<?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 implements IConnector{
    protected $model;
	protected $fileName = 'data/answers/answers.rdf';
	protected $db;
    
    /**
     * Constructor for AnswerConnector
     */
    public function __construct() {
        //Ensure the required folder for this connector exists
        if (!is_dir('data/answers/'))
            mkdir('data/answers/');
    }
    
    /**
     * 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()
	 * Get the answers corresponding to the arguments
	 * 'Question' argument is supposed to be the question ID
	 * 'Values' has to be an array to make sure multiple answers can be selected.
	 */
    public function get($arguments)
	{
		$this->load();
		$keys = array_keys($arguments);
		$uid = ""; $question = ""; $value = ""; 
		if(in_array("uid", $keys))
			$uid = 'predicates:uid \''.$arguments["uid"].'\'';
		if(in_array("question", $keys))
			$question = 'predicates:question_code \''.$arguments["question"].'\'';
		if(in_array("values", $keys))
		{
			foreach ($arguments["values"] as $val)
			{
				$value = $value . 'predicates:answered \'' . $val . '\' ';
			}
		}
		//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 ;
				' . $uid . $question . $value . '
			}';

		//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))
		{
            $this->db = new DatabaseInterface();
			foreach($results as $result)
			{
				$values = $this->getValues($result['?uid']->label);
				$questionResult = $this->db->get("question", array("uid" => $result['?question_code']->label));
				$answers[] = new Answer($result['?uid']->label, $questionResult[0], $values);
			}
		}
		return $answers;

	}
	/**
	 * Gets the values that belong to the answer
	 * specified by the UID
	 */
	private function getValues($uid)
	{
		$querystring = '
			PREFIX predicates: <' . SURVEYTOOL_PREDICATES_NAMESPACE . '>
			PREFIX resources: <' . SURVEYTOOL_RESOURCES_NAMESPACE . '>
			SELECT DISTINCT ?answered
			WHERE 
			{
				_answer predicates:resource_type resources:answer ;
				predicates:answered ?answered ;
				predicates:uid \''. $uid . '\'
		}';
		$values = $this->model->sparqlQuery($querystring);
		$returnArray = array();
		if(!empty($values))
		{
			foreach($values as $value)
			{
				$returnArray[] = $value['?answered']->label;
			}
		}
		return $returnArray;
	} 

    /**
     * Saves the answer Object to the RDF file.
     * @param type $rToolObject
     */
    public function set($rToolObject)
    {
        $this->load();
        
        $resourceAnswer = new Resource(ANSWER.'/'.$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();
    }
}

?>