<?php

/**
 * Description of SurveyConnector
 *
 * @author jkraaijeveld
 */
class SurveyConnector implements IConnector{
    protected $model;
    protected $fileName = 'data/surveys/surveys.rdf';
    protected $db;

    /**
     * Constructor for ApplicationConnector.
     */
    public function __construct()
    {
        //Ensure the required folder for this connector exists
        if (!is_dir('data/surveys/'))
            mkdir('data/surveys/');	
    }
    
    /**
     * function load()
     * Loads the file into the standard MemModel.
     */
    public function load() {
        //Get the Memory Model from the ModelFactory
        $this->model = ModelFactory::getDefaultModel();
        
        //Ensure the required file exists before loading
        if(file_exists($this->fileName))
            $this->model->load($this->fileName);
    }
    
    /**
     * function save()
     * Saves the MemModel into the given file.
     */
    public function save() {
        $this->model->saveAs($this->fileName,'rdf'); 
    }
    
    /**
     * function get($arguments)
     * Gets the array of Survey objects belonging to arguments supplied.
     * @param type $arguments : An array containing zero or more of the following keys:
     *                          'uid', 'title', 'description', 'questions'
     * Note: questions has to be an array of question IDs (codes) for this filter to work.
     */
    public function get($arguments)
    {
        $this->load();
        
        $keys = array_keys($arguments);
        //Set default values for arguments
        $uid = "?uid"; $title = "?title"; $description = "?description"; $questions = "";
        if(in_array("uid", $keys))
            $uid = '\''.$arguments["uid"].'\'';
        if(in_array("title", $keys))
            $title = '\''.$arguments["title"].'\'';
        if(in_array("description", $keys))
            $description = "\"".$arguments["description"]."\"";
        if(in_array("questions", $keys))
        {
            //Append the questions string to filter for questions properly
            foreach ($arguments["questions"] as $questionUid)
            {
                $questions = $questions . 'predicates:has_question \'' . $questionUid . '\' ';
            }
        }
        
        //Build the query string
        $querystring = '
            PREFIX  predicates: <' . SURVEYTOOL_PREDICATES_NAMESPACE . '>
            PREFIX  resources: <' . SURVEYTOOL_RESOURCES_NAMESPACE . '>
            SELECT DISTINCT ?uid, ?title, ?description
            WHERE
            {
                _survey     predicates:resource_type    resources:survey ;
                predicates:uid ?uid ;
                predicates:title ?title ;
                predicates:description ?description ;
                predicates:uid ' . $uid . ' 
                predicates:title ' . $title . '
                predicates:description ' . $description . '
                ' . $questions . '
            }';
        
        //Query the model
        $results = $this->model->sparqlQuery($querystring);
        
        //Create the corresponding Survey objects
        $surveys = array();
        if(!empty($results))
        {
            $this->db = new DatabaseInterface();
            foreach($results as $result)
            {
                $questions = $this->getQuestions($result['?uid']->label);
                $surveys[] = new Survey($result['?uid']->label, $result['?title']->label, $result['?description']->label, $questions);
            }
        }
        return $surveys;
    }
    
    /**
     * Gets the questions corresponding to the survey
     * @param type $uid 
     */
    private function getQuestions($uid)
    {
        //Create the querystring. Note that the UID is the only argument in this case.
        $querystring = '
            PREFIX  predicates: <' . SURVEYTOOL_PREDICATES_NAMESPACE . '>
            PREFIX  resources: <' . SURVEYTOOL_RESOURCES_NAMESPACE . '>
            SELECT DISTINCT ?has_question
            WHERE
            {
                 _survey	predicates:resource_type	resources:survey ;
                predicates:has_question ?has_question ; 
                predicates:uid \'' . $uid . '\'
            }';

        $results = $this->model->sparqlQuery($querystring);
        $questions = array();
        //For every question id, get the corresponding question
        if(!empty($results))
        {
            foreach($results as $questionId)
            {
                $resultQ = $this->db->get("question", array("uid" => $questionId['?has_question']->label));
                $questions[] = $resultQ[0];
            }
        }
        return $questions;
    }
    
    /**
     * Saves the given Survey object.
     * @param type $rToolObject 
     */
    public function set($rToolObject)
    {
        $this->load();
        
        $resourceSurvey = new Resource(SURVEY.'/'.$rToolObject->uid);
        //Remove the old value stored with the given id
        $this->model->subtract($this->model->find($resourceSurvey, null, null));
        
        $resourceSurveyType = new Resource(SURVEY);
        $predicateRType = new Resource(RTYPE);
        $this->model->add(new Statement($resourceSurvey,$predicateRType,$resourceSurveyType));

        $predicateUniqueID = new Resource(UID);
        $literalSurveyID = new Literal($rToolObject->uid);
        $this->model->add(new Statement($resourceSurvey,$predicateUniqueID,$literalSurveyID));

        $predicateTitle = new Resource(TITLE);		
        $surveyTitle = new Literal($rToolObject->title);
        $this->model->add(new Statement($resourceSurvey,$predicateTitle,$surveyTitle));		

        $predicateDescription = new Resource(DESCRIPTION);
        $surveyDescription = new Literal($rToolObject->description);
        $this->model->add(new Statement($resourceSurvey,$predicateDescription,$surveyDescription));
        
        if(isset($rToolObject->questions))
        {
            foreach($rToolObject->questions as $question)
            {
                $questionUid = new Literal($question->uid);
                $predicateQuid = new Resource(HAS_QUESTION);
                $this->model->add(new Statement($resourceSurvey,$predicateQuid,$questionUid));
            }
        }
        $this->save();
    }
}

?>