<?php
/**
 * Parser cache specific expiry check.
 *
 * 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
 * @ingroup Parser
 */

use MediaWiki\Json\JsonUnserializable;
use MediaWiki\Json\JsonUnserializableTrait;
use MediaWiki\Json\JsonUnserializer;
use MediaWiki\Parser\ParserCacheMetadata;
use Wikimedia\Reflection\GhostFieldAccessTrait;

/**
 * Parser cache specific expiry check.
 *
 * @ingroup Parser
 */
class CacheTime implements ParserCacheMetadata, JsonUnserializable {
	use GhostFieldAccessTrait;
	use JsonUnserializableTrait;

	/**
	 * @var true[] ParserOptions which have been taken into account
	 * to produce output, option names stored in array keys.
	 */
	protected $mParseUsedOptions = [];

	/**
	 * @var string|int TS_MW timestamp when this object was generated, or -1 for not cacheable. Used
	 * in ParserCache.
	 */
	public $mCacheTime = '';

	/**
	 * @var int|null Seconds after which the object should expire, use 0 for not cacheable. Used in
	 * ParserCache.
	 */
	public $mCacheExpiry = null;

	/**
	 * @var int|null Revision ID that was parsed
	 */
	public $mCacheRevisionId = null;

	/**
	 * @return string|int TS_MW timestamp
	 */
	public function getCacheTime() {
		// NOTE: keep support for undocumented used of -1 to mean "not cacheable".
		if ( $this->mCacheTime === '' ) {
			$this->mCacheTime = MWTimestamp::now();
		}
		return $this->mCacheTime;
	}

	/**
	 * setCacheTime() sets the timestamp expressing when the page has been rendered.
	 * This does not control expiry, see updateCacheExpiry() for that!
	 * @param string $t TS_MW timestamp
	 * @return string
	 */
	public function setCacheTime( $t ) {
		// NOTE: keep support for undocumented used of -1 to mean "not cacheable".
		if ( is_string( $t ) && $t !== '-1' ) {
			$t = MWTimestamp::convert( TS_MW, $t );
		}

		if ( $t === -1 || $t === '-1' ) {
			wfDeprecatedMsg( __METHOD__ . ' called with -1 as an argument', '1.36' );
		}

		return wfSetVar( $this->mCacheTime, $t );
	}

	/**
	 * @since 1.23
	 * @return int|null Revision id, if any was set
	 */
	public function getCacheRevisionId(): ?int {
		return $this->mCacheRevisionId;
	}

	/**
	 * @since 1.23
	 * @param int|null $id Revision ID
	 */
	public function setCacheRevisionId( $id ) {
		$this->mCacheRevisionId = $id;
	}

	/**
	 * Sets the number of seconds after which this object should expire.
	 *
	 * This value is used with the ParserCache.
	 * If called with a value greater than the value provided at any previous call,
	 * the new call has no effect. The value returned by getCacheExpiry is smaller
	 * or equal to the smallest number that was provided as an argument to
	 * updateCacheExpiry().
	 *
	 * Avoid using 0 if at all possible. Consider JavaScript for highly dynamic content.
	 *
	 * NOTE: Beware that reducing the TTL for reasons that do not relate to "dynamic content",
	 * may have the side-effect of incurring more RefreshLinksJob executions.
	 * See also WikiPage::triggerOpportunisticLinksUpdate.
	 *
	 * @param int $seconds
	 */
	public function updateCacheExpiry( $seconds ) {
		$seconds = (int)$seconds;

		if ( $this->mCacheExpiry === null || $this->mCacheExpiry > $seconds ) {
			$this->mCacheExpiry = $seconds;
		}
	}

	/**
	 * Returns the number of seconds after which this object should expire.
	 * This method is used by ParserCache to determine how long the ParserOutput can be cached.
	 * The timestamp of expiry can be calculated by adding getCacheExpiry() to getCacheTime().
	 * The value returned by getCacheExpiry is smaller or equal to the smallest number
	 * that was provided to a call of updateCacheExpiry(), and smaller or equal to the
	 * value of $wgParserCacheExpireTime.
	 * @return int
	 */
	public function getCacheExpiry(): int {
		global $wgParserCacheExpireTime;

		// NOTE: keep support for undocumented used of -1 to mean "not cacheable".
		if ( $this->mCacheTime !== '' && $this->mCacheTime < 0 ) {
			return 0;
		}

		$expire = $this->mCacheExpiry;

		if ( $expire === null ) {
			$expire = $wgParserCacheExpireTime;
		} else {
			$expire = min( $expire, $wgParserCacheExpireTime );
		}

		if ( $expire <= 0 ) {
			return 0; // not cacheable
		} else {
			return $expire;
		}
	}

	/**
	 * @return bool
	 */
	public function isCacheable() {
		return $this->getCacheExpiry() > 0;
	}

	/**
	 * Return true if this cached output object predates the global or
	 * per-article cache invalidation timestamps, or if it comes from
	 * an incompatible older version.
	 *
	 * @param string $touched The affected article's last touched timestamp
	 * @return bool
	 */
	public function expired( $touched ) {
		global $wgCacheEpoch;

		$expiry = MWTimestamp::convert( TS_MW, MWTimestamp::time() - $this->getCacheExpiry() );

		return !$this->isCacheable() // parser says it's not cacheable
			|| $this->getCacheTime() < $touched
			|| $this->getCacheTime() <= $wgCacheEpoch
			|| $this->getCacheTime() < $expiry; // expiry period has passed
	}

	/**
	 * Return true if this cached output object is for a different revision of
	 * the page.
	 *
	 * @todo We always return false if $this->getCacheRevisionId() is null;
	 * this prevents invalidating the whole parser cache when this change is
	 * deployed. Someday that should probably be changed.
	 *
	 * @since 1.23
	 * @param int $id The affected article's current revision id
	 * @return bool
	 */
	public function isDifferentRevision( $id ) {
		$cached = $this->getCacheRevisionId();
		return $cached !== null && $id !== $cached;
	}

	/**
	 * Returns the options from its ParserOptions which have been taken
	 * into account to produce the output.
	 * @since 1.36
	 * @return string[]
	 */
	public function getUsedOptions(): array {
		return array_keys( $this->mParseUsedOptions );
	}

	/**
	 * Tags a parser option for use in the cache key for this parser output.
	 * Registered as a watcher at ParserOptions::registerWatcher() by Parser::clearState().
	 * The information gathered here is available via getUsedOptions(),
	 * and is used by ParserCache::save().
	 *
	 * @see ParserCache::getMetadata
	 * @see ParserCache::save
	 * @see ParserOptions::addExtraKey
	 * @see ParserOptions::optionsHash
	 * @param string $option
	 */
	public function recordOption( string $option ) {
		$this->mParseUsedOptions[$option] = true;
	}

	/**
	 * Tags a list of parser option names for use in the cache key for this parser output.
	 *
	 * @see recordOption()
	 * @param string[] $options
	 */
	public function recordOptions( array $options ) {
		$this->mParseUsedOptions = array_merge(
			$this->mParseUsedOptions,
			array_fill_keys( $options, true )
		);
	}

	/**
	 * Returns a JSON serializable structure representing this CacheTime instance.
	 * @see newFromJson()
	 *
	 * @return array
	 */
	protected function toJsonArray(): array {
		return [
			'ParseUsedOptions' => $this->mParseUsedOptions,
			'CacheExpiry' => $this->mCacheExpiry,
			'CacheTime' => $this->mCacheTime,
			'CacheRevisionId' => $this->mCacheRevisionId,
		];
	}

	public static function newFromJsonArray( JsonUnserializer $unserializer, array $json ) {
		$cacheTime = new CacheTime();
		$cacheTime->initFromJson( $unserializer, $json );
		return $cacheTime;
	}

	/**
	 * Initialize member fields from an array returned by jsonSerialize().
	 * @param JsonUnserializer $unserializer
	 * @param array $jsonData
	 */
	protected function initFromJson( JsonUnserializer $unserializer, array $jsonData ) {
		if ( array_key_exists( 'AccessedOptions', $jsonData ) ) {
			// Backwards compatibility for ParserOutput
			$this->mParseUsedOptions = $jsonData['AccessedOptions'] ?: [];
		} elseif ( array_key_exists( 'UsedOptions', $jsonData ) ) {
			// Backwards compatibility
			$this->recordOptions( $jsonData['UsedOptions'] ?: [] );
		} else {
			$this->mParseUsedOptions = $jsonData['ParseUsedOptions'] ?: [];
		}
		$this->mCacheExpiry = $jsonData['CacheExpiry'];
		$this->mCacheTime = $jsonData['CacheTime'];
		$this->mCacheRevisionId = $jsonData['CacheRevisionId'];
	}

	public function __wakeup() {
		// Backwards compatibility, pre 1.36
		$priorOptions = $this->getGhostFieldValue( 'mUsedOptions' );
		if ( $priorOptions ) {
			$this->recordOptions( $priorOptions );
		}
	}
}
