<?php

namespace MailPoet\Util;

/*
 * @license MIT License
 * */

if (!class_exists('ZipArchive')) { throw new Exception('ZipArchive not found'); }

class XLSXWriter
{
  //------------------------------------------------------------------
  //http://office.microsoft.com/en-us/excel-help/excel-specifications-and-limits-HP010073849.aspx
  const EXCEL_2007_MAX_ROW=1048576;
  const EXCEL_2007_MAX_COL=16384;
  //------------------------------------------------------------------
  protected $author ='MailPoet';
  protected $sheets = array();
  protected $shared_strings = array();//unique set
  protected $shared_string_count = 0;//count of non-unique references to the unique set
  protected $temp_files = array();
  protected $current_sheet = '';
  public $rtl = false;

  public function __construct()
  {
    if(!ini_get('date.timezone'))
    {
      //using date functions can kick out warning if this isn't set
      date_default_timezone_set('UTC');
    }
  }

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

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

  protected function tempFilename()
  {
    $filename = tempnam(sys_get_temp_dir(), "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);
    $string = file_get_contents($temp_file);
    return $string;
  }

  public function writeToFile($filename)
  {
    foreach($this->sheets as $sheet_name => $sheet) {
      self::finalizeSheet($sheet_name);//making sure all footers have been written
    }

    @unlink($filename);//if the zip already exists, overwrite it
    $zip = new \ZipArchive();
    if (empty($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/".$sheet->xmlname );
    }
    if (!empty($this->shared_strings)) {
      $zip->addFile($this->writeSharedStringsXML(), "xl/sharedStrings.xml" );  //$zip->addFromString("xl/sharedStrings.xml",     self::buildSharedStringsXML() );
    }
    $zip->addFromString("xl/workbook.xml"         , self::buildWorkbookXML() );
    $zip->addFile($this->writeStylesXML(), "xl/styles.xml" );  //$zip->addFromString("xl/styles.xml"           , self::buildStylesXML() );
    $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($sheet_name)
  {
    //if already initialized
    if ($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),
      'cell_formats' => array(),
      'max_cell_tag_start' => 0,
      'max_cell_tag_end' => 0,
      'finalized' => false,
    );
    $sheet = &$this->sheets[$sheet_name];
    $tabselected = count($this->sheets) == 1 ? 'true' : 'false';//only first sheet is selected
    $max_cell=XLSXWriter::xlsCell(self::EXCEL_2007_MAX_ROW, self::EXCEL_2007_MAX_COL);//XFE1048577
    $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="' . $this->rtl . '" 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">');
    $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>');
    $sheet->file_writer->write(    '<col collapsed="false" hidden="false" max="1025" min="1" style="0" width="11.5"/>');
    $sheet->file_writer->write(  '</cols>');
    $sheet->file_writer->write(  '<sheetData>');
  }

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

    self::initializeSheet($sheet_name);
    $sheet = &$this->sheets[$sheet_name];
    $sheet->cell_formats = array_values($header_types);
    $header_row = array_keys($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 $k => $v) {
      $this->writeCell($sheet->file_writer, 0, $k, $v, $cell_format = 'string');
    }
    $sheet->file_writer->write('</row>');
    $sheet->row_count++;
    $this->current_sheet = $sheet_name;
  }

  public function writeSheetRow($sheet_name, array $row)
  {
    if (empty($sheet_name) || empty($row))
      return;

    self::initializeSheet($sheet_name);
    $sheet = &$this->sheets[$sheet_name];
    if (empty($sheet->cell_formats))
    {
      $sheet->cell_formats = array_fill(0, count($row), 'string');
    }

    $sheet->file_writer->write('<row collapsed="false" customFormat="false" customHeight="false" hidden="false" ht="12.1" outlineLevel="0" r="' . ($sheet->row_count + 1) . '">');
    foreach ($row as $k => $v) {
      $this->writeCell($sheet->file_writer, $sheet->row_count, $k, $v, $sheet->cell_formats[$k]);
    }
    $sheet->file_writer->write('</row>');
    $sheet->row_count++;
    $this->current_sheet = $sheet_name;
  }

  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>');
    $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>');

    $max_cell = self::xlsCell($sheet->row_count - 1, count($sheet->cell_formats) - 1);
    $max_cell_tag = '<dimension ref="A1:' . $max_cell . '"/>';
    $padding_length = $sheet->max_cell_tag_end - $sheet->max_cell_tag_start - strlen($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 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, $cell_format)
  {
    static $styles = array('money'=>1,'dollar'=>1,'datetime'=>2,'date'=>3,'string'=>0);
    $cell = self::xlsCell($row_number, $column_number);
    $s = isset($styles[$cell_format]) ? $styles[$cell_format] : '0';

    if (!is_scalar($value) || $value=='') { //objects, array, empty
      $file->write('<c r="'.$cell.'" s="'.$s.'"/>');
    } elseif ($cell_format=='date') {
      $file->write('<c r="'.$cell.'" s="'.$s.'" t="n"><v>'.intval(self::convert_date_time($value)).'</v></c>');
    } elseif ($cell_format=='datetime') {
      $file->write('<c r="'.$cell.'" s="'.$s.'" t="n"><v>'.self::convert_date_time($value).'</v></c>');
    } elseif (!is_string($value)) {
      $file->write('<c r="'.$cell.'" s="'.$s.'" t="n"><v>'.($value*1).'</v></c>');//int,float, etc
    } elseif ($value{0}!='0' && filter_var($value, FILTER_VALIDATE_INT)){ //excel wants to trim leading zeros
      $file->write('<c r="'.$cell.'" s="'.$s.'" t="n"><v>'.($value).'</v></c>');//numeric string
    } elseif ($value{0}=='='){
      $file->write('<c r="'.$cell.'" s="'.$s.'" t="s"><f>'.self::xmlspecialchars($value).'</f></c>');
    } elseif ($value!==''){
      $file->write('<c r="'.$cell.'" s="'.$s.'" t="s"><v>'.self::xmlspecialchars($this->setSharedString($value)).'</v></c>');
    }
  }

  protected function writeStylesXML()
  {
    $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="4">');
    $file->write(		'<numFmt formatCode="GENERAL" numFmtId="164"/>');
    $file->write(		'<numFmt formatCode="[$$-1009]#,##0.00;[RED]\-[$$-1009]#,##0.00" numFmtId="165"/>');
    $file->write(		'<numFmt formatCode="YYYY-MM-DD\ HH:MM:SS" numFmtId="166"/>');
    $file->write(		'<numFmt formatCode="YYYY-MM-DD" numFmtId="167"/>');
    $file->write('</numFmts>');
    $file->write('<fonts count="4">');
    $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>');
    $file->write('</fonts>');
    $file->write('<fills count="2"><fill><patternFill patternType="none"/></fill><fill><patternFill patternType="gray125"/></fill></fills>');
    $file->write('<borders count="1"><border diagonalDown="false" diagonalUp="false"><left/><right/><top/><bottom/><diagonal/></border></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="4">');
    $file->write(		'<xf applyAlignment="false" applyBorder="false" applyFont="false" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="164" xfId="0"/>');
    $file->write(		'<xf applyAlignment="false" applyBorder="false" applyFont="false" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="165" xfId="0"/>');
    $file->write(		'<xf applyAlignment="false" applyBorder="false" applyFont="false" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="166" xfId="0"/>');
    $file->write(		'<xf applyAlignment="false" applyBorder="false" applyFont="false" applyProtection="false" borderId="0" fillId="0" fontId="0" numFmtId="167" xfId="0"/>');
    $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 setSharedString($v)
  {
    if (isset($this->shared_strings[$v]))
    {
      $string_value = $this->shared_strings[$v];
    }
    else
    {
      $string_value = count($this->shared_strings);
      $this->shared_strings[$v] = $string_value;
    }
    $this->shared_string_count++;//non-unique count
    return $string_value;
  }

  protected function writeSharedStringsXML()
  {
    $temporary_filename = $this->tempFilename();
    $file = new XLSXWriter_BuffererWriter($temporary_filename, $fd_flags='w', $check_utf8=true);
    $file->write('<?xml version="1.0" encoding="UTF-8" standalone="yes"?>'."\n");
    $file->write('<sst count="'.($this->shared_string_count).'" uniqueCount="'.count($this->shared_strings).'" xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">');
    foreach($this->shared_strings as $s=>$c)
    {
      $file->write('<si><t>'.self::xmlspecialchars($s).'</t></si>');
    }
    $file->write('</sst>');
    $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"><TotalTime>0</TotalTime></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">';
    $core_xml.='<dcterms:created xsi:type="dcterms:W3CDTF">'.date("Y-m-d\TH:i:s.00\Z").'</dcterms:created>';//$date_time = '2014-10-25T15:54:37.00Z';
    $core_xml.='<dc:creator>'.self::xmlspecialchars($this->author).'</dc:creator>';
    $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) {
      $workbook_xml.='<sheet name="'.self::xmlspecialchars($sheet->sheetname).'" sheetId="'.($i+1).'" state="visible" r:id="rId'.($i+2).'"/>';
      $i++;
    }
    $workbook_xml.='</sheets>';
    $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).'"/>';
      $i++;
    }
    if (!empty($this->shared_strings)) {
      $wkbkrels_xml.='<Relationship Id="rId'.(count($this->sheets)+2).'" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/sharedStrings" Target="sharedStrings.xml"/>';
    }
    $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"/>';
    }
    if (!empty($this->shared_strings)) {
      $content_types_xml.='<Override PartName="/xl/sharedStrings.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sharedStrings+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;
  }

  //------------------------------------------------------------------
  /*
   * @param $row_number int, zero based
   * @param $column_number int, zero based
   * @return Cell label/coordinates, ex: A1, C3, AA42
   * */
  public static function xlsCell($row_number, $column_number)
  {
    $n = $column_number;
    for($r = ""; $n >= 0; $n = intval($n / 26) - 1) {
      $r = chr($n%26 + 0x41) . $r;
    }
    return $r . ($row_number+1);
  }
  //------------------------------------------------------------------
  public static function log($string)
  {
    file_put_contents("php://stderr", date("Y-m-d H:i:s:").rtrim(is_array($string) ? json_encode($string) : $string)."\n");
  }
  //------------------------------------------------------------------
  public static function sanitize_filename($filename) //http://msdn.microsoft.com/en-us/library/aa365247%28VS.85%29.aspx
  {
    $nonprinting = array_map('chr', range(0,31));
    $invalid_chars = array('<', '>', '?', '"', ':', '|', '\\', '/', '*', '&');
    $all_invalids = array_merge($nonprinting,$invalid_chars);
    return str_replace($all_invalids, "", $filename);
  }
  //------------------------------------------------------------------
  public static function xmlspecialchars($val)
  {
    return str_replace("'", "&#39;", htmlspecialchars($val));
  }
  //------------------------------------------------------------------
  public static function array_first_key(array $arr)
  {
    reset($arr);
    $first_key = key($arr);
    return $first_key;
  }
  //------------------------------------------------------------------
  public static function convert_date_time($date_input) //thanks to Excel::Writer::XLSX::Worksheet.pm (perl)
  {
    $days    = 0;    # Number of days since epoch
    $seconds = 0;    # Time expressed as fraction of 24h hours in seconds
    $year=$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{2}):(\d{2}):(\d{2})/", $date_time, $matches))
    {
      list($junk,$hour,$min,$sec) = $matches;
      $seconds = ( $hour * 60 * 60 + $min * 60 + $sec ) / ( 24 * 60 * 60 );
    }

    //using 1900 as epoch, not 1904, ignoring 1904 special case

    # Special cases for Excel.
    if ("$year-$month-$day"=='1899-12-31')  return $seconds      ;    # Excel 1900 epoch
    if ("$year-$month-$day"=='1900-01-00')  return $seconds      ;    # Excel 1900 epoch
    if ("$year-$month-$day"=='1900-02-29')  return 60 + $seconds ;    # Excel false leapday

    # We calculate the date by calculating the number of days since the epoch
    # and adjust for the number of leap days. We calculate the number of leap
    # days by normalising the year in relation to the epoch. Thus the year 2000
    # becomes 100 for 4 and 100 year leapdays and 400 for 400 year leapdays.
    $epoch  = 1900;
    $offset = 0;
    $norm   = 300;
    $range  = $year - $epoch;

    # Set month days and check for leap year.
    $leap = (($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 );

    # Some boundary checks
    if($year < $epoch || $year > 9999) return 0;
    if($month < 1     || $month > 12)  return 0;
    if($day < 1       || $day > $mdays[ $month - 1 ]) return 0;

    # Accumulate the number of days since the epoch.
    $days = $day;    # Add days for current month
    $days += array_sum( array_slice($mdays, 0, $month-1 ) );    # Add days for past months
    $days += $range * 365;                      # Add days for past years
    $days += intval( ( $range ) / 4 );             # Add leapdays
    $days -= intval( ( $range + $offset ) / 100 ); # Subtract 100 year leapdays
    $days += intval( ( $range + $offset + $norm ) / 400 );  # Add 400 year leapdays
    $days -= $leap;                                      # Already counted above

    # Adjust for Excel erroneously treating 1900 as a leap year.
    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;
  }
}