xlnt/source/detail/serialization/xlsx_producer.cpp

// Copyright (c) 2014-2021 Thomas Fussell
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE
//
// @license: http://www.opensource.org/licenses/mit-license.php
// @author: see AUTHORS file

#include <cmath>
#include <numeric> // for std::accumulate
#include <string>
#include <type_traits>
#include <unordered_set>

#include <xlnt/cell/cell.hpp>
#include <xlnt/cell/hyperlink.hpp>
#include <xlnt/packaging/manifest.hpp>
#include <xlnt/utils/numeric.hpp>
#include <xlnt/utils/path.hpp>
#include <xlnt/utils/scoped_enum_hash.hpp>
#include <xlnt/workbook/workbook.hpp>
#include <xlnt/workbook/workbook_view.hpp>
#include <xlnt/worksheet/header_footer.hpp>
#include <xlnt/worksheet/worksheet.hpp>
#include <detail/constants.hpp>
#include <detail/header_footer/header_footer_code.hpp>
#include <detail/implementations/workbook_impl.hpp>
#include <detail/serialization/custom_value_traits.hpp>
#include <detail/serialization/vector_streambuf.hpp>
#include <detail/serialization/xlsx_producer.hpp>
#include <detail/serialization/zstream.hpp>

namespace {

std::vector<std::pair<std::string, std::string>> core_property_namespace(xlnt::core_property type)
{
    using xlnt::constants;
    using xlnt::core_property;

    if (type == core_property::created
        || type == core_property::modified)
    {
        return {{constants::ns("dcterms"), "dcterms"},
            {constants::ns("xsi"), "xsi"}};
    }
    else if (type == core_property::title
        || type == core_property::subject
        || type == core_property::creator
        || type == core_property::description)
    {
        return {{constants::ns("dc"), "dc"}};
    }
    else if (type == core_property::keywords)
    {
        return {{constants::ns("core-properties"), "cp"},
            {constants::ns("vt"), "vt"}};
    }

    return {{constants::ns("core-properties"), "cp"}};
}

} // namespace

namespace xlnt {
namespace detail {

xlsx_producer::xlsx_producer(const workbook &target)
    : source_(target),
      current_part_stream_(nullptr),
      current_cell_(nullptr),
      current_worksheet_(nullptr)
{
}

xlsx_producer::~xlsx_producer()
{
    end_part();
    archive_.reset();
}

void xlsx_producer::write(std::ostream &destination)
{
    archive_.reset(new ozstream(destination));
    populate_archive(false);
}

void xlsx_producer::open(std::ostream &destination)
{
    archive_.reset(new ozstream(destination));
    populate_archive(true);
}

cell xlsx_producer::add_cell(const cell_reference &ref)
{
    current_cell_->column_ = ref.column();
    current_cell_->row_ = ref.row();

    return cell(current_cell_);
}

worksheet xlsx_producer::add_worksheet(const std::string &title)
{
    current_worksheet_->title_ = title;
    return worksheet(current_worksheet_);
}

// Part Writing Methods

void xlsx_producer::populate_archive(bool streaming)
{
    streaming_ = streaming;

    write_content_types();

    const auto root_rels = source_.manifest().relationships(path("/"));
    write_relationships(root_rels, path("/"));

    for (auto &rel : root_rels)
    {
        // thumbnail is binary content so we don't want to open an xml serializer stream
        if (rel.type() == relationship_type::thumbnail)
        {
            write_image(rel.target().path());
            continue;
        }

        begin_part(rel.target().path());

        if (rel.type() == relationship_type::core_properties)
        {
            write_core_properties(rel);
        }
        else if (rel.type() == relationship_type::extended_properties)
        {
            write_extended_properties(rel);
        }
        else if (rel.type() == relationship_type::custom_properties)
        {
            write_custom_properties(rel);
        }
        else if (rel.type() == relationship_type::office_document)
        {
            write_workbook(rel);
        }
    }

    // Unknown Parts

    void write_unknown_parts();
    void write_unknown_relationships();

    end_part();
}

void xlsx_producer::end_part()
{
    if (current_part_serializer_)
    {
        current_part_serializer_.reset();
    }

    current_part_streambuf_.reset();
}

void xlsx_producer::begin_part(const path &part)
{
    end_part();
    current_part_streambuf_ = archive_->open(part);
    current_part_stream_.rdbuf(current_part_streambuf_.get());

    auto xml_serializer = new xml::serializer(current_part_stream_, part.string(), 0);
    xml_serializer->xml_decl("1.0", "UTF-8", "yes");
    current_part_serializer_.reset(xml_serializer);
}

// Package Parts

void xlsx_producer::write_content_types()
{
    const auto content_types_path = path("[Content_Types].xml");
    begin_part(content_types_path);

    const auto xmlns = "http://schemas.openxmlformats.org/package/2006/content-types";

    write_start_element(xmlns, "Types");
    write_namespace(xmlns, "");

    for (const auto &extension : source_.manifest().extensions_with_default_types())
    {
        write_start_element(xmlns, "Default");
        write_attribute("Extension", extension);
        write_attribute("ContentType", source_.manifest().default_type(extension));
        write_end_element(xmlns, "Default");
    }

    for (const auto &part : source_.manifest().parts_with_overriden_types())
    {
        write_start_element(xmlns, "Override");
        write_attribute("PartName", part.resolve(path("/")).string());
        write_attribute("ContentType", source_.manifest().override_type(part));
        write_end_element(xmlns, "Override");
    }

    write_end_element(xmlns, "Types");
}

void xlsx_producer::write_property(const std::string &name, const variant &value,
    const std::string &ns, bool custom, std::size_t pid)
{
    if (custom)
    {
        write_start_element(ns, "property");
        write_attribute("name", name);
    }
    else
    {
        write_start_element(ns, name);
    }

    switch (value.value_type())
    {
    case variant::type::null: {
        break;
    }

    case variant::type::boolean: {
        if (custom)
        {
            write_attribute("fmtid", "{D5CDD505-2E9C-101B-9397-08002B2CF9AE}");
            write_attribute("pid", pid);
            write_start_element(constants::ns("vt"), "bool");
        }

        write_characters(value.get<bool>() ? "true" : "false");

        if (custom)
        {
            write_end_element(constants::ns("vt"), "bool");
        }

        break;
    }

    case variant::type::i4: {
        if (custom)
        {
            write_attribute("fmtid", "{D5CDD505-2E9C-101B-9397-08002B2CF9AE}");
            write_attribute("pid", pid);
            write_start_element(constants::ns("vt"), "i4");
        }

        write_characters(value.get<std::int32_t>());

        if (custom)
        {
            write_end_element(constants::ns("vt"), "i4");
        }

        break;
    }

    case variant::type::lpstr: {
        if (custom)
        {
            write_attribute("fmtid", "{D5CDD505-2E9C-101B-9397-08002B2CF9AE}");
            write_attribute("pid", pid);
            write_start_element(constants::ns("vt"), "lpwstr");
        }

        if (!custom && ns == constants::ns("dcterms") && (name == "created" || name == "modified"))
        {
            write_attribute(xml::qname(constants::ns("xsi"), "type"), "dcterms:W3CDTF");
        }

        write_characters(value.get<std::string>());

        if (custom)
        {
            write_end_element(constants::ns("vt"), "lpwstr");
        }

        break;
    }

    case variant::type::date: {
        write_attribute(xml::qname(constants::ns("xsi"), "type"), "dcterms:W3CDTF");
        write_characters(value.get<datetime>().to_iso_string());

        break;
    }

    case variant::type::vector: {
        write_start_element(constants::ns("vt"), "vector");

        auto vector = value.get<std::vector<variant>>();
        std::unordered_set<variant::type, scoped_enum_hash<variant::type>> types;

        for (const auto &element : vector)
        {
            types.insert(element.value_type());
        }

        const auto is_mixed = types.size() > 1;
        const auto vector_type = !is_mixed ? to_string(*types.begin()) : "variant";

        write_attribute("size", vector.size());
        write_attribute("baseType", vector_type);

        for (std::size_t i = 0; i < vector.size(); ++i)
        {
            const auto &vector_element = vector.at(i);

            if (is_mixed)
            {
                write_start_element(constants::ns("vt"), "variant");
            }

            if (vector_element.value_type() == variant::type::lpstr)
            {
                write_element(constants::ns("vt"), "lpstr", vector_element.get<std::string>());
            }
            else if (vector_element.value_type() == variant::type::i4)
            {
                write_element(constants::ns("vt"), "i4", vector_element.get<std::int32_t>());
            }

            if (is_mixed)
            {
                write_end_element(constants::ns("vt"), "variant");
            }
        }

        write_end_element(constants::ns("vt"), "vector");

        break;
    }
    }

    if (custom)
    {
        write_end_element(ns, "property");
    }
    else
    {
        write_end_element(ns, name);
    }
}

void xlsx_producer::write_core_properties(const relationship & /*rel*/)
{
    write_start_element(constants::ns("core-properties"), "coreProperties");

    auto core_properties = source_.core_properties();
    std::unordered_map<std::string, std::string> namespaces;

    write_namespace(constants::ns("core-properties"), "cp");

    for (const auto &prop : core_properties)
    {
        for (const auto &ns : core_property_namespace(prop))
        {
            if (namespaces.count(ns.first) > 0) continue;

            write_namespace(ns.first, ns.second);
            namespaces.emplace(ns);
        }
    }

    for (const auto &prop : core_properties)
    {
        write_property(to_string(prop), source_.core_property(prop),
            core_property_namespace(prop).front().first, false, 0);
    }

    write_end_element(constants::ns("core-properties"), "coreProperties");
}

void xlsx_producer::write_extended_properties(const relationship & /*rel*/)
{
    write_start_element(constants::ns("extended-properties"), "Properties");
    write_namespace(constants::ns("extended-properties"), "");

    if (source_.has_extended_property(extended_property::heading_pairs)
        || source_.has_extended_property(extended_property::titles_of_parts))
    {
        write_namespace(constants::ns("vt"), "vt");
    }

    for (const auto &prop : source_.extended_properties())
    {
        write_property(to_string(prop), source_.extended_property(prop),
            constants::ns("extended-properties"), false, 0);
    }

    write_end_element(constants::ns("extended-properties"), "Properties");
}

void xlsx_producer::write_custom_properties(const relationship & /*rel*/)
{
    write_start_element(constants::ns("custom-properties"), "Properties");
    write_namespace(constants::ns("custom-properties"), "");
    write_namespace(constants::ns("vt"), "vt");

    auto pid = std::size_t(2); // why does this start at 2?

    for (const auto &prop : source_.custom_properties())
    {
        write_property(prop, source_.custom_property(prop),
            constants::ns("custom-properties"), true, pid++);
    }

    write_end_element(constants::ns("custom-properties"), "Properties");
}

// Write SpreadsheetML-Specific Package Parts

void xlsx_producer::write_workbook(const relationship &rel)
{
    std::size_t num_visible = 0;
    bool any_defined_names = false;

    for (auto ws : source_)
    {
        if (!ws.has_page_setup() || ws.page_setup().sheet_state() == sheet_state::visible)
        {
            num_visible++;
        }

        if (ws.has_auto_filter())
        {
            any_defined_names = true;
        }
    }

    if (num_visible == 0)
    {
        throw no_visible_worksheets();
    }

    static const auto &xmlns = constants::ns("workbook");
    static const auto &xmlns_r = constants::ns("r");
    static const auto &xmlns_s = constants::ns("spreadsheetml");
    static const auto &xmlns_mx = constants::ns("mx");
    static const auto &xmlns_x15ac = constants::ns("x15ac");
    static const auto &xmlns_x15 = constants::ns("x15");
    static const auto &xmlns_mc = constants::ns("mc");

    write_start_element(xmlns, "workbook");
    write_namespace(xmlns, "");
    write_namespace(xmlns_r, "r");

    if (source_.d_->abs_path_.is_set())
    {
        write_namespace(xmlns_mc, "mc");
        write_namespace(xmlns_x15, "x15");
        write_attribute(xml::qname(xmlns_mc, "Ignorable"), "x15");
    }

    if (source_.has_file_version())
    {
        write_start_element(xmlns, "fileVersion");

        write_attribute("appName", source_.app_name());
        write_attribute("lastEdited", source_.last_edited());
        write_attribute("lowestEdited", source_.lowest_edited());
        write_attribute("rupBuild", source_.rup_build());

        write_end_element(xmlns, "fileVersion");
    }

    write_start_element(xmlns, "workbookPr");

    if (source_.has_code_name())
    {
        write_attribute("codeName", source_.code_name());
    }

    if (source_.base_date() == calendar::mac_1904)
    {
        write_attribute("date1904", "1");
    }

    write_end_element(xmlns, "workbookPr");

    if (source_.d_->abs_path_.is_set())
    {
        write_start_element(xmlns_mc, "AlternateContent");
        write_namespace(xmlns_mc, "mc");
        write_start_element(xmlns_mc, "Choice");
        write_attribute("Requires", "x15");
        write_start_element(xmlns_x15ac, "absPath");
        write_namespace(xmlns_x15ac, "x15ac");
        write_attribute("url", source_.d_->abs_path_.get());
        write_end_element(xmlns_x15ac, "absPath");
        write_end_element(xmlns_mc, "Choice");
        write_end_element(xmlns_mc, "AlternateContent");
    }

    if (source_.has_view())
    {
        write_start_element(xmlns, "bookViews");
        write_start_element(xmlns, "workbookView");

        const auto &view = source_.view();

        if (view.active_tab.is_set() && view.active_tab.get() != std::size_t(0))
        {
            write_attribute("activeTab", view.active_tab.get());
        }

        if (!view.auto_filter_date_grouping)
        {
            write_attribute("autoFilterDateGrouping", write_bool(view.auto_filter_date_grouping));
        }

        if (view.first_sheet.is_set())
        {
            write_attribute("firstSheet", view.first_sheet.get());
        }

        if (view.minimized)
        {
            write_attribute("minimized", write_bool(view.minimized));
        }

        if (!view.show_horizontal_scroll)
        {
            write_attribute("showHorizontalScroll", write_bool(view.show_horizontal_scroll));
        }

        if (!view.show_sheet_tabs)
        {
            write_attribute("showSheetTabs", write_bool(view.show_sheet_tabs));
        }

        if (!view.show_vertical_scroll)
        {
            write_attribute("showVerticalScroll", write_bool(view.show_vertical_scroll));
        }

        if (!view.visible)
        {
            write_attribute("visibility", write_bool(view.visible));
        }

        if (view.x_window.is_set())
        {
            write_attribute("xWindow", view.x_window.get());
        }

        if (view.y_window.is_set())
        {
            write_attribute("yWindow", view.y_window.get());
        }

        if (view.window_width.is_set())
        {
            write_attribute("windowWidth", view.window_width.get());
        }

        if (view.window_height.is_set())
        {
            write_attribute("windowHeight", view.window_height.get());
        }

        if (view.tab_ratio.is_set())
        {
            write_attribute("tabRatio", view.tab_ratio.get());
        }

        write_end_element(xmlns, "workbookView");
        write_end_element(xmlns, "bookViews");
    }

    write_start_element(xmlns, "sheets");

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wrange-loop-analysis"
    for (const auto ws : source_)
    {
        auto sheet_rel_id = source_.d_->sheet_title_rel_id_map_[ws.title()];
        auto sheet_rel = source_.d_->manifest_.relationship(rel.target().path(), sheet_rel_id);

        write_start_element(xmlns, "sheet");
        write_attribute("name", ws.title());
        write_attribute("sheetId", ws.id());

        if (ws.has_page_setup() && ws.sheet_state() == xlnt::sheet_state::hidden)
        {
            write_attribute("state", "hidden");
        }

        write_attribute(xml::qname(xmlns_r, "id"), sheet_rel_id);
        write_end_element(xmlns, "sheet");
    }
#pragma clang diagnostic pop

    write_end_element(xmlns, "sheets");

    if (any_defined_names)
    {
        write_start_element(xmlns, "definedNames");
        /*
        write_attribute("name", "_xlnm._FilterDatabase");
        write_attribute("hidden", write_bool(true));
        write_attribute("localSheetId", "0");
        write_characters("'" + ws.title() + "'!" +
            range_reference::make_absolute(ws.auto_filter()).to_string());
        */
        write_end_element(xmlns, "definedNames");
    }

    if (source_.has_calculation_properties())
    {
        write_start_element(xmlns, "calcPr");
        write_attribute("calcId", source_.calculation_properties().calc_id);
        //write_attribute("calcMode", "auto");
        //write_attribute("fullCalcOnLoad", "1");
        write_attribute("concurrentCalc", write_bool(source_.calculation_properties().concurrent_calc));
        write_end_element(xmlns, "calcPr");
    }

    if (!source_.named_ranges().empty())
    {
        write_start_element(xmlns, "definedNames");

        for (auto &named_range : source_.named_ranges())
        {
            write_start_element(xmlns_s, "definedName");
            write_namespace(xmlns_s, "s");
            write_attribute("name", named_range.name());
            const auto &target = named_range.targets().front();
            write_characters("'" + target.first.title() + "\'!" + target.second.to_string());
            write_end_element(xmlns_s, "definedName");
        }

        write_end_element(xmlns, "definedNames");
    }

    if (source_.d_->arch_id_flags_.is_set())
    {
        write_start_element(xmlns, "extLst");
        write_start_element(xmlns, "ext");
        write_namespace(xmlns_mx, "mx");
        write_attribute("uri", "{7523E5D3-25F3-A5E0-1632-64F254C22452}");
        write_start_element(xmlns_mx, "ArchID");
        write_attribute("Flags", source_.d_->arch_id_flags_.get());
        write_end_element(xmlns_mx, "ArchID");
        write_end_element(xmlns, "ext");
        write_end_element(xmlns, "extLst");
    }

    write_end_element(xmlns, "workbook");

    auto workbook_rels = source_.manifest().relationships(rel.target().path());
    write_relationships(workbook_rels, rel.target().path());

    for (const auto &child_rel : workbook_rels)
    {
        if (child_rel.type() == relationship_type::calculation_chain) continue;

        path archive_path(child_rel.source().path().parent().append(child_rel.target().path()));
        
        // write binary
        switch (child_rel.type())
        {
        case relationship_type::vbaproject:
            write_binary(archive_path);
            continue;
        }

        // write xml
        begin_part(archive_path);

        switch (child_rel.type())
        {
        case relationship_type::chartsheet:
            write_chartsheet(child_rel);
            break;

        case relationship_type::connections:
            write_connections(child_rel);
            break;

        case relationship_type::custom_xml_mappings:
            write_custom_xml_mappings(child_rel);
            break;

        case relationship_type::dialogsheet:
            write_dialogsheet(child_rel);
            break;

        case relationship_type::external_workbook_references:
            write_external_workbook_references(child_rel);
            break;

        case relationship_type::pivot_table:
            write_pivot_table(child_rel);
            break;

        case relationship_type::shared_string_table:
            write_shared_string_table(child_rel);
            break;

        case relationship_type::shared_workbook_revision_headers:
            write_shared_workbook_revision_headers(child_rel);
            break;

        case relationship_type::stylesheet:
            write_styles(child_rel);
            break;

        case relationship_type::theme:
            write_theme(child_rel);
            break;

        case relationship_type::volatile_dependencies:
            write_volatile_dependencies(child_rel);
            break;

        case relationship_type::worksheet:
            write_worksheet(child_rel);
            break;

        case relationship_type::calculation_chain:
            break;
        case relationship_type::office_document:
            break;
        case relationship_type::thumbnail:
            break;
        case relationship_type::extended_properties:
            break;
        case relationship_type::core_properties:
            break;
        case relationship_type::hyperlink:
            break;
        case relationship_type::comments:
            break;
        case relationship_type::vml_drawing:
            break;
        case relationship_type::unknown:
            break;
        case relationship_type::custom_properties:
            break;
        case relationship_type::printer_settings:
            break;
        case relationship_type::custom_property:
            break;
        case relationship_type::drawings:
            break;
        case relationship_type::pivot_table_cache_definition:
            break;
        case relationship_type::pivot_table_cache_records:
            break;
        case relationship_type::query_table:
            break;
        case relationship_type::shared_workbook:
            break;
        case relationship_type::revision_log:
            break;
        case relationship_type::shared_workbook_user_data:
            break;
        case relationship_type::single_cell_table_definitions:
            break;
        case relationship_type::table_definition:
            break;
        case relationship_type::vbaproject:
            break;
        case relationship_type::image:
            break;
        }
    }
}

// Write Workbook Relationship Target Parts

void xlsx_producer::write_chartsheet(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "chartsheet");
    write_start_element(constants::ns("spreadsheetml"), "chartsheet");
}

void xlsx_producer::write_connections(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "connections");
    write_end_element(constants::ns("spreadsheetml"), "connections");
}

void xlsx_producer::write_custom_xml_mappings(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "MapInfo");
    write_end_element(constants::ns("spreadsheetml"), "MapInfo");
}

void xlsx_producer::write_dialogsheet(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "dialogsheet");
    write_end_element(constants::ns("spreadsheetml"), "dialogsheet");
}

void xlsx_producer::write_external_workbook_references(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "externalLink");
    write_end_element(constants::ns("spreadsheetml"), "externalLink");
}

void xlsx_producer::write_pivot_table(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "pivotTableDefinition");
    write_end_element(constants::ns("spreadsheetml"), "pivotTableDefinition");
}

void xlsx_producer::write_rich_text(const std::string &ns, const xlnt::rich_text &text)
{
    if (text.runs().size() == 1 && !text.runs().at(0).second.is_set())
    {
        write_start_element(ns, "t");
        write_characters(text.plain_text(), text.runs().front().preserve_space);
        write_end_element(ns, "t");
    }
    else
    {
        for (const auto &run : text.runs())
        {
            write_start_element(ns, "r");

            if (run.second.is_set())
            {
                write_start_element(ns, "rPr");

                if (run.second.get().bold())
                {
                    write_start_element(ns, "b");
                    write_end_element(ns, "b");
                }

                if (run.second.get().has_size())
                {
                    write_start_element(ns, "sz");
                    write_attribute<double>("val", run.second.get().size());
                    write_end_element(ns, "sz");
                }

                if (run.second.get().has_color())
                {
                    write_start_element(ns, "color");
                    write_color(run.second.get().color());
                    write_end_element(ns, "color");
                }

                if (run.second.get().has_name())
                {
                    write_start_element(ns, "rFont");
                    write_attribute("val", run.second.get().name());
                    write_end_element(ns, "rFont");
                }

                if (run.second.get().has_family())
                {
                    write_start_element(ns, "family");
                    write_attribute("val", run.second.get().family());
                    write_end_element(ns, "family");
                }

                if (run.second.get().has_scheme())
                {
                    write_start_element(ns, "scheme");
                    write_attribute("val", run.second.get().scheme());
                    write_end_element(ns, "scheme");
                }

                write_end_element(ns, "rPr");
            }

            write_element(ns, "t", run.first, run.preserve_space);
            write_end_element(ns, "r");
        }
    }

    for (const auto &run : text.phonetic_runs())
    {
        write_start_element(ns, "rPh");
        write_attribute("sb", run.start);
        write_attribute("eb", run.end);
        write_start_element(ns, "t");
        write_characters(run.text, run.preserve_space);
        write_end_element(ns, "t");
        write_end_element(ns, "rPh");
    }

    if (text.has_phonetic_properties())
    {
        const auto &phonetic_properties = text.phonetic_properties();

        write_start_element(ns, "phoneticPr");
        write_attribute("fontId", phonetic_properties.font_id());

        if (text.phonetic_properties().has_type())
        {
            const auto type = phonetic_properties.type();
            write_attribute("type", phonetic_properties.type_as_string(type));
        }

        if (text.phonetic_properties().has_alignment())
        {
            const auto alignment = phonetic_properties.alignment();
            write_attribute("alignment", phonetic_properties.alignment_as_string(alignment));
        }

        write_end_element(ns, "phoneticPr");
    }
}

void xlsx_producer::write_shared_string_table(const relationship & /*rel*/)
{
    static const auto &xmlns = constants::ns("spreadsheetml");

    write_start_element(xmlns, "sst");
    write_namespace(xmlns, "");

    // todo: is there a more elegant way to get this number?
    std::size_t string_count = 0;

    for (const auto ws : source_)
    {
        auto dimension = ws.calculate_dimension();
        auto current_cell = dimension.top_left();

        while (current_cell.row() <= dimension.bottom_right().row())
        {
            while (current_cell.column() <= dimension.bottom_right().column())
            {
                auto c_iter = ws.d_->cell_map_.find(current_cell);
                if (c_iter != ws.d_->cell_map_.end() && c_iter->second.type_ == cell_type::shared_string)
                {
                    ++string_count;
                }

                current_cell.column_index(current_cell.column_index() + 1);
            }

            current_cell.row(current_cell.row() + 1);
            current_cell.column_index(dimension.top_left().column_index());
        }
    }

    write_attribute("count", string_count);
    write_attribute("uniqueCount", source_.shared_strings().size());

    for (const auto &text : source_.shared_strings())
    {
        write_start_element(xmlns, "si");
        write_rich_text(xmlns, text);
        write_end_element(xmlns, "si");
    }

    write_end_element(xmlns, "sst");
}

void xlsx_producer::write_shared_workbook_revision_headers(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "headers");
    write_end_element(constants::ns("spreadsheetml"), "headers");
}

void xlsx_producer::write_shared_workbook(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "revisions");
    write_end_element(constants::ns("spreadsheetml"), "revisions");
}

void xlsx_producer::write_shared_workbook_user_data(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "users");
    write_end_element(constants::ns("spreadsheetml"), "users");
}

void xlsx_producer::write_font(const font &f)
{
    static const auto &xmlns = constants::ns("spreadsheetml");

    write_start_element(xmlns, "font");

    if (f.bold())
    {
        write_start_element(xmlns, "b");
        write_end_element(xmlns, "b");
    }

    if (f.italic())
    {
        write_start_element(xmlns, "i");
        write_end_element(xmlns, "i");
    }

    if (f.strikethrough())
    {
        write_start_element(xmlns, "strike");
        write_end_element(xmlns, "strike");
    }

    if (f.underlined())
    {
        write_start_element(xmlns, "u");
        if (f.underline() != font::underline_style::single)
        {
            write_attribute("val", f.underline());
        }
        write_end_element(xmlns, "u");
    }

    if (f.superscript())
    {
        write_start_element(xmlns, "vertAlign");
        write_attribute("val", "superscript");
        write_end_element(xmlns, "vertAlign");
    }
    else if (f.subscript())
    {
        write_start_element(xmlns, "vertAlign");
        write_attribute("val", "subscript");
        write_end_element(xmlns, "vertAlign");
    }

    if (f.has_size())
    {
        write_start_element(xmlns, "sz");
        write_attribute<double>("val", f.size());
        write_end_element(xmlns, "sz");
    }

    if (f.has_color())
    {
        write_start_element(xmlns, "color");
        write_color(f.color());
        write_end_element(xmlns, "color");
    }

    if (f.has_name())
    {
        write_start_element(xmlns, "name");
        write_attribute("val", f.name());
        write_end_element(xmlns, "name");
    }

    if (f.has_family())
    {
        write_start_element(xmlns, "family");
        write_attribute("val", f.family());
        write_end_element(xmlns, "family");
    }

    if (f.has_scheme())
    {
        write_start_element(xmlns, "scheme");
        write_attribute("val", f.scheme());
        write_end_element(xmlns, "scheme");
    }

    write_end_element(xmlns, "font");
}

void xlsx_producer::write_fill(const fill &f)
{
    static const auto &xmlns = constants::ns("spreadsheetml");

    write_start_element(xmlns, "fill");

    if (f.type() == xlnt::fill_type::pattern)
    {
        const auto &pattern = f.pattern_fill();

        write_start_element(xmlns, "patternFill");

        write_attribute("patternType", pattern.type());

        if (pattern.foreground().is_set())
        {
            write_start_element(xmlns, "fgColor");
            write_color(pattern.foreground().get());
            write_end_element(xmlns, "fgColor");
        }

        if (pattern.background().is_set())
        {
            write_start_element(xmlns, "bgColor");
            write_color(pattern.background().get());
            write_end_element(xmlns, "bgColor");
        }

        write_end_element(xmlns, "patternFill");
    }
    else if (f.type() == xlnt::fill_type::gradient)
    {
        const auto &gradient = f.gradient_fill();

        write_start_element(xmlns, "gradientFill");
        write_attribute("gradientType", gradient.type());

        if (gradient.degree() != 0.)
        {
            write_attribute<double>("degree", gradient.degree());
        }

        if (gradient.left() != 0.)
        {
            write_attribute<double>("left", gradient.left());
        }

        if (gradient.right() != 0.)
        {
            write_attribute<double>("right", gradient.right());
        }

        if (gradient.top() != 0.)
        {
            write_attribute<double>("top", gradient.top());
        }

        if (gradient.bottom() != 0.)
        {
            write_attribute<double>("bottom", gradient.bottom());
        }

        for (const auto &stop : gradient.stops())
        {
            write_start_element(xmlns, "stop");
            write_attribute<double>("position", stop.first);
            write_start_element(xmlns, "color");
            write_color(stop.second);
            write_end_element(xmlns, "color");
            write_end_element(xmlns, "stop");
        }

        write_end_element(xmlns, "gradientFill");
    }

    write_end_element(xmlns, "fill");
}

void xlsx_producer::write_border(const border &current_border)
{
    static const auto &xmlns = constants::ns("spreadsheetml");

    write_start_element(xmlns, "border");

    if (current_border.diagonal().is_set())
    {
        auto up = current_border.diagonal().get() == diagonal_direction::both
            || current_border.diagonal().get() == diagonal_direction::up;
        write_attribute("diagonalUp", write_bool(up));

        auto down = current_border.diagonal().get() == diagonal_direction::both
            || current_border.diagonal().get() == diagonal_direction::down;
        write_attribute("diagonalDown", write_bool(down));
    }

    for (const auto &side : xlnt::border::all_sides())
    {
        if (current_border.side(side).is_set())
        {
            const auto current_side = current_border.side(side).get();

            auto side_name = to_string(side);
            write_start_element(xmlns, side_name);

            if (current_side.style().is_set())
            {
                write_attribute("style", current_side.style().get());
            }

            if (current_side.color().is_set())
            {
                write_start_element(xmlns, "color");
                write_color(current_side.color().get());
                write_end_element(xmlns, "color");
            }

            write_end_element(xmlns, side_name);
        }
    }

    write_end_element(xmlns, "border");
}

void xlsx_producer::write_styles(const relationship & /*rel*/)
{
    static const auto &xmlns = constants::ns("spreadsheetml");
    static const auto &xmlns_mc = constants::ns("mc");
    static const auto &xmlns_x14 = constants::ns("x14");
    static const auto &xmlns_x14ac = constants::ns("x14ac");

    write_start_element(xmlns, "styleSheet");
    write_namespace(xmlns, "");

    const auto &stylesheet = source_.impl().stylesheet_.get();

    auto using_namespace = [&stylesheet](const std::string &ns) {
        if (ns == "x14ac")
        {
            return stylesheet.known_fonts_enabled;
        }

        return false;
    };

    if (using_namespace("x14ac"))
    {
        write_namespace(xmlns_mc, "mc");
        write_namespace(xmlns_x14ac, "x14ac");
        write_attribute(xml::qname(xmlns_mc, "Ignorable"), "x14ac");
    }

    // Number Formats

    if (!stylesheet.number_formats.empty())
    {
        const auto &number_formats = stylesheet.number_formats;

        auto num_custom = std::count_if(number_formats.begin(), number_formats.end(),
            [](const number_format &nf) { return nf.id() >= 164; });

        if (num_custom > 0)
        {
            write_start_element(xmlns, "numFmts");
            write_attribute("count", num_custom);

            for (const auto &num_fmt : number_formats)
            {
                if (num_fmt.id() < 164) continue;
                write_start_element(xmlns, "numFmt");
                write_attribute("numFmtId", num_fmt.id());
                write_attribute("formatCode", num_fmt.format_string());
                write_end_element(xmlns, "numFmt");
            }

            write_end_element(xmlns, "numFmts");
        }
    }

    // Fonts

    if (!stylesheet.fonts.empty())
    {
        const auto &fonts = stylesheet.fonts;

        write_start_element(xmlns, "fonts");
        write_attribute("count", fonts.size());

        if (stylesheet.known_fonts_enabled)
        {
            auto is_known_font = [](const font &f) {
                const auto known_fonts = std::vector<font>{
                    font().name("Calibri").family(2).size(12).color(theme_color(1)).scheme("minor")};

                return std::find(known_fonts.begin(), known_fonts.end(), f) != known_fonts.end();
            };

            std::size_t num_known_fonts = 0;

            for (const auto &current_font : fonts)
            {
                if (is_known_font(current_font))
                {
                    num_known_fonts += 1;
                }
            }

            write_attribute(xml::qname(xmlns_x14ac, "knownFonts"), num_known_fonts);
        }

        for (const auto &current_font : fonts)
        {
            write_font(current_font);
        }

        write_end_element(xmlns, "fonts");
    }

    // Fills

    if (!stylesheet.fills.empty())
    {
        const auto &fills = stylesheet.fills;

        write_start_element(xmlns, "fills");
        write_attribute("count", fills.size());

        for (auto &current_fill : fills)
        {
            write_fill(current_fill);
        }

        write_end_element(xmlns, "fills");
    }

    // Borders

    if (!stylesheet.borders.empty())
    {
        const auto &borders = stylesheet.borders;

        write_start_element(xmlns, "borders");
        write_attribute("count", borders.size());

        for (const auto &current_border : borders)
        {
            write_border(current_border);
        }

        write_end_element(xmlns, "borders");
    }

    // Style XFs
    if (stylesheet.style_impls.size() > 0)
    {
        write_start_element(xmlns, "cellStyleXfs");
        write_attribute("count", stylesheet.style_impls.size());

        for (const auto &current_style_name : stylesheet.style_names)
        {
            const auto &current_style_impl = stylesheet.style_impls.at(current_style_name);

            write_start_element(xmlns, "xf");

            if (current_style_impl.number_format_id.is_set())
            {
                write_attribute("numFmtId", current_style_impl.number_format_id.get());
            }

            if (current_style_impl.font_id.is_set())
            {
                write_attribute("fontId", current_style_impl.font_id.get());
            }

            if (current_style_impl.fill_id.is_set())
            {
                write_attribute("fillId", current_style_impl.fill_id.get());
            }

            if (current_style_impl.border_id.is_set())
            {
                write_attribute("borderId", current_style_impl.border_id.get());
            }

            if (current_style_impl.number_format_id.is_set()
                && current_style_impl.number_format_applied.is_set())
            {
                write_attribute("applyNumberFormat",
                    write_bool(current_style_impl.number_format_applied.get()));
            }

            if (current_style_impl.fill_id.is_set()
                && current_style_impl.fill_applied.is_set())
            {
                write_attribute("applyFill",
                    write_bool(current_style_impl.fill_applied.get()));
            }

            if (current_style_impl.font_id.is_set()
                && current_style_impl.font_applied.is_set())
            {
                write_attribute("applyFont",
                    write_bool(current_style_impl.font_applied.get()));
            }

            if (current_style_impl.border_id.is_set()
                && current_style_impl.border_applied.is_set())
            {
                write_attribute("applyBorder",
                    write_bool(current_style_impl.border_applied.get()));
            }

            if (current_style_impl.alignment_id.is_set()
                && current_style_impl.alignment_applied.is_set())
            {
                write_attribute("applyAlignment",
                    write_bool(current_style_impl.alignment_applied.get()));
            }

            if (current_style_impl.protection_id.is_set()
                && current_style_impl.protection_applied.is_set())
            {
                write_attribute("applyProtection",
                    write_bool(current_style_impl.protection_applied.get()));
            }

            if (current_style_impl.pivot_button_)
            {
                write_attribute("pivotButton", write_bool(true));
            }

            if (current_style_impl.quote_prefix_)
            {
                write_attribute("quotePrefix", write_bool(true));
            }

            if (current_style_impl.alignment_id.is_set())
            {
                const auto &current_alignment = stylesheet.alignments[current_style_impl.alignment_id.get()];

                write_start_element(xmlns, "alignment");

                if (current_alignment.vertical().is_set())
                {
                    write_attribute("vertical", current_alignment.vertical().get());
                }

                if (current_alignment.horizontal().is_set())
                {
                    write_attribute("horizontal", current_alignment.horizontal().get());
                }

                if (current_alignment.rotation().is_set())
                {
                    write_attribute("textRotation", current_alignment.rotation().get());
                }

                if (current_alignment.wrap())
                {
                    write_attribute("wrapText", write_bool(current_alignment.wrap()));
                }

                if (current_alignment.indent().is_set())
                {
                    write_attribute("indent", current_alignment.indent().get());
                }

                if (current_alignment.shrink())
                {
                    write_attribute("shrinkToFit", write_bool(current_alignment.shrink()));
                }

                write_end_element(xmlns, "alignment");
            }

            if (current_style_impl.protection_id.is_set())
            {
                const auto &current_protection = stylesheet.protections[current_style_impl.protection_id.get()];

                write_start_element(xmlns, "protection");
                write_attribute("locked", write_bool(current_protection.locked()));
                write_attribute("hidden", write_bool(current_protection.hidden()));
                write_end_element(xmlns, "protection");
            }

            write_end_element(xmlns, "xf");
        }

        write_end_element(xmlns, "cellStyleXfs");
    }

    // Format XFs

    write_start_element(xmlns, "cellXfs");
    write_attribute("count", stylesheet.format_impls.size());

    for (auto &current_format_impl : stylesheet.format_impls)
    {
        write_start_element(xmlns, "xf");

        if (current_format_impl.number_format_id.is_set())
        {
            write_attribute("numFmtId", current_format_impl.number_format_id.get());
        }

        if (current_format_impl.font_id.is_set())
        {
            write_attribute("fontId", current_format_impl.font_id.get());
        }

        if (current_format_impl.fill_id.is_set())
        {
            write_attribute("fillId", current_format_impl.fill_id.get());
        }

        if (current_format_impl.border_id.is_set())
        {
            write_attribute("borderId", current_format_impl.border_id.get());
        }

        if (current_format_impl.style.is_set())
        {
            write_attribute("xfId", stylesheet.style_index(current_format_impl.style.get()));
        }

        if (current_format_impl.number_format_id.is_set()
            && current_format_impl.number_format_applied.is_set())
        {
            write_attribute("applyNumberFormat",
                write_bool(current_format_impl.number_format_applied.get()));
        }

        if (current_format_impl.fill_id.is_set()
            && current_format_impl.fill_applied.is_set())
        {
            write_attribute("applyFill",
                write_bool(current_format_impl.fill_applied.get()));
        }

        if (current_format_impl.font_id.is_set()
            && current_format_impl.font_applied.is_set())
        {
            write_attribute("applyFont",
                write_bool(current_format_impl.font_applied.get()));
        }

        if (current_format_impl.border_id.is_set()
            && current_format_impl.border_applied.is_set())
        {
            write_attribute("applyBorder",
                write_bool(current_format_impl.border_applied.get()));
        }

        if (current_format_impl.alignment_applied.is_set())
        {
            write_attribute("applyAlignment",
                write_bool(current_format_impl.alignment_applied.get()));
        }

        if (current_format_impl.protection_applied.is_set())
        {
            write_attribute("applyProtection",
                write_bool(current_format_impl.protection_applied.get()));
        }

        if (current_format_impl.pivot_button_)
        {
            write_attribute("pivotButton", write_bool(true));
        }

        if (current_format_impl.quote_prefix_)
        {
            write_attribute("quotePrefix", write_bool(true));
        }

        if (current_format_impl.alignment_id.is_set())
        {
            const auto &current_alignment = stylesheet.alignments[current_format_impl.alignment_id.get()];

            write_start_element(xmlns, "alignment");

            if (current_alignment.horizontal().is_set())
            {
                write_attribute("horizontal", current_alignment.horizontal().get());
            }

            if (current_alignment.vertical().is_set())
            {
                write_attribute("vertical", current_alignment.vertical().get());
            }

            if (current_alignment.rotation().is_set())
            {
                write_attribute("textRotation", current_alignment.rotation().get());
            }

            if (current_alignment.wrap())
            {
                write_attribute("wrapText", write_bool(current_alignment.wrap()));
            }

            if (current_alignment.indent().is_set())
            {
                write_attribute("indent", current_alignment.indent().get());
            }

            if (current_alignment.shrink())
            {
                write_attribute("shrinkToFit", write_bool(current_alignment.shrink()));
            }

            write_end_element(xmlns, "alignment");
        }

        if (current_format_impl.protection_id.is_set())
        {
            const auto &current_protection = stylesheet.protections[current_format_impl.protection_id.get()];

            write_start_element(xmlns, "protection");
            write_attribute("locked", write_bool(current_protection.locked()));
            write_attribute("hidden", write_bool(current_protection.hidden()));
            write_end_element(xmlns, "protection");
        }

        write_end_element(xmlns, "xf");
    }

    write_end_element(xmlns, "cellXfs");

    // Styles
    if (stylesheet.style_impls.size() > 0)
    {
        write_start_element(xmlns, "cellStyles");
        write_attribute("count", stylesheet.style_impls.size());
        std::size_t style_index = 0;

        for (auto &current_style_name : stylesheet.style_names)
        {
            const auto &current_style = stylesheet.style_impls.at(current_style_name);

            write_start_element(xmlns, "cellStyle");

            write_attribute("name", current_style.name);
            write_attribute("xfId", style_index++);

            if (current_style.builtin_id.is_set())
            {
                write_attribute("builtinId", current_style.builtin_id.get());
            }

            if (current_style.hidden_style)
            {
                write_attribute("hidden", write_bool(true));
            }

            if (current_style.builtin_id.is_set() && current_style.custom_builtin)
            {
                write_attribute("customBuiltin", write_bool(current_style.custom_builtin));
            }

            write_end_element(xmlns, "cellStyle");
        }

        write_end_element(xmlns, "cellStyles");
    }

    // Conditional Formats
    write_start_element(xmlns, "dxfs");
    write_attribute("count", stylesheet.conditional_format_impls.size());

    for (auto &rule : stylesheet.conditional_format_impls)
    {
        write_start_element(xmlns, "dxf");

        if (rule.border_id.is_set())
        {
            const auto &current_border = stylesheet.borders.at(rule.border_id.get());
            write_border(current_border);
        }

        if (rule.fill_id.is_set())
        {
            const auto &current_fill = stylesheet.fills.at(rule.fill_id.get());
            write_fill(current_fill);
        }

        if (rule.font_id.is_set())
        {
            const auto &current_font = stylesheet.fonts.at(rule.font_id.get());
            write_font(current_font);
        }

        write_end_element(xmlns, "dxf");
    }

    write_end_element(xmlns, "dxfs");

    write_start_element(xmlns, "tableStyles");
    write_attribute("count", "0");
    write_attribute("defaultTableStyle", "TableStyleMedium9");
    write_attribute("defaultPivotStyle", "PivotStyleMedium7");
    write_end_element(xmlns, "tableStyles");

    if (!stylesheet.colors.empty())
    {
        write_start_element(xmlns, "colors");
        write_start_element(xmlns, "indexedColors");

        for (auto &c : stylesheet.colors)
        {
            write_start_element(xmlns, "rgbColor");
            write_attribute("rgb", c.rgb().hex_string());
            write_end_element(xmlns, "rgbColor");
        }

        write_end_element(xmlns, "indexedColors");
        write_end_element(xmlns, "colors");
    }

    auto using_extensions = stylesheet.default_slicer_style.is_set();

    if (using_extensions)
    {
        write_start_element(xmlns, "extLst");

        if (stylesheet.default_slicer_style.is_set())
        {
            write_start_element(xmlns, "ext");
            write_namespace(xmlns_x14, "x14");
            write_attribute("uri", "{EB79DEF2-80B8-43e5-95BD-54CBDDF9020C}"); // slicerStyles URI
            write_start_element(xmlns_x14, "slicerStyles");
            write_attribute("defaultSlicerStyle", stylesheet.default_slicer_style.get());
            write_end_element(xmlns_x14, "slicerStyles");
            write_end_element(xmlns, "ext");
        }

        write_end_element(xmlns, "extLst");
    }

    write_end_element(xmlns, "styleSheet");
}

void xlsx_producer::write_theme(const relationship &theme_rel)
{
    static const auto &xmlns_a = constants::ns("drawingml");
    static const auto &xmlns_thm15 = constants::ns("thm15");

    write_start_element(xmlns_a, "theme");
    write_namespace(xmlns_a, "a");
    write_attribute("name", "Office Theme");

    write_start_element(xmlns_a, "themeElements");
    write_start_element(xmlns_a, "clrScheme");
    write_attribute("name", "Office");

    struct scheme_element
    {
        std::string name;
        std::string sub_element_name;
        std::string val;
    };

    std::vector<scheme_element> scheme_elements = {
        {"dk1", "sysClr", "windowText"},
        {"lt1", "sysClr", "window"},
        {"dk2", "srgbClr", "44546A"},
        {"lt2", "srgbClr", "E7E6E6"},
        {"accent1", "srgbClr", "5B9BD5"},
        {"accent2", "srgbClr", "ED7D31"},
        {"accent3", "srgbClr", "A5A5A5"},
        {"accent4", "srgbClr", "FFC000"},
        {"accent5", "srgbClr", "4472C4"},
        {"accent6", "srgbClr", "70AD47"},
        {"hlink", "srgbClr", "0563C1"},
        {"folHlink", "srgbClr", "954F72"},
    };

    for (auto element : scheme_elements)
    {
        write_start_element(xmlns_a, element.name);
        write_start_element(xmlns_a, element.sub_element_name);
        write_attribute("val", element.val);

        if (element.name == "dk1")
        {
            write_attribute("lastClr", "000000");
        }
        else if (element.name == "lt1")
        {
            write_attribute("lastClr", "FFFFFF");
        }

        write_end_element(xmlns_a, element.sub_element_name);
        write_end_element(xmlns_a, element.name);
    }

    write_end_element(xmlns_a, "clrScheme");

    struct font_scheme
    {
        bool typeface;
        std::string script;
        std::string major;
        std::string minor;
    };

    static const auto font_schemes = std::vector<font_scheme>{{true, "latin", "Calibri Light", "Calibri"},
        {true, "ea", "", ""}, {true, "cs", "", ""}, {false, "Jpan", "Yu Gothic Light", "Yu Gothic"},
        {false, "Hang", "\xeb\xa7\x91\xec\x9d\x80 \xea\xb3\xa0\xeb\x94\x95",
            "\xeb\xa7\x91\xec\x9d\x80 \xea\xb3\xa0\xeb\x94\x95"},
        {false, "Hans", "DengXian Light", "DengXian"},
        {false, "Hant", "\xe6\x96\xb0\xe7\xb4\xb0\xe6\x98\x8e\xe9\xab\x94",
            "\xe6\x96\xb0\xe7\xb4\xb0\xe6\x98\x8e\xe9\xab\x94"},
        {false, "Arab", "Times New Roman", "Arial"}, {false, "Hebr", "Times New Roman", "Arial"},
        {false, "Thai", "Tahoma", "Tahoma"}, {false, "Ethi", "Nyala", "Nyala"}, {false, "Beng", "Vrinda", "Vrinda"},
        {false, "Gujr", "Shruti", "Shruti"}, {false, "Khmr", "MoolBoran", "DaunPenh"},
        {false, "Knda", "Tunga", "Tunga"}, {false, "Guru", "Raavi", "Raavi"}, {false, "Cans", "Euphemia", "Euphemia"},
        {false, "Cher", "Plantagenet Cherokee", "Plantagenet Cherokee"},
        {false, "Yiii", "Microsoft Yi Baiti", "Microsoft Yi Baiti"},
        {false, "Tibt", "Microsoft Himalaya", "Microsoft Himalaya"}, {false, "Thaa", "MV Boli", "MV Boli"},
        {false, "Deva", "Mangal", "Mangal"}, {false, "Telu", "Gautami", "Gautami"}, {false, "Taml", "Latha", "Latha"},
        {false, "Syrc", "Estrangelo Edessa", "Estrangelo Edessa"}, {false, "Orya", "Kalinga", "Kalinga"},
        {false, "Mlym", "Kartika", "Kartika"}, {false, "Laoo", "DokChampa", "DokChampa"},
        {false, "Sinh", "Iskoola Pota", "Iskoola Pota"}, {false, "Mong", "Mongolian Baiti", "Mongolian Baiti"},
        {false, "Viet", "Times New Roman", "Arial"}, {false, "Uigh", "Microsoft Uighur", "Microsoft Uighur"},
        {false, "Geor", "Sylfaen", "Sylfaen"}};

    write_start_element(xmlns_a, "fontScheme");
    write_attribute("name", "Office");

    for (auto major : {true, false})
    {
        write_start_element(xmlns_a, major ? "majorFont" : "minorFont");

        for (const auto &scheme : font_schemes)
        {
            const auto scheme_value = major ? scheme.major : scheme.minor;

            if (scheme.typeface)
            {
                write_start_element(xmlns_a, scheme.script);
                write_attribute("typeface", scheme_value);

                if (scheme_value == "Calibri Light")
                {
                    write_attribute("panose", "020F0302020204030204");
                }
                else if (scheme_value == "Calibri")
                {
                    write_attribute("panose", "020F0502020204030204");
                }

                write_end_element(xmlns_a, scheme.script);
            }
            else
            {
                write_start_element(xmlns_a, "font");
                write_attribute("script", scheme.script);
                write_attribute("typeface", scheme_value);
                write_end_element(xmlns_a, "font");
            }
        }

        write_end_element(xmlns_a, major ? "majorFont" : "minorFont");
    }

    write_end_element(xmlns_a, "fontScheme");

    write_start_element(xmlns_a, "fmtScheme");
    write_attribute("name", "Office");

    write_start_element(xmlns_a, "fillStyleLst");
    write_start_element(xmlns_a, "solidFill");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "solidFill");

    write_start_element(xmlns_a, "gradFill");
    write_attribute("rotWithShape", "1");
    write_start_element(xmlns_a, "gsLst");

    write_start_element(xmlns_a, "gs");
    write_attribute("pos", "0");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "lumMod");
    write_attribute("val", "110000");
    write_end_element(xmlns_a, "lumMod");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "105000");
    write_end_element(xmlns_a, "satMod");
    write_start_element(xmlns_a, "tint");
    write_attribute("val", "67000");
    write_end_element(xmlns_a, "tint");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "gs");

    write_start_element(xmlns_a, "gs");
    write_attribute("pos", "50000");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "lumMod");
    write_attribute("val", "105000");
    write_end_element(xmlns_a, "lumMod");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "103000");
    write_end_element(xmlns_a, "satMod");
    write_start_element(xmlns_a, "tint");
    write_attribute("val", "73000");
    write_end_element(xmlns_a, "tint");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "gs");

    write_start_element(xmlns_a, "gs");
    write_attribute("pos", "100000");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "lumMod");
    write_attribute("val", "105000");
    write_end_element(xmlns_a, "lumMod");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "109000");
    write_end_element(xmlns_a, "satMod");
    write_start_element(xmlns_a, "tint");
    write_attribute("val", "81000");
    write_end_element(xmlns_a, "tint");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "gs");

    write_end_element(xmlns_a, "gsLst");

    write_start_element(xmlns_a, "lin");
    write_attribute("ang", "5400000");
    write_attribute("scaled", "0");
    write_end_element(xmlns_a, "lin");

    write_end_element(xmlns_a, "gradFill");

    write_start_element(xmlns_a, "gradFill");
    write_attribute("rotWithShape", "1");
    write_start_element(xmlns_a, "gsLst");

    write_start_element(xmlns_a, "gs");
    write_attribute("pos", "0");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "103000");
    write_end_element(xmlns_a, "satMod");
    write_start_element(xmlns_a, "lumMod");
    write_attribute("val", "102000");
    write_end_element(xmlns_a, "lumMod");
    write_start_element(xmlns_a, "tint");
    write_attribute("val", "94000");
    write_end_element(xmlns_a, "tint");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "gs");

    write_start_element(xmlns_a, "gs");
    write_attribute("pos", "50000");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "110000");
    write_end_element(xmlns_a, "satMod");
    write_start_element(xmlns_a, "lumMod");
    write_attribute("val", "100000");
    write_end_element(xmlns_a, "lumMod");
    write_start_element(xmlns_a, "shade");
    write_attribute("val", "100000");
    write_end_element(xmlns_a, "shade");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "gs");

    write_start_element(xmlns_a, "gs");
    write_attribute("pos", "100000");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "lumMod");
    write_attribute("val", "99000");
    write_end_element(xmlns_a, "lumMod");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "120000");
    write_end_element(xmlns_a, "satMod");
    write_start_element(xmlns_a, "shade");
    write_attribute("val", "78000");
    write_end_element(xmlns_a, "shade");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "gs");

    write_end_element(xmlns_a, "gsLst");

    write_start_element(xmlns_a, "lin");
    write_attribute("ang", "5400000");
    write_attribute("scaled", "0");
    write_end_element(xmlns_a, "lin");

    write_end_element(xmlns_a, "gradFill");
    write_end_element(xmlns_a, "fillStyleLst");

    write_start_element(xmlns_a, "lnStyleLst");

    write_start_element(xmlns_a, "ln");
    write_attribute("w", "6350");
    write_attribute("cap", "flat");
    write_attribute("cmpd", "sng");
    write_attribute("algn", "ctr");
    write_start_element(xmlns_a, "solidFill");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "solidFill");
    write_start_element(xmlns_a, "prstDash");
    write_attribute("val", "solid");
    write_end_element(xmlns_a, "prstDash");
    write_start_element(xmlns_a, "miter");
    write_attribute("lim", "800000");
    write_end_element(xmlns_a, "miter");
    write_end_element(xmlns_a, "ln");

    write_start_element(xmlns_a, "ln");
    write_attribute("w", "12700");
    write_attribute("cap", "flat");
    write_attribute("cmpd", "sng");
    write_attribute("algn", "ctr");
    write_start_element(xmlns_a, "solidFill");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "solidFill");
    write_start_element(xmlns_a, "prstDash");
    write_attribute("val", "solid");
    write_end_element(xmlns_a, "prstDash");
    write_start_element(xmlns_a, "miter");
    write_attribute("lim", "800000");
    write_end_element(xmlns_a, "miter");
    write_end_element(xmlns_a, "ln");

    write_start_element(xmlns_a, "ln");
    write_attribute("w", "19050");
    write_attribute("cap", "flat");
    write_attribute("cmpd", "sng");
    write_attribute("algn", "ctr");
    write_start_element(xmlns_a, "solidFill");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "solidFill");
    write_start_element(xmlns_a, "prstDash");
    write_attribute("val", "solid");
    write_end_element(xmlns_a, "prstDash");
    write_start_element(xmlns_a, "miter");
    write_attribute("lim", "800000");
    write_end_element(xmlns_a, "miter");
    write_end_element(xmlns_a, "ln");

    write_end_element(xmlns_a, "lnStyleLst");

    write_start_element(xmlns_a, "effectStyleLst");

    write_start_element(xmlns_a, "effectStyle");
    write_element(xmlns_a, "effectLst", "");
    write_end_element(xmlns_a, "effectStyle");

    write_start_element(xmlns_a, "effectStyle");
    write_element(xmlns_a, "effectLst", "");
    write_end_element(xmlns_a, "effectStyle");

    write_start_element(xmlns_a, "effectStyle");
    write_start_element(xmlns_a, "effectLst");
    write_start_element(xmlns_a, "outerShdw");
    write_attribute("blurRad", "57150");
    write_attribute("dist", "19050");
    write_attribute("dir", "5400000");
    write_attribute("algn", "ctr");
    write_attribute("rotWithShape", "0");
    write_start_element(xmlns_a, "srgbClr");
    write_attribute("val", "000000");
    write_start_element(xmlns_a, "alpha");
    write_attribute("val", "63000");
    write_end_element(xmlns_a, "alpha");
    write_end_element(xmlns_a, "srgbClr");
    write_end_element(xmlns_a, "outerShdw");
    write_end_element(xmlns_a, "effectLst");
    write_end_element(xmlns_a, "effectStyle");

    write_end_element(xmlns_a, "effectStyleLst");

    write_start_element(xmlns_a, "bgFillStyleLst");

    write_start_element(xmlns_a, "solidFill");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "solidFill");

    write_start_element(xmlns_a, "solidFill");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "tint");
    write_attribute("val", "95000");
    write_end_element(xmlns_a, "tint");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "170000");
    write_end_element(xmlns_a, "satMod");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "solidFill");

    write_start_element(xmlns_a, "gradFill");
    write_attribute("rotWithShape", "1");
    write_start_element(xmlns_a, "gsLst");

    write_start_element(xmlns_a, "gs");
    write_attribute("pos", "0");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "tint");
    write_attribute("val", "93000");
    write_end_element(xmlns_a, "tint");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "150000");
    write_end_element(xmlns_a, "satMod");
    write_start_element(xmlns_a, "shade");
    write_attribute("val", "98000");
    write_end_element(xmlns_a, "shade");
    write_start_element(xmlns_a, "lumMod");
    write_attribute("val", "102000");
    write_end_element(xmlns_a, "lumMod");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "gs");

    write_start_element(xmlns_a, "gs");
    write_attribute("pos", "50000");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "tint");
    write_attribute("val", "98000");
    write_end_element(xmlns_a, "tint");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "130000");
    write_end_element(xmlns_a, "satMod");
    write_start_element(xmlns_a, "shade");
    write_attribute("val", "90000");
    write_end_element(xmlns_a, "shade");
    write_start_element(xmlns_a, "lumMod");
    write_attribute("val", "103000");
    write_end_element(xmlns_a, "lumMod");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "gs");

    write_start_element(xmlns_a, "gs");
    write_attribute("pos", "100000");
    write_start_element(xmlns_a, "schemeClr");
    write_attribute("val", "phClr");
    write_start_element(xmlns_a, "shade");
    write_attribute("val", "63000");
    write_end_element(xmlns_a, "shade");
    write_start_element(xmlns_a, "satMod");
    write_attribute("val", "120000");
    write_end_element(xmlns_a, "satMod");
    write_end_element(xmlns_a, "schemeClr");
    write_end_element(xmlns_a, "gs");

    write_end_element(xmlns_a, "gsLst");

    write_start_element(xmlns_a, "lin");
    write_attribute("ang", "5400000");
    write_attribute("scaled", "0");
    write_end_element(xmlns_a, "lin");

    write_end_element(xmlns_a, "gradFill");

    write_end_element(xmlns_a, "bgFillStyleLst");
    write_end_element(xmlns_a, "fmtScheme");
    write_end_element(xmlns_a, "themeElements");

    write_element(xmlns_a, "objectDefaults", "");
    write_element(xmlns_a, "extraClrSchemeLst", "");

    write_start_element(xmlns_a, "extLst");
    write_start_element(xmlns_a, "ext");
    write_attribute("uri", "{05A4C25C-085E-4340-85A3-A5531E510DB2}");
    write_start_element(xmlns_thm15, "themeFamily");
    write_namespace(xmlns_thm15, "thm15");
    write_attribute("name", "Office Theme");
    write_attribute("id", "{62F939B6-93AF-4DB8-9C6B-D6C7DFDC589F}");
    write_attribute("vid", "{4A3C46E8-61CC-4603-A589-7422A47A8E4A}");
    write_end_element(xmlns_thm15, "themeFamily");
    write_end_element(xmlns_a, "ext");
    write_end_element(xmlns_a, "extLst");

    write_end_element(xmlns_a, "theme");

    const auto workbook_rel = source_.manifest().relationship(path("/"), relationship_type::office_document);
    const auto theme_part = source_.manifest().canonicalize({workbook_rel, theme_rel});
    const auto theme_rels = source_.manifest().relationships(theme_part);

    if (!theme_rels.empty())
    {
        write_relationships(theme_rels, theme_part);

        for (auto rel : theme_rels)
        {
            if (rel.type() == relationship_type::image)
            {
                const auto image_path = source_.manifest().canonicalize({workbook_rel, theme_rel, rel});
                write_image(image_path);
            }
        }
    }
}

void xlsx_producer::write_volatile_dependencies(const relationship & /*rel*/)
{
    write_start_element(constants::ns("spreadsheetml"), "volTypes");
    write_end_element(constants::ns("spreadsheetml"), "volTypes");
}

void xlsx_producer::write_worksheet(const relationship &rel)
{
    static const auto &xmlns = constants::ns("spreadsheetml");
    static const auto &xmlns_r = constants::ns("r");
    static const auto &xmlns_mc = constants::ns("mc");
    static const auto &xmlns_x14ac = constants::ns("x14ac");

    auto worksheet_part = rel.source().path().parent().append(rel.target().path());
    auto worksheet_rels = source_.manifest().relationships(worksheet_part);

    auto title = std::find_if(source_.d_->sheet_title_rel_id_map_.begin(), source_.d_->sheet_title_rel_id_map_.end(),
        [&](const std::pair<std::string, std::string> &p) {
            return p.second == rel.id();
        })->first;

    auto ws = source_.sheet_by_title(title);

    write_start_element(xmlns, "worksheet");
    write_namespace(xmlns, "");
    write_namespace(xmlns_r, "r");

    auto using_namespace = [&ws](const std::string &ns) {
        if (ns == "x14ac")
        {
            if (ws.format_properties().dy_descent.is_set())
            {
                return true;
            }

            auto highest = ws.highest_row();
            for (auto row = ws.lowest_row(); row <= highest; ++row)
            {
                if (ws.has_row_properties(row) && ws.row_properties(row).dy_descent.is_set())
                {
                    return true;
                }
            }
        }

        return false;
    };

    if (using_namespace("x14ac"))
    {
        write_namespace(xmlns_mc, "mc");
        write_namespace(xmlns_x14ac, "x14ac");
        write_attribute(xml::qname(xmlns_mc, "Ignorable"), "x14ac");
    }

    if (ws.d_->sheet_properties_.is_set())
    {
        write_start_element(xmlns, "sheetPr");
        auto &props = ws.d_->sheet_properties_.get();
        if (props.sync_horizontal.is_set())
        {
            write_attribute("syncHorizontal", props.sync_horizontal.get());
        }
        if (props.sync_vertical.is_set())
        {
            write_attribute("syncVertical", props.sync_vertical.get());
        }
        if (props.sync_ref.is_set())
        {
            write_attribute("syncRef", props.sync_ref.get().to_string());
        }
        if (props.transition_evaluation.is_set())
        {
            write_attribute("transitionEvaluation", props.transition_evaluation.get());
        }
        if (props.transition_entry.is_set())
        {
            write_attribute("transitionEntry", props.transition_entry.get());
        }
        if (props.published.is_set())
        {
            write_attribute("published", props.published.get());
        }
        if (props.code_name.is_set())
        {
            write_attribute("codeName", props.code_name.get());
        }
        if (props.filter_mode.is_set())
        {
            write_attribute("filterMode", props.filter_mode.get());
        }
        if (props.enable_format_condition_calculation.is_set())
        {
            write_attribute("enableFormatConditionsCalculation", props.enable_format_condition_calculation.get());
        }
        // outlinePr is optional in the spec but is being written every time?
        write_start_element(xmlns, "outlinePr");
        write_attribute("summaryBelow", "1");
        write_attribute("summaryRight", "1");
        write_end_element(xmlns, "outlinePr");

        if (ws.has_page_setup())
        {
            write_start_element(xmlns, "pageSetUpPr");
            write_attribute("fitToPage", write_bool(ws.page_setup().fit_to_page()));
            write_end_element(xmlns, "pageSetUpPr");
        }
        write_end_element(xmlns, "sheetPr");
    }

    write_start_element(xmlns, "dimension");
    const auto dimension = ws.calculate_dimension();
    write_attribute("ref", dimension.is_single_cell() ? dimension.top_left().to_string() : dimension.to_string());
    write_end_element(xmlns, "dimension");

    if (ws.has_view())
    {
        write_start_element(xmlns, "sheetViews");
        write_start_element(xmlns, "sheetView");

        const auto wb_view = source_.view();
        const auto view = ws.view();

        if (!view.show_grid_lines())
        {
            write_attribute("showGridLines", write_bool(view.show_grid_lines()));
        }

        if ((wb_view.active_tab.is_set() && (ws.id() - 1) == wb_view.active_tab.get())
            || (!wb_view.active_tab.is_set() && ws.id() == 1))
        {
            write_attribute("tabSelected", write_bool(true));
        }

        if (view.type() != sheet_view_type::normal)
        {
            write_attribute("view", view.type() == sheet_view_type::page_break_preview ? "pageBreakPreview" : "pageLayout");
        }
        if (view.has_top_left_cell())
        {
            write_attribute("topLeftCell", view.top_left_cell().to_string());
        }

        write_attribute("workbookViewId", view.id());

        if (view.has_pane())
        {
            const auto &current_pane = view.pane();
            write_start_element(xmlns, "pane"); // CT_Pane

            if (current_pane.top_left_cell.is_set())
            {
                write_attribute("topLeftCell", current_pane.top_left_cell.get().to_string());
            }

            if (current_pane.x_split + 1 == current_pane.top_left_cell.get().column())
            {
                write_attribute("xSplit", current_pane.x_split.index);
            }

            if (current_pane.y_split + 1 == current_pane.top_left_cell.get().row())
            {
                write_attribute("ySplit", current_pane.y_split);
            }

            if (current_pane.active_pane != pane_corner::top_left)
            {
                write_attribute("activePane", current_pane.active_pane);
            }

            if (current_pane.state != pane_state::split)
            {
                write_attribute("state", current_pane.state);
            }

            write_end_element(xmlns, "pane");
        }

        for (const auto &current_selection : view.selections())
        {
            write_start_element(xmlns, "selection"); // CT_Selection

            if (current_selection.has_active_cell())
            {
                write_attribute("activeCell", current_selection.active_cell().to_string());
            }

            if (current_selection.has_sqref())
            {
                const auto sqref = current_selection.sqref();
                write_attribute("sqref", sqref.is_single_cell() ? sqref.top_left().to_string() : sqref.to_string());
            }

            if (current_selection.pane() != pane_corner::top_left)
            {
                write_attribute("pane", current_selection.pane());
            }

            write_end_element(xmlns, "selection");
        }

        write_end_element(xmlns, "sheetView");
        write_end_element(xmlns, "sheetViews");
    }

    write_start_element(xmlns, "sheetFormatPr");
    const auto &format_properties = ws.d_->format_properties_;

    if (format_properties.base_col_width.is_set())
    {
        write_attribute<double>("baseColWidth",
            format_properties.base_col_width.get());
    }
    if (format_properties.default_column_width.is_set())
    {
        write_attribute<double>("defaultColWidth",
            format_properties.default_column_width.get());
    }

    write_attribute<double>("defaultRowHeight",
        format_properties.default_row_height);

    if (format_properties.dy_descent.is_set())
    {
        write_attribute<double>(xml::qname(xmlns_x14ac, "dyDescent"),
            format_properties.dy_descent.get());
    }

    write_end_element(xmlns, "sheetFormatPr");

    bool has_column_properties = false;
    const auto first_column = ws.lowest_column_or_props();
    const auto last_column = ws.highest_column_or_props();

    for (auto column = first_column; column <= last_column; column++)
    {
        if (!ws.has_column_properties(column)) continue;

        if (!has_column_properties)
        {
            write_start_element(xmlns, "cols");
            has_column_properties = true;
        }

        const auto &props = ws.column_properties(column);

        write_start_element(xmlns, "col");
        write_attribute("min", column.index);
        write_attribute("max", column.index);

        if (props.width.is_set())
        {
            double width = (props.width.get() * 7 + 5) / 7;
            write_attribute("width", converter_.serialise(width));
        }

        if (props.best_fit)
        {
            write_attribute("bestFit", write_bool(true));
        }

        if (props.style.is_set())
        {
            write_attribute("style", props.style.get());
        }

        if (props.hidden)
        {
            write_attribute("hidden", write_bool(true));
        }

        if (props.custom_width)
        {
            write_attribute("customWidth", write_bool(true));
        }

        write_end_element(xmlns, "col");
    }

    if (has_column_properties)
    {
        write_end_element(xmlns, "cols");
    }

    std::vector<std::pair<std::string, hyperlink>> hyperlinks;
    std::vector<cell_reference> cells_with_comments;

    write_start_element(xmlns, "sheetData");
    auto first_row = ws.lowest_row_or_props();
    auto last_row = ws.highest_row_or_props();
    auto first_block_column = constants::max_column();
    auto last_block_column = constants::min_column();

    for (auto row = first_row; row <= last_row; ++row)
    {
        bool any_non_null = false;
        auto first_check_row = row;
        auto last_check_row = row;
        auto first_row_in_block = row == first_row || row % 16 == 1;

        // See note for CT_Row, span attribute about block optimization
        if (first_row_in_block)
        {
            // reset block column range
            first_block_column = constants::max_column();
            last_block_column = constants::min_column();

            first_check_row = row;
            // round up to the next multiple of 16
            last_check_row = ((row / 16) + 1) * 16;
        }

        for (auto check_row = first_check_row; check_row <= last_check_row; ++check_row)
        {
            for (auto column = dimension.top_left().column(); column <= dimension.bottom_right().column(); ++column)
            {
                auto ref = cell_reference(column, check_row);
                auto cell = ws.d_->cell_map_.find(ref);
                if (cell == ws.d_->cell_map_.end())
                {
                    continue;
                }
                if (cell->second.is_garbage_collectible())
                {
                    continue;
                }

                first_block_column = std::min(first_block_column, cell->second.column_);
                last_block_column = std::max(last_block_column, cell->second.column_);

                if (row == check_row)
                {
                    any_non_null = true;
                }
            }
        }

        if (!any_non_null && !ws.has_row_properties(row)) continue;

        write_start_element(xmlns, "row");
        write_attribute("r", row);

        auto span_string = std::to_string(first_block_column.index) + ":"
            + std::to_string(last_block_column.index);
        write_attribute("spans", span_string);

        if (ws.has_row_properties(row))
        {
            const auto &props = ws.row_properties(row);

            if (props.style.is_set())
            {
                write_attribute("s", props.style.get());
            }
            if (props.custom_format.is_set())
            {
                write_attribute("customFormat", write_bool(props.custom_format.get()));
            }

            if (props.height.is_set())
            {
                auto height = props.height.get();
                write_attribute("ht", converter_.serialise(height));
            }

            if (props.hidden)
            {
                write_attribute("hidden", write_bool(true));
            }

            if (props.custom_height)
            {
                write_attribute("customHeight", write_bool(true));
            }

            if (props.dy_descent.is_set())
            {
                write_attribute<double>(xml::qname(xmlns_x14ac, "dyDescent"), props.dy_descent.get());
            }
        }

        if (any_non_null)
        {
            for (auto column = dimension.top_left().column(); column <= dimension.bottom_right().column(); ++column)
            {
                if (!ws.has_cell(cell_reference(column, row))) continue;

                auto cell = ws.cell(cell_reference(column, row));

                if (cell.garbage_collectible()) continue;

                // record data about the cell needed later

                if (cell.has_comment())
                {
                    cells_with_comments.push_back(cell.reference());
                }

                if (cell.has_hyperlink())
                {
                    hyperlinks.push_back(std::make_pair(cell.reference().to_string(), cell.hyperlink()));
                }

                write_start_element(xmlns, "c");

                // begin cell attributes

                write_attribute("r", cell.reference().to_string());

                if (cell.phonetics_visible())
                {
                    write_attribute("ph", write_bool(true));
                }

                if (cell.has_format())
                {
                    write_attribute("s", cell.format().d_->id);
                }

                switch (cell.data_type())
                {
                case cell::type::empty:
                    break;

                case cell::type::boolean:
                    write_attribute("t", "b");
                    break;

                case cell::type::date:
                    write_attribute("t", "d");
                    break;

                case cell::type::error:
                    write_attribute("t", "e");
                    break;

                case cell::type::inline_string:
                    write_attribute("t", "inlineStr");
                    break;

                case cell::type::number: // default, don't write it
                    //write_attribute("t", "n");
                    break;

                case cell::type::shared_string:
                    write_attribute("t", "s");
                    break;

                case cell::type::formula_string:
                    write_attribute("t", "str");
                    break;
                }

                //write_attribute("cm", "");
                //write_attribute("vm", "");
                //write_attribute("ph", "");

                // begin child elements

                if (cell.has_formula())
                {
                    write_element(xmlns, "f", cell.formula());
                }

                switch (cell.data_type())
                {
                case cell::type::empty:
                    break;

                case cell::type::boolean:
                    write_element(xmlns, "v", write_bool(cell.value<bool>()));
                    break;

                case cell::type::date:
                    write_element(xmlns, "v", cell.value<std::string>());
                    break;

                case cell::type::error:
                    write_element(xmlns, "v", cell.value<std::string>());
                    break;

                case cell::type::inline_string:
                    write_start_element(xmlns, "is");
                    write_rich_text(xmlns, cell.value<xlnt::rich_text>());
                    write_end_element(xmlns, "is");
                    break;

                case cell::type::number:
                    write_start_element(xmlns, "v");
                    write_characters(converter_.serialise(cell.value<double>()));
                    write_end_element(xmlns, "v");
                    break;

                case cell::type::shared_string:
                    write_element(xmlns, "v", static_cast<std::size_t>(cell.d_->value_numeric_));
                    break;

                case cell::type::formula_string:
                    write_element(xmlns, "v", cell.value<std::string>());
                    break;
                }

                write_end_element(xmlns, "c");
            }
        }

        write_end_element(xmlns, "row");
    }

    write_end_element(xmlns, "sheetData");

    if (ws.has_auto_filter())
    {
        write_start_element(xmlns, "autoFilter");
        write_attribute("ref", ws.auto_filter().to_string());
        write_end_element(xmlns, "autoFilter");
    }

    if (!ws.merged_ranges().empty())
    {
        write_start_element(xmlns, "mergeCells");
        write_attribute("count", ws.merged_ranges().size());

        for (auto merged_range : ws.merged_ranges())
        {
            write_start_element(xmlns, "mergeCell");
            write_attribute("ref", merged_range.to_string());
            write_end_element(xmlns, "mergeCell");
        }

        write_end_element(xmlns, "mergeCells");
    }

    if (source_.impl().stylesheet_.is_set())
    {
        const auto &stylesheet = source_.impl().stylesheet_.get();
        const auto &cf_impls = stylesheet.conditional_format_impls;

        std::unordered_map<std::string, std::vector<const conditional_format_impl *>> range_map;

        for (auto &cf : cf_impls)
        {
            if (cf.target_sheet != ws.d_) continue;

            if (range_map.find(cf.target_range.to_string()) == range_map.end())
            {
                range_map[cf.target_range.to_string()] = {};
            }

            range_map[cf.target_range.to_string()].push_back(&cf);
        }

        for (const auto &range_rules_pair : range_map)
        {
            write_start_element(xmlns, "conditionalFormatting");
            write_attribute("sqref", range_rules_pair.first);

            std::size_t i = 1;

            for (auto rule : range_rules_pair.second)
            {
                write_start_element(xmlns, "cfRule");
                write_attribute("type", "containsText");
                write_attribute("operator", "containsText");
                write_attribute("dxfId", rule->differential_format_id);
                write_attribute("priority", i++);
                write_attribute("text", rule->when.text_comparand_);
                //TODO: what does this formula mean and why is it necessary?
                write_element(xmlns, "formula", "NOT(ISERROR(SEARCH(\"" + rule->when.text_comparand_ + "\",A1)))");
                write_end_element(xmlns, "cfRule");
            }

            write_end_element(xmlns, "conditionalFormatting");
        }
    }

    if (!hyperlinks.empty())
    {
        write_start_element(xmlns, "hyperlinks");

        for (const auto &hyperlink : hyperlinks)
        {
            write_start_element(xmlns, "hyperlink");
            write_attribute("ref", hyperlink.first);
            if (hyperlink.second.external())
            {
                write_attribute(xml::qname(xmlns_r, "id"),
                    hyperlink.second.relationship().id());
            }
            else
            {
                write_attribute("location", hyperlink.second.target_range());
                write_attribute("display", hyperlink.second.display());
            }
            write_end_element(xmlns, "hyperlink");
        }

        write_end_element(xmlns, "hyperlinks");
    }

    if (ws.has_phonetic_properties())
    {
        write_start_element(xmlns, phonetic_pr::Serialised_ID());
        const auto &ph_props = ws.phonetic_properties();
        write_attribute("fontId", ph_props.font_id());
        if (ph_props.has_type())
        {
            write_attribute("type", phonetic_pr::type_as_string(ph_props.type()));
        }
        if (ph_props.has_alignment())
        {
            write_attribute("alignment", phonetic_pr::alignment_as_string(ph_props.alignment()));
        }
        write_end_element(xmlns, phonetic_pr::Serialised_ID());
    }

    if (ws.d_->print_options_.is_set())
    {
        auto &opts = ws.d_->print_options_.get();
        write_start_element(xmlns, "printOptions");
        if (opts.print_grid_lines.is_set())
        {
            write_attribute("gridLines", write_bool(opts.print_grid_lines.get()));
        }
        if (opts.grid_lines_set.is_set())
        {
            write_attribute("gridLineSet", write_bool(opts.grid_lines_set.get()));
        }
        if (opts.print_headings.is_set())
        {
            write_attribute("headings", write_bool(opts.print_headings.get()));
        }
        if (opts.horizontal_centered.is_set())
        {
            write_attribute("horizontalCentered", write_bool(opts.horizontal_centered.get()));
        }
        if (opts.vertical_centered.is_set())
        {
            write_attribute("verticalCentered", write_bool(opts.vertical_centered.get()));
        }
        write_end_element(xmlns, "printOptions");
    }

    if (ws.has_page_margins())
    {
        write_start_element(xmlns, "pageMargins");

        write_attribute<double>("left", ws.page_margins().left());
        write_attribute<double>("right", ws.page_margins().right());
        write_attribute<double>("top", ws.page_margins().top());
        write_attribute<double>("bottom", ws.page_margins().bottom());
        write_attribute<double>("header", ws.page_margins().header());
        write_attribute<double>("footer", ws.page_margins().footer());

        write_end_element(xmlns, "pageMargins");
    }

    if (ws.has_page_setup())
    {
        const xlnt::page_setup &ps = ws.page_setup();
        write_start_element(xmlns, "pageSetup");
        if (ws.page_setup().orientation_.is_set())
        {
            write_attribute("orientation", ws.page_setup().orientation_.get());
        }
        if (ws.page_setup().horizontal_dpi_.is_set())
        {
            write_attribute("horizontalDpi", ws.page_setup().horizontal_dpi_.get());
        }
        if (ws.page_setup().vertical_dpi_.is_set())
        {
            write_attribute("verticalDpi", ws.page_setup().vertical_dpi_.get());
        }
        
        if (ps.has_paper_size())
        {
            write_attribute("paperSize", static_cast<std::size_t>(ps.paper_size()));
        }

        if (ps.has_scale())
        {
            write_attribute("scale", ps.scale());
        }

        if (ps.has_rel_id())
        {
            write_attribute(xml::qname(xmlns_r, "id"), ps.rel_id());
        }
        /*write_attribute("fitToHeight", write_bool(ws.page_setup().fit_to_height()));
        write_attribute("fitToWidth", write_bool(ws.page_setup().fit_to_width()));*/
        write_end_element(xmlns, "pageSetup");
    }

    if (ws.has_header_footer())
    {
        const auto hf = ws.header_footer();

        write_start_element(xmlns, "headerFooter");

        auto odd_header = std::string();
        auto odd_footer = std::string();
        auto even_header = std::string();
        auto even_footer = std::string();
        auto first_header = std::string();
        auto first_footer = std::string();

        const auto locations =
            {
                header_footer::location::left,
                header_footer::location::center,
                header_footer::location::right};

        using xlnt::detail::encode_header_footer;

        for (auto location : locations)
        {
            if (hf.different_odd_even())
            {
                if (hf.has_odd_even_header(location))
                {
                    odd_header.append(encode_header_footer(hf.odd_header(location), location, converter_));
                    even_header.append(encode_header_footer(hf.even_header(location), location, converter_));
                }

                if (hf.has_odd_even_footer(location))
                {
                    odd_footer.append(encode_header_footer(hf.odd_footer(location), location, converter_));
                    even_footer.append(encode_header_footer(hf.even_footer(location), location, converter_));
                }
            }
            else
            {
                if (hf.has_header(location))
                {
                    odd_header.append(encode_header_footer(hf.header(location), location, converter_));
                }

                if (hf.has_footer(location))
                {
                    odd_footer.append(encode_header_footer(hf.footer(location), location, converter_));
                }
            }

            if (hf.different_first())
            {
                if (hf.has_first_page_header(location))
                {
                    first_header.append(encode_header_footer(hf.first_page_header(location), location, converter_));
                }

                if (hf.has_first_page_footer(location))
                {
                    first_footer.append(encode_header_footer(hf.first_page_footer(location), location, converter_));
                }
            }
        }

        if (!odd_header.empty())
        {
            write_element(xmlns, "oddHeader", odd_header);
        }

        if (!odd_footer.empty())
        {
            write_element(xmlns, "oddFooter", odd_footer);
        }

        if (!even_header.empty())
        {
            write_element(xmlns, "evenHeader", even_header);
        }

        if (!even_footer.empty())
        {
            write_element(xmlns, "evenFooter", even_footer);
        }

        if (!first_header.empty())
        {
            write_element(xmlns, "firstHeader", first_header);
        }

        if (!first_footer.empty())
        {
            write_element(xmlns, "firstFooter", first_footer);
        }

        write_end_element(xmlns, "headerFooter");
    }

    if (!ws.page_break_rows().empty())
    {
        write_start_element(xmlns, "rowBreaks");

        write_attribute("count", ws.page_break_rows().size());
        write_attribute("manualBreakCount", ws.page_break_rows().size());

        for (auto break_id : ws.page_break_rows())
        {
            write_start_element(xmlns, "brk");
            write_attribute("id", break_id);
            write_attribute("max", 16383);
            write_attribute("man", 1);
            write_end_element(xmlns, "brk");
        }

        write_end_element(xmlns, "rowBreaks");
    }

    if (!ws.page_break_columns().empty())
    {
        write_start_element(xmlns, "colBreaks");

        write_attribute("count", ws.page_break_columns().size());
        write_attribute("manualBreakCount", ws.page_break_columns().size());

        for (auto break_id : ws.page_break_columns())
        {
            write_start_element(xmlns, "brk");
            write_attribute("id", break_id.index);
            write_attribute("max", 1048575);
            write_attribute("man", 1);
            write_end_element(xmlns, "brk");
        }

        write_end_element(xmlns, "colBreaks");
    }

    if (!worksheet_rels.empty())
    {
        for (const auto &child_rel : worksheet_rels)
        {
            if (child_rel.type() == xlnt::relationship_type::vml_drawing)
            {
                write_start_element(xmlns, "legacyDrawing");
                write_attribute(xml::qname(xmlns_r, "id"), child_rel.id());
                write_end_element(xmlns, "legacyDrawing");
            }
            else if (child_rel.type() == xlnt::relationship_type::drawings)
            {
                write_start_element(xmlns, "drawing");
                write_attribute(xml::qname(xmlns_r, "id"), child_rel.id());
                write_end_element(xmlns, "drawing");
            }
        }
    }

    if (ws.d_->extension_list_.is_set())
    {
        ws.d_->extension_list_.get().serialize(*current_part_serializer_, xmlns);
    }

    write_end_element(xmlns, "worksheet");

    if (!worksheet_rels.empty())
    {
        write_relationships(worksheet_rels, worksheet_part);

        for (const auto &child_rel : worksheet_rels)
        {
            if (child_rel.target_mode() == target_mode::external) continue;

            // todo: this is ugly
            path archive_path(worksheet_part.parent().append(child_rel.target().path()));
            auto split_part_path = archive_path.split();
            auto part_path_iter = split_part_path.begin();

            while (part_path_iter != split_part_path.end())
            {
                if (*part_path_iter == "..")
                {
                    part_path_iter = split_part_path.erase(part_path_iter - 1, part_path_iter + 1);
                    continue;
                }

                ++part_path_iter;
            }

            archive_path = std::accumulate(split_part_path.begin(), split_part_path.end(), path(""),
                [](const path &a, const std::string &b) { return a.append(b); });

            if (child_rel.type() == relationship_type::printer_settings)
            {
                write_binary(archive_path);
            }
            else
            {
                begin_part(archive_path);

                if (child_rel.type() == relationship_type::comments)
                {
                    write_comments(child_rel, ws, cells_with_comments);
                }
                else if (child_rel.type() == relationship_type::vml_drawing)
                {
                    write_vml_drawings(child_rel, ws, cells_with_comments);
                }
                else if (child_rel.type() == relationship_type::drawings)
                {
                    write_drawings(child_rel, ws);
                }
            }
        }
    }
}

// Sheet Relationship Target Parts

void xlsx_producer::write_comments(const relationship & /*rel*/, worksheet ws, const std::vector<cell_reference> &cells)
{
    static const auto &xmlns = constants::ns("spreadsheetml");

    write_start_element(xmlns, "comments");
    write_namespace(xmlns, "");

    if (!cells.empty())
    {
        std::unordered_map<std::string, std::size_t> authors;

        for (auto cell_ref : cells)
        {
            auto cell = ws.cell(cell_ref);
            auto author = cell.comment().author();

            if (authors.find(author) == authors.end())
            {
                auto author_index = authors.size();
                authors[author] = author_index;
            }
        }

        write_start_element(xmlns, "authors");

        for (const auto &author : authors)
        {
            write_start_element(xmlns, "author");
            write_characters(author.first);
            write_end_element(xmlns, "author");
        }

        write_end_element(xmlns, "authors");
        write_start_element(xmlns, "commentList");

        for (const auto &cell_ref : cells)
        {
            write_start_element(xmlns, "comment");

            auto cell = ws.cell(cell_ref);
            auto cell_comment = cell.comment();

            write_attribute("ref", cell_ref.to_string());
            auto author_id = authors.at(cell_comment.author());
            write_attribute("authorId", author_id);

            write_start_element(xmlns, "text");
            write_rich_text(xmlns, cell_comment.text());
            write_end_element(xmlns, "text");

            write_end_element(xmlns, "comment");
        }

        write_end_element(xmlns, "commentList");
    }

    write_end_element(xmlns, "comments");
}

void xlsx_producer::write_vml_drawings(const relationship &rel, worksheet ws, const std::vector<cell_reference> &cells)
{
    static const auto &xmlns_mv = std::string("http://macVmlSchemaUri");
    static const auto &xmlns_o = std::string("urn:schemas-microsoft-com:office:office");
    static const auto &xmlns_v = std::string("urn:schemas-microsoft-com:vml");
    static const auto &xmlns_x = std::string("urn:schemas-microsoft-com:office:excel");

    write_start_element("xml");
    write_namespace(xmlns_v, "v");
    write_namespace(xmlns_o, "o");
    write_namespace(xmlns_x, "x");
    write_namespace(xmlns_mv, "mv");

    write_start_element(xmlns_o, "shapelayout");
    write_attribute(xml::qname(xmlns_v, "ext"), "edit");
    write_start_element(xmlns_o, "idmap");
    write_attribute(xml::qname(xmlns_v, "ext"), "edit");

    auto filename = rel.target().path().split_extension().first;
    auto index_pos = filename.size() - 1;

    while (filename[index_pos] >= '0' && filename[index_pos] <= '9')
    {
        index_pos--;
    }

    auto file_index = std::stoull(filename.substr(index_pos + 1));

    write_attribute("data", file_index);
    write_end_element(xmlns_o, "idmap");
    write_end_element(xmlns_o, "shapelayout");

    write_start_element(xmlns_v, "shapetype");
    write_attribute("id", "_x0000_t202");
    write_attribute("coordsize", "21600,21600");
    write_attribute(xml::qname(xmlns_o, "spt"), "202");
    write_attribute("path", "m0,0l0,21600,21600,21600,21600,0xe");
    write_start_element(xmlns_v, "stroke");
    write_attribute("joinstyle", "miter");
    write_end_element(xmlns_v, "stroke");
    write_start_element(xmlns_v, "path");
    write_attribute("gradientshapeok", "t");
    write_attribute(xml::qname(xmlns_o, "connecttype"), "rect");
    write_end_element(xmlns_v, "path");
    write_end_element(xmlns_v, "shapetype");

    std::size_t comment_index = 0;

    for (const auto &cell_ref : cells)
    {
        auto comment = ws.cell(cell_ref).comment();
        auto shape_id = 1024 * file_index + 1 + comment_index * 2;

        write_start_element(xmlns_v, "shape");
        write_attribute("id", "_x0000_s" + std::to_string(shape_id));
        write_attribute("type", "#_x0000_t202");

        std::vector<std::pair<std::string, std::string>> style;

        style.push_back({"position", "absolute"});
        style.push_back({"margin-left", std::to_string(comment.left()) + "pt"});
        style.push_back({"margin-top", std::to_string(comment.top()) + "pt"});
        style.push_back({"width", std::to_string(comment.width()) + "pt"});
        style.push_back({"height", std::to_string(comment.height()) + "pt"});
        style.push_back({"z-index", std::to_string(comment_index + 1)});
        style.push_back({"visibility", comment.visible() ? "visible" : "hidden"});

        std::string style_string;

        for (auto part : style)
        {
            style_string.append(part.first);
            style_string.append(":");
            style_string.append(part.second);
            style_string.append(";");
        }

        write_attribute("style", style_string);
        write_attribute("fillcolor", "#fbf6d6");
        write_attribute("strokecolor", "#edeaa1");

        write_start_element(xmlns_v, "fill");
        write_attribute("color2", "#fbfe82");
        write_attribute("angle", -180);
        write_attribute("type", "gradient");
        write_start_element(xmlns_o, "fill");
        write_attribute(xml::qname(xmlns_v, "ext"), "view");
        write_attribute("type", "gradientUnscaled");
        write_end_element(xmlns_o, "fill");
        write_end_element(xmlns_v, "fill");

        write_start_element(xmlns_v, "shadow");
        write_attribute("on", "t");
        write_attribute("obscured", "t");
        write_end_element(xmlns_v, "shadow");

        write_start_element(xmlns_v, "path");
        write_attribute(xml::qname(xmlns_o, "connecttype"), "none");
        write_end_element(xmlns_v, "path");

        write_start_element(xmlns_v, "textbox");
        write_attribute("style", "mso-direction-alt:auto");
        write_start_element("div");
        write_attribute("style", "text-align:left");
        write_characters("");
        write_end_element("div");
        write_end_element(xmlns_v, "textbox");

        write_start_element(xmlns_x, "ClientData");
        write_attribute("ObjectType", "Note");
        write_start_element(xmlns_x, "MoveWithCells");
        write_end_element(xmlns_x, "MoveWithCells");
        write_start_element(xmlns_x, "SizeWithCells");
        write_end_element(xmlns_x, "SizeWithCells");
        write_start_element(xmlns_x, "Anchor");
        write_characters("1, 15, 0, " + std::to_string(2 + comment_index * 4) + ", 2, 54, 4, 14");
        write_end_element(xmlns_x, "Anchor");
        write_start_element(xmlns_x, "AutoFill");
        write_characters("False");
        write_end_element(xmlns_x, "AutoFill");
        write_start_element(xmlns_x, "Row");
        write_characters(cell_ref.row() - 1);
        write_end_element(xmlns_x, "Row");
        write_start_element(xmlns_x, "Column");
        write_characters(cell_ref.column_index() - 1);
        write_end_element(xmlns_x, "Column");
        write_end_element(xmlns_x, "ClientData");

        write_end_element(xmlns_v, "shape");

        ++comment_index;
    }

    write_end_element("xml");
}

void xlsx_producer::write_drawings(const relationship &drawing_rel, worksheet ws)
{
    const auto workbook_rel = source_.manifest().relationship(path("/"), relationship_type::office_document);
    const auto worksheet_rel = ws.referring_relationship();
    const auto drawing_part = source_.manifest().canonicalize({workbook_rel, worksheet_rel, drawing_rel});
    const auto drawing_rels = source_.manifest().relationships(drawing_part);

    if (ws.d_->drawing_.is_set())
    {
        ws.d_->drawing_.get().serialize(*current_part_serializer_);
    }

    if (!drawing_rels.empty())
    {
        write_relationships(drawing_rels, drawing_part);

        for (auto rel : drawing_rels)
        {
            if (rel.type() == relationship_type::image)
            {
                const auto image_path = source_.manifest().canonicalize({workbook_rel, worksheet_rel, rel});
                if (image_path.string().find("cid:") != std::string::npos)
                {
                    // skip cid attachments
                    continue;
                }
                write_image(image_path);
            }
        }
    }
}

// Other Parts

void xlsx_producer::write_custom_property()
{
}

void xlsx_producer::write_unknown_parts()
{
}

void xlsx_producer::write_unknown_relationships()
{
}

void xlsx_producer::write_image(const path &image_path)
{
    end_part();

    vector_istreambuf buffer(source_.d_->images_.at(image_path.string()));
    auto image_streambuf = archive_->open(image_path);
    std::ostream(image_streambuf.get()) << &buffer;
}

void xlsx_producer::write_binary(const path &binary_path)
{
    end_part();

    vector_istreambuf buffer(source_.d_->binaries_.at(binary_path.string()));
    auto image_streambuf = archive_->open(binary_path);
    std::ostream(image_streambuf.get()) << &buffer;
}

std::string xlsx_producer::write_bool(bool boolean) const
{
    return boolean ? "1" : "0";
}

void xlsx_producer::write_relationships(const std::vector<xlnt::relationship> &relationships, const path &part)
{
    path parent = part.parent();

    if (parent.is_absolute())
    {
        parent = path(parent.string().substr(1));
    }

    path rels_path(parent.append("_rels").append(part.filename() + ".rels").string());
    begin_part(rels_path);

    const auto xmlns = xlnt::constants::ns("relationships");

    write_start_element(xmlns, "Relationships");
    write_namespace(xmlns, "");

    for (std::size_t i = 1; i <= relationships.size(); ++i)
    {
        auto rel_iter = std::find_if(relationships.begin(), relationships.end(),
            [&i](const relationship &r) { return r.id() == "rId" + std::to_string(i); });
        auto relationship = *rel_iter;

        write_start_element(xmlns, "Relationship");

        write_attribute("Id", relationship.id());
        write_attribute("Type", relationship.type());
        write_attribute("Target", relationship.target().path().string());

        if (relationship.target_mode() == xlnt::target_mode::external)
        {
            write_attribute("TargetMode", "External");
        }

        write_end_element(xmlns, "Relationship");
    }

    write_end_element(xmlns, "Relationships");
}

void xlsx_producer::write_color(const xlnt::color &color)
{
    if (color.auto_())
    {
        write_attribute("auto", write_bool(true));
        return;
    }
    switch (color.type())
    {
    case xlnt::color_type::theme:
        write_attribute("theme", color.theme().index());
        break;

    case xlnt::color_type::indexed:
        write_attribute("indexed", color.indexed().index());
        break;

    case xlnt::color_type::rgb:
        write_attribute("rgb", color.rgb().hex_string());
        break;
    }
    if (color.has_tint())
    {
        write_attribute("tint", converter_.serialise(color.tint()));
    }
}

void xlsx_producer::write_start_element(const std::string &name)
{
    current_part_serializer_->start_element(name);
}

void xlsx_producer::write_start_element(const std::string &ns, const std::string &name)
{
    current_part_serializer_->start_element(ns, name);
}

void xlsx_producer::write_end_element(const std::string &name)
{
    current_part_serializer_->end_element(name);
}

void xlsx_producer::write_end_element(const std::string &ns, const std::string &name)
{
    current_part_serializer_->end_element(ns, name);
}

void xlsx_producer::write_namespace(const std::string &ns, const std::string &prefix)
{
    current_part_serializer_->namespace_decl(ns, prefix);
}

} // namespace detail
} // namespace xlnt