<?php


namespace backend\components;

class XLSXWriter
{
    
    
    const EXCEL_2007_MAX_ROW = 1048576;
    const EXCEL_2007_MAX_COL = 16384;
    
    protected $title;
    protected $subject;
    protected $author;
    protected $isRightToLeft;
    protected $company;
    protected $description;
    protected $tempdir;
    protected $keywords = array();

    protected $current_sheet;
    protected $sheets = array();
    protected $temp_files = array();
    protected $cell_styles = array();
    protected $number_formats = array();

    public function __construct()
    {
        defined('ENT_XML1') or define('ENT_XML1', 16);
        date_default_timezone_get() or date_default_timezone_set('UTC');
        is_writeable($this->tempFilename()) or self::log("Warning: tempdir " . sys_get_temp_dir() . " not writeable, use ->setTempDir()");
        class_exists('\ZipArchive') or self::log("Error: \ZipArchive class does not exist");
        $this->addCellStyle($number_format = 'GENERAL', $style_string = null);
    }

    public function setTitle($title = '')
    {
        $this->title = $title;
    }

    public function setSubject($subject = '')
    {
        $this->subject = $subject;
    }

    public function setAuthor($author = '')
    {
        $this->author = $author;
    }

    public function setCompany($company = '')
    {
        $this->company = $company;
    }

    public function setKeywords($keywords = '')
    {
        $this->keywords = $keywords;
    }

    public function setDescription($description = '')
    {
        $this->description = $description;
    }

    public function setTempDir($tempdir = '')
    {
        $this->tempdir = $tempdir;
    }

    public function setRightToLeft($isRightToLeft = false)
    {
        $this->isRightToLeft = $isRightToLeft;
    }

    public function __destruct()
    {
        if (!empty($this->temp_files)) {
            foreach ($this->temp_files as $temp_file) {
                unlink($temp_file);
            }
        }
    }

    protected function tempFilename()
    {
        $tempdir = !empty($this->tempdir) ? $this->tempdir : sys_get_temp_dir();
        $filename = tempnam($tempdir, "xlsx_writer_");
        $this->temp_files[] = $filename;
        return $filename;
    }

    public function writeToStdOut()
    {
        $temp_file = $this->tempFilename();
        self::writeToFile($temp_file);
        readfile($temp_file);
    }

    public function writeToString()
    {
        $temp_file = $this->tempFilename();
        self::writeToFile($temp_file);
        return file_get_contents($temp_file);
    }

    public function writeToFile($filename)
    {
        foreach ($this->sheets as $sheet_name => $sheet) {
            self::finalizeSheet($sheet_name);
        }

        if (file_exists($filename)) {
            if (is_writable($filename)) {
                unlink($filename); 
            } else {
                self::log("Error in " . __CLASS__ . "::" . __FUNCTION__ . ", file is not writeable.");
                return;
            }
        }
        $zip = new \ZipArchive();
        if (empty($this->sheets)) {
            self::log("Error in " . __CLASS__ . "::" . __FUNCTION__ . ", no worksheets defined.");
            return;
        }
        if (!$zip->open($filename, \ZipArchive::CREATE)) {
            self::log("Error in " . __CLASS__ . "::" . __FUNCTION__ . ", unable to create zip.");
            return;
        }

        $zip->addEmptyDir("docProps/");
        $zip->addFromString("docProps/app.xml", self::buildAppXML());
        $zip->addFromString("docProps/core.xml", self::buildCoreXML());

        $zip->addEmptyDir("_rels/");
        $zip->addFromString("_rels/.rels", self::buildRelationshipsXML());

        $zip->addEmptyDir("xl/worksheets/");
        foreach ($this->sheets as $sheet) {
            $zip->addFile($sheet->filename, "xl/worksheets/" . $sheet->xmlname);
        }
        $zip->addFromString("xl/workbook.xml", self::buildWorkbookXML());
        $zip->addFile($this->writeStylesXML(), "xl/styles.xml");  
        $zip->addFromString("[Content_Types].xml", self::buildContentTypesXML());

        $zip->addEmptyDir("xl/_rels/");
        $zip->addFromString("xl/_rels/workbook.xml.rels", self::buildWorkbookRelsXML());
        $zip->close();
    }

    protected function initializeSheet($sheet_name, $col_widths = array(), $auto_filter = false, $freeze_rows = false, $freeze_columns = false)
    {
        
        if ($this->current_sheet == $sheet_name || isset($this->sheets[$sheet_name])) {
            return;
        }

        $sheet_filename = $this->tempFilename();
        $sheet_xmlname = 'sheet' . (count($this->sheets) + 1) . ".xml";
        $this->sheets[$sheet_name] = (object)array(
            'filename' => $sheet_filename,
            'sheetname' => $sheet_name,
            'xmlname' => $sheet_xmlname,
            'row_count' => 0,
            'file_writer' => new XLSXWriter_BuffererWriter($sheet_filename),
            'columns' => array(),
            'merge_cells' => array(),
            'max_cell_tag_start' => 0,
            'max_cell_tag_end' => 0,
            'auto_filter' => $auto_filter,
            'freeze_rows' => $freeze_rows,
            'freeze_columns' => $freeze_columns,
            'finalized' => false,
        );
        $rightToLeftValue = $this->isRightToLeft ? 'true' : 'false';
        $sheet = &$this->sheets[$sheet_name];
        $tabselected = count($this->sheets) == 1 ? 'true' : 'false';
        $max_cell = XLSXWriter::xlsCell(self::EXCEL_2007_MAX_ROW, self::EXCEL_2007_MAX_COL);
        $sheet->file_writer->write('<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n");
        $sheet->file_writer->write('<worksheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">');
        $sheet->file_writer->write('<sheetPr filterMode="false">');
        $sheet->file_writer->write('<pageSetUpPr fitToPage="false"/>');
        $sheet->file_writer->write('</sheetPr>');
        $sheet->max_cell_tag_start = $sheet->file_writer->ftell();
        $sheet->file_writer->write('<dimension ref="A1:' . $max_cell . '"/>');
        $sheet->max_cell_tag_end = $sheet->file_writer->ftell();
        $sheet->file_writer->write('<sheetViews>');
        $sheet->file_writer->write('<sheetView colorId="64" defaultGridColor="true" rightToLeft="' . $rightToLeftValue . '" showFormulas="false" showGridLines="true" showOutlineSymbols="true" showRowColHeaders="true" showZeros="true" tabSelected="' . $tabselected . '" topLeftCell="A1" view="normal" windowProtection="false" workbookViewId="0" zoomScale="100" zoomScaleNormal="100" zoomScalePageLayoutView="100">');
        if ($sheet->freeze_rows && $sheet->freeze_columns) {
            $sheet->file_writer->write('<pane ySplit="' . $sheet->freeze_rows . '" xSplit="' . $sheet->freeze_columns . '" topLeftCell="' . self::xlsCell($sheet->freeze_rows, $sheet->freeze_columns) . '" activePane="bottomRight" state="frozen"/>');
            $sheet->file_writer->write('<selection activeCell="' . self::xlsCell($sheet->freeze_rows, 0) . '" activeCellId="0" pane="topRight" sqref="' . self::xlsCell($sheet->freeze_rows, 0) . '"/>');
            $sheet->file_writer->write('<selection activeCell="' . self::xlsCell(0, $sheet->freeze_columns) . '" activeCellId="0" pane="bottomLeft" sqref="' . self::xlsCell(0, $sheet->freeze_columns) . '"/>');
            $sheet->file_writer->write('<selection activeCell="' . self::xlsCell($sheet->freeze_rows, $sheet->freeze_columns) . '" activeCellId="0" pane="bottomRight" sqref="' . self::xlsCell($sheet->freeze_rows, $sheet->freeze_columns) . '"/>');
        } elseif ($sheet->freeze_rows) {
            $sheet->file_writer->write('<pane ySplit="' . $sheet->freeze_rows . '" topLeftCell="' . self::xlsCell($sheet->freeze_rows, 0) . '" activePane="bottomLeft" state="frozen"/>');
            $sheet->file_writer->write('<selection activeCell="' . self::xlsCell($sheet->freeze_rows, 0) . '" activeCellId="0" pane="bottomLeft" sqref="' . self::xlsCell($sheet->freeze_rows, 0) . '"/>');
        } elseif ($sheet->freeze_columns) {
            $sheet->file_writer->write('<pane xSplit="' . $sheet->freeze_columns . '" topLeftCell="' . self::xlsCell(0, $sheet->freeze_columns) . '" activePane="topRight" state="frozen"/>');
            $sheet->file_writer->write('<selection activeCell="' . self::xlsCell(0, $sheet->freeze_columns) . '" activeCellId="0" pane="topRight" sqref="' . self::xlsCell(0, $sheet->freeze_columns) . '"/>');
        } else { 
            $sheet->file_writer->write('<selection activeCell="A1" activeCellId="0" pane="topLeft" sqref="A1"/>');
        }
        $sheet->file_writer->write('</sheetView>');
        $sheet->file_writer->write('</sheetViews>');
        $sheet->file_writer->write('<cols>');
        $i = 0;
        if (!empty($col_widths)) {
            foreach ($col_widths as $column_width) {
                $sheet->file_writer->write('<col collapsed="false" hidden="false" max="' . ($i + 1) . '" min="' . ($i + 1) . '" style="0" customWidth="true" width="' . floatval($column_width) . '"/>');
                $i++;
            }
        }
        $sheet->file_writer->write('<col collapsed="false" hidden="false" max="1024" min="' . ($i + 1) . '" style="0" customWidth="false" width="11.5"/>');
        $sheet->file_writer->write('</cols>');
        $sheet->file_writer->write('<sheetData>');
    }

    private function addCellStyle($number_format, $cell_style_string)
    {
        $number_format_idx = self::add_to_list_get_index($this->number_formats, $number_format);
        $lookup_string = $number_format_idx . ";" . $cell_style_string;
        $cell_style_idx = self::add_to_list_get_index($this->cell_styles, $lookup_string);
        return $cell_style_idx;
    }

    private function initializeColumnTypes($header_types)
    {
        $column_types = array();
        foreach ($header_types as $v) {
            $number_format = self::numberFormatStandardized($v);
            $number_format_type = self::determineNumberFormatType($number_format);
            $cell_style_idx = $this->addCellStyle($number_format, $style_string = null);
            $column_types[] = array('number_format' => $number_format,
                'number_format_type' => $number_format_type, 
                'default_cell_style' => $cell_style_idx,
            );
        }
        return $column_types;
    }

    public function writeSheetHeader($sheet_name, array $header_types, $col_options = null)
    {
        if (empty($sheet_name) || empty($header_types) || !empty($this->sheets[$sheet_name])) {
            return;
        }

        $suppress_row = isset($col_options['suppress_row']) ? intval($col_options['suppress_row']) : false;
        if (is_bool($col_options)) {
            self::log("Warning! passing $suppress_row=false|true to writeSheetHeader() is deprecated, this will be removed in a future version.");
            $suppress_row = intval($col_options);
        }
        $style = &$col_options;

        $col_widths = isset($col_options['widths']) ? (array)$col_options['widths'] : array();
        $auto_filter = isset($col_options['auto_filter']) ? intval($col_options['auto_filter']) : false;
        $freeze_rows = isset($col_options['freeze_rows']) ? intval($col_options['freeze_rows']) : false;
        $freeze_columns = isset($col_options['freeze_columns']) ? intval($col_options['freeze_columns']) : false;
        self::initializeSheet($sheet_name, $col_widths, $auto_filter, $freeze_rows, $freeze_columns);
        $sheet = &$this->sheets[$sheet_name];
        $sheet->columns = $this->initializeColumnTypes($header_types);
        if (!$suppress_row) {
            $header_row = array_keys($header_types);

            $sheet->file_writer->write('<row collapsed="false" customFormat="false" customHeight="false" hidden="false" ht="12.1" outlineLevel="0" r="' . (1) . '">');
            foreach ($header_row as $c => $v) {
                $cell_style_idx = empty($style) ? $sheet->columns[$c]['default_cell_style'] : $this->addCellStyle('GENERAL', json_encode(isset($style[0]) ? $style[$c] : $style));
                $this->writeCell($sheet->file_writer, 0, $c, $v, $number_format_type = 'n_string', $cell_style_idx);
            }
            $sheet->file_writer->write('</row>');
            $sheet->row_count++;
        }
        $this->current_sheet = $sheet_name;
    }

    public function writeSheetRow($sheet_name, array $row, $row_options = null)
    {
        if (empty($sheet_name))
            return;

        $this->initializeSheet($sheet_name);
        $sheet = &$this->sheets[$sheet_name];
        if (count($sheet->columns) < count($row)) {
            $default_column_types = $this->initializeColumnTypes(array_fill($from = 0, $until = count($row), 'GENERAL'));
            $sheet->columns = array_merge((array)$sheet->columns, $default_column_types);
        }

        if (!empty($row_options)) {
            $ht = isset($row_options['height']) ? floatval($row_options['height']) : 12.1;
            $customHt = isset($row_options['height']) ? true : false;
            $hidden = isset($row_options['hidden']) ? (bool)($row_options['hidden']) : false;
            $collapsed = isset($row_options['collapsed']) ? (bool)($row_options['collapsed']) : false;
            $sheet->file_writer->write('<row collapsed="' . ($collapsed) . '" customFormat="false" customHeight="' . ($customHt) . '" hidden="' . ($hidden) . '" ht="' . ($ht) . '" outlineLevel="0" r="' . ($sheet->row_count + 1) . '">');
        } else {
            $sheet->file_writer->write('<row collapsed="false" customFormat="false" customHeight="false" hidden="false" ht="12.1" outlineLevel="0" r="' . ($sheet->row_count + 1) . '">');
        }

        $style = &$row_options;
        $c = 0;
        foreach ($row as $v) {
            $number_format = $sheet->columns[$c]['number_format'];
            $number_format_type = $sheet->columns[$c]['number_format_type'];
            $cell_style_idx = empty($style) ? $sheet->columns[$c]['default_cell_style'] : $this->addCellStyle($number_format, json_encode(isset($style[0]) ? $style[$c] : $style));
            $this->writeCell($sheet->file_writer, $sheet->row_count, $c, $v, $number_format_type, $cell_style_idx);
            $c++;
        }
        $sheet->file_writer->write('</row>');
        $sheet->row_count++;
        $this->current_sheet = $sheet_name;
    }

    public function countSheetRows($sheet_name = '')
    {
        $sheet_name = $sheet_name ? $sheet_name : $this->current_sheet;
        return array_key_exists($sheet_name, $this->sheets) ? $this->sheets[$sheet_name]->row_count : 0;
    }

    protected function finalizeSheet($sheet_name)
    {
        if (empty($sheet_name) || $this->sheets[$sheet_name]->finalized)
            return;

        $sheet = &$this->sheets[$sheet_name];

        $sheet->file_writer->write('</sheetData>');

        if (!empty($sheet->merge_cells)) {
            $sheet->file_writer->write('<mergeCells>');
            foreach ($sheet->merge_cells as $range) {
                $sheet->file_writer->write('<mergeCell ref="' . $range . '"/>');
            }
            $sheet->file_writer->write('</mergeCells>');
        }

        $max_cell = self::xlsCell($sheet->row_count - 1, count($sheet->columns) - 1);

        if ($sheet->auto_filter) {
            $sheet->file_writer->write('<autoFilter ref="A1:' . $max_cell . '"/>');
        }

        $sheet->file_writer->write('<printOptions headings="false" gridLines="false" gridLinesSet="true" horizontalCentered="false" verticalCentered="false"/>');
        $sheet->file_writer->write('<pageMargins left="0.5" right="0.5" top="1.0" bottom="1.0" header="0.5" footer="0.5"/>');
        $sheet->file_writer->write('<pageSetup blackAndWhite="false" cellComments="none" copies="1" draft="false" firstPageNumber="1" fitToHeight="1" fitToWidth="1" horizontalDpi="300" orientation="portrait" pageOrder="downThenOver" paperSize="1" scale="100" useFirstPageNumber="true" usePrinterDefaults="false" verticalDpi="300"/>');
        $sheet->file_writer->write('<headerFooter differentFirst="false" differentOddEven="false">');
        $sheet->file_writer->write('<oddHeader>&amp;C&amp;&quot;Times New Roman,Regular&quot;&amp;12&amp;A</oddHeader>');
        $sheet->file_writer->write('<oddFooter>&amp;C&amp;&quot;Times New Roman,Regular&quot;&amp;12Page &amp;P</oddFooter>');
        $sheet->file_writer->write('</headerFooter>');
        $sheet->file_writer->write('</worksheet>');

        $max_cell_tag = '<dimension ref="A1:' . $max_cell . '"/>';
        $padding_length = $sheet->max_cell_tag_end - $sheet->max_cell_tag_start - strlen((string)$max_cell_tag);
        $sheet->file_writer->fseek($sheet->max_cell_tag_start);
        $sheet->file_writer->write($max_cell_tag . str_repeat(" ", $padding_length));
        $sheet->file_writer->close();
        $sheet->finalized = true;
    }

    public function markMergedCell($sheet_name, $start_cell_row, $start_cell_column, $end_cell_row, $end_cell_column)
    {
        if (empty($sheet_name) || $this->sheets[$sheet_name]->finalized)
            return;

        self::initializeSheet($sheet_name);
        $sheet = &$this->sheets[$sheet_name];

        $startCell = self::xlsCell($start_cell_row, $start_cell_column);
        $endCell = self::xlsCell($end_cell_row, $end_cell_column);
        $sheet->merge_cells[] = $startCell . ":" . $endCell;
    }

    public function writeSheet(array $data, $sheet_name = '', array $header_types = array())
    {
        $sheet_name = empty($sheet_name) ? 'Sheet1' : $sheet_name;
        $data = empty($data) ? array(array('')) : $data;
        if (!empty($header_types)) {
            $this->writeSheetHeader($sheet_name, $header_types);
        }
        foreach ($data as $i => $row) {
            $this->writeSheetRow($sheet_name, $row);
        }
        $this->finalizeSheet($sheet_name);
    }

    protected function writeCell(XLSXWriter_BuffererWriter &$file, $row_number, $column_number, $value, $num_format_type, $cell_style_idx)
    {
        $cell_name = self::xlsCell($row_number, $column_number);

        if (!is_scalar($value) || $value === '') { 
            $file->write('<c r="' . $cell_name . '" s="' . $cell_style_idx . '"/>');
        } elseif (is_string($value) && $value[0] == '=') {
            $file->write('<c r="' . $cell_name . '" s="' . $cell_style_idx . '" t="s"><f>' . self::xmlspecialchars($value) . '</f></c>');
        } elseif ($num_format_type == 'n_date') {
            $file->write('<c r="' . $cell_name . '" s="' . $cell_style_idx . '" t="n"><v>' . intval(self::convert_date_time($value)) . '</v></c>');
        } elseif ($num_format_type == 'n_datetime') {
            $file->write('<c r="' . $cell_name . '" s="' . $cell_style_idx . '" t="n"><v>' . self::convert_date_time($value) . '</v></c>');
        } elseif ($num_format_type == 'n_numeric') {
            $file->write('<c r="' . $cell_name . '" s="' . $cell_style_idx . '" t="n"><v>' . self::xmlspecialchars($value) . '</v></c>');
        } elseif ($num_format_type == 'n_string') {
            $file->write('<c r="' . $cell_name . '" s="' . $cell_style_idx . '" t="inlineStr"><is><t>' . self::xmlspecialchars($value) . '</t></is></c>');
        } elseif ($num_format_type == 'n_auto' || 1) { 
            if (!is_string($value) || $value == '0' || ($value[0] != '0' && ctype_digit($value)) || preg_match("/^\-?(0|[1-9][0-9]*)(\.[0-9]+)?$/", $value)) {
                $file->write('<c r="' . $cell_name . '" s="' . $cell_style_idx . '" t="n"><v>' . self::xmlspecialchars($value) . '</v></c>');
            } else { 
                $file->write('<c r="' . $cell_name . '" s="' . $cell_style_idx . '" t="inlineStr"><is><t>' . self::xmlspecialchars($value) . '</t></is></c>');
            }
        }
    }

    protected function styleFontIndexes()
    {
        static $border_allowed = array('left', 'right', 'top', 'bottom');
        static $border_style_allowed = array('thin', 'medium', 'thick', 'dashDot', 'dashDotDot', 'dashed', 'dotted', 'double', 'hair', 'mediumDashDot', 'mediumDashDotDot', 'mediumDashed', 'slantDashDot');
        static $horizontal_allowed = array('general', 'left', 'right', 'justify', 'center');
        static $vertical_allowed = array('bottom', 'center', 'distributed', 'top');
        $default_font = array('size' => '10', 'name' => 'Arial', 'family' => '2');
        $fills = array('', '');
        $fonts = array('', '', '', '');
        $borders = array('');
        $style_indexes = array();
        foreach ($this->cell_styles as $i => $cell_style_string) {
            $semi_colon_pos = strpos($cell_style_string, ";");
            $number_format_idx = substr($cell_style_string, 0, $semi_colon_pos);
            $style_json_string = substr($cell_style_string, $semi_colon_pos + 1);
            $style = json_decode((string)$style_json_string, $as_assoc = true);

            $style_indexes[$i] = array('num_fmt_idx' => $number_format_idx);
            if (isset($style['border']) && is_string($style['border']))
            {
                $border_value['side'] = array_intersect(explode(",", $style['border']), $border_allowed);
                if (isset($style['border-style']) && in_array($style['border-style'], $border_style_allowed)) {
                    $border_value['style'] = $style['border-style'];
                }
                if (isset($style['border-color']) && is_string($style['border-color']) && $style['border-color'][0] == '#') {
                    $v = substr($style['border-color'], 1, 6);
                    $v = strlen((string)$v) == 3 ? $v[0] . $v[0] . $v[1] . $v[1] . $v[2] . $v[2] : $v;
                    $border_value['color'] = "FF" . strtoupper($v);
                }
                $style_indexes[$i]['border_idx'] = self::add_to_list_get_index($borders, json_encode($border_value));
            }
            if (isset($style['fill']) && is_string($style['fill']) && $style['fill'][0] == '#') {
                $v = substr($style['fill'], 1, 6);
                $v = strlen((string)$v) == 3 ? $v[0] . $v[0] . $v[1] . $v[1] . $v[2] . $v[2] : $v;
                $style_indexes[$i]['fill_idx'] = self::add_to_list_get_index($fills, "FF" . strtoupper($v));
            }
            if (isset($style['halign']) && in_array($style['halign'], $horizontal_allowed)) {
                $style_indexes[$i]['alignment'] = true;
                $style_indexes[$i]['halign'] = $style['halign'];
            }
            if (isset($style['valign']) && in_array($style['valign'], $vertical_allowed)) {
                $style_indexes[$i]['alignment'] = true;
                $style_indexes[$i]['valign'] = $style['valign'];
            }
            if (isset($style['wrap_text'])) {
                $style_indexes[$i]['alignment'] = true;
                $style_indexes[$i]['wrap_text'] = (bool)$style['wrap_text'];
            }

            $font = $default_font;
            if (isset($style['font-size'])) {
                $font['size'] = floatval($style['font-size']);
            }
            if (isset($style['font']) && is_string($style['font'])) {
                if ($style['font'] == 'Comic Sans MS') {
                    $font['family'] = 4;
                }
                if ($style['font'] == 'Times New Roman') {
                    $font['family'] = 1;
                }
                if ($style['font'] == 'Courier New') {
                    $font['family'] = 3;
                }
                $font['name'] = strval($style['font']);
            }
            if (isset($style['font-style']) && is_string($style['font-style'])) {
                if (strpos($style['font-style'], 'bold') !== false) {
                    $font['bold'] = true;
                }
                if (strpos($style['font-style'], 'italic') !== false) {
                    $font['italic'] = true;
                }
                if (strpos($style['font-style'], 'strike') !== false) {
                    $font['strike'] = true;
                }
                if (strpos($style['font-style'], 'underline') !== false) {
                    $font['underline'] = true;
                }
            }
            if (isset($style['color']) && is_string($style['color']) && $style['color'][0] == '#') {
                $v = substr($style['color'], 1, 6);
                $v = strlen((string)$v) == 3 ? $v[0] . $v[0] . $v[1] . $v[1] . $v[2] . $v[2] : $v;
                $font['color'] = "FF" . strtoupper($v);
            }
            if ($font != $default_font) {
                $style_indexes[$i]['font_idx'] = self::add_to_list_get_index($fonts, json_encode($font));
            }
        }
        return array('fills' => $fills, 'fonts' => $fonts, 'borders' => $borders, 'styles' => $style_indexes);
    }

    protected function writeStylesXML()
    {
        $r = self::styleFontIndexes();
        $fills = $r['fills'];
        $fonts = $r['fonts'];
        $borders = $r['borders'];
        $style_indexes = $r['styles'];

        $temporary_filename = $this->tempFilename();
        $file = new XLSXWriter_BuffererWriter($temporary_filename);
        $file->write('<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n");
        $file->write('<styleSheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">');
        $file->write('<numFmts count="' . count($this->number_formats) . '">');
        foreach ($this->number_formats as $i => $v) {
            $file->write('<numFmt numFmtId="' . (164 + $i) . '" formatCode="' . self::xmlspecialchars($v) . '" />');
        }
        
        
        $file->write('</numFmts>');

        $file->write('<fonts count="' . (count($fonts)) . '">');
        $file->write('<font><name val="Arial"/><charset val="1"/><family val="2"/><sz val="10"/></font>');
        $file->write('<font><name val="Arial"/><family val="0"/><sz val="10"/></font>');
        $file->write('<font><name val="Arial"/><family val="0"/><sz val="10"/></font>');
        $file->write('<font><name val="Arial"/><family val="0"/><sz val="10"/></font>');

        foreach ($fonts as $font) {
            if (!empty($font)) { 
                $f = json_decode((string)$font, true);
                $file->write('<font>');
                $file->write('<name val="' . htmlspecialchars($f['name']) . '"/><charset val="1"/><family val="' . intval($f['family']) . '"/>');
                $file->write('<sz val="' . intval($f['size']) . '"/>');
                if (!empty($f['color'])) {
                    $file->write('<color rgb="' . strval($f['color']) . '"/>');
                }
                if (!empty($f['bold'])) {
                    $file->write('<b val="true"/>');
                }
                if (!empty($f['italic'])) {
                    $file->write('<i val="true"/>');
                }
                if (!empty($f['underline'])) {
                    $file->write('<u val="single"/>');
                }
                if (!empty($f['strike'])) {
                    $file->write('<strike val="true"/>');
                }
                $file->write('</font>');
            }
        }
        $file->write('</fonts>');

        $file->write('<fills count="' . (count($fills)) . '">');
        $file->write('<fill><patternFill patternType="none"/></fill>');
        $file->write('<fill><patternFill patternType="gray125"/></fill>');
        foreach ($fills as $fill) {
            if (!empty($fill)) { 
                $file->write('<fill><patternFill patternType="solid"><fgColor rgb="' . strval($fill) . '"/><bgColor indexed="64"/></patternFill></fill>');
            }
        }
        $file->write('</fills>');

        $file->write('<borders count="' . (count($borders)) . '">');
        $file->write('<border diagonalDown="false" diagonalUp="false"><left/><right/><top/><bottom/><diagonal/></border>');
        foreach ($borders as $border) {
            if (!empty($border)) { 
                $pieces = json_decode((string)$border, true);
                $border_style = !empty($pieces['style']) ? $pieces['style'] : 'hair';
                $border_color = !empty($pieces['color']) ? '<color rgb="' . strval($pieces['color']) . '"/>' : '';
                $file->write('<border diagonalDown="false" diagonalUp="false">');
                foreach (array('left', 'right', 'top', 'bottom') as $side) {
                    $show_side = in_array($side, $pieces['side']) ? true : false;
                    $file->write($show_side ? "<$side style=\"$border_style\">$border_color</$side>" : "<$side/>");
                }
                $file->write('<diagonal/>');
                $file->write('</border>');
            }
        }
        $file->write('</borders>');

        $file->write('<cellStyleXfs count="20">');
        $file->write('<xf applyAlignment="true" applyBorder="true" applyFont="true" applyProtection="true" borderId="0" fillId="0" fontId="0" numFmtId="164">');
        $file->write('<alignment horizontal="general" indent="0" shrinkToFit="false" textRotation="0" vertical="bottom" wrapText="false"/>');
        $file->write('<protection hidden="false" locked="true"/>');
        $file->write('</xf>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="1" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="1" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="2" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="2" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="0"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="1" numFmtId="43"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="1" numFmtId="41"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="1" numFmtId="44"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="1" numFmtId="42"/>');
        $file->write('<xf applyAlignment="false" applyBorder="false" applyFont="true" applyProtection="false" borderId="0" fillId="0" fontId="1" numFmtId="9"/>');
        $file->write('</cellStyleXfs>');

        $file->write('<cellXfs count="' . (count($style_indexes)) . '">');
        
        
        foreach ($style_indexes as $v) {
            $applyAlignment = isset($v['alignment']) ? 'true' : 'false';
            $wrapText = !empty($v['wrap_text']) ? 'true' : 'false';
            $horizAlignment = isset($v['halign']) ? $v['halign'] : 'general';
            $vertAlignment = isset($v['valign']) ? $v['valign'] : 'bottom';
            $applyBorder = isset($v['border_idx']) ? 'true' : 'false';
            $applyFont = 'true';
            $borderIdx = isset($v['border_idx']) ? intval($v['border_idx']) : 0;
            $fillIdx = isset($v['fill_idx']) ? intval($v['fill_idx']) : 0;
            $fontIdx = isset($v['font_idx']) ? intval($v['font_idx']) : 0;
            
            $file->write('<xf applyAlignment="' . $applyAlignment . '" applyBorder="' . $applyBorder . '" applyFont="' . $applyFont . '" applyProtection="false" borderId="' . ($borderIdx) . '" fillId="' . ($fillIdx) . '" fontId="' . ($fontIdx) . '" numFmtId="' . (164 + $v['num_fmt_idx']) . '" xfId="0">');
            $file->write('	<alignment horizontal="' . $horizAlignment . '" vertical="' . $vertAlignment . '" textRotation="0" wrapText="' . $wrapText . '" indent="0" shrinkToFit="false"/>');
            $file->write('	<protection locked="true" hidden="false"/>');
            $file->write('</xf>');
        }
        $file->write('</cellXfs>');
        $file->write('<cellStyles count="6">');
        $file->write('<cellStyle builtinId="0" customBuiltin="false" name="Normal" xfId="0"/>');
        $file->write('<cellStyle builtinId="3" customBuiltin="false" name="Comma" xfId="15"/>');
        $file->write('<cellStyle builtinId="6" customBuiltin="false" name="Comma [0]" xfId="16"/>');
        $file->write('<cellStyle builtinId="4" customBuiltin="false" name="Currency" xfId="17"/>');
        $file->write('<cellStyle builtinId="7" customBuiltin="false" name="Currency [0]" xfId="18"/>');
        $file->write('<cellStyle builtinId="5" customBuiltin="false" name="Percent" xfId="19"/>');
        $file->write('</cellStyles>');
        $file->write('</styleSheet>');
        $file->close();
        return $temporary_filename;
    }

    protected function buildAppXML()
    {
        $app_xml = "";
        $app_xml .= '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n";
        $app_xml .= '<Properties xmlns="http://schemas.openxmlformats.org/officeDocument/2006/extended-properties" xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes">';
        $app_xml .= '<TotalTime>0</TotalTime>';
        $app_xml .= '<Company>' . self::xmlspecialchars($this->company) . '</Company>';
        $app_xml .= '</Properties>';
        return $app_xml;
    }

    protected function buildCoreXML()
    {
        $core_xml = "";
        $core_xml .= '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n";
        $core_xml .= '<cp:coreProperties xmlns:cp="http://schemas.openxmlformats.org/package/2006/metadata/core-properties" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcmitype="http://purl.org/dc/dcmitype/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">';
        $core_xml .= '<dcterms:created xsi:type="dcterms:W3CDTF">' . date("Y-m-d\TH:i:s.00\Z") . '</dcterms:created>';
        $core_xml .= '<dc:title>' . self::xmlspecialchars($this->title) . '</dc:title>';
        $core_xml .= '<dc:subject>' . self::xmlspecialchars($this->subject) . '</dc:subject>';
        $core_xml .= '<dc:creator>' . self::xmlspecialchars($this->author) . '</dc:creator>';
        if (!empty($this->keywords)) {
            $core_xml .= '<cp:keywords>' . self::xmlspecialchars(implode(", ", (array)$this->keywords)) . '</cp:keywords>';
        }
        $core_xml .= '<dc:description>' . self::xmlspecialchars($this->description) . '</dc:description>';
        $core_xml .= '<cp:revision>0</cp:revision>';
        $core_xml .= '</cp:coreProperties>';
        return $core_xml;
    }

    protected function buildRelationshipsXML()
    {
        $rels_xml = "";
        $rels_xml .= '<?xml version="1.0" encoding="UTF-8"?>' . "\n";
        $rels_xml .= '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">';
        $rels_xml .= '<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="xl/workbook.xml"/>';
        $rels_xml .= '<Relationship Id="rId2" Type="http://schemas.openxmlformats.org/package/2006/relationships/metadata/core-properties" Target="docProps/core.xml"/>';
        $rels_xml .= '<Relationship Id="rId3" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/extended-properties" Target="docProps/app.xml"/>';
        $rels_xml .= "\n";
        $rels_xml .= '</Relationships>';
        return $rels_xml;
    }

    protected function buildWorkbookXML()
    {
        $i = 0;
        $workbook_xml = "";
        $workbook_xml .= '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>' . "\n";
        $workbook_xml .= '<workbook xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">';
        $workbook_xml .= '<fileVersion appName="Calc"/><workbookPr backupFile="false" showObjects="all" date1904="false"/><workbookProtection/>';
        $workbook_xml .= '<bookViews><workbookView activeTab="0" firstSheet="0" showHorizontalScroll="true" showSheetTabs="true" showVerticalScroll="true" tabRatio="212" windowHeight="8192" windowWidth="16384" xWindow="0" yWindow="0"/></bookViews>';
        $workbook_xml .= '<sheets>';
        foreach ($this->sheets as $sheet_name => $sheet) {
            $sheetname = self::sanitize_sheetname($sheet->sheetname);
            $workbook_xml .= '<sheet name="' . self::xmlspecialchars($sheetname) . '" sheetId="' . ($i + 1) . '" state="visible" r:id="rId' . ($i + 2) . '"/>';
            $i++;
        }
        $workbook_xml .= '</sheets>';
        $workbook_xml .= '<definedNames>';
        foreach ($this->sheets as $sheet_name => $sheet) {
            if ($sheet->auto_filter) {
                $sheetname = self::sanitize_sheetname($sheet->sheetname);
                $workbook_xml .= '<definedName name="_xlnm._FilterDatabase" localSheetId="0" hidden="1">\'' . self::xmlspecialchars($sheetname) . '\'!$A$1:' . self::xlsCell($sheet->row_count - 1, count($sheet->columns) - 1, true) . '</definedName>';
                $i++;
            }
        }
        $workbook_xml .= '</definedNames>';
        $workbook_xml .= '<calcPr iterateCount="100" refMode="A1" iterate="false" iterateDelta="0.001"/></workbook>';
        return $workbook_xml;
    }

    protected function buildWorkbookRelsXML()
    {
        $i = 0;
        $wkbkrels_xml = "";
        $wkbkrels_xml .= '<?xml version="1.0" encoding="UTF-8"?>' . "\n";
        $wkbkrels_xml .= '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">';
        $wkbkrels_xml .= '<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles" Target="styles.xml"/>';
        foreach ($this->sheets as $sheet_name => $sheet) {
            $wkbkrels_xml .= '<Relationship Id="rId' . ($i + 2) . '" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet" Target="worksheets/' . ($sheet->xmlname) . '"/>';
            $i++;
        }
        $wkbkrels_xml .= "\n";
        $wkbkrels_xml .= '</Relationships>';
        return $wkbkrels_xml;
    }

    protected function buildContentTypesXML()
    {
        $content_types_xml = "";
        $content_types_xml .= '<?xml version="1.0" encoding="UTF-8"?>' . "\n";
        $content_types_xml .= '<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">';
        $content_types_xml .= '<Override PartName="/_rels/.rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>';
        $content_types_xml .= '<Override PartName="/xl/_rels/workbook.xml.rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>';
        foreach ($this->sheets as $sheet_name => $sheet) {
            $content_types_xml .= '<Override PartName="/xl/worksheets/' . ($sheet->xmlname) . '" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml"/>';
        }
        $content_types_xml .= '<Override PartName="/xl/workbook.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"/>';
        $content_types_xml .= '<Override PartName="/xl/styles.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml"/>';
        $content_types_xml .= '<Override PartName="/docProps/app.xml" ContentType="application/vnd.openxmlformats-officedocument.extended-properties+xml"/>';
        $content_types_xml .= '<Override PartName="/docProps/core.xml" ContentType="application/vnd.openxmlformats-package.core-properties+xml"/>';
        $content_types_xml .= "\n";
        $content_types_xml .= '</Types>';
        return $content_types_xml;
    }

    
    public static function xlsCell($row_number, $column_number, $absolute = false)
    {
        $n = $column_number;
        for ($r = ""; $n >= 0; $n = intval($n / 26) - 1) {
            $r = chr($n % 26 + 0x41) . $r;
        }
        if ($absolute) {
            return '$' . $r . '$' . ($row_number + 1);
        }
        return $r . ($row_number + 1);
    }

    
    public static function log($string)
    {
        
        error_log(date("Y-m-d H:i:s:") . rtrim(is_array($string) ? json_encode($string) : $string) . "\n");
    }

    
    public static function sanitize_filename($filename) 
    {
        $nonprinting = array_map('chr', range(0, 31));
        $invalid_chars = array('<', '>', '?', '"', ':', '|', '\\', '/', '*', '&');
        $all_invalids = array_merge($nonprinting, $invalid_chars);
        return str_replace($all_invalids, "", $filename);
    }

    
    public static function sanitize_sheetname($sheetname)
    {
        static $badchars = '\\/?*:[]';
        static $goodchars = '        ';
        $sheetname = strtr($sheetname, $badchars, $goodchars);
        $sheetname = function_exists('mb_substr') ? mb_substr($sheetname, 0, 31) : substr($sheetname, 0, 31);
        $sheetname = trim(trim(trim((string)$sheetname), "'"));
        return !empty($sheetname) ? $sheetname : 'Sheet' . ((rand() % 900) + 100);
    }

    
    public static function xmlspecialchars($val)
    {
        
        static $badchars = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x0b\x0c\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x7f";
        static $goodchars = "                              ";
        return strtr(htmlspecialchars($val, ENT_QUOTES | ENT_XML1), $badchars, $goodchars);
    }

    
    public static function array_first_key(array $arr)
    {
        reset($arr);
        return key($arr);
    }

    
    private static function determineNumberFormatType($num_format)
    {
        $num_format = preg_replace("/\[(Black|Blue|Cyan|Green|Magenta|Red|White|Yellow)\]/i", "", $num_format);
        if ($num_format == 'GENERAL') {
            return 'n_auto';
        }
        if ($num_format == '@') {
            return 'n_string';
        }
        if ($num_format == '0') {
            return 'n_numeric';
        }
        if (preg_match('/[H]{1,2}:[M]{1,2}(?![^"]*+")/i', $num_format)) {
            return 'n_datetime';
        }
        if (preg_match('/[M]{1,2}:[S]{1,2}(?![^"]*+")/i', $num_format)) {
            return 'n_datetime';
        }
        if (preg_match('/[Y]{2,4}(?![^"]*+")/i', $num_format)) {
            return 'n_date';
        }
        if (preg_match('/[D]{1,2}(?![^"]*+")/i', $num_format)) {
            return 'n_date';
        }
        if (preg_match('/[M]{1,2}(?![^"]*+")/i', $num_format)) {
            return 'n_date';
        }
        if (preg_match('/$(?![^"]*+")/', $num_format)) {
            return 'n_numeric';
        }
        if (preg_match('/%(?![^"]*+")/', $num_format)) {
            return 'n_numeric';
        }
        if (preg_match('/0(?![^"]*+")/', $num_format)) {
            return 'n_numeric';
        }
        return 'n_auto';
    }

    
    private static function numberFormatStandardized($num_format)
    {
        if ($num_format == 'money') {
            $num_format = 'dollar';
        }
        if ($num_format == 'number') {
            $num_format = 'integer';
        }

        if ($num_format == 'string') $num_format = '@';
        else if ($num_format == 'integer') $num_format = '0';
        else if ($num_format == 'date') $num_format = 'YYYY-MM-DD';
        else if ($num_format == 'datetime') $num_format = 'YYYY-MM-DD HH:MM:SS';
        else if ($num_format == 'time') $num_format = 'HH:MM:SS';
        else if ($num_format == 'price') $num_format = '#,##0.00';
        else if ($num_format == 'dollar') $num_format = '[$$-1009]#,##0.00;[RED]-[$$-1009]#,##0.00';
        else if ($num_format == 'euro') $num_format = '#,##0.00 [$€-407];[RED]-#,##0.00 [$€-407]';
        $ignore_until = '';
        $escaped = '';
        for ($i = 0, $ix = strlen((string)$num_format); $i < $ix; $i++) {
            $c = $num_format[$i];
            if ($ignore_until == '' && $c == '[')
                $ignore_until = ']';
            else if ($ignore_until == '' && $c == '"')
                $ignore_until = '"';
            else if ($ignore_until == $c)
                $ignore_until = '';
            if ($ignore_until == '' && ($c == ' ' || $c == '-' || $c == '(' || $c == ')') && ($i == 0 || $num_format[$i - 1] != '_'))
                $escaped .= "\\" . $c;
            else
                $escaped .= $c;
        }
        return $escaped;
    }

    
    public static function add_to_list_get_index(&$haystack, $needle)
    {
        $existing_idx = array_search($needle, $haystack, $strict = true);
        if ($existing_idx === false) {
            $existing_idx = count($haystack);
            $haystack[] = $needle;
        }
        return $existing_idx;
    }

    
    public static function convert_date_time($date_input) 
    {
        $days = 0;    
        $seconds = 0;    
        $year = $month = $day = 0;
        $hour = $min = $sec = 0;

        $date_time = $date_input;
        if (preg_match("/(\d{4})\-(\d{2})\-(\d{2})/", $date_time, $matches)) {
            list($junk, $year, $month, $day) = $matches;
        }
        if (preg_match("/(\d+):(\d{2}):(\d{2})/", $date_time, $matches)) {
            list($junk, $hour, $min, $sec) = $matches;
            $seconds = ($hour * 60 * 60 + $min * 60 + $sec) / (24 * 60 * 60);
        }

        
        if ("$year-$month-$day" == '1899-12-31') return $seconds;    
        if ("$year-$month-$day" == '1900-01-00') return $seconds;    
        if ("$year-$month-$day" == '1900-02-29') return 60 + $seconds;    

        
        $epoch = 1900;
        $offset = 0;
        $norm = 300;
        $range = $year - $epoch;

        
        $leap = (($year % 400 == 0) || (($year % 4 == 0) && ($year % 100))) ? 1 : 0;
        $mdays = array(31, ($leap ? 29 : 28), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

        
        if ($year != 0 || $month != 0 || $day != 0) {
            if ($year < $epoch || $year > 9999) return 0;
            if ($month < 1 || $month > 12) return 0;
            if ($day < 1 || $day > $mdays[$month - 1]) return 0;
        }

        
        $days = $day;    
        $days += array_sum(array_slice($mdays, 0, $month - 1));    
        $days += $range * 365;                      
        $days += intval(($range) / 4);             
        $days -= intval(($range + $offset) / 100); 
        $days += intval(($range + $offset + $norm) / 400);  
        $days -= $leap;                                      

        
        if ($days > 59) {
            $days++;
        }

        return $days + $seconds;
    }
    
}

class XLSXWriter_BuffererWriter
{
    protected $fd = null;
    protected $buffer = '';
    protected $check_utf8 = false;

    public function __construct($filename, $fd_fopen_flags = 'w', $check_utf8 = false)
    {
        $this->check_utf8 = $check_utf8;
        $this->fd = fopen($filename, $fd_fopen_flags);
        if ($this->fd === false) {
            XLSXWriter::log("Unable to open $filename for writing.");
        }
    }

    public function write($string)
    {
        $this->buffer .= $string;
        if (isset($this->buffer[8191])) {
            $this->purge();
        }
    }

    protected function purge()
    {
        if ($this->fd) {
            if ($this->check_utf8 && !self::isValidUTF8($this->buffer)) {
                XLSXWriter::log("Error, invalid UTF8 encoding detected.");
                $this->check_utf8 = false;
            }
            fwrite($this->fd, $this->buffer);
            $this->buffer = '';
        }
    }

    public function close()
    {
        $this->purge();
        if ($this->fd) {
            fclose($this->fd);
            $this->fd = null;
        }
    }

    public function __destruct()
    {
        $this->close();
    }

    public function ftell()
    {
        if ($this->fd) {
            $this->purge();
            return ftell($this->fd);
        }
        return -1;
    }

    public function fseek($pos)
    {
        if ($this->fd) {
            $this->purge();
            return fseek($this->fd, $pos);
        }
        return -1;
    }

    protected static function isValidUTF8($string)
    {
        if (function_exists('mb_check_encoding')) {
            return mb_check_encoding($string, 'UTF-8') ? true : false;
        }
        return preg_match("//u", $string) ? true : false;
    }
}