spout/src/Spout/Reader/XLSX/Helper/SharedStringsHelper.php

<?php

namespace Box\Spout\Reader\XLSX\Helper;

use Box\Spout\Common\Exception\IOException;
use Box\Spout\Reader\Exception\XMLProcessingException;
use Box\Spout\Reader\Wrapper\SimpleXMLElement;
use Box\Spout\Reader\Wrapper\XMLReader;
use Box\Spout\Reader\XLSX\Helper\SharedStringsCaching\CachingStrategyFactory;
use Box\Spout\Reader\XLSX\Helper\SharedStringsCaching\CachingStrategyInterface;

/**
 * Class SharedStringsHelper
 * This class provides helper functions for reading sharedStrings XML file
 *
 * @package Box\Spout\Reader\XLSX\Helper
 */
class SharedStringsHelper
{
    /** Path of sharedStrings XML file inside the XLSX file */
    const SHARED_STRINGS_XML_FILE_PATH = 'xl/sharedStrings.xml';

    /** Main namespace for the sharedStrings.xml file */
    const MAIN_NAMESPACE_FOR_SHARED_STRINGS_XML = 'http://schemas.openxmlformats.org/spreadsheetml/2006/main';

    /** @var string Path of the XLSX file being read */
    protected $filePath;

    /** @var string Temporary folder where the temporary files to store shared strings will be stored */
    protected $tempFolder;

    /** @var CachingStrategyInterface The best caching strategy for storing shared strings */
    protected $cachingStrategy;

    /**
     * @param string $filePath Path of the XLSX file being read
     * @param string|void $tempFolder Temporary folder where the temporary files to store shared strings will be stored
     */
    public function __construct($filePath, $tempFolder = null)
    {
        $this->filePath = $filePath;
        $this->tempFolder = $tempFolder;
    }

    /**
     * Returns whether the XLSX file contains a shared strings XML file
     *
     * @return bool
     */
    public function hasSharedStrings()
    {
        $hasSharedStrings = false;
        $zip = new \ZipArchive();

        if ($zip->open($this->filePath) === true) {
            $hasSharedStrings = ($zip->locateName(self::SHARED_STRINGS_XML_FILE_PATH) !== false);
            $zip->close();
        }

        return $hasSharedStrings;
    }

    /**
     * Builds an in-memory array containing all the shared strings of the sheet.
     * All the strings are stored in a XML file, located at 'xl/sharedStrings.xml'.
     * It is then accessed by the sheet data, via the string index in the built table.
     *
     * More documentation available here: http://msdn.microsoft.com/en-us/library/office/gg278314.aspx
     *
     * The XML file can be really big with sheets containing a lot of data. That is why
     * we need to use a XML reader that provides streaming like the XMLReader library.
     * Please note that SimpleXML does not provide such a functionality but since it is faster
     * and more handy to parse few XML nodes, it is used in combination with XMLReader for that purpose.
     *
     * @return void
     * @throws \Box\Spout\Common\Exception\IOException If sharedStrings.xml can't be read
     */
    public function extractSharedStrings()
    {
        $xmlReader = new XMLReader();
        $sharedStringIndex = 0;
        $escaper = new \Box\Spout\Common\Escaper\XLSX();

        $sharedStringsFilePath = $this->getSharedStringsFilePath();
        if ($xmlReader->open($sharedStringsFilePath, null, LIBXML_NONET) === false) {
            throw new IOException('Could not open "' . self::SHARED_STRINGS_XML_FILE_PATH . '".');
        }

        try {
            $sharedStringsUniqueCount = $this->getSharedStringsUniqueCount($xmlReader);
            $this->cachingStrategy = $this->getBestSharedStringsCachingStrategy($sharedStringsUniqueCount);

            while ($xmlReader->read() && $xmlReader->name !== 'si') {
                // do nothing until a 'si' tag is reached
            }

            while ($xmlReader->name === 'si') {
                $node = $this->getSimpleXmlElementNodeFromXMLReader($xmlReader);
                $node->registerXPathNamespace('ns', self::MAIN_NAMESPACE_FOR_SHARED_STRINGS_XML);

                // removes nodes that should not be read, like the pronunciation of the Kanji characters
                $cleanNode = $this->removeSuperfluousTextNodes($node);

                // find all text nodes 't'; there can be multiple if the cell contains formatting
                $textNodes = $cleanNode->xpath('//ns:t');

                $textValue = '';
                foreach ($textNodes as $textNode) {
                    if ($this->shouldPreserveWhitespace($textNode)) {
                        $textValue .= $textNode->__toString();
                    } else {
                        $textValue .= trim($textNode->__toString());
                    }
                }

                $unescapedTextValue = $escaper->unescape($textValue);
                $this->cachingStrategy->addStringForIndex($unescapedTextValue, $sharedStringIndex);

                $sharedStringIndex++;

                // jump to the next 'si' tag
                $xmlReader->next('si');
            }

        } catch (XMLProcessingException $exception) {
            throw new IOException("The sharedStrings.xml file is invalid and cannot be read. [{$exception->getMessage()}]");
        }

        $this->cachingStrategy->closeCache();

        $xmlReader->close();
    }

    /**
     * @return string The path to the shared strings XML file
     */
    protected function getSharedStringsFilePath()
    {
        return 'zip://' . $this->filePath . '#' . self::SHARED_STRINGS_XML_FILE_PATH;
    }

    /**
     * Returns the shared strings unique count, as specified in <sst> tag.
     *
     * @param \Box\Spout\Reader\Wrapper\XMLReader $xmlReader XMLReader instance
     * @return int Number of unique shared strings in the sharedStrings.xml file
     * @throws \Box\Spout\Common\Exception\IOException If sharedStrings.xml is invalid and can't be read
     */
    protected function getSharedStringsUniqueCount($xmlReader)
    {
        $xmlReader->next('sst');

        // Iterate over the "sst" elements to get the actual "sst ELEMENT" (skips any DOCTYPE)
        while ($xmlReader->name === 'sst' && $xmlReader->nodeType !== XMLReader::ELEMENT) {
            $xmlReader->read();
        }

        return intval($xmlReader->getAttribute('uniqueCount'));
    }

    /**
     * Returns the best shared strings caching strategy.
     *
     * @param int $sharedStringsUniqueCount
     * @return CachingStrategyInterface
     */
    protected function getBestSharedStringsCachingStrategy($sharedStringsUniqueCount)
    {
        return CachingStrategyFactory::getInstance()
                ->getBestCachingStrategy($sharedStringsUniqueCount, $this->tempFolder);
    }

    /**
     * Returns a SimpleXMLElement node from the current node in the given XMLReader instance.
     * This is to simplify the parsing of the subtree.
     *
     * @param \Box\Spout\Reader\Wrapper\XMLReader $xmlReader
     * @return \Box\Spout\Reader\Wrapper\SimpleXMLElement
     * @throws \Box\Spout\Common\Exception\IOException If the current node cannot be read
     */
    protected function getSimpleXmlElementNodeFromXMLReader($xmlReader)
    {
        $node = null;
        try {
            $node = new SimpleXMLElement($xmlReader->readOuterXml());
        } catch (XMLProcessingException $exception) {
            throw new IOException("The sharedStrings.xml file contains unreadable data [{$exception->getMessage()}].");
        }

        return $node;
    }

    /**
     * Removes nodes that should not be read, like the pronunciation of the Kanji characters.
     * By keeping them, their text content would be added to the read string.
     *
     * @param \Box\Spout\Reader\Wrapper\SimpleXMLElement $parentNode Parent node that may contain nodes to remove
     * @return \Box\Spout\Reader\Wrapper\SimpleXMLElement Cleaned parent node
     */
    protected function removeSuperfluousTextNodes($parentNode)
    {
        $tagsToRemove = [
            'rPh', // Pronunciation of the text
        ];

        foreach ($tagsToRemove as $tagToRemove) {
            $xpath = '//ns:' . $tagToRemove;
            $parentNode->removeNodesMatchingXPath($xpath);
        }

        return $parentNode;
    }

    /**
     * If the text node has the attribute 'xml:space="preserve"', then preserve whitespace.
     *
     * @param \Box\Spout\Reader\Wrapper\SimpleXMLElement $textNode The text node element (<t>) whitespace may be preserved
     * @return bool Whether whitespace should be preserved
     */
    protected function shouldPreserveWhitespace($textNode)
    {
        $spaceValue = $textNode->getAttribute('space', 'xml');
        return ($spaceValue === 'preserve');
    }

    /**
     * Returns the shared string at the given index, using the previously chosen caching strategy.
     *
     * @param int $sharedStringIndex Index of the shared string in the sharedStrings.xml file
     * @return string The shared string at the given index
     * @throws \Box\Spout\Reader\Exception\SharedStringNotFoundException If no shared string found for the given index
     */
    public function getStringAtIndex($sharedStringIndex)
    {
        return $this->cachingStrategy->getStringAtIndex($sharedStringIndex);
    }

    /**
     * Destroys the cache, freeing memory and removing any created artifacts
     *
     * @return void
     */
    public function cleanup()
    {
        if ($this->cachingStrategy) {
            $this->cachingStrategy->clearCache();
        }
    }
}