<?php
/**
 * 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 MediaWiki\Logger\Spi as LoggerSpi;
use MediaWiki\Revision\RevisionRecord;
use MediaWiki\Revision\RevisionRenderer;
use Wikimedia\Rdbms\ILBFactory;

/**
 * PoolWorkArticleView for the current revision of a page, using ParserCache.
 *
 * @internal
 */
class PoolWorkArticleViewCurrent extends PoolWorkArticleView {

	/** @var string */
	private $workKey;

	/** @var WikiPage */
	private $page;

	/** @var ParserCache */
	private $parserCache;

	/** @var ILBFactory */
	private $lbFactory;

	/**
	 * @param string $workKey
	 * @param WikiPage $page
	 * @param RevisionRecord $revision Revision to render
	 * @param ParserOptions $parserOptions ParserOptions to use for the parse
	 * @param RevisionRenderer $revisionRenderer
	 * @param ParserCache $parserCache
	 * @param ILBFactory $lbFactory
	 * @param LoggerSpi $loggerSpi
	 */
	public function __construct(
		string $workKey,
		WikiPage $page,
		RevisionRecord $revision,
		ParserOptions $parserOptions,
		RevisionRenderer $revisionRenderer,
		ParserCache $parserCache,
		ILBFactory $lbFactory,
		LoggerSpi $loggerSpi
	) {
		// TODO: Remove support for partially initialized RevisionRecord instances once
		//       Article no longer uses fake revisions.
		if ( $revision->getPageId() && $revision->getPageId() !== $page->getTitle()->getArticleID() ) {
			throw new InvalidArgumentException( '$page parameter mismatches $revision parameter' );
		}

		parent::__construct( $workKey, $revision, $parserOptions, $revisionRenderer, $loggerSpi );

		$this->workKey = $workKey;
		$this->page = $page;
		$this->parserCache = $parserCache;
		$this->lbFactory = $lbFactory;
		$this->cacheable = true;
	}

	/**
	 * @param ParserOutput $output
	 * @param string $cacheTime
	 */
	protected function saveInCache( ParserOutput $output, string $cacheTime ) {
		$this->parserCache->save(
			$output,
			$this->page,
			$this->parserOptions,
			$cacheTime,
			$this->revision->getId()
		);
	}

	/**
	 * @param ParserOutput $output
	 */
	protected function afterWork( ParserOutput $output ) {
		$this->page->triggerOpportunisticLinksUpdate( $this->parserOutput );
	}

	/**
	 * @return bool
	 */
	public function getCachedWork() {
		$this->parserOutput = $this->parserCache->get( $this->page, $this->parserOptions );

		$logger = $this->getLogger();
		if ( $this->parserOutput === false ) {
			$logger->debug( 'parser cache miss' );
			return false;
		} else {
			$logger->debug( 'parser cache hit' );
			return true;
		}
	}

	/**
	 * @param bool $fast Fast stale request
	 * @return bool
	 */
	public function fallback( $fast ) {
		$this->parserOutput = $this->parserCache->getDirty( $this->page, $this->parserOptions );

		$logger = $this->getLogger( 'dirty' );

		$fastMsg = '';
		if ( $this->parserOutput && $fast ) {
			/* Check if the stale response is from before the last write to the
			 * DB by this user. Declining to return a stale response in this
			 * case ensures that the user will see their own edit after page
			 * save.
			 *
			 * Note that the CP touch time is the timestamp of the shutdown of
			 * the save request, so there is a bias towards avoiding fast stale
			 * responses of potentially several seconds.
			 */
			$lastWriteTime = $this->lbFactory->getChronologyProtectorTouched();
			$cacheTime = MWTimestamp::convert( TS_UNIX, $this->parserOutput->getCacheTime() );
			if ( $lastWriteTime && $cacheTime <= $lastWriteTime ) {
				$logger->info(
					'declining to send dirty output since cache time ' .
						'{cacheTime} is before last write time {lastWriteTime}',
					[
						'workKey' => $this->workKey,
						'cacheTime' => $cacheTime,
						'lastWriteTime' => $lastWriteTime,
					]
				);
				// Forget this ParserOutput -- we will request it again if
				// necessary in slow mode. There might be a newer entry
				// available by that time.
				$this->parserOutput = false;
				return false;
			}
			$this->isFast = true;
			$fastMsg = 'fast ';
		}

		if ( $this->parserOutput === false ) {
			$logger->info( 'dirty missing' );
			return false;
		} else {
			$logger->info( "{$fastMsg}dirty output", [ 'workKey' => $this->workKey ] );
			$this->isDirty = true;
			return true;
		}
	}
}