/*!
 * \file hybrid_observables_cc.cc
 * \brief Implementation of the pseudorange computation block for Galileo E1
 * \author Javier Arribas 2017. jarribas(at)cttc.es
 *
 * -------------------------------------------------------------------------
 *
 * Copyright (C) 2010-2015  (see AUTHORS file for a list of contributors)
 *
 * GNSS-SDR is a software defined Global Navigation
 *          Satellite Systems receiver
 *
 * This file is part of GNSS-SDR.
 *
 * GNSS-SDR 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.
 *
 * GNSS-SDR 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 GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
 *
 * -------------------------------------------------------------------------
 */

#include "hybrid_observables_cc.h"
#include <algorithm>
#include <cmath>
#include <iostream>
#include <map>
#include <vector>
#include <utility>
#include <armadillo>
#include <gnuradio/io_signature.h>
#include <gnuradio/block_detail.h>
#include <gnuradio/buffer.h>
#include <glog/logging.h>
#include <matio.h>
#include "Galileo_E1.h"
#include "GPS_L1_CA.h"

using google::LogMessage;


hybrid_observables_cc_sptr hybrid_make_observables_cc(unsigned int nchannels_in, unsigned int nchannels_out, bool dump, std::string dump_filename, unsigned int deep_history)
{
    return hybrid_observables_cc_sptr(new hybrid_observables_cc(nchannels_in, nchannels_out, dump, dump_filename, deep_history));
}


hybrid_observables_cc::hybrid_observables_cc(unsigned int nchannels_in, unsigned int nchannels_out, bool dump, std::string dump_filename, unsigned int deep_history) :
                        gr::block("hybrid_observables_cc", gr::io_signature::make(nchannels_in, nchannels_in, sizeof(Gnss_Synchro)),
                                  gr::io_signature::make(nchannels_out, nchannels_out, sizeof(Gnss_Synchro)))
{
    // initialize internal vars
    d_dump = dump;
    d_nchannels = nchannels_out;
    d_dump_filename = dump_filename;
    history_deep = deep_history;
    T_rx_s = 0.0;
    T_rx_step_s = 1e-3; // todo: move to gnss-sdr config
    for (unsigned int i = 0; i < d_nchannels; i++)
        {
            d_gnss_synchro_history_queue.push_back(std::deque<Gnss_Synchro>());
        }

    // ############# ENABLE DATA FILE LOG #################
    if (d_dump == true)
        {
            if (d_dump_file.is_open() == false)
                {
                    try
                    {
                            d_dump_file.exceptions (std::ifstream::failbit | std::ifstream::badbit );
                            d_dump_file.open(d_dump_filename.c_str(), std::ios::out | std::ios::binary);
                            LOG(INFO) << "Observables dump enabled Log file: " << d_dump_filename.c_str();
                    }
                    catch (const std::ifstream::failure & e)
                    {
                            LOG(WARNING) << "Exception opening observables dump file " << e.what();
                    }
                }
        }
}


hybrid_observables_cc::~hybrid_observables_cc()
{
    if (d_dump_file.is_open() == true)
        {
            try
            {
                    d_dump_file.close();
            }
            catch(const std::exception & ex)
            {
                    LOG(WARNING) << "Exception in destructor closing the dump file " << ex.what();
            }
        }
    if(d_dump == true)
        {
            std::cout << "Writing observables .mat files ...";
            hybrid_observables_cc::save_matfile();
            std::cout << " done." << std::endl;
        }
}


int hybrid_observables_cc::save_matfile()
{
    // READ DUMP FILE
    std::ifstream::pos_type size;
    int number_of_double_vars = 7;
    int epoch_size_bytes = sizeof(double) * number_of_double_vars * d_nchannels;
    std::ifstream dump_file;
    dump_file.exceptions(std::ifstream::failbit | std::ifstream::badbit);
    try
    {
            dump_file.open(d_dump_filename.c_str(), std::ios::binary | std::ios::ate);
    }
    catch(const std::ifstream::failure &e)
    {
            std::cerr << "Problem opening dump file:" <<  e.what() << std::endl;
            return 1;
    }
    // count number of epochs and rewind
    long int num_epoch = 0;
    if (dump_file.is_open())
        {
            size = dump_file.tellg();
            num_epoch = static_cast<long int>(size) / static_cast<long int>(epoch_size_bytes);
            dump_file.seekg(0, std::ios::beg);
        }
    else
        {
            return 1;
        }
    double ** RX_time = new double * [d_nchannels];
    double ** TOW_at_current_symbol_s = new double * [d_nchannels];
    double ** Carrier_Doppler_hz = new double * [d_nchannels];
    double ** Carrier_phase_cycles = new double * [d_nchannels];
    double ** Pseudorange_m = new double * [d_nchannels];
    double ** PRN = new double * [d_nchannels];
    double ** Flag_valid_pseudorange = new double * [d_nchannels];

    for(unsigned int i = 0; i < d_nchannels; i++)
        {
            RX_time[i] = new double [num_epoch];
            TOW_at_current_symbol_s[i] = new double[num_epoch];
            Carrier_Doppler_hz[i] = new double[num_epoch];
            Carrier_phase_cycles[i] = new double[num_epoch];
            Pseudorange_m[i] = new double[num_epoch];
            PRN[i] = new double[num_epoch];
            Flag_valid_pseudorange[i] = new double[num_epoch];
        }

    try
    {
            if (dump_file.is_open())
                {
                    for(long int i = 0; i < num_epoch; i++)
                        {
                            for(unsigned int chan = 0; chan < d_nchannels; chan++)
                                {
                                    dump_file.read(reinterpret_cast<char *>(&RX_time[chan][i]), sizeof(double));
                                    dump_file.read(reinterpret_cast<char *>(&TOW_at_current_symbol_s[chan][i]), sizeof(double));
                                    dump_file.read(reinterpret_cast<char *>(&Carrier_Doppler_hz[chan][i]), sizeof(double));
                                    dump_file.read(reinterpret_cast<char *>(&Carrier_phase_cycles[chan][i]), sizeof(double));
                                    dump_file.read(reinterpret_cast<char *>(&Pseudorange_m[chan][i]), sizeof(double));
                                    dump_file.read(reinterpret_cast<char *>(&PRN[chan][i]), sizeof(double));
                                    dump_file.read(reinterpret_cast<char *>(&Flag_valid_pseudorange[chan][i]), sizeof(double));
                                }
                        }
                }
            dump_file.close();
    }
    catch (const std::ifstream::failure &e)
    {
            std::cerr << "Problem reading dump file:" <<  e.what() << std::endl;
            for(unsigned int i = 0; i < d_nchannels; i++)
                {
                    delete[] RX_time[i];
                    delete[] TOW_at_current_symbol_s[i];
                    delete[] Carrier_Doppler_hz[i];
                    delete[] Carrier_phase_cycles[i];
                    delete[] Pseudorange_m[i];
                    delete[] PRN[i];
                    delete[] Flag_valid_pseudorange[i];
                }
            delete[] RX_time;
            delete[] TOW_at_current_symbol_s;
            delete[] Carrier_Doppler_hz;
            delete[] Carrier_phase_cycles;
            delete[] Pseudorange_m;
            delete[] PRN;
            delete[] Flag_valid_pseudorange;

            return 1;
    }

    double * RX_time_aux = new double [d_nchannels * num_epoch];
    double * TOW_at_current_symbol_s_aux = new double [d_nchannels * num_epoch];
    double * Carrier_Doppler_hz_aux = new double [d_nchannels * num_epoch];
    double * Carrier_phase_cycles_aux = new double [d_nchannels * num_epoch];
    double * Pseudorange_m_aux = new double [d_nchannels * num_epoch];
    double * PRN_aux = new double [d_nchannels * num_epoch];
    double * Flag_valid_pseudorange_aux = new double[d_nchannels * num_epoch];
    unsigned int k = 0;
    for(long int j = 0; j < num_epoch; j++ )
        {
            for(unsigned int i = 0; i < d_nchannels; i++ )
                {
                    RX_time_aux[k] = RX_time[i][j];
                    TOW_at_current_symbol_s_aux[k] = TOW_at_current_symbol_s[i][j];
                    Carrier_Doppler_hz_aux[k] = Carrier_Doppler_hz[i][j];
                    Carrier_phase_cycles_aux[k] = Carrier_phase_cycles[i][j];
                    Pseudorange_m_aux[k] = Pseudorange_m[i][j];
                    PRN_aux[k] = PRN[i][j];
                    Flag_valid_pseudorange_aux[k] = Flag_valid_pseudorange[i][j];
                    k++;
                }
        }

    // WRITE MAT FILE
    mat_t *matfp;
    matvar_t *matvar;
    std::string filename = d_dump_filename;
    filename.erase(filename.length() - 4, 4);
    filename.append(".mat");
    matfp = Mat_CreateVer(filename.c_str(), NULL, MAT_FT_MAT73);
    if(reinterpret_cast<long*>(matfp) != NULL)
        {
            size_t dims[2] = {static_cast<size_t>(d_nchannels), static_cast<size_t>(num_epoch)};
            matvar = Mat_VarCreate("RX_time", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, RX_time_aux, MAT_F_DONT_COPY_DATA);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("TOW_at_current_symbol_s", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, TOW_at_current_symbol_s_aux, MAT_F_DONT_COPY_DATA);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("Carrier_Doppler_hz", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, Carrier_Doppler_hz_aux, MAT_F_DONT_COPY_DATA);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("Carrier_phase_cycles", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, Carrier_phase_cycles_aux, MAT_F_DONT_COPY_DATA);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("Pseudorange_m", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, Pseudorange_m_aux, MAT_F_DONT_COPY_DATA);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("PRN", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, PRN_aux, MAT_F_DONT_COPY_DATA);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("Flag_valid_pseudorange", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims, Flag_valid_pseudorange_aux, MAT_F_DONT_COPY_DATA);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB); // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);
        }
    Mat_Close(matfp);

    for(unsigned int i = 0; i < d_nchannels; i++)
        {
            delete[] RX_time[i];
            delete[] TOW_at_current_symbol_s[i];
            delete[] Carrier_Doppler_hz[i];
            delete[] Carrier_phase_cycles[i];
            delete[] Pseudorange_m[i];
            delete[] PRN[i];
            delete[] Flag_valid_pseudorange[i];

        }
    delete[] RX_time;
    delete[] TOW_at_current_symbol_s;
    delete[] Carrier_Doppler_hz;
    delete[] Carrier_phase_cycles;
    delete[] Pseudorange_m;
    delete[] PRN;
    delete[] Flag_valid_pseudorange;

    delete[] RX_time_aux;
    delete[] TOW_at_current_symbol_s_aux;
    delete[] Carrier_Doppler_hz_aux;
    delete[] Carrier_phase_cycles_aux;
    delete[] Pseudorange_m_aux;
    delete[] PRN_aux;
    delete[] Flag_valid_pseudorange_aux;
    return 0;
}


bool Hybrid_pairCompare_gnss_synchro_sample_counter(const std::pair<int,Gnss_Synchro>& a, const std::pair<int,Gnss_Synchro>& b)
{
    return (a.second.Tracking_sample_counter) < (b.second.Tracking_sample_counter);
}


bool Hybrid_valueCompare_gnss_synchro_sample_counter(const Gnss_Synchro& a, unsigned long int b)
{
    return (a.Tracking_sample_counter) < (b);
}


bool Hybrid_valueCompare_gnss_synchro_receiver_time(const Gnss_Synchro& a, double b)
{
    return ((static_cast<double>(a.Tracking_sample_counter) + static_cast<double>(a.Code_phase_samples)) / static_cast<double>(a.fs) ) < (b);
}


bool Hybrid_pairCompare_gnss_synchro_d_TOW(const std::pair<int,Gnss_Synchro>& a, const std::pair<int,Gnss_Synchro>& b)
{
    return (a.second.TOW_at_current_symbol_s) < (b.second.TOW_at_current_symbol_s);
}


bool Hybrid_valueCompare_gnss_synchro_d_TOW(const Gnss_Synchro& a, double b)
{
    return (a.TOW_at_current_symbol_s) < (b);
}


void hybrid_observables_cc::forecast (int noutput_items __attribute__((unused)), gr_vector_int &ninput_items_required)
{
    for(unsigned int i = 0; i < d_nchannels; i++)
    {
        ninput_items_required[i] = 0;
        //std::cout << "IN buffer "<< i << ". Number of items " << detail()->input(i)->items_available() << std::endl;
    }
    //std::cout << "SC buffer. Number of items " << detail()->input(d_nchannels)->items_available() << std::endl;
    ninput_items_required[d_nchannels] = 1; // set the required available samples in each call
}


int hybrid_observables_cc::general_work (int noutput_items ,
        gr_vector_int &ninput_items,
        gr_vector_const_void_star &input_items,
        gr_vector_void_star &output_items)
{
    const Gnss_Synchro **in = reinterpret_cast<const Gnss_Synchro **>(&input_items[0]); // Get the input buffer pointer
    Gnss_Synchro **out = reinterpret_cast<Gnss_Synchro **>(&output_items[0]);           // Get the output buffer pointer
    int n_outputs = 0;
    int n_consume[d_nchannels];
    double past_history_s = 100e-3;

    Gnss_Synchro current_gnss_synchro[d_nchannels];
    Gnss_Synchro aux = Gnss_Synchro();
    for(unsigned int i = 0; i < d_nchannels; i++)
    {
        current_gnss_synchro[i] = aux;
    }
    /*
     * 1. Read the GNSS SYNCHRO objects from available channels.
     *  Multi-rate GNURADIO Block. Read how many input items are avaliable in each channel
     *  Record all synchronization data into queues
     */
    for (unsigned int i = 0; i < d_nchannels; i++)
    {
        n_consume[i] = ninput_items[i]; // full throttle
        for (int j = 0; j < n_consume[i]; j++)
        {
            d_gnss_synchro_history_queue[i].push_back(in[i][j]);
        }
    }

    bool channel_history_ok;
    do
    {
        channel_history_ok = true;
        for (unsigned int i = 0; i < d_nchannels; i++)
        {
            if (d_gnss_synchro_history_queue[i].size() < history_deep && !d_gnss_synchro_history_queue[i].empty())
            {
                channel_history_ok = false;
            }
        }
        if (channel_history_ok == true)
        {
            std::map<int,Gnss_Synchro>::const_iterator gnss_synchro_map_iter;
            std::deque<Gnss_Synchro>::const_iterator gnss_synchro_deque_iter;

            // 1. If the RX time is not set, set the Rx time
            if (T_rx_s == 0)
            {
                // 0. Read a gnss_synchro snapshot from the queue and store it in a map
                std::map<int,Gnss_Synchro> gnss_synchro_map;
                for (unsigned int i = 0; i < d_nchannels; i++)
                {
                    if (!d_gnss_synchro_history_queue[i].empty())
                    {
                        gnss_synchro_map.insert(std::pair<int, Gnss_Synchro>(d_gnss_synchro_history_queue[i].front().Channel_ID,
                                d_gnss_synchro_history_queue[i].front()));
                    }
                }
                if (gnss_synchro_map.empty()) break;

                gnss_synchro_map_iter = min_element(gnss_synchro_map.cbegin(),
                        gnss_synchro_map.cend(),
                        Hybrid_pairCompare_gnss_synchro_sample_counter);
                T_rx_s = static_cast<double>(gnss_synchro_map_iter->second.Tracking_sample_counter) / static_cast<double>(gnss_synchro_map_iter->second.fs);
                T_rx_s = floor(T_rx_s * 1000.0) / 1000.0; // truncate to ms
                T_rx_s += past_history_s; // increase T_rx to have a minimum past history to interpolate
            }

            // 2. Realign RX time in all valid channels
            std::map<int,Gnss_Synchro> realigned_gnss_synchro_map; // container for the aligned set of observables for the selected T_rx
            std::map<int,Gnss_Synchro> adjacent_gnss_synchro_map;  // container for the previous observable values to interpolate
            // shift channels history to match the reference TOW
            for (unsigned int i = 0; i < d_nchannels; i++)
            {
                if (!d_gnss_synchro_history_queue[i].empty())
                {
                    gnss_synchro_deque_iter = std::lower_bound(d_gnss_synchro_history_queue[i].cbegin(),
                            d_gnss_synchro_history_queue[i].cend(),
                            T_rx_s,
                            Hybrid_valueCompare_gnss_synchro_receiver_time);
                    if (gnss_synchro_deque_iter != d_gnss_synchro_history_queue[i].cend())
                    {
                        if (gnss_synchro_deque_iter->Flag_valid_word == true)
                        {
                            double T_rx_channel = static_cast<double>(gnss_synchro_deque_iter->Tracking_sample_counter) / static_cast<double>(gnss_synchro_deque_iter->fs);
                            double delta_T_rx_s = T_rx_channel - T_rx_s;

                            // check that T_rx difference is less than a threshold (the correlation interval)
                            if (delta_T_rx_s * 1000.0 < static_cast<double>(gnss_synchro_deque_iter->correlation_length_ms))
                            {
                                // record the word structure in a map for pseudorange computation
                                // save the previous observable
                                int distance = std::distance(d_gnss_synchro_history_queue[i].cbegin(), gnss_synchro_deque_iter);
                                if (distance > 0)
                                {
                                    if (d_gnss_synchro_history_queue[i].at(distance - 1).Flag_valid_word)
                                    {
                                        double T_rx_channel_prev = static_cast<double>(d_gnss_synchro_history_queue[i].at(distance - 1).Tracking_sample_counter) / static_cast<double>(gnss_synchro_deque_iter->fs);
                                        double delta_T_rx_s_prev = T_rx_channel_prev - T_rx_s;
                                        if (fabs(delta_T_rx_s_prev) < fabs(delta_T_rx_s))
                                        {
                                            realigned_gnss_synchro_map.insert(std::pair<int, Gnss_Synchro>(d_gnss_synchro_history_queue[i].at(distance - 1).Channel_ID,
                                                    d_gnss_synchro_history_queue[i].at(distance - 1)));
                                            adjacent_gnss_synchro_map.insert(std::pair<int, Gnss_Synchro>(gnss_synchro_deque_iter->Channel_ID, *gnss_synchro_deque_iter));
                                        }
                                        else
                                        {
                                            realigned_gnss_synchro_map.insert(std::pair<int, Gnss_Synchro>(gnss_synchro_deque_iter->Channel_ID, *gnss_synchro_deque_iter));
                                            adjacent_gnss_synchro_map.insert(std::pair<int, Gnss_Synchro>(d_gnss_synchro_history_queue[i].at(distance - 1).Channel_ID,
                                                    d_gnss_synchro_history_queue[i].at(distance - 1)));
                                        }
                                    }

                                }
                                else
                                {
                                    realigned_gnss_synchro_map.insert(std::pair<int, Gnss_Synchro>(gnss_synchro_deque_iter->Channel_ID, *gnss_synchro_deque_iter));
                                }

                            }
                        }
                    }
                }
            }

            if(!realigned_gnss_synchro_map.empty())
            {
                /*
                 *  2.1 Use CURRENT set of measurements and find the nearest satellite
                 *  common RX time algorithm
                 */
                // what is the most recent symbol TOW in the current set? -> this will be the reference symbol
                gnss_synchro_map_iter = max_element(realigned_gnss_synchro_map.cbegin(),
                        realigned_gnss_synchro_map.cend(),
                        Hybrid_pairCompare_gnss_synchro_d_TOW);
                double ref_fs_hz = static_cast<double>(gnss_synchro_map_iter->second.fs);

                // compute interpolated TOW value at T_rx_s
                int ref_channel_key = gnss_synchro_map_iter->second.Channel_ID;
                Gnss_Synchro adj_obs;
                adj_obs = adjacent_gnss_synchro_map.at(ref_channel_key);
                double ref_adj_T_rx_s = static_cast<double>(adj_obs.Tracking_sample_counter) / ref_fs_hz + adj_obs.Code_phase_samples / ref_fs_hz;

                double d_TOW_reference = gnss_synchro_map_iter->second.TOW_at_current_symbol_s;
                double d_ref_T_rx_s = static_cast<double>(gnss_synchro_map_iter->second.Tracking_sample_counter) / ref_fs_hz + gnss_synchro_map_iter->second.Code_phase_samples / ref_fs_hz;

                double selected_T_rx_s = T_rx_s;
                // two points linear interpolation using adjacent (adj) values: y=y1+(x-x1)*(y2-y1)/(x2-x1)
                double ref_TOW_at_T_rx_s = adj_obs.TOW_at_current_symbol_s +
                        (selected_T_rx_s - ref_adj_T_rx_s) * (d_TOW_reference - adj_obs.TOW_at_current_symbol_s) / (d_ref_T_rx_s - ref_adj_T_rx_s);

                // Now compute RX time differences due to the PRN alignment in the correlators
                double traveltime_ms;
                double pseudorange_m;
                double channel_T_rx_s;
                double channel_fs_hz;
                double channel_TOW_s;
                for(gnss_synchro_map_iter = realigned_gnss_synchro_map.cbegin(); gnss_synchro_map_iter != realigned_gnss_synchro_map.cend(); gnss_synchro_map_iter++)
                {
                    channel_fs_hz = static_cast<double>(gnss_synchro_map_iter->second.fs);
                    channel_TOW_s = gnss_synchro_map_iter->second.TOW_at_current_symbol_s;
                    channel_T_rx_s = static_cast<double>(gnss_synchro_map_iter->second.Tracking_sample_counter) / channel_fs_hz + gnss_synchro_map_iter->second.Code_phase_samples / channel_fs_hz;
                    // compute interpolated observation values
                    // two points linear interpolation using adjacent (adj) values: y=y1+(x-x1)*(y2-y1)/(x2-x1)
                    // TOW at the selected receiver time T_rx_s
                    int element_key = gnss_synchro_map_iter->second.Channel_ID;
                    try{
                        adj_obs = adjacent_gnss_synchro_map.at(element_key);
                    }catch(const std::exception & ex)
                    {
                        continue;
                    }

                    double adj_T_rx_s = static_cast<double>(adj_obs.Tracking_sample_counter) / channel_fs_hz + adj_obs.Code_phase_samples / channel_fs_hz;

                    double channel_TOW_at_T_rx_s = adj_obs.TOW_at_current_symbol_s + (selected_T_rx_s - adj_T_rx_s) * (channel_TOW_s - adj_obs.TOW_at_current_symbol_s) / (channel_T_rx_s - adj_T_rx_s);

                    // Doppler and Accumulated carrier phase
                    double Carrier_phase_lin_rads = adj_obs.Carrier_phase_rads + (selected_T_rx_s - adj_T_rx_s) * (gnss_synchro_map_iter->second.Carrier_phase_rads - adj_obs.Carrier_phase_rads) / (channel_T_rx_s - adj_T_rx_s);
                    double Carrier_Doppler_lin_hz = adj_obs.Carrier_Doppler_hz + (selected_T_rx_s - adj_T_rx_s) * (gnss_synchro_map_iter->second.Carrier_Doppler_hz - adj_obs.Carrier_Doppler_hz) / (channel_T_rx_s - adj_T_rx_s);

                    // compute the pseudorange (no rx time offset correction)
                    traveltime_ms = (ref_TOW_at_T_rx_s - channel_TOW_at_T_rx_s) * 1000.0 + GPS_STARTOFFSET_ms;
                    // convert to meters
                    pseudorange_m = traveltime_ms * GPS_C_m_ms; // [m]
                    // update the pseudorange object
                    current_gnss_synchro[gnss_synchro_map_iter->second.Channel_ID] = gnss_synchro_map_iter->second;
                    current_gnss_synchro[gnss_synchro_map_iter->second.Channel_ID].Pseudorange_m = pseudorange_m;
                    current_gnss_synchro[gnss_synchro_map_iter->second.Channel_ID].Flag_valid_pseudorange = true;
                    // Save the estimated RX time (no RX clock offset correction yet!)
                    current_gnss_synchro[gnss_synchro_map_iter->second.Channel_ID].RX_time = ref_TOW_at_T_rx_s + GPS_STARTOFFSET_ms / 1000.0;

                    current_gnss_synchro[gnss_synchro_map_iter->second.Channel_ID].Carrier_phase_rads = Carrier_phase_lin_rads;
                    current_gnss_synchro[gnss_synchro_map_iter->second.Channel_ID].Carrier_Doppler_hz = Carrier_Doppler_lin_hz;
                }

                if(d_dump == true)
                {
                    // MULTIPLEXED FILE RECORDING - Record results to file
                    try
                    {
                        double tmp_double;
                        for (unsigned int i = 0; i < d_nchannels; i++)
                        {
                            tmp_double = current_gnss_synchro[i].RX_time;
                            d_dump_file.write(reinterpret_cast<char*>(&tmp_double), sizeof(double));
                            tmp_double = current_gnss_synchro[i].TOW_at_current_symbol_s;
                            d_dump_file.write(reinterpret_cast<char*>(&tmp_double), sizeof(double));
                            tmp_double = current_gnss_synchro[i].Carrier_Doppler_hz;
                            d_dump_file.write(reinterpret_cast<char*>(&tmp_double), sizeof(double));
                            tmp_double = current_gnss_synchro[i].Carrier_phase_rads / GPS_TWO_PI;
                            d_dump_file.write(reinterpret_cast<char*>(&tmp_double), sizeof(double));
                            tmp_double = current_gnss_synchro[i].Pseudorange_m;
                            d_dump_file.write(reinterpret_cast<char*>(&tmp_double), sizeof(double));
                            tmp_double = current_gnss_synchro[i].PRN;
                            d_dump_file.write(reinterpret_cast<char*>(&tmp_double), sizeof(double));
                            tmp_double = static_cast<double>(current_gnss_synchro[i].Flag_valid_pseudorange);
                            d_dump_file.write(reinterpret_cast<char*>(&tmp_double), sizeof(double));
                        }
                    }
                    catch (const std::ifstream::failure& e)
                    {
                        LOG(WARNING) << "Exception writing observables dump file " << e.what();
                    }
                }

                for (unsigned int i = 0; i < d_nchannels; i++)
                {
                    out[i][n_outputs] = current_gnss_synchro[i];
                }

                n_outputs++;
            }

            // Move RX time
            T_rx_s = T_rx_s + T_rx_step_s;
            // pop old elements from queue
            for (unsigned int i = 0; i < d_nchannels; i++)
            {
                if (!d_gnss_synchro_history_queue[i].empty())
                {
                    while (static_cast<double>(d_gnss_synchro_history_queue[i].front().Tracking_sample_counter) / static_cast<double>(d_gnss_synchro_history_queue[i].front().fs) < (T_rx_s - past_history_s))
                    {
                        d_gnss_synchro_history_queue[i].pop_front();
                    }
                }
            }
        }
    } while(channel_history_ok == true && noutput_items > n_outputs);

    // Multi-rate consume!
    for (unsigned int i = 0; i < d_nchannels; i++)
    {
        consume(i, n_consume[i]); // which input, how many items
    }

    //consume monitor channel always
    consume(d_nchannels, 1);
    return n_outputs;
}