    // Copyright (C) 2010  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_LIBSVM_iO_H__
    #define DLIB_LIBSVM_iO_H__

    #include "libsvm_io_abstract.h"

    #include <fstream>
    #include <string>
    #include <utility>
    #include "../algs.h"
    #include "../matrix.h"
    #include "../string.h"
    #include "../svm/sparse_vector.h"
    #include <vector>

    namespace dlib
    {
        struct sample_data_io_error : public error
        {
            sample_data_io_error(const std::string& message): error(message) {}
        };

    // ----------------------------------------------------------------------------------------

        template <typename sample_type, typename label_type, typename alloc1, typename alloc2>
        void load_libsvm_formatted_data (
            const std::string& file_name,
            std::vector<sample_type, alloc1>& samples,
            std::vector<label_type, alloc2>& labels
        )
        {
            using namespace std;
            typedef typename sample_type::value_type pair_type;
            typedef typename basic_type<typename pair_type::first_type>::type key_type;
            typedef typename pair_type::second_type value_type;

            // You must use unsigned integral key types in your sparse vectors
            COMPILE_TIME_ASSERT(is_unsigned_type<key_type>::value);

            samples.clear();
            labels.clear();

            ifstream fin(file_name.c_str());

            if (!fin)
                throw sample_data_io_error("Unable to open file " + file_name);

            string line;
            istringstream sin;
            key_type key;
            value_type value;
            label_type label;
            sample_type sample;
            long line_num = 0;
            while (fin.peek() != EOF)
            {
                ++line_num;
                getline(fin, line);

                string::size_type pos = line.find_first_not_of(" \t\r\n");

                // ignore empty lines or comment lines
                if (pos == string::npos || line[pos] == '#')
                    continue;

                sin.clear();
                sin.str(line);
                sample.clear();

                sin >> label;

                if (!sin)
                    throw sample_data_io_error("On line: " + cast_to_string(line_num) + ", error while reading file " + file_name );

                // eat whitespace
                sin >> ws;

                while (sin.peek() != EOF && sin.peek() != '#')
                {

                    sin >> key >> ws;

                    // ignore what should be a : character
                    if (sin.get() != ':')
                        throw sample_data_io_error("On line: " + cast_to_string(line_num) + ", error while reading file " + file_name);

                    sin >> value >> ws;

                    if (sin && value != 0)
                    {
                        sample.insert(sample.end(), make_pair(key, value));
                    }
                }

                samples.push_back(sample);
                labels.push_back(label);
            }

        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        template <typename sample_type, typename alloc>
        typename enable_if<is_const_type<typename sample_type::value_type::first_type> >::type
        fix_nonzero_indexing (
            std::vector<sample_type,alloc>& samples
        )
        {
            typedef typename sample_type::value_type pair_type;
            typedef typename basic_type<typename pair_type::first_type>::type key_type;

            if (samples.size() == 0)
                return;

            // figure out the min index value
            key_type min_idx = samples[0].begin()->first;
            for (unsigned long i = 0; i < samples.size(); ++i)
                min_idx = std::min(min_idx, samples[i].begin()->first);

            // Now adjust all the samples so that their min index value is zero.
            if (min_idx != 0)
            {
                sample_type temp;
                for (unsigned long i = 0; i < samples.size(); ++i)
                {
                    // copy samples[i] into temp but make sure it has a min index of zero.
                    temp.clear();
                    typename sample_type::iterator j;
                    for (j = samples[i].begin(); j != samples[i].end(); ++j)
                    {
                        temp.insert(temp.end(), std::make_pair(j->first-min_idx, j->second));
                    }

                    // replace the current sample with temp.
                    samples[i].swap(temp);
                }
            }
        }

    // ----------------------------------------------------------------------------------------

    // If the "first" values in the std::pair objects are not const then we can modify them
    // directly and that is what this version of fix_nonzero_indexing() does.
        template <typename sample_type, typename alloc>
        typename disable_if<is_const_type<typename sample_type::value_type::first_type> >::type
        fix_nonzero_indexing (
            std::vector<sample_type,alloc>& samples
        )
        {
            typedef typename sample_type::value_type pair_type;
            typedef typename basic_type<typename pair_type::first_type>::type key_type;

            if (samples.size() == 0)
                return;

            // figure out the min index value
            key_type min_idx = samples[0].begin()->first;
            for (unsigned long i = 0; i < samples.size(); ++i)
                min_idx = std::min(min_idx, samples[i].begin()->first);

            // Now adjust all the samples so that their min index value is zero.
            if (min_idx != 0)
            {
                for (unsigned long i = 0; i < samples.size(); ++i)
                {
                    typename sample_type::iterator j;
                    for (j = samples[i].begin(); j != samples[i].end(); ++j)
                    {
                        j->first -= min_idx;
                    }
                }
            }
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

    // This is an overload for sparse vectors
        template <typename sample_type, typename label_type, typename alloc1, typename alloc2>
        typename disable_if<is_matrix<sample_type>,void>::type save_libsvm_formatted_data (
            const std::string& file_name,
            const std::vector<sample_type, alloc1>& samples,
            const std::vector<label_type, alloc2>& labels
        )
        {
            typedef typename sample_type::value_type pair_type;
            typedef typename basic_type<typename pair_type::first_type>::type key_type;

            // You must use unsigned integral key types in your sparse vectors
            COMPILE_TIME_ASSERT(is_unsigned_type<key_type>::value);

            // make sure requires clause is not broken
            DLIB_ASSERT(samples.size() == labels.size(),
                "\t void save_libsvm_formatted_data()"
                << "\n\t You have to have labels for each sample and vice versa"
                << "\n\t samples.size(): " << samples.size()
                << "\n\t labels.size():  " << labels.size()
                );

            using namespace std;
            ofstream fout(file_name.c_str());
            fout.precision(14);

            if (!fout)
                throw sample_data_io_error("Unable to open file " + file_name);

            for (unsigned long i = 0; i < samples.size(); ++i)
            {
                fout << labels[i];

                for (typename sample_type::const_iterator j = samples[i].begin(); j != samples[i].end(); ++j)
                {
                    if (j->second != 0)
                        fout << " " << j->first << ":" << j->second;
                }
                fout << "\n";

                if (!fout)
                    throw sample_data_io_error("Error while writing to file " + file_name);
            }

        }

    // ----------------------------------------------------------------------------------------

    // This is an overload for dense vectors
        template <typename sample_type, typename label_type, typename alloc1, typename alloc2>
        typename enable_if<is_matrix<sample_type>,void>::type save_libsvm_formatted_data (
            const std::string& file_name,
            const std::vector<sample_type, alloc1>& samples,
            const std::vector<label_type, alloc2>& labels
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(samples.size() == labels.size(),
                "\t void save_libsvm_formatted_data()"
                << "\n\t You have to have labels for each sample and vice versa"
                << "\n\t samples.size(): " << samples.size()
                << "\n\t labels.size():  " << labels.size()
                );

            using namespace std;
            ofstream fout(file_name.c_str());
            fout.precision(14);

            if (!fout)
                throw sample_data_io_error("Unable to open file " + file_name);

            for (unsigned long i = 0; i < samples.size(); ++i)
            {
                fout << labels[i];

                for (long j = 0; j < samples[i].size(); ++j)
                {
                    if (samples[i](j) != 0)
                        fout << " " << j << ":" << samples[i](j);
                }
                fout << "\n";

                if (!fout)
                    throw sample_data_io_error("Error while writing to file " + file_name);
            }

        }

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_LIBSVM_iO_H__