<?php


/**
 * A query module to list all wiki links on a given set of pages.
 *
 * @ingroup API
 */
class ApiQueryLinks extends ApiQueryGeneratorBase {

	const LINKS = 'links';
	const TEMPLATES = 'templates';

	private $table, $prefix, $description, $helpUrl;

	public function __construct( $query, $moduleName ) {
		switch ( $moduleName ) {
			case self::LINKS:
				$this->table = 'pagelinks';
				$this->prefix = 'pl';
				$this->description = 'link';
				$this->titlesParam = 'titles';
				$this->titlesParamDescription = 'Only list links to these titles. Useful for checking whether a certain page links to a certain title.';
				$this->helpUrl = 'https://www.mediawiki.org/wiki/API:Properties#links_.2F_pl';
				break;
			case self::TEMPLATES:
				$this->table = 'templatelinks';
				$this->prefix = 'tl';
				$this->description = 'template';
				$this->titlesParam = 'templates';
				$this->titlesParamDescription = 'Only list these templates. Useful for checking whether a certain page uses a certain template.';
				$this->helpUrl = 'https://www.mediawiki.org/wiki/API:Properties#templates_.2F_tl';
				break;
			default:
				ApiBase::dieDebug( __METHOD__, 'Unknown module name' );
		}

		parent::__construct( $query, $moduleName, $this->prefix );
	}

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

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

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

	/**
	 * @param $resultPageSet ApiPageSet
	 * @return
	 */
	private function run( $resultPageSet = null ) {
		if ( $this->getPageSet()->getGoodTitleCount() == 0 ) {
			return; // nothing to do
		}

		$params = $this->extractRequestParams();

		$this->addFields( array(
			'pl_from' => $this->prefix . '_from',
			'pl_namespace' => $this->prefix . '_namespace',
			'pl_title' => $this->prefix . '_title'
		) );

		$this->addTables( $this->table );
		$this->addWhereFld( $this->prefix . '_from', array_keys( $this->getPageSet()->getGoodTitles() ) );
		$this->addWhereFld( $this->prefix . '_namespace', $params['namespace'] );

		if ( !is_null( $params[$this->titlesParam] ) ) {
			$lb = new LinkBatch;
			foreach ( $params[$this->titlesParam] as $t ) {
				$title = Title::newFromText( $t );
				if ( !$title ) {
					$this->setWarning( "\"$t\" is not a valid title" );
				} else {
					$lb->addObj( $title );
				}
			}
			$cond = $lb->constructSet( $this->prefix, $this->getDB() );
			if ( $cond ) {
				$this->addWhere( $cond );
			}
		}

		if ( !is_null( $params['continue'] ) ) {
			$cont = explode( '|', $params['continue'] );
			$this->dieContinueUsageIf( count( $cont ) != 3 );
			$op = $params['dir'] == 'descending' ? '<' : '>';
			$plfrom = intval( $cont[0] );
			$plns = intval( $cont[1] );
			$pltitle = $this->getDB()->addQuotes( $cont[2] );
			$this->addWhere(
				"{$this->prefix}_from $op $plfrom OR " .
				"({$this->prefix}_from = $plfrom AND " .
				"({$this->prefix}_namespace $op $plns OR " .
				"({$this->prefix}_namespace = $plns AND " .
				"{$this->prefix}_title $op= $pltitle)))"
			);
		}

		$sort = ( $params['dir'] == 'descending' ? ' DESC' : '' );
		// Here's some MySQL craziness going on: if you use WHERE foo='bar'
		// and later ORDER BY foo MySQL doesn't notice the ORDER BY is pointless
		// but instead goes and filesorts, because the index for foo was used
		// already. To work around this, we drop constant fields in the WHERE
		// clause from the ORDER BY clause
		$order = array();
		if ( count( $this->getPageSet()->getGoodTitles() ) != 1 ) {
			$order[] = $this->prefix . '_from' . $sort;
		}
		if ( count( $params['namespace'] ) != 1 ) {
			$order[] = $this->prefix . '_namespace' . $sort;
		}

		$order[] = $this->prefix . '_title' . $sort;
		$this->addOption( 'ORDER BY', $order );
		$this->addOption( 'USE INDEX', $this->prefix . '_from' );
		$this->addOption( 'LIMIT', $params['limit'] + 1 );

		$res = $this->select( __METHOD__ );

		if ( is_null( $resultPageSet ) ) {
			$count = 0;
			foreach ( $res as $row ) {
				if ( ++$count > $params['limit'] ) {
					// We've reached the one extra which shows that
					// there are additional pages to be had. Stop here...
					$this->setContinueEnumParameter( 'continue',
						"{$row->pl_from}|{$row->pl_namespace}|{$row->pl_title}" );
					break;
				}
				$vals = array();
				ApiQueryBase::addTitleInfo( $vals, Title::makeTitle( $row->pl_namespace, $row->pl_title ) );
				$fit = $this->addPageSubItem( $row->pl_from, $vals );
				if ( !$fit ) {
					$this->setContinueEnumParameter( 'continue',
						"{$row->pl_from}|{$row->pl_namespace}|{$row->pl_title}" );
					break;
				}
			}
		} else {
			$titles = array();
			$count = 0;
			foreach ( $res as $row ) {
				if ( ++$count > $params['limit'] ) {
					// We've reached the one extra which shows that
					// there are additional pages to be had. Stop here...
					$this->setContinueEnumParameter( 'continue',
						"{$row->pl_from}|{$row->pl_namespace}|{$row->pl_title}" );
					break;
				}
				$titles[] = Title::makeTitle( $row->pl_namespace, $row->pl_title );
			}
			$resultPageSet->populateFromTitles( $titles );
		}
	}

	public function getAllowedParams() {
		return array(
			'namespace' => array(
				ApiBase::PARAM_TYPE => 'namespace',
				ApiBase::PARAM_ISMULTI => true
			),
			'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
			),
			'continue' => null,
			$this->titlesParam => array(
				ApiBase::PARAM_ISMULTI => true,
			),
			'dir' => array(
				ApiBase::PARAM_DFLT => 'ascending',
				ApiBase::PARAM_TYPE => array(
					'ascending',
					'descending'
				)
			),
		);
	}

	public function getParamDescription() {
		$desc = $this->description;
		return array(
			'namespace' => "Show {$desc}s in this namespace(s) only",
			'limit' => "How many {$desc}s to return",
			'continue' => 'When more results are available, use this to continue',
			$this->titlesParam => $this->titlesParamDescription,
			'dir' => 'The direction in which to list',
		);
	}

	public function getResultProperties() {
		return array(
			'' => array(
				'ns' => 'namespace',
				'title' => 'string'
			)
		);
	}

	public function getDescription() {
		return "Returns all {$this->description}s from the given page(s)";
	}

	public function getExamples() {
		$desc = $this->description;
		$name = $this->getModuleName();
		return array(
			"api.php?action=query&prop={$name}&titles=Main%20Page" => "Get {$desc}s from the [[Main Page]]",
			"api.php?action=query&generator={$name}&titles=Main%20Page&prop=info" => "Get information about the {$desc} pages in the [[Main Page]]",
			"api.php?action=query&prop={$name}&titles=Main%20Page&{$this->prefix}namespace=2|10" => "Get {$desc}s from the Main Page in the User and Template namespaces",
		);
	}

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