<?php
require_once 'rdfConstants.php';
include(RDFAPI_INCLUDE_DIR . "RDFAPI.php");
/**
 * Description of SurveyInstance
 *
 * @author jkraaijeveld
 */
class SurveyInstance extends ResearchToolObject{
    public static $filename = 'data/surveys/surveyinstances.rdf';
    
    public $survey;
    public $starttime;
    public $endtime;
    public $open;
    public $presetanswers;
    public $answersets;

    /**
     * Constructor for a SurveyInstance object
     * @param type $uid: The UID of the survey instance object.
     * @param type $starttime: The starttime of the survey round.
     * @param type $endtime: The endtime of the survey round.
     * @param type $open: A boolean to specify whether the survey is open.
     * @param type $presetanswers: A list of answers which are preset for everyone doing the survey.
     * @param type $answersets: A list of answersets.
     */
	public function __construct($uid = null, $survey = null, $starttime = null, $endtime = null, $open = null, $presetanswers = null, $answersets = null)
    {
        if(!isset($uid))
        {
                $uid = md5(uniqid(rand(), true));
        }

        $this->uid = $uid;
        $this->survey = $survey;
        $this->starttime = $starttime;
        $this->endtime = $endtime;
        $this->open = $open;
        $this->presetanswers = $presetanswers;
        $this->answersets = $answersets;
	}


    /**
     * function evaluate()
     * Evaluates the references in this object
     */
    public function evaluate()
    {
        if(is_string($this->survey))
        {
            $result = Survey::get(array("uid" => $this->survey));
            if(!isset($result[0]))
            {
                return false;
            }
            $this->survey = $result[0];
        }
        
        /* Check if all preset answers exist */
        if(!empty($this->presetanswers) && is_string($this->presetanswers[0]))
        {
                $newPresets = array();
                foreach($this->presetanswers as $answer)
                {
                        $result = Answer::get(array("uid" => $answer));
                        if(!isset($result[0]))
                                return false;
                        $newPresets[] = $result[0];
                }
                $this->presetanswers = $newPresets;
        }

        /* Check if all answersets exist */
        if(!empty($this->answersets) && is_string($this->answersets[0]))
        {
                $newAnswerSets = array();
                foreach($this->answersets as $answerSet)
                {
                        $result = AnswerSet::get(array("uid" => $answerSet));
                        if(!isset($result[0]))
                        {
                                return false;
                        }
                        $newAnswerSets[] = $result[0];
                }
                $this->answersets = $newAnswerSets;
        }
        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.
        //TODO: Decide how to fix invalid references graciously.
        if(!$this->evaluate()) 
                throw new Exception('Evaluation failed.');

        //Ensure the required folder exists.
        if(!is_dir('data/surveys/'))
                mkdir('data/surveys/');

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

        $resourceSI = new Resource(SURVEYINSTANCE . '/' . $this->uid);
        //Remove the old value stored with the given id
        $model->subtract($model->find($resourceSI, null, null));

        //Set the new values
        $resourceSIType = new Resource(SURVEYINSTANCE);
        $predicateRType = new Resource(RTYPE);
        $model->add(new Statement($resourceSI, $predicateRType, $resourceSIType));

        $SIID = new Literal($this->uid);
        $predicateId = new Resource(UID);
        $model->add(new Statement($resourceSI, $predicateId, $SIID));
        
        $SISurvey = new Resource(SURVEY . '/' . $this->survey->uid);
        $predicateSurvey = new Resource(OF_SURVEY);
        $model->add(new Statement($resourceSI, $predicateSurvey, $SISurvey));

        $SIStartTime = new Literal($this->starttime->getTimestamp());
        $predicateStartTime = new Resource(STARTTIME);
        $model->add(new Statement($resourceSI, $predicateStartTime, $SIStartTime));

        $SIEndTime = new Literal($this->endtime->getTimestamp());
        $predicateEndTime = new Resource(ENDTIME);
        $model->add(new Statement($resourceSI, $predicateEndTime, $SIEndTime));

        $SIOpen = new Literal((bool) $this->open);
        $predicateOpen = new Resource(OPEN);
        $model->add(new Statement($resourceSI, $predicateOpen, $SIOpen));

        if(isset($this->presetanswers))
        {
                foreach($this->presetanswers as $answer)
                {
                        $answerId = new Resource(ANSWER . '/' . $answer->uid);
                        $predicateAnswer = new Resource(PRESET_ANSWER);
                        $model->add(new Statement($resourceSI, $predicateAnswer, $answerId));
                }
        }

        if(isset($this->answersets))
        {
                foreach($this->answersets as $answer)
                {
                        $answerSetId = new Resource(ANSWERSET . '/' . $answer->uid);
                        $predicateAnswerSet = new Resource(HAS_ANSWERSET);
                        $model->add(new Statement($resourceSI, $predicateAnswerSet, $answerSetId));
                }
        }
        $model->saveAs(SurveyInstance::$filename, 'rdf');
        return true;
    }
   /**
	* function get($arguments)
	* Gets the array of SurveyInstance objects belonging tothe arguments supplied.
	* @param type $arguments: An array containing zero or more of the following keys:
	* 						  'uid', 'of_survey', 'starttime', 'endtime', 'open', 'preset_answers', 'has_answerset'
	*/
	public static function get($arguments)
	{
		$model = ResearchToolObject::load(SurveyInstance::$filename);
		//Build the query string
		$querystring = '
			PREFIX predicates: <' . SURVEYTOOL_PREDICATES_NAMESPACE . '>
			PREFIX resources: <' . SURVEYTOOL_RESOURCES_NAMESPACE . '>
			SELECT DISTINCT ?uid, ?of_survey, ?starttime, ?endtime, ?open
			WHERE
			{
				_surveyinstance 	predicates:resource_type	resources:surveyinstance;
				predicates:uid ?uid ;
				predicates:of_survey ?of_survey ;
				predicates:starttime ?starttime ;
				predicates:endtime ?endtime ;
				predicates:open ?open ;
				' . ResearchToolObject::createArguments($arguments) . '
			}';
		//Query the model
		$results = $model->sparqlQuery($querystring);
		//Create the corresponding SurveyInstance objects
		$sInstances = array();
		if(!empty($results))
		{
			foreach($results as $result)
			{
				$startTime = new DateTime();
				$startTime->setTimestamp(intval($result['?starttime']->label));
				$endTime = new DateTime();
				$endTime->setTimestamp(intval($result['?endtime']->label));
				$open = (bool) $result['?open'];
				$presetAnswers = SurveyInstance::getPresetAnswers($model, $result['?uid']->label);
				$answerSets = SurveyInstance::getAnswerSets($model, $result['?uid']->label);
				$sInstances[] = new SurveyInstance($result['?uid']->label, $result['?of_survey']->uri, $startTime, $endTime, $open, $presetAnswers, $answerSets);
			}
		}
		return $sInstances;
	}

	/**
	 * function getFields()
	 * @param type $model : The RDF model to query against.
	 * @param type $uid : The UID of the SurveyInstance for which the preset answers and answersets should be retrieved.
	 * returns : an array with [0] => all preset answers and [1] => all answersets.
	 */
	private static function getPresetAnswers($model, $uid)
	{
		$result = $model->findRegex("[(".$uid.")]", "[(preset_answer)|(has_answerset)]", null);
		$iterator = $result->getStatementIterator();
		$answers = array();
		$sets = array();
		while($iterator->hasNext())
		{
			$element = $iterator->next();
			if($element->getLabelPredicate() == PRESET_ANSWER)
				$answers[] = $element->getLabelObject();
			else if($element->getLabelPredicate() == HAS_ANSWERSET)
				$sets[] = $element->getLabelObject();
		}
		return array($answers, $sets);
	}

	/**
	 * function getAnswerSets()
	 * @param type $model : The RDF model to query against.
	 * @param type $uid : The UID of the SurveyInstance for which the preset answers should be retrieved.
	 */
	private static function getAnswerSets($model, $uid)
	{
		$result = $model->findRegex("[(".$uid.")]", "[(has_answerset)]", null);
		$iterator = $result->getStatementIterator();
		$answersets = array();
		while($iterator->hasNext())
		{
			$element = $iterator->next();
			$answersets[] = $element->getLabelObject();
		}
		return $answersets;
	}

	/**
	 * Creates a new SurveyInstance object out of the given object.
	 */
	public static function create($obj)
	{
		return new Survey($obj->uid, $obj->survey, $obj->starttime, $obj->endtime, $obj->open, $obj->presetanswers, $obj->answersets);	
	}

}

?>