<?php
/**
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; under version 2
 * of the License (non-upgradable).
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Copyright (c) 2008-2010 (original work) Deutsche Institut für Internationale Pädagogische Forschung (under the project TAO-TRANSFER);
 *               2009-2012 (update and modification) Public Research Centre Henri Tudor (under the project TAO-SUSTAIN & TAO-DEV);
 *
 */

/**
 * A FileWriter aiming at writing RDF files.
 *
 * @access public
 * @author Jerome Bogaerts, <jerome.bogaerts@tudor.lu>
 * @package tao

 */
class tao_helpers_translation_RDFFileWriter extends tao_helpers_translation_TranslationFileWriter
{
    // --- ASSOCIATIONS ---


    // --- ATTRIBUTES ---

    // --- OPERATIONS ---

    /**
     * Writes the RDF file on the file system.
     *
     * @access public
     * @author Jerome Bogaerts, <jerome.bogaerts@tudor.lu>
     * @return mixed
     */
    public function write()
    {
        
        $targetPath = $this->getFilePath();
        $file = $this->getTranslationFile();
        $semanticNamespaces = ['rdf' => 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
                                    'rdfs' => 'http://www.w3.org/2000/01/rdf-schema#'];
        
        $xmlNS = 'http://www.w3.org/XML/1998/namespace';
        $xmlnsNS = 'http://www.w3.org/2000/xmlns/';
        
        try {
            $targetFile = new DOMDocument('1.0', 'UTF-8');
            $targetFile->formatOutput = true;
            
            // Create the RDF root node and annotate if possible.
            $rdfNode = $targetFile->createElementNS($semanticNamespaces['rdf'], 'rdf:RDF');
            $targetFile->appendChild($rdfNode);
            $rootAnnotations = $this->getTranslationFile()->getAnnotations();
            if (count($rootAnnotations)) {
                $annotationsString = tao_helpers_translation_RDFUtils::serializeAnnotations($rootAnnotations);
                $annotationsNode = $targetFile->createComment("\n    " . $annotationsString . "\n");
                $targetFile->insertBefore($annotationsNode, $rdfNode);
            }
            
            $rdfNode->setAttributeNS($xmlNS, 'xml:base', $file->getBase());
            $rdfNode->setAttributeNS($xmlnsNS, 'xmlns:rdfs', $semanticNamespaces['rdfs']);
            
            $xPath = new DOMXPath($targetFile);
            $xPath->registerNamespace($semanticNamespaces['rdf'], 'rdf');
            $xPath->registerNamespace($semanticNamespaces['rdfs'], 'rdfs');
            
            foreach ($file->getTranslationUnits() as $tu) {
                // Look if the predicate is a semantic namespace.
                $uri = explode('#', $tu->getPredicate());
                if (count($uri) == 2) {
                    $namespace = $uri[0] . '#';
                    $qName = $uri[1];
                    if (($searchedNS = array_search($namespace, $semanticNamespaces)) !== false) {
                        $tuNode = $targetFile->createElement("${searchedNS}:${qName}");
                        $tuNode->setAttributeNS($xmlNS, 'xml:lang', $tu->getTargetLanguage());
                        $cdataValue = (($tu->getTarget() == '') ? $tu->getSource() : $tu->getTarget());
                        $tuNodeValue = $targetFile->createCDATASection($cdataValue);
                        
                        $tuNode->appendChild($tuNodeValue);
                        // Check if an rdf:Description exists for
                        // the target of the TranslationUnit.
                        $subject = $tu->getSubject();
                        $result = $xPath->query("//rdf:Description[@rdf:about='${subject}']");
                
                        if ($result->length > 0) {
                            // Append to the existing rdf:Description.
                            $existingDescription = $result->item(0);
                            $existingDescription->appendChild($tuNode);
                        } else {
                            // Append to a new rdf:Description node.
                            $descriptionNode = $targetFile->createElementNS($semanticNamespaces['rdf'], 'rdf:Description');
                            $descriptionNode->setAttributeNS($semanticNamespaces['rdf'], 'rdf:about', $subject);
                            $descriptionNode->appendChild($tuNode);
                            $rdfNode->appendChild($descriptionNode);
                        }
                        
                        // Finally add annotations.
                        $annotations = $tu->getAnnotations();
                        
                        if (count($annotations) > 0) {
                            $annotationString = "\n    " . tao_helpers_translation_RDFUtils::serializeAnnotations($annotations) . "\n    ";
                            $annotationNode = $targetFile->createComment($annotationString);
                            $tuNode->parentNode->insertBefore($annotationNode, $tuNode);
                        }
                    }
                }
            }

            $targetFile->save($targetPath);
        } catch (DOMException $e) {
            throw new tao_helpers_translation_TranslationException("An error occured while writing the RDF File at '${targetPath}'.");
        }
    }
}