<?php
/**
 * Accessors and mutators for the site-wide statistics.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IDatabase;
use MediaWiki\MediaWikiServices;
use Wikimedia\Rdbms\LoadBalancer;

/**
 * Static accessor class for site_stats and related things
 */
class SiteStats {
	/** @var stdClass */
	private static $row;

	/**
	 * Trigger a reload next time a field is accessed
	 */
	public static function unload() {
		self::$row = null;
	}

	protected static function load() {
		if ( self::$row === null ) {
			self::$row = self::loadAndLazyInit();
		}
	}

	/**
	 * @return stdClass
	 */
	protected static function loadAndLazyInit() {
		$config = MediaWikiServices::getInstance()->getMainConfig();

		$lb = self::getLB();
		$dbr = $lb->getConnection( DB_REPLICA );
		wfDebug( __METHOD__ . ": reading site_stats from replica DB\n" );
		$row = self::doLoadFromDB( $dbr );

		if ( !self::isRowSane( $row ) && $lb->hasOrMadeRecentMasterChanges() ) {
			// Might have just been initialized during this request? Underflow?
			wfDebug( __METHOD__ . ": site_stats damaged or missing on replica DB\n" );
			$row = self::doLoadFromDB( $lb->getConnection( DB_MASTER ) );
		}

		if ( !self::isRowSane( $row ) ) {
			if ( $config->get( 'MiserMode' ) ) {
				// Start off with all zeroes, assuming that this is a new wiki or any
				// repopulations where done manually via script.
				SiteStatsInit::doPlaceholderInit();
			} else {
				// Normally the site_stats table is initialized at install time.
				// Some manual construction scenarios may leave the table empty or
				// broken, however, for instance when importing from a dump into a
				// clean schema with mwdumper.
				wfDebug( __METHOD__ . ": initializing damaged or missing site_stats\n" );
				SiteStatsInit::doAllAndCommit( $dbr );
			}

			$row = self::doLoadFromDB( $lb->getConnection( DB_MASTER ) );
		}

		if ( !self::isRowSane( $row ) ) {
			wfDebug( __METHOD__ . ": site_stats persistently nonsensical o_O\n" );
			// Always return a row-like object
			$row = self::salvageInsaneRow( $row );
		}

		return $row;
	}

	/**
	 * @return int
	 */
	public static function edits() {
		self::load();

		return (int)self::$row->ss_total_edits;
	}

	/**
	 * @return int
	 */
	public static function articles() {
		self::load();

		return (int)self::$row->ss_good_articles;
	}

	/**
	 * @return int
	 */
	public static function pages() {
		self::load();

		return (int)self::$row->ss_total_pages;
	}

	/**
	 * @return int
	 */
	public static function users() {
		self::load();

		return (int)self::$row->ss_users;
	}

	/**
	 * @return int
	 */
	public static function activeUsers() {
		self::load();

		return (int)self::$row->ss_active_users;
	}

	/**
	 * @return int
	 */
	public static function images() {
		self::load();

		return (int)self::$row->ss_images;
	}

	/**
	 * Find the number of users in a given user group.
	 * @param string $group Name of group
	 * @return int
	 */
	public static function numberingroup( $group ) {
		$cache = MediaWikiServices::getInstance()->getMainWANObjectCache();

		return $cache->getWithSetCallback(
			$cache->makeKey( 'SiteStats', 'groupcounts', $group ),
			$cache::TTL_HOUR,
			function ( $oldValue, &$ttl, array &$setOpts ) use ( $group ) {
				$dbr = self::getLB()->getConnection( DB_REPLICA );
				$setOpts += Database::getCacheSetOptions( $dbr );

				return (int)$dbr->selectField(
					'user_groups',
					'COUNT(*)',
					[
						'ug_group' => $group,
						'ug_expiry IS NULL OR ug_expiry >= ' . $dbr->addQuotes( $dbr->timestamp() )
					],
					__METHOD__
				);
			},
			[ 'pcTTL' => $cache::TTL_PROC_LONG ]
		);
	}

	/**
	 * Total number of jobs in the job queue.
	 * @return int
	 */
	public static function jobs() {
		$cache = MediaWikiServices::getInstance()->getMainWANObjectCache();

		return $cache->getWithSetCallback(
			$cache->makeKey( 'SiteStats', 'jobscount' ),
			$cache::TTL_MINUTE,
			function ( $oldValue, &$ttl, array &$setOpts ) {
				try{
					$jobs = array_sum( JobQueueGroup::singleton()->getQueueSizes() );
				} catch ( JobQueueError $e ) {
					$jobs = 0;
				}
				return $jobs;
			},
			[ 'pcTTL' => $cache::TTL_PROC_LONG ]
		);
	}

	/**
	 * @param int $ns
	 * @return int
	 */
	public static function pagesInNs( $ns ) {
		$cache = MediaWikiServices::getInstance()->getMainWANObjectCache();

		return $cache->getWithSetCallback(
			$cache->makeKey( 'SiteStats', 'page-in-namespace', $ns ),
			$cache::TTL_HOUR,
			function ( $oldValue, &$ttl, array &$setOpts ) use ( $ns ) {
				$dbr = self::getLB()->getConnection( DB_REPLICA );
				$setOpts += Database::getCacheSetOptions( $dbr );

				return (int)$dbr->selectField(
					'page',
					'COUNT(*)',
					[ 'page_namespace' => $ns ],
					__METHOD__
				);
			},
			[ 'pcTTL' => $cache::TTL_PROC_LONG ]
		);
	}

	/**
	 * @return array
	 */
	public static function selectFields() {
		return [
			'ss_total_edits',
			'ss_good_articles',
			'ss_total_pages',
			'ss_users',
			'ss_active_users',
			'ss_images',
		];
	}

	/**
	 * @param IDatabase $db
	 * @return stdClass|bool
	 */
	private static function doLoadFromDB( IDatabase $db ) {
		return $db->selectRow(
			'site_stats',
			self::selectFields(),
			[ 'ss_row_id' => 1 ],
			__METHOD__
		);
	}

	/**
	 * Is the provided row of site stats sane, or should it be regenerated?
	 *
	 * Checks only fields which are filled by SiteStatsInit::refresh.
	 *
	 * @param bool|object $row
	 * @return bool
	 */
	private static function isRowSane( $row ) {
		if ( $row === false
			|| $row->ss_total_pages < $row->ss_good_articles
			|| $row->ss_total_edits < $row->ss_total_pages
		) {
			return false;
		}
		// Now check for underflow/overflow
		foreach ( [
			'ss_total_edits',
			'ss_good_articles',
			'ss_total_pages',
			'ss_users',
			'ss_images',
		] as $member ) {
			if ( $row->$member < 0 ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * @param stdClass|bool $row
	 * @return stdClass
	 */
	private static function salvageInsaneRow( $row ) {
		$map = $row ? (array)$row : [];
		// Fill in any missing values with zero
		$map += array_fill_keys( self::selectFields(), 0 );
		// Convert negative values to zero
		foreach ( $map as $field => $value ) {
			$map[$field] = max( 0, $value );
		}

		return (object)$row;
	}

	/**
	 * @return LoadBalancer
	 */
	private static function getLB() {
		return MediaWikiServices::getInstance()->getDBLoadBalancer();
	}
}
