ApiQueryBacklinks.php

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<?php
class ApiQueryBacklinks extends ApiQueryGeneratorBase {

    private $rootTitle;

    private $params, $contID, $redirID, $redirect;
    private $bl_ns, $bl_from, $bl_table, $bl_code, $bl_title, $bl_fields, $hasNS;

    private $pageMap = array();
    private $resultArr;

    private $redirTitles = array();
    private $continueStr = null;

    // output element name, database column field prefix, database table
    private $backlinksSettings = array(
        'backlinks' => array(
            'code' => 'bl',
            'prefix' => 'pl',
            'linktbl' => 'pagelinks',
            'helpurl' => 'https://www.mediawiki.org/wiki/API:Backlinks',
        ),
        'embeddedin' => array(
            'code' => 'ei',
            'prefix' => 'tl',
            'linktbl' => 'templatelinks',
            'helpurl' => 'https://www.mediawiki.org/wiki/API:Embeddedin',
        ),
        'imageusage' => array(
            'code' => 'iu',
            'prefix' => 'il',
            'linktbl' => 'imagelinks',
            'helpurl' => 'https://www.mediawiki.org/wiki/API:Imageusage',
        )
    );

    public function __construct( ApiQuery $query, $moduleName ) {
        $settings = $this->backlinksSettings[$moduleName];
        $prefix = $settings['prefix'];
        $code = $settings['code'];
        $this->resultArr = array();

        parent::__construct( $query, $moduleName, $code );
        $this->bl_ns = $prefix . '_namespace';
        $this->bl_from = $prefix . '_from';
        $this->bl_table = $settings['linktbl'];
        $this->bl_code = $code;
        $this->helpUrl = $settings['helpurl'];

        $this->hasNS = $moduleName !== 'imageusage';
        if ( $this->hasNS ) {
            $this->bl_title = $prefix . '_title';
            $this->bl_fields = array(
                $this->bl_ns,
                $this->bl_title
            );
        } else {
            $this->bl_title = $prefix . '_to';
            $this->bl_fields = array(
                $this->bl_title
            );
        }
    }

    public function execute() {
        $this->run();
    }

    public function getCacheMode( $params ) {
        return 'public';
    }

    public function executeGenerator( $resultPageSet ) {
        $this->run( $resultPageSet );
    }

    private function prepareFirstQuery( $resultPageSet = null ) {
        /* SELECT page_id, page_title, page_namespace, page_is_redirect
         * FROM pagelinks, page WHERE pl_from=page_id
         * AND pl_title='Foo' AND pl_namespace=0
         * LIMIT 11 ORDER BY pl_from
         */
        $this->addTables( array( $this->bl_table, 'page' ) );
        $this->addWhere( "{$this->bl_from}=page_id" );
        if ( is_null( $resultPageSet ) ) {
            $this->addFields( array( 'page_id', 'page_title', 'page_namespace' ) );
        } else {
            $this->addFields( $resultPageSet->getPageTableFields() );
        }

        $this->addFields( 'page_is_redirect' );
        $this->addWhereFld( $this->bl_title, $this->rootTitle->getDBkey() );

        if ( $this->hasNS ) {
            $this->addWhereFld( $this->bl_ns, $this->rootTitle->getNamespace() );
        }
        $this->addWhereFld( 'page_namespace', $this->params['namespace'] );

        if ( !is_null( $this->contID ) ) {
            $op = $this->params['dir'] == 'descending' ? '<' : '>';
            $this->addWhere( "{$this->bl_from}$op={$this->contID}" );
        }

        if ( $this->params['filterredir'] == 'redirects' ) {
            $this->addWhereFld( 'page_is_redirect', 1 );
        } elseif ( $this->params['filterredir'] == 'nonredirects' && !$this->redirect ) {
            // bug 22245 - Check for !redirect, as filtering nonredirects, when
            // getting what links to them is contradictory
            $this->addWhereFld( 'page_is_redirect', 0 );
        }

        $this->addOption( 'LIMIT', $this->params['limit'] + 1 );
        $sort = ( $this->params['dir'] == 'descending' ? ' DESC' : '' );
        $this->addOption( 'ORDER BY', $this->bl_from . $sort );
        $this->addOption( 'STRAIGHT_JOIN' );
    }

    private function prepareSecondQuery( $resultPageSet = null ) {
        /* SELECT page_id, page_title, page_namespace, page_is_redirect, pl_title, pl_namespace
           FROM pagelinks, page WHERE pl_from=page_id
           AND (pl_title='Foo' AND pl_namespace=0) OR (pl_title='Bar' AND pl_namespace=1)
           ORDER BY pl_namespace, pl_title, pl_from LIMIT 11
         */
        $db = $this->getDB();
        $this->addTables( array( 'page', $this->bl_table ) );
        $this->addWhere( "{$this->bl_from}=page_id" );

        if ( is_null( $resultPageSet ) ) {
            $this->addFields( array( 'page_id', 'page_title', 'page_namespace', 'page_is_redirect' ) );
        } else {
            $this->addFields( $resultPageSet->getPageTableFields() );
        }

        $this->addFields( $this->bl_title );
        if ( $this->hasNS ) {
            $this->addFields( $this->bl_ns );
        }

        // We can't use LinkBatch here because $this->hasNS may be false
        $titleWhere = array();
        $allRedirNs = array();
        $allRedirDBkey = array();
        foreach ( $this->redirTitles as $t ) {
            $redirNs = $t->getNamespace();
            $redirDBkey = $t->getDBkey();
            $titleWhere[] = "{$this->bl_title} = " . $db->addQuotes( $redirDBkey ) .
                ( $this->hasNS ? " AND {$this->bl_ns} = {$redirNs}" : '' );
            $allRedirNs[] = $redirNs;
            $allRedirDBkey[] = $redirDBkey;
        }
        $this->addWhere( $db->makeList( $titleWhere, LIST_OR ) );
        $this->addWhereFld( 'page_namespace', $this->params['namespace'] );

        if ( !is_null( $this->redirID ) ) {
            $op = $this->params['dir'] == 'descending' ? '<' : '>';
            $first = $this->redirTitles[0];
            $title = $db->addQuotes( $first->getDBkey() );
            $ns = $first->getNamespace();
            $from = $this->redirID;
            if ( $this->hasNS ) {
                $this->addWhere( "{$this->bl_ns} $op $ns OR " .
                    "({$this->bl_ns} = $ns AND " .
                    "({$this->bl_title} $op $title OR " .
                    "({$this->bl_title} = $title AND " .
                    "{$this->bl_from} $op= $from)))" );
            } else {
                $this->addWhere( "{$this->bl_title} $op $title OR " .
                    "({$this->bl_title} = $title AND " .
                    "{$this->bl_from} $op= $from)" );
            }
        }
        if ( $this->params['filterredir'] == 'redirects' ) {
            $this->addWhereFld( 'page_is_redirect', 1 );
        } elseif ( $this->params['filterredir'] == 'nonredirects' ) {
            $this->addWhereFld( 'page_is_redirect', 0 );
        }

        $this->addOption( 'LIMIT', $this->params['limit'] + 1 );
        $orderBy = array();
        $sort = ( $this->params['dir'] == 'descending' ? ' DESC' : '' );
        // Don't order by namespace/title if it's constant in the WHERE clause
        if ( $this->hasNS && count( array_unique( $allRedirNs ) ) != 1 ) {
            $orderBy[] = $this->bl_ns . $sort;
        }
        if ( count( array_unique( $allRedirDBkey ) ) != 1 ) {
            $orderBy[] = $this->bl_title . $sort;
        }
        $orderBy[] = $this->bl_from . $sort;
        $this->addOption( 'ORDER BY', $orderBy );
        $this->addOption( 'USE INDEX', array( 'page' => 'PRIMARY' ) );
    }

    private function run( $resultPageSet = null ) {
        $this->params = $this->extractRequestParams( false );
        $this->redirect = isset( $this->params['redirect'] ) && $this->params['redirect'];
        $userMax = ( $this->redirect ? ApiBase::LIMIT_BIG1 / 2 : ApiBase::LIMIT_BIG1 );
        $botMax = ( $this->redirect ? ApiBase::LIMIT_BIG2 / 2 : ApiBase::LIMIT_BIG2 );

        $result = $this->getResult();

        if ( $this->params['limit'] == 'max' ) {
            $this->params['limit'] = $this->getMain()->canApiHighLimits() ? $botMax : $userMax;
            $result->setParsedLimit( $this->getModuleName(), $this->params['limit'] );
        } else {
            $this->params['limit'] = intval( $this->params['limit'] );
            $this->validateLimit( 'limit', $this->params['limit'], 1, $userMax, $botMax );
        }

        $this->processContinue();
        $this->prepareFirstQuery( $resultPageSet );

        $res = $this->select( __METHOD__ . '::firstQuery' );

        $count = 0;

        foreach ( $res as $row ) {
            if ( ++$count > $this->params['limit'] ) {
                // We've reached the one extra which shows that there are
                // additional pages to be had. Stop here...
                // Continue string preserved in case the redirect query doesn't pass the limit
                $this->continueStr = $this->getContinueStr( $row->page_id );
                break;
            }

            if ( is_null( $resultPageSet ) ) {
                $this->extractRowInfo( $row );
            } else {
                $this->pageMap[$row->page_namespace][$row->page_title] = $row->page_id;
                if ( $row->page_is_redirect ) {
                    $this->redirTitles[] = Title::makeTitle( $row->page_namespace, $row->page_title );
                }

                $resultPageSet->processDbRow( $row );
            }
        }

        if ( $this->redirect && count( $this->redirTitles ) ) {
            $this->resetQueryParams();
            $this->prepareSecondQuery( $resultPageSet );
            $res = $this->select( __METHOD__ . '::secondQuery' );
            $count = 0;
            foreach ( $res as $row ) {
                if ( ++$count > $this->params['limit'] ) {
                    // We've reached the one extra which shows that there are
                    // additional pages to be had. Stop here...
                    // We need to keep the parent page of this redir in
                    if ( $this->hasNS ) {
                        $parentID = $this->pageMap[$row->{$this->bl_ns}][$row->{$this->bl_title}];
                    } else {
                        $parentID = $this->pageMap[NS_FILE][$row->{$this->bl_title}];
                    }
                    $this->continueStr = $this->getContinueRedirStr( $parentID, $row->page_id );
                    break;
                }

                if ( is_null( $resultPageSet ) ) {
                    $this->extractRedirRowInfo( $row );
                } else {
                    $resultPageSet->processDbRow( $row );
                }
            }
        }
        if ( is_null( $resultPageSet ) ) {
            // Try to add the result data in one go and pray that it fits
            $fit = $result->addValue( 'query', $this->getModuleName(), array_values( $this->resultArr ) );
            if ( !$fit ) {
                // It didn't fit. Add elements one by one until the
                // result is full.
                foreach ( $this->resultArr as $pageID => $arr ) {
                    // Add the basic entry without redirlinks first
                    $fit = $result->addValue(
                        array( 'query', $this->getModuleName() ),
                        null, array_diff_key( $arr, array( 'redirlinks' => '' ) ) );
                    if ( !$fit ) {
                        $this->continueStr = $this->getContinueStr( $pageID );
                        break;
                    }

                    $hasRedirs = false;
                    $redirLinks = isset( $arr['redirlinks'] ) ? $arr['redirlinks'] : array();
                    foreach ( (array)$redirLinks as $key => $redir ) {
                        $fit = $result->addValue(
                            array( 'query', $this->getModuleName(), $pageID, 'redirlinks' ),
                            $key, $redir );
                        if ( !$fit ) {
                            $this->continueStr = $this->getContinueRedirStr( $pageID, $redir['pageid'] );
                            break;
                        }
                        $hasRedirs = true;
                    }
                    if ( $hasRedirs ) {
                        $result->setIndexedTagName_internal(
                            array( 'query', $this->getModuleName(), $pageID, 'redirlinks' ),
                            $this->bl_code );
                    }
                    if ( !$fit ) {
                        break;
                    }
                }
            }

            $result->setIndexedTagName_internal(
                array( 'query', $this->getModuleName() ),
                $this->bl_code
            );
        }
        if ( !is_null( $this->continueStr ) ) {
            $this->setContinueEnumParameter( 'continue', $this->continueStr );
        }
    }

    private function extractRowInfo( $row ) {
        $this->pageMap[$row->page_namespace][$row->page_title] = $row->page_id;
        $t = Title::makeTitle( $row->page_namespace, $row->page_title );
        $a = array( 'pageid' => intval( $row->page_id ) );
        ApiQueryBase::addTitleInfo( $a, $t );
        if ( $row->page_is_redirect ) {
            $a['redirect'] = '';
            $this->redirTitles[] = $t;
        }
        // Put all the results in an array first
        $this->resultArr[$a['pageid']] = $a;
    }

    private function extractRedirRowInfo( $row ) {
        $a['pageid'] = intval( $row->page_id );
        ApiQueryBase::addTitleInfo( $a, Title::makeTitle( $row->page_namespace, $row->page_title ) );
        if ( $row->page_is_redirect ) {
            $a['redirect'] = '';
        }
        $ns = $this->hasNS ? $row->{$this->bl_ns} : NS_FILE;
        $parentID = $this->pageMap[$ns][$row->{$this->bl_title}];
        // Put all the results in an array first
        $this->resultArr[$parentID]['redirlinks'][] = $a;
        $this->getResult()->setIndexedTagName(
            $this->resultArr[$parentID]['redirlinks'],
            $this->bl_code
        );
    }

    protected function processContinue() {
        if ( !is_null( $this->params['continue'] ) ) {
            $this->parseContinueParam();
        } else {
            $this->rootTitle = $this->getTitleOrPageId( $this->params )->getTitle();
        }

        // only image titles are allowed for the root in imageinfo mode
        if ( !$this->hasNS && $this->rootTitle->getNamespace() !== NS_FILE ) {
            $this->dieUsage(
                "The title for {$this->getModuleName()} query must be an image",
                'bad_image_title'
            );
        }
    }

    protected function parseContinueParam() {
        $continueList = explode( '|', $this->params['continue'] );
        // expected format:
        // ns | key | id1 [| id2]
        // ns+key: root title
        // id1: first-level page ID to continue from
        // id2: second-level page ID to continue from

        // null stuff out now so we know what's set and what isn't
        $this->rootTitle = $this->contID = $this->redirID = null;
        $rootNs = intval( $continueList[0] );
        $this->dieContinueUsageIf( $rootNs === 0 && $continueList[0] !== '0' );

        $this->rootTitle = Title::makeTitleSafe( $rootNs, $continueList[1] );
        $this->dieContinueUsageIf( !$this->rootTitle );

        $contID = intval( $continueList[2] );
        $this->dieContinueUsageIf( $contID === 0 && $continueList[2] !== '0' );

        $this->contID = $contID;
        $id2 = isset( $continueList[3] ) ? $continueList[3] : null;
        $redirID = intval( $id2 );

        if ( $redirID === 0 && $id2 !== '0' ) {
            // This one isn't required
            return;
        }
        $this->redirID = $redirID;
    }

    protected function getContinueStr( $lastPageID ) {
        return $this->rootTitle->getNamespace() .
        '|' . $this->rootTitle->getDBkey() .
        '|' . $lastPageID;
    }

    protected function getContinueRedirStr( $lastPageID, $lastRedirID ) {
        return $this->getContinueStr( $lastPageID ) . '|' . $lastRedirID;
    }

    public function getAllowedParams() {
        $retval = array(
            'title' => array(
                ApiBase::PARAM_TYPE => 'string',
            ),
            'pageid' => array(
                ApiBase::PARAM_TYPE => 'integer',
            ),
            'continue' => null,
            'namespace' => array(
                ApiBase::PARAM_ISMULTI => true,
                ApiBase::PARAM_TYPE => 'namespace'
            ),
            'dir' => array(
                ApiBase::PARAM_DFLT => 'ascending',
                ApiBase::PARAM_TYPE => array(
                    'ascending',
                    'descending'
                )
            ),
            'filterredir' => array(
                ApiBase::PARAM_DFLT => 'all',
                ApiBase::PARAM_TYPE => array(
                    'all',
                    'redirects',
                    'nonredirects'
                )
            ),
            'limit' => array(
                ApiBase::PARAM_DFLT => 10,
                ApiBase::PARAM_TYPE => 'limit',
                ApiBase::PARAM_MIN => 1,
                ApiBase::PARAM_MAX => ApiBase::LIMIT_BIG1,
                ApiBase::PARAM_MAX2 => ApiBase::LIMIT_BIG2
            )
        );
        if ( $this->getModuleName() == 'embeddedin' ) {
            return $retval;
        }
        $retval['redirect'] = false;

        return $retval;
    }

    public function getParamDescription() {
        $retval = array(
            'title' => "Title to search. Cannot be used together with {$this->bl_code}pageid",
            'pageid' => "Pageid to search. Cannot be used together with {$this->bl_code}title",
            'continue' => 'When more results are available, use this to continue',
            'namespace' => 'The namespace to enumerate',
            'dir' => 'The direction in which to list',
        );
        if ( $this->getModuleName() != 'embeddedin' ) {
            return array_merge( $retval, array(
                'redirect' => 'If linking page is a redirect, find all pages ' .
                    'that link to that redirect as well. Maximum limit is halved.',
                'filterredir' => 'How to filter for redirects. If set to ' .
                    "nonredirects when {$this->bl_code}redirect is enabled, " .
                    'this is only applied to the second level',
                'limit' => 'How many total pages to return. If ' .
                    "{$this->bl_code}redirect is enabled, limit applies to each " .
                    'level separately (which means you may get up to 2 * limit results).'
            ) );
        }

        return array_merge( $retval, array(
            'filterredir' => 'How to filter for redirects',
            'limit' => 'How many total pages to return'
        ) );
    }

    public function getDescription() {
        switch ( $this->getModuleName() ) {
            case 'backlinks':
                return 'Find all pages that link to the given page.';
            case 'embeddedin':
                return 'Find all pages that embed (transclude) the given title.';
            case 'imageusage':
                return 'Find all pages that use the given image title.';
            default:
                ApiBase::dieDebug( __METHOD__, 'Unknown module name.' );
        }
    }

    public function getExamples() {
        static $examples = array(
            'backlinks' => array(
                'api.php?action=query&list=backlinks&bltitle=Main%20Page',
                'api.php?action=query&generator=backlinks&gbltitle=Main%20Page&prop=info'
            ),
            'embeddedin' => array(
                'api.php?action=query&list=embeddedin&eititle=Template:Stub',
                'api.php?action=query&generator=embeddedin&geititle=Template:Stub&prop=info'
            ),
            'imageusage' => array(
                'api.php?action=query&list=imageusage&iutitle=File:Albert%20Einstein%20Head.jpg',
                'api.php?action=query&generator=imageusage&giutitle=File:Albert%20Einstein%20Head.jpg&prop=info'
            )
        );

        return $examples[$this->getModuleName()];
    }

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