/includes/ChangeTags.php

<?php
/**
 * Functions related to change tags.
 *
 * @file
 */
class ChangeTags {

	/**
	 * Creates HTML for the given tags
	 *
	 * @param $tags String: Comma-separated list of tags
	 * @param $page String: A label for the type of action which is being displayed,
	 *                     for example: 'history', 'contributions' or 'newpages'
	 *
	 * @return Array with two items: (html, classes)
	 *            - html: String: HTML for displaying the tags (empty string when param $tags is empty)
	 *            - classes: Array of strings: CSS classes used in the generated html, one class for each tag
	 *
	 */
	static function formatSummaryRow( $tags, $page ) {
		if( !$tags )
			return array( '', array() );

		$classes = array();

		$tags = explode( ',', $tags );
		$displayTags = array();
		foreach( $tags as $tag ) {
			$displayTags[] = Xml::tags(
				'span',
				array( 'class' => 'mw-tag-marker ' .
								Sanitizer::escapeClass( "mw-tag-marker-$tag" ) ),
				self::tagDescription( $tag )
			);
			$classes[] = Sanitizer::escapeClass( "mw-tag-$tag" );
		}
		$markers = '(' . implode( ', ', $displayTags ) . ')';
		$markers = Xml::tags( 'span', array( 'class' => 'mw-tag-markers' ), $markers );

		return array( $markers, $classes );
	}

	/**
	 * Get a short description for a tag
	 *
	 * @param $tag String: tag
	 *
	 * @return String: Short description of the tag from "mediawiki:tag-$tag" if this message exists,
	 *                 html-escaped version of $tag otherwise
	 */
	static function tagDescription( $tag ) {
		$msg = wfMessage( "tag-$tag" );
		return $msg->exists() ? $msg->parse() : htmlspecialchars( $tag );
	}

	/**
	 * Add tags to a change given its rc_id, rev_id and/or log_id
	 *
	 * @param $tags String|Array: Tags to add to the change
	 * @param $rc_id int: rc_id of the change to add the tags to
	 * @param $rev_id int: rev_id of the change to add the tags to
	 * @param $log_id int: log_id of the change to add the tags to
	 * @param $params String: params to put in the ct_params field of tabel 'change_tag'
	 *
	 * @return bool: false if no changes are made, otherwise true
	 *
	 * @exception MWException when $rc_id, $rev_id and $log_id are all null
	 */
	static function addTags( $tags, $rc_id = null, $rev_id = null, $log_id = null, $params = null ) {
		if ( !is_array( $tags ) ) {
			$tags = array( $tags );
		}

		$tags = array_filter( $tags ); // Make sure we're submitting all tags...

		if( !$rc_id && !$rev_id && !$log_id ) {
			throw new MWException( "At least one of: RCID, revision ID, and log ID MUST be specified when adding a tag to a change!" );
		}

		$dbr = wfGetDB( DB_SLAVE );

		// Might as well look for rcids and so on.
		if( !$rc_id ) {
			$dbr = wfGetDB( DB_MASTER ); // Info might be out of date, somewhat fractionally, on slave.
			if( $log_id ) {
				$rc_id = $dbr->selectField( 'recentchanges', 'rc_id', array( 'rc_logid' => $log_id ), __METHOD__ );
			} elseif( $rev_id ) {
				$rc_id = $dbr->selectField( 'recentchanges', 'rc_id', array( 'rc_this_oldid' => $rev_id ), __METHOD__ );
			}
		} elseif( !$log_id && !$rev_id ) {
			$dbr = wfGetDB( DB_MASTER ); // Info might be out of date, somewhat fractionally, on slave.
			$log_id = $dbr->selectField( 'recentchanges', 'rc_logid', array( 'rc_id' => $rc_id ), __METHOD__ );
			$rev_id = $dbr->selectField( 'recentchanges', 'rc_this_oldid', array( 'rc_id' => $rc_id ), __METHOD__ );
		}

		$tsConds = array_filter( array( 'ts_rc_id' => $rc_id, 'ts_rev_id' => $rev_id, 'ts_log_id' => $log_id ) );

		## Update the summary row.
		$prevTags = $dbr->selectField( 'tag_summary', 'ts_tags', $tsConds, __METHOD__ );
		$prevTags = $prevTags ? $prevTags : '';
		$prevTags = array_filter( explode( ',', $prevTags ) );
		$newTags = array_unique( array_merge( $prevTags, $tags ) );
		sort( $prevTags );
		sort( $newTags );

		if ( $prevTags == $newTags ) {
			// No change.
			return false;
		}

		$dbw = wfGetDB( DB_MASTER );
		$dbw->replace(
			'tag_summary',
			array( 'ts_rev_id', 'ts_rc_id', 'ts_log_id' ),
			array_filter( array_merge( $tsConds, array( 'ts_tags' => implode( ',', $newTags ) ) ) ),
			__METHOD__
		);

		// Insert the tags rows.
		$tagsRows = array();
		foreach( $tags as $tag ) { // Filter so we don't insert NULLs as zero accidentally.
			$tagsRows[] = array_filter(
				array(
					'ct_tag' => $tag,
					'ct_rc_id' => $rc_id,
					'ct_log_id' => $log_id,
					'ct_rev_id' => $rev_id,
					'ct_params' => $params
				)
			);
		}

		$dbw->insert( 'change_tag', $tagsRows, __METHOD__, array( 'IGNORE' ) );

		return true;
	}

	/**
	 * Applies all tags-related changes to a query.
	 * Handles selecting tags, and filtering.
	 * Needs $tables to be set up properly, so we can figure out which join conditions to use.
	 *
	 * @param $tables String|Array: Tabel names, see DatabaseBase::select
	 * @param $fields String|Array: Fields used in query, see DatabaseBase::select
	 * @param $conds String|Array: conditions used in query, see DatabaseBase::select
	 * @param $join_conds Array: join conditions, see DatabaseBase::select
	 * @param $options Array: options, see Database::select
	 * @param $filter_tag String: tag to select on
	 *
	 * @exception MWException when unable to determine appropriate JOIN condition for tagging
	 *
	 */
	static function modifyDisplayQuery( &$tables, &$fields,  &$conds,
										&$join_conds, &$options, $filter_tag = false ) {
		global $wgRequest, $wgUseTagFilter;

		if( $filter_tag === false ) {
			$filter_tag = $wgRequest->getVal( 'tagfilter' );
		}

		// Figure out which conditions can be done.
		if ( in_array( 'recentchanges', $tables ) ) {
			$join_cond = 'rc_id';
		} elseif( in_array( 'logging', $tables ) ) {
			$join_cond = 'log_id';
		} elseif ( in_array( 'revision', $tables ) ) {
			$join_cond = 'rev_id';
		} else {
			throw new MWException( 'Unable to determine appropriate JOIN condition for tagging.' );
		}

		// JOIN on tag_summary
		$tables[] = 'tag_summary';
		$join_conds['tag_summary'] = array( 'LEFT JOIN', "ts_$join_cond=$join_cond" );
		$fields[] = 'ts_tags';

		if( $wgUseTagFilter && $filter_tag ) {
			// Somebody wants to filter on a tag.
			// Add an INNER JOIN on change_tag

			// FORCE INDEX -- change_tags will almost ALWAYS be the correct query plan.
			global $wgOldChangeTagsIndex;
			$index = $wgOldChangeTagsIndex ? 'ct_tag' : 'change_tag_tag_id';
			$options['USE INDEX'] = array( 'change_tag' => $index );
			unset( $options['FORCE INDEX'] );
			$tables[] = 'change_tag';
			$join_conds['change_tag'] = array( 'INNER JOIN', "ct_$join_cond=$join_cond" );
			$conds['ct_tag'] = $filter_tag;
		}
	}

	/**
	 * Build a text box to select a change tag
	 *
	 * @param $selected String: tag to select by default
	 * @param $fullForm Boolean:
	 *        - if false, then it returns an array of (label, form).
	 *        - if true, it returns an entire form around the selector.
	 * @param $title Title object to send the form to.
	 *        Used when, and only when $fullForm is true.
	 * @return String or array:
	 *        - if $fullForm is false: Array with
	 *        - if $fullForm is true: String, html fragment
	 */
	public static function buildTagFilterSelector( $selected='', $fullForm = false, Title $title = null ) {
		global $wgUseTagFilter;

		if ( !$wgUseTagFilter || !count( self::listDefinedTags() ) )
			return $fullForm ? '' : array();

		$data = array( Html::rawElement( 'label', array( 'for' => 'tagfilter' ), wfMsgExt( 'tag-filter', 'parseinline' ) ),
			Xml::input( 'tagfilter', 20, $selected ) );

		if ( !$fullForm ) {
			return $data;
		}

		$html = implode( '&#160;', $data );
		$html .= "\n" . Xml::element( 'input', array( 'type' => 'submit', 'value' => wfMsg( 'tag-filter-submit' ) ) );
		$html .= "\n" . Html::hidden( 'title', $title->getPrefixedText() );
		$html = Xml::tags( 'form', array( 'action' => $title->getLocalURL(), 'method' => 'get' ), $html );

		return $html;
	}

	/**
	 * Basically lists defined tags which count even if they aren't applied to anything.
	 * Tags on items in table 'change_tag' which are not (or no longer) in table 'valid_tag'
	 * are not included.
	 *
	 * Tries memcached first.
	 *
	 * @return Array of strings: tags
	 */
	static function listDefinedTags() {
		// Caching...
		global $wgMemc;
		$key = wfMemcKey( 'valid-tags' );
		$tags = $wgMemc->get( $key );
		if ( $tags ) {
			return $tags;
		}

		$emptyTags = array();

		// Some DB stuff
		$dbr = wfGetDB( DB_SLAVE );
		$res = $dbr->select( 'valid_tag', 'vt_tag', array(), __METHOD__ );
		foreach ( $res as $row ) {
			$emptyTags[] = $row->vt_tag;
		}

		wfRunHooks( 'ListDefinedTags', array( &$emptyTags ) );

		$emptyTags = array_filter( array_unique( $emptyTags ) );

		// Short-term caching.
		$wgMemc->set( $key, $emptyTags, 300 );
		return $emptyTags;
	}
}