<?php

use MediaWiki\Html\Html;
use MediaWiki\MediaWikiServices;
use MediaWiki\Parser\Sanitizer;
use SMW\DIWikiPage;
use SMW\Localizer\Localizer;
use SMW\Localizer\Message;
use SMW\MediaWiki\Pipetrick;
use SMW\Services\ServicesFactory as ApplicationFactory;
use SMW\Utils\Image;

/**
 * @ingroup SMWDataValues
 */

/**
 * This datavalue implements special processing suitable for defining
 * wikipages as values of properties.
 *
 * The class can support general wiki pages, or pages of a fixed
 * namespace, Whether a namespace is fixed is decided based on the
 * type ID when the object is constructed.
 *
 * The short display simulates the behavior of the MediaWiki "pipe trick"
 * but always includes fragments. This can be overwritten by setting a
 * caption, which is also done by default when generating a value from user
 * input. The long display always includes all relevant information. Only if a
 * fixed namespace is used for the datatype, the namespace prefix is omitted.
 * This behavior has changed in SMW 1.7: up to this time, short displays have
 * always included the namespace and long displays used the pipe trick, leading
 * to a paradoxical confusion of "long" and "short".
 *
 * @author Nikolas Iwan
 * @author Markus Krötzsch
 * @ingroup SMWDataValues
 */
class SMWWikiPageValue extends SMWDataValue {

	/**
	 * Whether text transformation should be suppressed or not.
	 */
	const NO_TEXT_TRANSFORMATION = 'no.text.transformation';

	/**
	 * Whether images should be displayed as media or simple link.
	 */
	const NO_IMAGE = 'no.image';

	/**
	 * Whether to use the short form or not.
	 */
	const SHORT_FORM = 'form/short';

	/**
	 * Whether to use the prefixed form or not.
	 */
	const PREFIXED_FORM = 'form/prefixed';

	/**
	 * Fragment text for user-specified title. Not stored, but kept for
	 * printout on page.
	 * @var string
	 */
	protected $m_fragment = '';

	/**
	 * Full titletext with prefixes, including interwiki prefix.
	 * Set to empty string if not computed yet.
	 * @var string
	 */
	protected $m_prefixedtext = '';

	/**
	 * Cache for the related MW page ID.
	 * Set to -1 if not computed yet.
	 * @var int
	 */
	protected $m_id = -1;

	/**
	 * Cache for the related MW title object.
	 * Set to null if not computed yet.
	 * @var Title
	 */
	protected $m_title = null;

	/**
	 * If this has a value other than NS_MAIN, the datavalue will only
	 * accept pages in this namespace. This field is initialized when
	 * creating the object (based on the type id or base on the preference
	 * of some subclass); it is not usually changed afterwards.
	 * @var int
	 */
	protected $m_fixNamespace = NS_MAIN;

	/**
	 * @var array
	 */
	protected $linkAttributes = [];

	/**
	 * @var array
	 */
	protected $queryParameters = [];

	public function __construct( $typeid ) {
		parent::__construct( $typeid );
		switch ( $typeid ) {
			case '_wpp':
			case '__sup':
				$this->m_fixNamespace = SMW_NS_PROPERTY;
				break;
			case '_wpc':
			case '__suc':
			case '__sin':
				$this->m_fixNamespace = NS_CATEGORY;
				break;
			case '_wps':
				$this->m_fixNamespace = SMW_NS_SCHEMA;
				break;
			case '_wpu':
				$this->m_fixNamespace = NS_USER;
				break;
			default: // case '_wpg':
				$this->m_fixNamespace = NS_MAIN;
		}
	}

	protected function parseUserValue( $value ) {
		$localizer = Localizer::getInstance();
		$titleFactory = MediaWikiServices::getInstance()->getTitleFactory();

		// support inputs like " [[Test]] ";
		// note that this only works when SMW_PARSER_LINV is set
		$value = ltrim( rtrim( (string)$value, ' ]' ), ' [' );

		// #1066, Manipulate the output only for when the value has no caption
		// assigned and only if a single :Foo is being present, ::Foo is not permitted
		if ( $this->m_caption === false && isset( $value[2] ) && $value[0] === ':' && $value[1] !== ':' ) {
			$value = substr( $value, 1 );
		}

		if ( $this->m_caption === false ) {
			$this->m_caption = $value;
		}

		if ( $value === '' && !$this->getOption( self::OPT_QUERY_CONTEXT ) ) {
			$this->addErrorMsg( [ 'smw-datavalue-wikipage-empty' ], Message::ESCAPED );
			return;
		}

		// #1701 If the DV is part of a Description and an approximate search
		// (e.g. ~foo* / ~Foo*) then use the value as-is and avoid being
		// transformed by the Title object
		// If the vaue contains a valid NS then use the Title to create a correct
		// instance to distinguish [[~Foo*]] from [[Help:~Foo*]]
		if ( $this->getOption( self::OPT_QUERY_COMP_CONTEXT ) || $this->getOption( self::OPT_QUERY_CONTEXT ) ) {

			$title = $titleFactory->newFromText( $value, $this->m_fixNamespace );

			// T:P0427 If the user value says `ab c*` then make sure to use this one
			// instead of the transformed DBKey which would be `Ab c*`
			if ( $title !== null && $title->getNamespace() === NS_MAIN && $this->getOption( 'isCapitalLinks' ) === false ) {
				return $this->m_dataitem = new DIWikiPage( $value, NS_MAIN );
			// If we know that it is a wikipage in a query context and the wiki
			// requires `isCapitalLinks` then use the standard transformation so
			// they appear as standard links even though the user input was `abc`.
			// T:P0902 (`[[Help:]]`)
			} elseif ( $title !== null ) {
				return $this->m_dataitem = DIWikiPage::newFromTitle( $title );
			} elseif ( !$localizer->getNsIndex( substr( $value, 0, -1 ) ) ) {
				return $this->m_dataitem = new DIWikiPage( $value, NS_MAIN );
			}
		}

		if ( $value[0] == '#' ) {
			if ( $this->m_contextPage === null ) {
				$this->addErrorMsg( [ 'smw-datavalue-wikipage-missing-fragment-context', $value ] );
				return;
			} else {
				$this->m_title = $titleFactory->makeTitle( $this->m_contextPage->getNamespace(),
					$this->m_contextPage->getDBkey(), substr( $value, 1 ),
					$this->m_contextPage->getInterwiki() );
			}
		} else {
			$this->m_title = $titleFactory->newFromText( $value, $this->m_fixNamespace );
		}

		$property = $this->getProperty();

		/// TODO: Escape the text so users can see punctuation problems (bug 11666).
		if ( $this->m_title === null && $property !== null ) {
			$this->addErrorMsg( [ 'smw-datavalue-wikipage-property-invalid-title', $property->getLabel(), $value ] );
		} elseif ( $this->m_title === null ) {
			$this->addErrorMsg( [ 'smw-datavalue-wikipage-invalid-title', $value ] );
		} elseif ( ( $this->m_fixNamespace != NS_MAIN ) &&
			 ( $this->m_fixNamespace != $this->m_title->getNamespace() ) ) {
			$this->addErrorMsg( [ 'smw_wrong_namespace', $localizer->getNsText( $this->m_fixNamespace ) ] );
		} else {
			$this->m_fragment = str_replace( ' ', '_', $this->m_title->getFragment() );
			$this->m_prefixedtext = '';
			$this->m_id = -1; // unset id
			$this->m_dataitem = DIWikiPage::newFromTitle( $this->m_title, $this->m_typeid );
		}
	}

	/**
	 * @see SMWDataValue::loadDataItem()
	 * @param $dataItem SMWDataItem
	 * @return bool
	 */
	protected function loadDataItem( SMWDataItem $dataItem ) {
		if ( $dataItem->getDIType() == SMWDataItem::TYPE_CONTAINER ) {
			// might throw an exception, we just pass it through
			$dataItem = $dataItem->getSemanticData()->getSubject();
		}

		if ( $dataItem->getDIType() !== SMWDataItem::TYPE_WIKIPAGE ) {
			return false;
		}

		$this->m_dataitem = $dataItem;
		$this->m_id = -1;
		$this->m_title = null;
		$this->m_fragment = (string)$dataItem->getSubobjectName();
		$this->m_prefixedtext = '';
		$this->m_caption = false; // this class can handle this
		$this->linkAttributes = [];

		if ( ( $this->m_fixNamespace != NS_MAIN ) &&
			( $this->m_fixNamespace != $dataItem->getNamespace() ) ) {
				$this->addErrorMsg(
					[
						'smw_wrong_namespace',
						Localizer::getInstance()->getNsText( $this->m_fixNamespace )
					]
				);
		}

		return true;
	}

	/**
	 * @since 2.4
	 *
	 * @param array $linkAttributes
	 */
	public function setLinkAttributes( array $linkAttributes ) {
		$this->linkAttributes = $linkAttributes;
	}

	/**
	 * @since 2.5
	 *
	 * @param array $queryParameters
	 */
	public function setQueryParameters( array $queryParameters ) {
		$this->queryParameters = $queryParameters;
	}

	/**
	 * Display the value on a wiki page. This is used to display the value
	 * in the place where it was annotated on a wiki page. The desired
	 * behavior is that the display in this case looks as if no property
	 * annotation had been given, i.e. an annotation [[property::page|foo]]
	 * should display like [[page|foo]] in MediaWiki. But this should lead
	 * to a link, not to a category assignment. This means that:
	 *
	 * (1) If Image: is used (instead of Media:) then let MediaWiki embed
	 * the image.
	 *
	 * (2) If Category: is used, treat it as a page and link to it (do not
	 * categorize the page)
	 *
	 * (3) Preserve everything given after "|" for display (caption, image
	 * parameters, ...)
	 *
	 * (4) Use the (default) caption for display. When the value comes from
	 * user input, this includes the full value that one would also see in
	 * MediaWiki.
	 *
	 * @param null $linked mixed generate links if not null or false
	 * @return string
	 */
	public function getShortWikiText( $linked = null ) {
		if ( $linked === null || $linked === false ||
			$this->m_outformat == '-' || !$this->isValid() ||
			$this->m_caption === '' ) {
			$text = $this->m_caption !== false ? $this->m_caption : $this->getWikiValue();

			// #4037
			if ( $this->linkAttributes !== [] ) {
				$text = Html::rawElement(
					'span',
					$this->linkAttributes,
					$text
				);
			}

			return $text;
		}

		$noImage = $this->getOption( self::NO_IMAGE, false );

		if ( $this->m_outformat == 'noimage' ) {
			$noImage = true;
		}

		if ( Image::isImage( $this->m_dataitem ) && $this->m_dataitem->getInterwiki() === '' && !$noImage ) {
			$linkEscape = '';
			$sanitizedHtml = Sanitizer::removeSomeTags( $this->m_outformat );
			$options = $this->m_outformat === false ? 'frameless|border|text-top|' : str_replace( ';', '|', $sanitizedHtml );
			$defaultCaption = '|' . $this->getShortCaptionText() . '|' . $options;
		} else {
			$linkEscape = ':';
			$defaultCaption = '|' . $this->getShortCaptionText();
		}

		if ( $this->m_caption === false ) {
			$link = '[[' . $linkEscape . $this->getWikiLinkTarget() . $defaultCaption . ']]';
		} else {
			$link = '[[' . $linkEscape . $this->getWikiLinkTarget() . '|' . $this->m_caption . ']]';
		}

		if ( $this->m_fragment !== '' ) {
			$this->linkAttributes['class'] = 'smw-subobject-entity';
		}

		if ( $this->linkAttributes !== [] ) {
			$link = Html::rawElement(
				'span',
				$this->linkAttributes,
				$link
			);
		}

		return $link;
	}

	/**
	 * Display the value as in getShortWikiText() but create HTML.
	 * The only difference is that images are not embedded.
	 *
	 * @param Linker|null $linker mixed the Linker object to use or null if no linking is desired
	 * @return string
	 */
	public function getShortHTMLText( $linker = null ) {
		if ( $this->m_fragment !== '' ) {
			$this->linkAttributes['class'] = 'smw-subobject-entity';
		}

		// init the Title object, may reveal hitherto unnoticed errors:
		if ( $linker !== null && $linker !== false &&
				$this->m_caption !== '' && $this->m_outformat != '-' ) {
			$this->getTitle();
		}

		if ( $linker === null || $linker === false || !$this->isValid() ||
				$this->m_outformat == '-' || $this->m_caption === '' ) {

			$caption = $this->m_caption === false ? $this->getWikiValue() : $this->m_caption;
			return Sanitizer::removeSomeTags( $caption );
		}

		$caption = $this->m_caption === false ? $this->getShortCaptionText() : $this->m_caption;
		$caption = Sanitizer::removeSomeTags( $caption );

		if ( $this->getNamespace() == NS_MEDIA ) { // this extra case *is* needed
			return $linker->makeMediaLinkObj( $this->getTitle(), $caption );
		}

		return $linker->link(
			$this->getTitle(),
			$caption,
			$this->linkAttributes,
			$this->queryParameters
		);
	}

	/**
	 * Display the "long" value on a wiki page. This behaves largely like
	 * getShortWikiText() but does not use the caption. Instead, it always
	 * takes the long display form (wiki value).
	 *
	 * @param null $linked mixed if true the result will be linked
	 * @return string
	 */
	public function getLongWikiText( $linked = null ) {
		if ( !$this->isValid() ) {
			return $this->getErrorText();
		}

		$noImage = $this->getOption( self::NO_IMAGE, false );

		if ( $this->m_outformat == 'noimage' ) {
			$noImage = true;
		}

		if ( $linked === null || $linked === false || $this->m_outformat == '-' ) {
			return $this->getWikiValue();
		} elseif ( Image::isImage( $this->m_dataitem ) && $this->m_dataitem->getInterwiki() === '' && !$noImage ) {
			// Embed images and other files
			// Note that the embedded file links to the image, hence needs no additional link text.
			// There should not be a linebreak after an impage, just like there is no linebreak after
			// other values (whether formatted or not).
			return '[[' . $this->getWikiLinkTarget() . '|' .
				$this->getLongCaptionText() . '|frameless|border|text-top]]';
		}

		$link = '[[:' . $this->getWikiLinkTarget() . '|' . $this->getLongCaptionText() . ']]';

		if ( $this->m_fragment !== '' ) {
			$this->linkAttributes['class'] = 'smw-subobject-entity';
		}

		if ( $this->linkAttributes !== [] ) {
			$link = Html::rawElement(
				'span',
				$this->linkAttributes,
				$link
			);
		}

		return $link;
	}

	/**
	 * Display the "long" value in HTML. This behaves largely like
	 * getLongWikiText() but does not embed images.
	 *
	 * @param null $linker mixed if a Linker is given, the result will be linked
	 * @return string
	 */
	public function getLongHTMLText( $linker = null ) {
		if ( $this->m_fragment !== '' ) {
			$this->linkAttributes['class'] = 'smw-subobject-entity';
		}

		// init the Title object, may reveal hitherto unnoticed errors:
		if ( $linker !== null && ( $this->m_outformat != '-' ) ) {
			$this->getTitle();
		}

		if ( !$this->isValid() ) {
			return $this->getErrorText();
		}

		$sanitizerCallback = [ Sanitizer::class, 'removeSomeTags' ];

		if ( $linker === null || $linker === false || $this->m_outformat == '-' ) {
			return call_user_func( $sanitizerCallback, $this->getWikiValue() );
		} elseif ( $this->getNamespace() == NS_MEDIA ) { // this extra case is really needed
			return $linker->makeMediaLinkObj(
				$this->getTitle(),
				call_user_func( $sanitizerCallback, $this->getLongCaptionText() )
			);
		}

		// all others use default linking, no embedding of images here
		return $linker->link(
			$this->getTitle(),
			call_user_func( $sanitizerCallback, $this->getLongCaptionText() ),
			$this->linkAttributes,
			$this->queryParameters
		);
	}

	/**
	 * Return a string that could be used in an in-page property assignment
	 * for setting this value. This does not include initial ":" for
	 * escaping things like Category: links since the property value does
	 * not include such escapes either. Fragment information is included.
	 * Namespaces are omitted if a fixed namespace is used, since they are
	 * not needed in this case when making a property assignment.
	 *
	 * @return string
	 */
	public function getWikiValue() {
		if ( $this->getOption( self::SHORT_FORM, false ) ) {
			$text = $this->getText();
		} elseif ( $this->getOption( self::PREFIXED_FORM, false ) ) {
			$text = $this->getPrefixedText();
		} elseif (
			in_array( $this->getTypeID(), [ '_wpp', '_wps', '_wpu', '__sup', '__sin', '__suc', '__con' ] ) ||
			$this->m_fixNamespace === NS_MAIN
		) {
			$text = $this->getPrefixedText();
		} else {
			$text = $this->getText();
		}

		return $text . ( $this->m_fragment !== '' ? "#{$this->m_fragment}" : '' );
	}

	public function getHash() {
		return $this->isValid() ? $this->getPrefixedText() : implode( "\t", $this->getErrors() );
	}

	/**
	 * Create links to mapping services based on a wiki-editable message.
	 * The parameters available to the message are:
	 * $1: urlencoded article name (no namespace)
	 *
	 * @return array
	 */
	protected function getServiceLinkParams() {
		if ( $this->isValid() ) {
			return [ rawurlencode( str_replace( '_', ' ', $this->m_dataitem->getDBkey() ) ) ];
		} else {
			return [];
		}
	}

///// special interface for wiki page values

	/**
	 * @deprecated since 3.1 use getDataItem()->getTitle() instead
	 *
	 * Return according Title object or null if no valid value was set.
	 * null can be returned even if this object returns true for isValid(),
	 * since the latter function does not check whether MediaWiki can really
	 * make a Title out of the given data.
	 * However, isValid() will return false *after* this function failed in
	 * trying to create a title.
	 *
	 * @return Title
	 */
	public function getTitle() {
		if ( $this->m_title !== null ) {
			return $this->m_title;
		}

		if ( $this->isValid() ) {

			if ( ( $title = $this->m_dataitem->getTitle() ) !== null ) {
				return $this->m_title = $title;
			}

			// #3278, Special handling of `>` in the user namespace
			// added a prefix to users that originate from imported content
			if (
				$this->m_dataitem->getNamespace() === NS_USER &&
				strpos( $this->m_dataitem->getDBkey(), '>' ) !== false ) {

				$this->setOption( self::OPT_DISABLE_INFOLINKS, true );

				$this->m_title = MediaWikiServices::getInstance()->getTitleFactory()->newFromText(
					$this->m_dataitem->getDBkey()
				);

				return $this->m_title;
			}
		}

		$errArg = $this->m_caption;

		if ( $this->isValid() ) {
			$ns = Localizer::getInstance()->getNsText(
				$this->m_dataitem->getNamespace()
			);

			$errArg = "$ns:" . $this->m_dataitem->getDBkey();
		}

		// Should not normally happen, but anyway ...
		$this->addErrorMsg( [ 'smw_notitle', $errArg ] );
	}

	/**
	 * @deprecated since 3.1
	 *
	 * Get MediaWiki's ID for this value or 0 if not available.
	 *
	 * @return integer
	 */
	private function getArticleID() {
		if ( $this->m_id === false ) {
			$this->m_id = $this->getTitle() !== null ? $this->m_title->getArticleID() : 0;
		}

		return $this->m_id;
	}

	/**
	 * @deprecated since 3.1
	 *
	 * Get namespace constant for this value.
	 *
	 * @return integer
	 */
	private function getNamespace() {
		return $this->m_dataitem->getNamespace();
	}

	/**
	 * @deprecated since 3.1
	 *
	 * Get DBKey for this value. Subclasses that allow for values that do not
	 * correspond to wiki pages may choose a DB key that is not a legal title
	 * DB key but rather another suitable internal ID. Thus it is not suitable
	 * to use this method in places where only MediaWiki Title keys are allowed.
	 *
	 * @return string
	 */
	private function getDBkey() {
		return $this->m_dataitem->getDBkey();
	}

	/**
	 * Get text label for this value, just like Title::getText().
	 *
	 * @return string
	 */
	public function getText() {
		if ( $this->getOption( self::NO_TEXT_TRANSFORMATION, false ) ) {
			return $this->m_dataitem->getDBkey();
		}

		return str_replace( '_', ' ', $this->m_dataitem->getDBkey() );
	}

	/**
	 * Get the prefixed text for this value, including a localized namespace
	 * prefix.
	 *
	 * @return string
	 */
	public function getPrefixedText() {
		if ( $this->m_prefixedtext !== '' ) {
			return $this->m_prefixedtext;
		}

		// In case something went wrong (invalid NS etc.), hint the ID to aid the
		// investigation
		if ( $this->m_dataitem !== null && $this->m_dataitem->getId() > 0 ) {
			$this->m_prefixedtext = 'NO_VALID_VALUE (ID: ' . $this->m_dataitem->getId() . ')';
		} else {
			$this->m_prefixedtext = 'NO_VALID_VALUE';
		}

		if ( $this->isValid() ) {
			$nstext = Localizer::getInstance()->getNsText( $this->m_dataitem->getNamespace() );
			$this->m_prefixedtext =
				( $this->m_dataitem->getInterwiki() !== '' ? $this->m_dataitem->getInterwiki() . ':' : '' ) .
				( $nstext !== '' ? "$nstext:" : '' ) . $this->getText();
		}

		return $this->m_prefixedtext;
	}

	/**
	 * @deprecated since 3.1
	 *
	 * Get interwiki prefix or empty string.
	 *
	 * @return string
	 */
	private function getInterwiki() {
		return $this->m_dataitem->getInterwiki();
	}

	/**
	 * @see SMWDataValue::getPreferredCaption
	 *
	 * @since 2.4
	 *
	 * @return string
	 */
	public function getPreferredCaption() {
		if ( ( $preferredCaption = parent::getPreferredCaption() ) !== '' && $preferredCaption !== false ) {
			return $preferredCaption;
		}

		$preferredCaption = $this->getDisplayTitle();

		if ( $preferredCaption === '' && $this->getOption( 'prefixed.preferred.caption' ) ) {
			$preferredCaption = $this->getPrefixedText();
		} elseif ( $preferredCaption === '' ) {
			$preferredCaption = $this->getText();
		}

		return $preferredCaption;
	}

	/**
	 * Get a short caption used to label this value. In particular, this
	 * omits namespace and interwiki prefixes (similar to the MediaWiki
	 * "pipe trick"). Fragments are included unless they start with an
	 * underscore (used for generated fragment names that are not helpful
	 * for users and that might change easily).
	 *
	 * @since 1.7
	 * @return string
	 */
	protected function getShortCaptionText() {
		if ( $this->m_fragment !== '' && $this->m_fragment[0] != '_' ) {
			$fragmentText = '#' . str_replace( '_', ' ', $this->m_fragment );
		} else {
			$fragmentText = '';
		}

		if ( $this->m_caption && $this->m_caption !== '' ) {
			return $this->m_caption;
		}

		$displayTitle = $this->getDisplayTitle();

		if ( $displayTitle === '' ) {
			$displayTitle = $this->getText();
		}

		// #3945 (Remove context as per pipe trick)
		if ( $this->hasFeature( SMW_DV_WPV_PIPETRICK ) ) {
			$displayTitle = Pipetrick::apply( $displayTitle );
		}

		return $displayTitle . $fragmentText;
	}

	/**
	 * Get a long caption used to label this value. In particular, this
	 * includes namespace and interwiki prefixes, while fragments are only
	 * included if they do not start with an underscore (used for generated
	 * fragment names that are not helpful for users and that might change
	 * easily).
	 *
	 * @since 1.7
	 * @return string
	 */
	protected function getLongCaptionText() {
		if ( $this->m_fragment !== '' && $this->m_fragment[0] != '_' ) {
			$fragmentText = '#' . str_replace( '_', ' ', $this->m_fragment );
		} else {
			$fragmentText = '';
		}

		if ( $this->m_caption && $this->m_caption !== '' ) {
			return $this->m_caption;
		}

		$displayTitle = $this->getDisplayTitle();

		if ( $displayTitle === '' ) {
			$displayTitle = $this->m_fixNamespace == NS_MAIN ? $this->getPrefixedText() : $this->getText();
		}

		return $displayTitle . $fragmentText;
	}

	/**
	 * Compute a text that can be used in wiki text to link to this
	 * datavalue. Processing includes some escaping and adding the
	 * fragment.
	 *
	 * @since 1.7
	 * @return string
	 */
	protected function getWikiLinkTarget() {
		return str_replace( "'", '&#x0027;', $this->getPrefixedText() ) .
			( $this->m_fragment !== '' ? "#{$this->m_fragment}" : '' );
	}

	/**
	 * Find the sortkey for this object.
	 *
	 * @deprecated Use \SMW\Store::getWikiPageSortKey(). Will vanish before SMW 1.7
	 *
	 * @return string sortkey
	 */
	private function getSortKey() {
		return ApplicationFactory::getInstance()->getStore()->getWikiPageSortKey( $this->m_dataitem );
	}

	/**
	 * @since 2.4
	 *
	 * @return string
	 */
	public function getDisplayTitle() {
		if ( $this->m_dataitem === null || !$this->hasFeature( SMW_DV_WPV_DTITLE ) ) {
			return '';
		}

		// Should come from the DataValueServiceFactory
		$displayTitleFinder = ApplicationFactory::getInstance()->singleton( 'DisplayTitleFinder' );

		return $displayTitleFinder->findDisplayTitle( $this->m_dataitem );
	}

}