<?php

/**
 * Description of Survey
 *
 * @author jkraaijeveld
 */
class Survey extends ResearchToolObject{
	private static $filename = 'data/surveys/surveys.rdf';

    public $title;
    public $description;
    public $creator;
    public $questions;
    
    public function __construct($uid = null, $title = null, $description = null, $creator = null, $questions = null) {
        if(!isset($uid))
        {
            $uid = md5(uniqid(rand(), true));
        }
        $this->uid = $uid;
        $this->title = $title;
		$this->description = $description;
		$this->creator = $creator;
        $this->questions = $questions;
	}

	/**
	 * function evaluate()
	 * Evaluates the references
	 */
	public function evaluate()
	{
		if(is_string($this->creator))
		{
			$result = User::get(array("uid" => $this->creator));	
			if(!isset($result[0]))
				return false;
			$this->creator = $result[0];
		}

		if(!empty($this->questions) && is_string($this->questions[0]))
		{
			$newQuestions = array();
			foreach($this->questions as $question)
			{
				$result = Question::get(array("code" => $question));
				if(!isset($result[0]))
					return false;
				$newQuestions[] = $result[0];			
			}
			$this->questions = $newQuestions;
		}
		return true;
	}

	/**
	 * function save()
	 * Saves the current object into the database.
	 */
    public function save()
    {
		//If evaluation fails, some references are incorrect.
		//We shouldn't save in this case. Instead - let the user know. This function returns false if the evaluation has failed.
		//TODO: Decide how to fix invalid references graciously.
		if(!$this->evaluate()) 
			return false;

		if(!is_dir('data/surveys/'))
			mkdir('data/surveys/');

		$model = ResearchToolObject::load(Survey::$filename);

        $resourceSurvey = new Resource(SURVEY.'/'.$this->uid);
        //Remove the old value stored with the given id
        $model->subtract($model->find($resourceSurvey, null, null));
        
        $resourceSurveyType = new Resource(SURVEY);
        $predicateRType = new Resource(RTYPE);
        $model->add(new Statement($resourceSurvey,$predicateRType,$resourceSurveyType));

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

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

        $predicateDescription = new Resource(DESCRIPTION);
        $surveyDescription = new Literal($this->description);
        $model->add(new Statement($resourceSurvey,$predicateDescription,$surveyDescription));
        
		$predicateCreator = new Resource(CREATOR);
		$surveyCreator = new Literal($this->creator->uid);
		$model->add(new Statement($resourceSurvey, $predicateCreator, $surveyCreator));

        if(isset($this->questions))
        {
            foreach($this->questions as $question)
            {
                $questionUid = new Literal($question->uid);
                $predicateQuid = new Resource(HAS_QUESTION);
                $model->add(new Statement($resourceSurvey,$predicateQuid,$questionUid));
            }
		}
		$model->saveAs(Survey::$filename, 'rdf');
		return true;
	}

    /**
     * function get($arguments)
     * Gets the array of Survey objects belonging to arguments supplied.
     * @param type $arguments : An array containing zero or more of the following keys:
     *                          'uid', 'title', 'description', 'questions'
     * Note: questions has to be an array of question IDs (codes) for this filter to work.
     */
    public static function get($arguments)
    {
		$model = ResearchToolObject::load(Survey::$filename);
        
        //Build the query string
        $querystring = '
            PREFIX  predicates: <' . SURVEYTOOL_PREDICATES_NAMESPACE . '>
            PREFIX  resources: <' . SURVEYTOOL_RESOURCES_NAMESPACE . '>
            SELECT DISTINCT ?uid, ?title, ?description, ?creator
            WHERE
            {
                _survey     predicates:resource_type    resources:survey ;
                predicates:uid ?uid ;
                predicates:title ?title ;
				predicates:description ?description ;
				predicates:creator ?creator ;
				' . ResearchToolObject::createArguments($arguments) . '
            }';
        
        //Query the model
        $results = $model->sparqlQuery($querystring);
        
        //Create the corresponding Survey objects
        $surveys = array();
        if(!empty($results))
        {
            foreach($results as $result)
            {
				$questions = Survey::getQuestions($model, $result['?uid']->label);
				$creator = $result['?creator']->label;
                $surveys[] = new Survey($result['?uid']->label, $result['?title']->label, $result['?description']->label, $creator, $questions);
            }
        }
        return $surveys;
    }
    
    /**
     * Gets the questions corresponding to the survey
     * @param type $uid : The uid for which the questions should be gotten.
     */
    private static function getQuestions($model, $uid)
    {
		$result = $model->findRegex("[(".$uid.")]", "[(has_question)]", null);
		$iterator = $result->getStatementIterator();
		$questions = array();
		while($iterator->hasNext())
		{
			$element = $iterator->next();
			$questions[] = $element->getLabelObject();
		}
		return $questions;
    }


}

?>