<?php

require_once RDFAPI_INCLUDE_DIR . 'RDFAPI.php';

interface RdfResource {

    function getUri();

    function getUid();

    function getType();
}

abstract class RdfObject implements RdfResource, IteratorAggregate {
    // namespace and uri functions

    const NS = 'http://tbm.tudelft.nl/researchtool/';
    const RESOURCES_NS = 'http://tbm.tudelft.nl/researchtool/resources/';
    const PREDICATES_NS = 'http://tbm.tudelft.nl/researchtool/predicates/';

    public static function isResourceUri($str) {
        $ptrn = '/^' . preg_quote(self::RESOURCES_NS, '/') . '\w+\/\w+$/';
        return (bool) preg_match($ptrn, $str);
    }

    public static function resourceUriToTypeAndUid($uri) {
        if (!self::isResourceUri($uri)) {
            throw new Exception("Given URI $uri is not a valid resource.");
        }
        $ptrn = '/^' . preg_quote(self::RESOURCES_NS, '/') . '(\w+)\/(\w+)$/';
        $matches = array();
        preg_match_all($ptrn, $uri, $matches);
        return array('type' => $matches[1][0], 'uid' => $matches[2][0]);
    }

    public static function typeAndUidToResourceUri($type, $uid) {
        return self::RESOURCES_NS . $type . '/' . $uid;
    }

    // type functions

    private static $fieldsCache = array();

    private static function TYPE() {
        return get_called_class();
    }

    private static function FIELDS() {
        $type = static::TYPE();
        if (!isset(self::$fieldsCache[$type])) {
            self::$fieldsCache[$type] = static::createFIELDS();
        }
        return self::$fieldsCache[$type];
    }

    /** Provides the field of this object - implemented by specific type classes
     * Retrieves an array with the specification of the fields of this object.
     * The array contains RdfField objects. This function is called only once
     * per type, because the result is cached.
     */
    protected abstract static function createFIELDS();

    // instance fields

    private $uid = null;
    private $uri = null;
    private $values = array();

    public function getUri() {
        return $this->uri;
    }

    public function getUid() {
        return $this->uid;
    }

    public function getType() {
        return static::TYPE();
    }

    // PHP magic functions to expose values

    public function __construct($uid = null, $values = array()) {
        if (empty($uid)) {
            $this->uid = md5(uniqid(rand(), true));
        } else {
            $this->uid = $uid;
        }
        $this->uri = self::typeAndUidToResourceUri(static::TYPE(), $this->uid);
        foreach ($values as $name => $value) {
            $this->$name = $value;
        }
    }

    private function ensure_field($name) {
        if (!array_key_exists($name, static::FIELDS())) {
            throw new Exception("Field " . $name . " not defined on " . self::TYPE());
        }
    }

    private function get_field($name) {
        self::ensure_field($name);
        $fields = static::FIELDS();
        return $fields[$name];
    }

    public function __isset($name) {
        $this->ensure_field($name);
        return isset($this->values[$name]);
    }

    public function __get($name) {
        $field = self::get_field($name);
        if (isset($this->values[$name])) {
            return $this->values[$name];
        }
        return $field->get_null();
    }

    public function __set($name, $value) {
        self::ensure_field($name);
        $this->values[$name] = $value;
    }

    public function __unset($name) {
        unset($this->values[$name]);
    }

    public function getIterator() {
        return new ArrayIterator($this->values);
    }

    public function __toString() {
        return self::TYPE() . '(uid=' . $this->uid . ')';
    }

    // RDF database functions

    private static function get_db_filename() {
        $fileName = 'data/' . static::TYPE() . 's/' . static::TYPE() . 's.rdf';
        $dirName = dirname($fileName);
        if (!is_dir($dirName)) {
            mkdir($dirName, 0777 /* PHP's default value */, $recursive = TRUE);
        }
        return $fileName;
    }

    private static function get_model() {
        $fileName = self::get_db_filename();
        $model = ModelFactory::getDefaultModel();
        if (file_exists($fileName)) {
            $model->load($fileName);
        }
        $model->addNamespace('rtr', self::RESOURCES_NS);
        $model->addNamespace('rtp', self::PREDICATES_NS);
        return $model;
    }

    private static function save_model($model) {
        $fileName = self::get_db_filename();
        return $model->saveAs($fileName, 'rdf');
    }

    protected function evaluate() {
        foreach (static::FIELDS() as $name => $field) {
            if ($field->required()
                    && (!is_set($this->values[$name])
                    || ( $field->multiple() && empty($this->values[$name]) ) )) {
                throw new Exception("Required field $name not found.");
            }
        }
    }

    public function save() {
        $this->evaluate();

        $model = self::get_model();

        // create new resource and remove old saved resource
        $resource = new Resource($this->uri);
        $model->subtract($model->find($resource, null, null));

        // set type
        $model->add(new Statement($resource,
                        new Resource(RDF_NAMESPACE_URI . 'type'),
                        new Resource(self::RESOURCES_NS . static::TYPE())));

        // add fields
        foreach (static::FIELDS() as $name => $field) {
            if (isset($this->values[$name])) {
                $values = $this->values[$name];
                if (!$field->multiple()) {
                    $values = array($values);
                }
                foreach ($values as $value) {
                    $type = $field->type();
                    $type::save($model, $resource, $name, $value);
                }
            }
        }

        if (!self::save_model($model)) {
            throw new Exception('Save failed: internal RDFAPI error.');
        }
    }

    public static function get($predicates = array()) {
        $model = self::get_model();

        $query = '';
        $query .= "PREFIX predicates: <" . self::PREDICATES_NS . ">\n";
        $query .= "PREFIX resources: <" . self::RESOURCES_NS . ">\n";
        $query .= "SELECT *\n";
        $query .= "WHERE {\n";
        $query .= "\t?object a resources:" . static::TYPE() . " .\n";
        foreach (static::FIELDS() as $name => $field) {
            if (!$field->multiple()) {
                $cond = "?object predicates:" . $name . " ?" . $name;
                if ($field->required() || array_key_exists($name, $predicates)) {
                    $query .= "\t$cond .\n";
                } else {
                    $query .= "\tOPTIONAL { $cond . }\n";
                }
            }
        }
        if (!empty($predicates)) {
            $preds = array();
            foreach ($predicates as $name => $value) {
                if ($name == 'uid') {
                    if (!is_string($value)) {
                        $value = $value->getUid();
                    }
                    $preds[] = 'str(?object) = "' . self::RESOURCES_NS . self::TYPE() . '/' . $value . '"';
                } else {
                    $type = self::get_field($name)->type();
                    $preds[] = $type::predicate($name, $value);
                }
            }
            $query .= "\tFILTER ( " . join(" && ", $preds) . " ) .\n";
        }
        $query .= "}\n";

        $results = $model->sparqlQuery($query);
        $objects = array();
        if (!empty($results)) {
            $realClass = self::TYPE();
            foreach ($results as $result) {
                $uri = $result['?object']->uri;
                $values = array();
                foreach (static::FIELDS() as $name => $field) {
                    if (!$field->multiple()) {
                        $queryName = "?$name";
                        if (isset($result[$queryName]) && !empty($result[$queryName])) {
                            $type = $field->type();
                            $values[$name] = $type::load($result[$queryName]);
                        }
                    } else {
                        $values[$name] = self::getMultiple($model, $uri, $name, $field);
                    }
                }
                $info = self::resourceUriToTypeAndUid($uri);
                $objects[] = new $realClass($info['uid'], $values);
            }
        }
        return $objects;
    }

    private static function getMultiple($model, $uri, $name, $field) {
        $query = '';
        $query .= "PREFIX predicates: <" . self::PREDICATES_NS . ">\n";
        $query .= "SELECT DISTINCT ?item\n";
        $query .= "WHERE { <$uri> predicates:$name ?item . }\n";

        $results = $model->sparqlQuery($query);
        $values = array();
        if (!empty($results)) {
            foreach ($results as $result) {
                $type = $field->type();
                $values[] = $type::load($result['?item']);
            }
        }
        return $values;
    }

}

class RdfPointer implements RdfResource {

    private $uri = null;
    private $uid = null;
    private $type = null;

    public function __construct($uri) {
        $this->uri = $uri;
        $info = RdfObject::resourceUriToTypeAndUid($uri);
        $this->uid = $info['uid'];
        $this->type = $info['type'];
    }

    public function getUri() {
        return $this->uri;
    }

    public function getUid() {
        return $this->uid;
    }

    public function getType() {
        return $this->type;
    }

    public function get() {
        $type = $this->type;
        return $type::get(array('uid' => $this->uid));
    }

}

class RdfField {

    const REQUIRED = 1;
    const MULTIPLE = 2;

    private $type;
    private $conditions;

    public function __construct($type, $conditions = array()) {
        $this->type = $type;
        $this->conditions = $conditions;
    }

    public function type() {
        return $this->type;
    }

    public function required() {
        return in_array(self::REQUIRED, $this->conditions);
    }

    public function multiple() {
        return in_array(self::MULTIPLE, $this->conditions);
    }

}

function RdfField($type, $conditions = array()) {
    return new RdfField($type, $conditions);
}

interface RdfType {

    static function save($model, $resource, $predicateUri, $value);

    static function load($value);

    static function predicate($name, $value);
}

class RdfString implements RdfType {

    static function save($model, $resource, $name, $value) {
        $obj = new Literal($value);
        $model->add(new Statement($resource, new Resource(RdfObject::PREDICATES_NS . $name), $obj));
    }

    static function load($value) {
        return $value->label;
    }

    static function predicate($name, $value) {
        return 'str(?' . $name . ') = "' . $value . '"';
    }

}

function RdfString() {
    return new RdfString();
}

class RdfDatetime implements RdfType {

    static function save($model, $resource, $name, $value) {
        $obj = new Literal($value->getTimestamp());
        $model->add(new Statement($resource, new Resource(RdfObject::PREDICATES_NS . $name), $obj));
    }

    static function load($value) {
        $obj = new DateTime();
        $obj->setTimestamp(intval($value->label));
        return $obj;
    }

    static function predicate($name, $value) {
        return 'str(?' . $name . ') = "' . $value . '"';
    }

}

function RdfDatetime() {
    return new RdfDatetime();
}

class RdfBoolean implements RdfType {

    static function save($model, $resource, $name, $value) {
        $model->add(new Statement($resource,
                        new Resource(RdfObject::PREDICATES_NS . $name),
                        new Literal((bool) $value)));
    }

    static function load($value) {
        return (bool) $value->label;
    }

    static function predicate($name, $value) {
        return 'str(?' . $name . ') = "' . $value . '"';
    }

}

function RdfBoolean() {
    return new RdfBoolean();
}

class RdfReference implements RdfType {

    static function save($model, $resource, $name, $value) {
        if (!is_string($value)) {
            $value = $value->getUri();
        }
        $obj = new Resource($value);
        $model->add(new Statement($resource, new Resource(RdfObject::PREDICATES_NS . $name), $obj));
    }

    static function load($value) {
        return new RdfPointer($value->uri);
    }

    static function predicate($name, $value) {
        return '?' . $name . ' = <' . $value . '>';
    }

}

function RdfReference() {
    return new RdfReference();
}

class Answer extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'question' => RdfField(RdfReference()),
            'values' => RdfField(RdfString(), array(RdfField::MULTIPLE))
        );
    }

}

class AnswerSet extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'survey' => RdfField(RdfReference()),
            'respondent' => RdfField(RdfReference()),
            'datetime' => RdfField(RdfDatetime()),
            'answers' => RdfField(RdfReference(), array(RdfField::MULTIPLE))
        );
    }

}

class Application extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'title' => RdfField(RdfString()),
            'description' => RdfField(RdfString()),
            'style' => RdfField(RdfString())
        );
    }

}

class ApplicationInstance extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'application' => RdfField(RdfReference()),
            'starttime' => RdfField(RdfDatetime()),
            'endtime' => RdfField(RdfDatetime()),
            'open' => RdfField(RdfBoolean())
        );
    }

}

class Question extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'code' => RdfField(RdfString()),
            'title' => RdfField(RdfString()),
            'type' => RdfField(RdfString()),
            'description' => RdfField(RdfString()),
            'category' => RdfField(RdfString()),
            'answers' => RdfField(RdfString(), array(RdfField::MULTIPLE))
        );
    }

}

class Session extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'title' => RdfField(RdfString()),
            'creator' => RdfField(RdfReference()),
            'creationdate' => RdfField(RdfDatetime()),
            'pipeline' => RdfField(RdfReference(), array(RdfField::MULTIPLE))
        );
    }

}

class SessionInstance extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'title' => RdfField(RdfString()),
            'location' => RdfField(RdfString()),
            'facilitator' => RdfField(RdfReference()),
            'starttime' => RdfField(RdfDatetime()),
            'endtime' => RdfField(RdfDatetime()),
            'notes' => RdfField(RdfString(), array(RdfField::MULTIPLE)),
            'session' => RdfField(RdfReference()),
            'surveyinstances' => RdfField(RdfReference(), array(RdfField::MULTIPLE)),
            'applicationinstances' => RdfField(RdfReference(), array(RdfField::MULTIPLE))
        );
    }

}

class Survey extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'title' => RdfField(RdfString()),
            'description' => RdfField(RdfString()),
            'creator' => RdfField(RdfReference()),
            'questions' => RdfField(RdfString(), array(RdfField::MULTIPLE))
        );
    }

}

class SurveyInstance extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'survey' => RdfField(RdfReference()),
            'starttime' => RdfField(RdfDatetime()),
            'endtime' => RdfField(RdfDatetime()),
            'open' => RdfField(RdfBoolean()),
            'presetanswers' => RdfField(RdfReference(), array(RdfField::MULTIPLE)),
            'answersets' => RdfField(RdfReference(), array(RdfField::MULTIPLE))
        );
    }

}

class User extends RdfObject {

    protected static function createFIELDS() {
        return array(
            'email' => RdfField(RdfString()),
            'passwordHash' => RdfField(RdfString()),
            'passwordSalt' => RdfField(RdfString())
        );
    }

}

?>