                        }
                }

            // Sample rate
            std::string ls3w_SMP_aux = ini_reader->Get("config", "SMP", empty_string);
            if (!ls3w_SMP_aux.empty())
                {
                    std::stringstream smp_ss(ls3w_SMP_aux);
                    smp_ss >> d_ls3w_SMP;
                    std::cout << "LabSat sample rate: " << d_ls3w_SMP << " Sps\n";
                }

            // Quantization
            std::string ls3w_QUA_aux = ini_reader->Get("config", "QUA", empty_string);
            if (!ls3w_QUA_aux.empty())
                {
                    std::stringstream qua_ss(ls3w_QUA_aux);
                    qua_ss >> d_ls3w_QUA;

                    // Sanity check
                    if (d_ls3w_QUA > 3)
                        {
                            std::cerr << "LabSat sample quantization of " << d_ls3w_QUA << " bits is not supported.\n";
                            d_ls3w_QUA = 0;
                        }
                    else
                        {
                            std::cout << "LabSat sample quantization: " << d_ls3w_QUA << " bits for I + " << d_ls3w_QUA << " bits for Q.\n";
                        }
                }

            // Number of RF channels
            std::string ls3w_CHN_aux = ini_reader->Get("config", "CHN", empty_string);
            if (!ls3w_CHN_aux.empty())
                {
                    std::stringstream chn_ss(ls3w_CHN_aux);
                    chn_ss >> d_ls3w_CHN;

                    // Sanity check
                    if (d_ls3w_CHN > 3)
                        {
                            std::cerr << "LabSat files with " << d_ls3w_CHN << " RF channels are not supported.\n";
                            d_ls3w_CHN = 0;
                        }
                    else
                        {
                            std::cout << "LabSat data file contains " << d_ls3w_CHN << " RF channels.\n";
                        }
                }

            // Number of bits shifted per channel
            std::string ls3w_SFT_aux = ini_reader->Get("config", "SFT", empty_string);
            if (!ls3w_SFT_aux.empty())
                {
                    std::stringstream sft_ss(ls3w_SFT_aux);
                    sft_ss >> d_ls3w_SFT;

                    // Sanity check
                    if (d_ls3w_SFT != d_ls3w_CHN * d_ls3w_QUA * 2)
                        {
                            std::cerr << "SFT parameter value in the .ini file is not valid.\n";
                            d_ls3w_SFT = d_ls3w_CHN * d_ls3w_QUA * 2;
                        }
                }
        }

    // Channel A
    if (ini_reader->HasSection("channel A"))
        {
            std::string ls3w_CFA_aux = ini_reader->Get("channel A", "CFA", empty_string);
            if (!ls3w_CFA_aux.empty())
                {
                    std::stringstream cfa_ss(ls3w_CFA_aux);
                    cfa_ss >> d_ls3w_CFA;
                    std::cout << "LabSat center frequency for RF channel A: " << d_ls3w_CFA << " Hz\n";
                }

            std::string ls3w_BWA_aux = ini_reader->Get("channel A", "BWA", empty_string);
            if (!ls3w_BWA_aux.empty())
                {
                    std::stringstream bwa_ss(ls3w_BWA_aux);
                    bwa_ss >> d_ls3w_BWA;
                    std::cout << "LabSat RF filter bandwidth for RF channel A: " << d_ls3w_BWA << " Hz\n";
                }
        }

    // Channel B
    if (ini_reader->HasSection("channel B"))
        {
            std::string ls3w_CFB_aux = ini_reader->Get("channel B", "CFB", empty_string);
            if (!ls3w_CFB_aux.empty())
                {
                    std::stringstream cfb_ss(ls3w_CFB_aux);
                    cfb_ss >> d_ls3w_CFB;
                    std::cout << "LabSat center frequency for RF channel B: " << d_ls3w_CFB << " Hz\n";
                }

            std::string ls3w_BWB_aux = ini_reader->Get("channel B", "BWB", empty_string);
            if (!ls3w_BWB_aux.empty())
                {
                    std::stringstream bwb_ss(ls3w_BWB_aux);
                    bwb_ss >> d_ls3w_BWB;
                    std::cout << "LabSat RF filter bandwidth for RF channel B: " << d_ls3w_BWB << " Hz\n";
                }
        }

    // Channel C
    if (ini_reader->HasSection("channel C"))
        {
            std::string ls3w_CFC_aux = ini_reader->Get("channel C", "CFC", empty_string);
            if (!ls3w_CFC_aux.empty())
                {
                    std::stringstream cfc_ss(ls3w_CFC_aux);
                    cfc_ss >> d_ls3w_CFC;
                    std::cout << "LabSat center frequency for RF channel C: " << d_ls3w_CFC << " Hz\n";
                }

            std::string ls3w_BWC_aux = ini_reader->Get("channel C", "BWC", empty_string);
            if (!ls3w_BWC_aux.empty())
                {
                    std::stringstream bwc_ss(ls3w_BWC_aux);
                    bwc_ss >> d_ls3w_BWC;
                    std::cout << "LabSat RF filter bandwidth for RF channel C: " << d_ls3w_BWC << " Hz\n";
                }
        }

    std::cout << "LabSat selected channel" << ((d_channel_selector_config.size() > 1) ? "s" : "") << ": ";
    if (std::find(d_channel_selector_config.begin(), d_channel_selector_config.end(), 1) != d_channel_selector_config.end())
        {
            std::cout << "A";
        }
    if (std::find(d_channel_selector_config.begin(), d_channel_selector_config.end(), 2) != d_channel_selector_config.end())
        {
            if (d_ls3w_CHN > 1)
                {
                    if (d_channel_selector_config.size() == 1)
                        {
                            std::cout << "B";
                        }
                    else
                        {
                            std::cout << ", B";
                        }
                }
            else
                {
                    std::cerr << "\nConfiguration error: RF channel B is selected but not found in data file.\n";
                    std::cerr << "Exiting the program.\n";
                    return -1;
                }
        }
    if (std::find(d_channel_selector_config.begin(), d_channel_selector_config.end(), 3) != d_channel_selector_config.end())
        {
            if (d_ls3w_CHN > 2)
                {
                    if (d_channel_selector_config.size() == 1)
                        {
                            std::cout << "C";
                        }
                    else
                        {
                            std::cout << ", C";
                        }
                }
            else
                {
                    std::cerr << "\nConfiguration error: RF channel C is selected but not found in data file.\n";
                    std::cerr << "Exiting the program.\n";
                    return -1;
                }
        }
    std::cout << '\n';

    d_ls3w_samples_per_register = this->number_of_samples_per_ls3w_register();
    d_ls3w_spare_bits = 64 - d_ls3w_samples_per_register * d_ls3w_QUA * 2;
    for (auto ch_select : d_channel_selector_config)
        {
            d_ls3w_selected_channel_offset.push_back((ch_select - 1) * d_ls3w_QUA * 2);
        }
    return 0;
}


int labsat23_source::number_of_samples_per_ls3w_register() const
{
    int number_samples = 0;
    switch (d_ls3w_QUA)
        {
        case 1:
            if (d_ls3w_CHN == 1)
                {
                    if (!d_ls3w_digital_io_enabled)
                        {
                            number_samples = 32;
                        }
                    else
                        {
                            number_samples = 30;
                        }
                }
            if (d_ls3w_CHN == 2)
                {
                    if (!d_ls3w_digital_io_enabled)
                        {
                            number_samples = 16;
                        }
                    else
                        {
                            number_samples = 15;
                        }
                }
            if (d_ls3w_CHN == 3)
                {
                    number_samples = 10;
                }
            break;
        case 2:
            if (d_ls3w_CHN == 1)
                {
                    if (!d_ls3w_digital_io_enabled)
                        {
                            number_samples = 16;
                        }
                    else
                        {
                            number_samples = 15;
                        }
                }
            if (d_ls3w_CHN == 2)
                {
                    if (!d_ls3w_digital_io_enabled)
                        {
                            number_samples = 8;
                        }
                    else
                        {
                            number_samples = 7;
                        }
                }
            if (d_ls3w_CHN == 3)
                {
                    number_samples = 5;
                }
            break;
        case 3:
            if (d_ls3w_CHN == 1)
                {
                    number_samples = 10;
                }
            if (d_ls3w_CHN == 2)
                {
                    number_samples = 5;
                }
            if (d_ls3w_CHN == 3)
                {
                    number_samples = 3;
                }
            break;
        default:
            number_samples = 0;
            break;
        }
    return number_samples;
}


void labsat23_source::decode_ls3w_register(uint64_t input, std::vector<gr_complex *> &out, size_t output_pointer) const
{
    std::bitset<64> bs(input);

    // Earlier samples are written in the MSBs of the register. Bit-reverse the register
    // for easier indexing. Note this bit-reverses individual samples as well for quant > 1 bit
    for (std::size_t i = 0; i < 32; ++i)
        {
            bool t = bs[i];
            bs[i] = bs[64 - i - 1];
            bs[64 - i - 1] = t;
        }

    int output_chan = 0;
    for (auto channel_offset : d_ls3w_selected_channel_offset)
        {
            for (int i = 0; i < d_ls3w_samples_per_register; i++)
                {
                    float sampleI = 0.0;
                    float sampleQ = 0.0;

                    const int bit_offset = d_ls3w_spare_bits + i * d_ls3w_SFT + channel_offset;
                    switch (d_ls3w_QUA)
                        {
                        case 1:
                            sampleI = bs[bit_offset] ? -1.0 : 1.0;
                            sampleQ = bs[bit_offset + 1] ? -1.0 : 1.0;
                            break;
                        case 2:
                            if (bs[bit_offset])
                                {
                                    if (bs[bit_offset + 1])  // 11
                                        {
                                            sampleI = -0.5;
                                        }
                                    else  // 10
                                        {
                                            sampleI = -1.0;
                                        }
                                }
                            else
                                {
                                    if (bs[bit_offset + 1])  // 01
                                        {
                                            sampleI = 1.0;
                                        }
                                    else  // 00
                                        {
                                            sampleI = 0.5;
                                        }
                                }
                            if (bs[bit_offset + 2])
                                {
                                    if (bs[bit_offset + 3])  // 11
                                        {
                                            sampleQ = -0.5;
                                        }
                                    else  // 10
                                        {
                                            sampleQ = -1.0;
                                        }
                                }
                            else
                                {
                                    if (bs[bit_offset + 3])  // 01
                                        {
                                            sampleQ = 1.0;
                                        }
                                    else  // 00
                                        {
                                            sampleQ = 0.5;
                                        }
                                }
                            break;

                        case 3:
                            if (bs[bit_offset])
                                {
                                    if (bs[bit_offset + 1])
                                        {
                                            if (bs[bit_offset + 2])  // 111
                                                {
                                                    sampleI = -0.25;
                                                }
                                            else  // 110
                                                {
                                                    sampleI = -0.5;
                                                }
                                        }
                                    else
                                        {
                                            if (bs[bit_offset + 2])  // 101
                                                {
                                                    sampleI = -0.75;
                                                }
                                            else  // 100
                                                {
                                                    sampleI = -1.0;
                                                }
                                        }
                                }
                            else
                                {
                                    if (bs[bit_offset + 1])
                                        {
                                            if (bs[bit_offset + 2])  // 011
                                                {
                                                    sampleI = 1;
                                                }
                                            else  // 010
                                                {
                                                    sampleI = 0.75;
                                                }
                                        }
                                    else
                                        {
                                            if (bs[bit_offset + 2])  // 001
                                                {
                                                    sampleI = 0.5;
                                                }
                                            else  // 000
                                                {
                                                    sampleI = 0.25;
                                                }
                                        }
                                }
                            if (bs[bit_offset + 3])
                                {
                                    if (bs[bit_offset + 4])
                                        {
                                            if (bs[bit_offset + 5])  // 111
                                                {
                                                    sampleQ = -0.25;
                                                }
                                            else  // 110
                                                {
                                                    sampleQ = -0.5;
                                                }
                                        }
                                    else
                                        {
                                            if (bs[bit_offset + 5])  // 101
                                                {
                                                    sampleQ = -0.75;
                                                }
                                            else  // 100
                                                {
                                                    sampleQ = -1.0;
                                                }
                                        }
                                }
                            else
                                {
                                    if (bs[bit_offset + 4])
                                        {
                                            if (bs[bit_offset + 5])  // 011
                                                {
                                                    sampleQ = 1;
                                                }
                                            else  // 010
                                                {
                                                    sampleQ = 0.75;
                                                }
                                        }
                                    else
                                        {
                                            if (bs[bit_offset + 5])  // 001
                                                {
                                                    sampleQ = 0.5;
                                                }
                                            else  // 000
                                                {
                                                    sampleQ = 0.25;
                                                }
                                        }
                                }

                            break;

                        default:
                            break;
                        }
                    gr_complex *aux = out[output_chan];
                    aux[output_pointer + i] = gr_complex(sampleI, sampleQ);
                }
            output_chan++;
        }
}


int labsat23_source::general_work(int noutput_items,
    __attribute__((unused)) gr_vector_int &ninput_items,
    __attribute__((unused)) gr_vector_const_void_star &input_items,
    gr_vector_void_star &output_items)
{
    std::vector<gr_complex *> out;
    for (auto &output_item : output_items)
        {
            out.push_back(reinterpret_cast<gr_complex *>(output_item));
        }
    if (!d_is_ls3w)
        {
            if (d_header_parsed == false)
                {
                    return parse_header();
                }

            // ready to start reading samples
            switch (d_bits_per_sample)
                {
                case 2:
                    switch (d_channel_selector)
                        {
                        case 0:
                            // dual channel 2 bits per complex sample
                            // todo: implement dual channel reader
                            break;
                        default:
                            // single channel 2 bits per complex sample (1 bit I + 1 bit Q, 8 samples per int16)
                            int n_int16_to_read = noutput_items / 8;
                            if (n_int16_to_read > 0)
                                {
                                    std::vector<int16_t> memblock(n_int16_to_read);
                                    binary_input_file.read(reinterpret_cast<char *>(memblock.data()), n_int16_to_read * 2);
                                    n_int16_to_read = static_cast<int>(binary_input_file.gcount()) / 2;  // from bytes to int16
                                    if (n_int16_to_read > 0)
                                        {
                                            int output_pointer = 0;
                                            for (int i = 0; i < n_int16_to_read; i++)
                                                {
                                                    decode_samples_one_channel(memblock[i], out[0] + output_pointer, d_bits_per_sample);
                                                    output_pointer += 8;
                                                }
                                            return output_pointer;
                                        }

                                    // trigger the read of the next file in the sequence
                                    d_current_file_number++;
                                    if (d_labsat_version == 3)
                                        {
                                            std::cout << "End of current file, reading the next LabSat file in sequence: " << generate_filename() << '\n';
                                        }
                                    binary_input_file.close();
                                    binary_input_file.open(generate_filename().c_str(), std::ios::in | std::ios::binary);
                                    if (binary_input_file.is_open())
                                        {
                                            std::cout << "LabSat file source is reading samples from " << generate_filename() << '\n';
                                            return 0;
                                        }

                                    if (d_labsat_version == 3)
                                        {
                                            std::cout << "Last file reached, LabSat source stop\n";
                                        }
                                    else
                                        {
                                            std::cout << "End of file reached, LabSat source stop\n";
                                        }

                                    d_queue->push(pmt::make_any(command_event_make(200, 0)));
                                    return -1;
                                }
                            else
                                {
                                    return 0;
                                }
                        }
                    break;
                case 4:
                    switch (d_channel_selector)
                        {
                        case 0:
                            // dual channel
                            // todo: implement dual channel reader
                            break;
                        default:
                            // single channel 4 bits per complex sample (2 bit I + 2 bit Q, 4 samples per int16)
                            int n_int16_to_read = noutput_items / 4;
                            if (n_int16_to_read > 0)
                                {
                                    std::vector<int16_t> memblock(n_int16_to_read);
                                    binary_input_file.read(reinterpret_cast<char *>(memblock.data()), n_int16_to_read * 2);
                                    n_int16_to_read = static_cast<int>(binary_input_file.gcount()) / 2;  // from bytes to int16
                                    if (n_int16_to_read > 0)
                                        {
                                            int output_pointer = 0;
                                            for (int i = 0; i < n_int16_to_read; i++)
                                                {
                                                    decode_samples_one_channel(memblock[i], out[0] + output_pointer, d_bits_per_sample);
                                                    output_pointer += 4;
                                                }
                                            return output_pointer;
                                        }

                                    // trigger the read of the next file in the sequence
                                    d_current_file_number++;
                                    if (d_labsat_version == 3)
                                        {
                                            std::cout << "End of current file, reading the next Labsat file in sequence: " << generate_filename() << '\n';
                                        }
                                    binary_input_file.close();
                                    binary_input_file.open(generate_filename().c_str(), std::ios::in | std::ios::binary);
                                    if (binary_input_file.is_open())
                                        {
                                            std::cout << "Labsat file source is reading samples from " << generate_filename() << '\n';
                                            return 0;
                                        }

                                    if (d_labsat_version == 3)
                                        {
                                            std::cout << "Last file reached, LabSat source stop\n";
                                        }
                                    else
                                        {
                                            std::cout << "End of file reached, LabSat source stop\n";
                                        }
                                    d_queue->push(pmt::make_any(command_event_make(200, 0)));
                                    return -1;
                                }
                            else
                                {
                                    return 0;
                                }
                        }
                    break;
                default:
                    return -1;
                }
        }
    else  // Labsat 3 Wideband
        {
            if (binary_input_file.eof() == false)
                {
                    // Integer division, any fractional part of the answer is discarded
                    int registers_to_read = noutput_items / d_ls3w_samples_per_register;
                    if (registers_to_read < 1)
                        {
                            return 0;
                        }
                    std::size_t output_pointer = 0;
                    for (int i = 0; i < registers_to_read; i++)
                        {
                            uint64_t read_register = 0ULL;
                            // Labsat3W writes its 64-bit shift register to files in little endian. Read and convert to host endianness.
#if HAS_BOOST_ENDIAN
                            binary_input_file.read(reinterpret_cast<char *>(&read_register), sizeof(read_register));
                            boost::endian::little_to_native_inplace(read_register);
#else
                            std::array<char, 8> memory_block{};
                            binary_input_file.read(memory_block.data(), 8);
                            for (int k = 7; k >= 0; --k)
                                {
                                    read_register <<= 8;
                                    read_register |= uint64_t(memory_block[k]);  // This is buggy if the MSB of the char is set.
                                }
#endif

                            if (binary_input_file.gcount() == 8)
                                {
                                    decode_ls3w_register(read_register, out, output_pointer);
                                    output_pointer += d_ls3w_samples_per_register;
                                }
                            else
                                {
                                    std::cout << "End of file reached, LabSat source stop.\n";
                                    d_queue->push(pmt::make_any(command_event_make(200, 0)));
                                    return -1;
                                }
                        }
                    return output_pointer;
                }
            else
                {
                    std::cout << "End of file reached, LabSat source stop.\n";
                    d_queue->push(pmt::make_any(command_event_make(200, 0)));
                    return -1;
                }
        }

    std::cout << "Warning!!\n";
    return 0;
}