<?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 AnswerConnector
 *
 * @author jkraaijeveld
 */
class AnswerConnector extends Connector{
    
    /**
     * Constructor for AnswerConnector
     */
    public function __construct() {
        //Ensure the required folder for this connector exists
        if (!is_dir('data/answers/'))
			mkdir('data/answers/');
		$this->fileName = 'data/answers/answers.rdf';
    }
    
	/**
	 * function get()
	 * @param type $arguments: An array having one or more of the following elements:
	 * 'uid', 'question', 'values'.
	 */
    public function get($arguments)
	{
		$this->load();
		//Create the querystring
		$querystring = '
			PREFIX predicates: <' . SURVEYTOOL_PREDICATES_NAMESPACE . '>
			PREFIX resources: <' . SURVEYTOOL_RESOURCES_NAMESPACE . '>
			SELECT DISTINCT ?uid, ?question_code
			WHERE
			{
				_answer predicates:resource_type resources:answer;

				predicates:uid ?uid ;
				predicates:question_code ?question_code ;
				' . $this->createArguments($arguments) . '
			}';

		//Query the model
		$results = $this->model->sparqlQuery($querystring);	
		//An answer can have multiple values, get all these values for the answer instances found.
		$answers = array();
		if(!empty($results))
		{
			foreach($results as $result)
			{
				$answers[] = new Answer($result['?uid']->label, $result['?question_code']->label, $this->getValues($result['?uid']->label));
			}
		}
		return $answers;
	}

	/**
	 * function getValues()
	 * @param type $uid : The uid of the Answer for which the values should be gotten.
	 */
	private function getValues($uid)
	{
		$result = $this->model->findRegex("[(".$uid.")]", "[(answered)]", null);
		$iterator = $result->getStatementIterator();
		$values = array();
		while($iterator->hasNext())
		{
			$element = $iterator->next();
			$values[] = $element->getLabelObject();
		}
		return $values;
	} 

    /**
	 * function set()
     * @param type $rToolObject : The ResearchToolObject to be saved.
     */
    public function set($rToolObject)
    {
		$this->load();
		//If evaluation fails, some references are incorrect.
		//We shouldn't save in this case. Instead - let the user know. This function returns false if the evaluation has failed.
		//TODO: Decide how to fix invalid references graciously.
		if(!$rToolObject->evaluate()) 
			return false;
        $resourceAnswer = new Resource(ANSWER.'/'.$rToolObject->uid);        
        //Remove the old value stored with the given id
        $this->model->subtract($this->model->find($resourceAnswer, null, null));
        
        //Save all the new values
        $resourceAnswerType = new Resource(ANSWER);
        $predicateRType = new Resource(RTYPE);
        $this->model->add(new Statement($resourceAnswer,$predicateRType,$resourceAnswerType));
        
		$answerId = new Literal($rToolObject->uid);
		$predicateId = new Resource(UID);
		$this->model->add(new Statement($resourceAnswer, $predicateId, $answerId));

		$questionId = new Literal($rToolObject->question->uid);
		$predicateQId = new Resource(QCODE);
		$this->model->add(new Statement($resourceAnswer, $predicateQId, $questionId));

		if(isset($rToolObject->values))
		{
			foreach($rToolObject->values as $value)
			{
				$answerValue = new Literal($value);
				$predicateAnswer = new Resource(ANSWERED);
				$this->model->add(new Statement($resourceAnswer, $predicateAnswer, $answerValue));
			}
		}
		$this->save();
		return true;
    }
}

?>