PdfTextPlugin.php

<?php
/**
 * PDF Text
 * 
 * @copyright Copyright 2007-2012 Roy Rosenzweig Center for History and New Media
 * @license http://www.gnu.org/licenses/gpl-3.0.txt GNU GPLv3
 */

/**
 * The PDF Text plugin.
 * 
 * @package Omeka\Plugins\PdfText
 */
class PdfTextPlugin extends Omeka_Plugin_AbstractPlugin
{
    const ELEMENT_SET_NAME = 'PDF Text';
    const ELEMENT_NAME = 'Text';

    protected $_hooks = array(
        'install',
        'uninstall',
        'initialize',
        'config_form',
        'config',
        'before_save_file',
    );

    protected $_pdfinfoMappings = [
        [
            'pdfinfo_field' => 'Title',
            'element_set'   => 'Dublin Core',
            'element'       => 'Title',
            'option'        => 'pdftext_extract_title',
            'label'         => 'Extract title',
        ],
        [
            'pdfinfo_field' => 'Author',
            'element_set'   => 'Dublin Core',
            'element'       => 'Creator',
            'option'        => 'pdftext_extract_creator',
            'label'         => 'Extract creator',
        ],
    ];

    protected $_pdfMimeTypes = array(
        'application/pdf',
        'application/x-pdf',
        'application/acrobat',
        'text/x-pdf',
        'text/pdf',
        'applications/vnd.pdf',
    );

    /**
     * Install the plugin.
     */
    public function hookInstall()
    {
        // Don't install if the pdftotext command doesn't exist.
        // See: http://stackoverflow.com/questions/592620/check-if-a-program-exists-from-a-bash-script
        if ((int) shell_exec('hash pdftotext 2>&- || echo 1')) {
            throw new Omeka_Plugin_Installer_Exception(__('The pdftotext command-line utility ' 
            . 'is not installed. pdftotext must be installed to install this plugin.'));
        }
        // Don't install if a PDF element set already exists.
        if ($this->_db->getTable('ElementSet')->findByName(self::ELEMENT_SET_NAME)) {
            throw new Omeka_Plugin_Installer_Exception(__('An element set by the name "%s" already ' 
            . 'exists. You must delete that element set to install this plugin.', self::ELEMENT_SET_NAME));
        }
        insert_element_set(
            array('name' => self::ELEMENT_SET_NAME, 'record_type' => 'File'),
            array(array('name' => self::ELEMENT_NAME))
        );
    }

    /**
     * Uninstall the plugin
     */
    public function hookUninstall()
    {
        // Delete the PDF element set.
        $elementSet = $this->_db->getTable('ElementSet')->findByName(self::ELEMENT_SET_NAME);
        if ($elementSet) {
            $elementSet->delete();
        }
    }

    /**
     * Initialize this plugin.
     */
    public function hookInitialize()
    {
        // Add translation.
        add_translation_source(dirname(__FILE__) . '/languages');
    }

    /**
     * Display the config form.
     */
    public function hookConfigForm()
    {
        $pdfinfoOptions = [];
        foreach ($this->_pdfinfoMappings as $mapping) {
            $pdfinfoOptions[$mapping['option']] = (bool) get_option($mapping['option']);
        }
        echo get_view()->partial(
            'plugins/pdf-text-config-form.php',
            [
                'valid_storage_adapter' => $this->isValidStorageAdapter(),
                'pdfinfo_mappings' => $this->_pdfinfoMappings,
                'pdfinfo_options' => $pdfinfoOptions,
            ]
        );
    }

    /**
     * Handle the config form.
     */
    public function hookConfig()
    {
        foreach ($this->_pdfinfoMappings as $mapping) {
            set_option($mapping['option'], (int) ($_POST[$mapping['option']] ?? false));
        }
        // Run the text extraction process if directed to do so.
        if ($_POST['pdf_text_process'] && $this->isValidStorageAdapter()) {
            Zend_Registry::get('bootstrap')->getResource('jobs')
                ->sendLongRunning('PdfTextProcess');
        }
    }

    /**
     * Add the PDF text to the file record.
     * 
     * This has a secondary effect of including the text in the search index.
     */
    public function hookBeforeSaveFile($args)
    {
        // Extract text only on file insert.
        if (!$args['insert']) {
            return;
        }
        $file = $args['record'];
        // Ignore non-PDF files.
        if (!in_array($file->mime_type, $this->_pdfMimeTypes)) {
            return;
        }
        // Add the PDF text to the file record.
        $path = $file->getPath();
        $element = $file->getElement(self::ELEMENT_SET_NAME, self::ELEMENT_NAME);
        $text = $this->pdfToText($path);
        // pdftotext must return a string to be saved to the element_texts table.
        if (is_string($text)) {
            $file->addTextForElement($element, $text);
        }
        $this->addPdfInfo($file);
    }

    /**
     * Extract the text from a PDF file.
     * 
     * @param string $path
     * @return string
     */
    public function pdfToText($path)
    {
        $path = escapeshellarg($path);
        return shell_exec("pdftotext -enc UTF-8 $path -");
    }

    /**
     * Add pdfinfo metadata fields to a file record if not already present.
     *
     * @param object $file
     * @return bool
     */
    public function addPdfInfo($file)
    {
        $enabledMappings = array_filter($this->_pdfinfoMappings, function($mapping) {
            return (bool) get_option($mapping['option']);
        });
        // Skip the shell exec if no pdfinfo options are enabled.
        if (empty($enabledMappings)) {
            return false;
        }
        $info = $this->getPdfInfo($file->getPath());
        if (!$info) {
            return false;
        }
        $added = false;
        foreach ($enabledMappings as $mapping) {
            if (!isset($info[$mapping['pdfinfo_field']])) {
                continue;
            }
            $element = $file->getElement($mapping['element_set'], $mapping['element']);
            if (!empty($file->getElementTextsByRecord($element))) {
                continue;
            }
            $file->addTextForElement($element, $info[$mapping['pdfinfo_field']]);
            $added = true;
        }
        return $added;
    }

    /**
     * Get metadata from a PDF file using pdfinfo.
     *
     * @param string $path
     * @return array|null
     */
    public function getPdfInfo($path)
    {
        $path = escapeshellarg($path);
        $output = shell_exec("pdfinfo -enc UTF-8 $path");
        if ($output === null) {
            return null;
        }
        $info = [];
        foreach (explode("\n", $output) as $line) {
            if (preg_match('/^([^:]+):\s+(.+)/', $line, $matches)) {
                $info[trim($matches[1])] = trim($matches[2]);
            }
        }
        return $info;
    }

    /**
     * Determine if the plugin supports the storage adapter.
     * 
     * pdftotext cannot be used on remote files, so only support the default 
     * Filesystem adapter, which stores files locally.
     * 
     * @return bool
     */
    public function isValidStorageAdapter()
    {
        $storageAdapter = Zend_Registry::get('bootstrap')
            ->getResource('storage')->getAdapter();
        if (!($storageAdapter instanceof Omeka_Storage_Adapter_Filesystem)) {
            return false;
        }
        return true;
    }

    /**
     * Get the PDF MIME types.
     * 
     * @return array
     */
    public function getPdfMimeTypes()
    {
        return $this->_pdfMimeTypes;
    }
}