<?php
// Survey database interface class as intermediate for storing data from the site to the RDF database 
require_once 'rdfConstants.php';
// Include RAP Library to write RDF files
include(RDFAPI_INCLUDE_DIR . "RDFAPI.php");

/**
 * Description of SessionInstance
 *
 * @author jkraaijeveld
 */

class SessionInstance extends ResearchToolObject
{
	public static $filename = 'data/sessions/sessioninstances.rdf';

	public $title;
	public $location;
	public $facilitator;
	public $starttime;
	public $endtime;
	public $notes;
	public $session;
	public $resultset;

	/**
	 * Constructor for a SessionInstance object
	 * @param type $uid
	 * @param type $title
	 * @param type $location
	 * @param type $facilitator
	 * @param type $starttime
	 * @param type $endtime
	 * @param type $notes
	 * @param type $session
	 * @param type $resultset
	 */
	public function __construct($uid = null, $title = null, $location = null, $facilitator = null, $starttime = null, $endtime = null, $notes = null, $session = null, $resultset = null)
	{
		if(!isset($uid))
		{
			$uid = md5(uniqid(rand(), true));
		}
		$this->uid = $uid;
		$this->title = $title;
		$this->location = $location;
		$this->facilitator = $facilitator;
		$this->starttime = $starttime;
		$this->endtime = $endtime;
		$this->notes = $notes;
		$this->session = $session;
		$this->resultset = $resultset;
	}

	/*
	 * function evaluate()
	 * Evaluates all the references of this object.
	 */
	public function evaluate()
	{
		if(is_string($this->facilitator))
		{
			$result = User::get(array("uid" => $this->facilitator));
			if(!isset($result[0]))
				return false;
			$this->facilitator = $result[0];
		}

		if(is_string($this->session))
		{
			$result = Session::get(array("uid" => $this->session));
			if(!isset($result[0]))
				return false;
			$this->session = $result[0]; 
		}

		if(is_string($this->resultset))
		{
			$result = ResultSet::get(array("uid" => $this->resultset));
			if(!isset($result[0]))
				return true;
			$newResultSets[] = $result[0];
		}
		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;

		//Ensure the required folder exists.
		if(!is_dir('data/sessions/'))
			mkdir('data/sessions/');

		$model = ResearchToolObject::load(SessionInstance::$filename);

		$resourceSInstance = new Resource(SESSIONINSTANCE . '/' . $this->uid);
		//Remove the old value stored with the given id
		$model->subtract($model->find($resourceSInstance, null, null));

		//Set the new values
		$resourceSInstanceType = new Resource(SESSIONINSTANCE);
		$predicateType = new Resource(RTYPE);
		$model->add(new Statement($resourceSInstance, $predicateType, $resourceSInstanceType));

		$sInstanceId = new Literal($this->uid);
		$predicateId = new Resource(UID);
		$model->add(new Statement($resourceSInstance, $predicateId, $sInstanceId));

		$sInstanceTitle = new Literal($this->title);
		$predicateTitle = new Resource(TITLE);
		$model->add(new Statement($resourceSInstance, $predicateTitle, $sInstanceTitle));

		$sInstanceLocation = new Literal($this->location);
		$predicateLocation = new Resource(LOCATION);
		$model->add(new Statement($resourceSInstance, $predicateLocation, $sInstanceLocation));

		$sInstanceFacilitator = new Literal($this->facilitator->uid);
		$predicateFacilitator = new Resource(FACILITATOR);
		$model->add(new Statement($resourceSInstance, $predicateFacilitator, $sInstanceFacilitator));

		$sInstanceStartTime = new Literal($this->starttime->getTimestamp());
		$predicateStartTime = new Resource(STARTTIME);
		$model->add(new Statement($resourceSInstance, $predicateStartTime, $sInstanceStartTime));

		$sInstanceEndTime = new Literal($this->endtime->getTimestamp());
		$predicateEndTime = new Resource(ENDTIME);
		$model->add(new Statement($resourceSInstance, $predicateEndTime, $sInstanceEndTime));

		if(isset($this->notes))
		{
			foreach($this->notes as $note)
			{
				$sInstanceNote = new Literal($note);
				$predicateNote = new Resource(HAS_NOTE);
				$model->add(new Statement($resourceSInstance, $predicateNote, $sInstanceNote));
			}
		}

		$sInstanceSession = new Literal($this->session->uid);
		$predicateSession = new Resource(OF_SESSION);
		$model->add(new Statement($resourceSInstance, $predicateSession, $sInstanceSession));

		if(isset($this->resultset))
		{
			//$sInstanceResultSet = new Literal($this->resultset->uid);
			$sInstanceResultSet = new Literal($this->resultset);
			$predicateResultSet = new Resource(HAS_RESULTSET);
			$model->add(new Statement($resourceSInstance, $predicateResultSet, $sInstanceResultSet));
		}
		$model->saveAs(SessionInstance::$filename, 'rdf');
		return true;
	}

	/**
	 * function get()
	 * @param type $arguments : An array containing one or more of the following elements:
	 * 'uid', 'title', 'location', 'facilitator', 'starttime', 'endtime' 'notes', 'session', 'resultset'
	 */
	public static function get($arguments)
	{
		$model = ResearchToolObject::load(SessionInstance::$filename);

		//Build the query string
		$querystring = '
			PREFIX predicates: <' . SURVEYTOOL_PREDICATES_NAMESPACE . '>
			PREFIX resources: <' . SURVEYTOOL_RESOURCES_NAMESPACE . '>
			SELECT DISTINCT ?uid, ?title, ?location, ?facilitator, ?starttime, ?endtime, ?of_session, ?has_resultset 
			WHERE
			{
				_sessioninstance predicates:resource_type resources:sessioninstance ;
				predicates:uid ?uid ;
				predicates:title ?title ;
				predicates:location ?location ;
				predicates:facilitator ?facilitator ;
				predicates:starttime ?starttime ;
				predicates:endtime ?endtime ;
				predicates:of_session ?of_session ;
				' . ResearchToolObject::createArguments($arguments) . '
	}';
		//Query the model
		$results = $model->sparqlQuery($querystring);
		$sessioninstances = array();
		if(!empty($results))
		{	
			foreach($results as $result)
			{
				//Create a SessionInstance object out of every result. Get all the required fields as well.
				$notes = SessionInstance::getNotes($model, $result['?uid']->label);
				$resultset = SessionInstance::getResultSet($model, $result['?uid']->label);
				$starttime = new DateTime();
				$starttime->setTimestamp(intval($result['?starttime']->label));
				$endtime = new DateTime();
				$endtime->setTimestamp(intval($result['?endtime']->label));
				$sessioninstances[] = new SessionInstance(  
					$result['?uid']->label,
					$result['?title']->label,
					$result['?location']->label,
					$result['?facilitator']->label,
					$starttime,
					$endtime,
					$notes,
					$result['?of_session'],
					$resultset
				);
			}
		}
		return $sessioninstances;
	}
	
	/**
	 * function getNotes()
	 * param type $uid : The SessionInstance uid for which the notes should be retrieved.
	 */
	public static function getNotes($model, $uid)
	{
		$result = $model->findRegex("[(".$uid.")]", "[(has_note)]", null);
		$iterator = $result->getStatementIterator();
		$notes = array();
		while($iterator->hasNext())
		{
			$element = $iterator->next();
			$notes[] = $element->getLabelObject();
		}
		return $notes;
	}

	/**
	 * function getResultSet($uid)
	 * param type $uid : The SessionInstance uid for which the ResultSet should be gotten.
	 */
	public static function getResultSet($model, $uid)
	{
		//TODO: Implement when ResultSet is in.
		return null;
	}



}