CacheHelper.php

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<?php
use MediaWiki\MediaWikiServices;

class CacheHelper implements ICacheHelper {
    protected $cacheExpiry = 3600;

    protected $cachedChunks;

    protected $hasCached = null;

    protected $cacheEnabled = true;

    protected $onInitHandler = false;

    protected $cacheKey = [];

    public function setCacheEnabled( $cacheEnabled ) {
        $this->cacheEnabled = $cacheEnabled;
    }

    public function startCache( $cacheExpiry = null, $cacheEnabled = null ) {
        if ( is_null( $this->hasCached ) ) {
            if ( !is_null( $cacheExpiry ) ) {
                $this->cacheExpiry = $cacheExpiry;
            }

            if ( !is_null( $cacheEnabled ) ) {
                $this->setCacheEnabled( $cacheEnabled );
            }

            $this->initCaching();
        }
    }

    public function getCachedNotice( IContextSource $context, $includePurgeLink = true ) {
        if ( $this->cacheExpiry < 86400 * 3650 ) {
            $message = $context->msg(
                'cachedspecial-viewing-cached-ttl',
                $context->getLanguage()->formatDuration( $this->cacheExpiry )
            )->escaped();
        } else {
            $message = $context->msg(
                'cachedspecial-viewing-cached-ts'
            )->escaped();
        }

        if ( $includePurgeLink ) {
            $refreshArgs = $context->getRequest()->getQueryValues();
            unset( $refreshArgs['title'] );
            $refreshArgs['action'] = 'purge';

            $subPage = $context->getTitle()->getFullText();
            $subPage = explode( '/', $subPage, 2 );
            $subPage = count( $subPage ) > 1 ? $subPage[1] : false;

            $message .= ' ' . MediaWikiServices::getInstance()->getLinkRenderer()->makeLink(
                $context->getTitle( $subPage ),
                $context->msg( 'cachedspecial-refresh-now' )->text(),
                [],
                $refreshArgs
            );
        }

        return $message;
    }

    protected function initCaching() {
        if ( $this->cacheEnabled && is_null( $this->hasCached ) ) {
            $cachedChunks = wfGetCache( CACHE_ANYTHING )->get( $this->getCacheKeyString() );

            $this->hasCached = is_array( $cachedChunks );
            $this->cachedChunks = $this->hasCached ? $cachedChunks : [];

            if ( $this->onInitHandler !== false ) {
                call_user_func( $this->onInitHandler, $this->hasCached );
            }
        }
    }

    public function getCachedValue( $computeFunction, $args = [], $key = null ) {
        $this->initCaching();

        if ( $this->cacheEnabled && $this->hasCached ) {
            $value = null;

            if ( is_null( $key ) ) {
                reset( $this->cachedChunks );
                $itemKey = key( $this->cachedChunks );

                if ( !is_int( $itemKey ) ) {
                    wfWarn( "Attempted to get item with non-numeric key while " .
                        "the next item in the queue has a key ($itemKey) in " . __METHOD__ );
                } elseif ( is_null( $itemKey ) ) {
                    wfWarn( "Attempted to get an item while the queue is empty in " . __METHOD__ );
                } else {
                    $value = array_shift( $this->cachedChunks );
                }
            } elseif ( array_key_exists( $key, $this->cachedChunks ) ) {
                $value = $this->cachedChunks[$key];
                unset( $this->cachedChunks[$key] );
            } else {
                wfWarn( "There is no item with key '$key' in this->cachedChunks in " . __METHOD__ );
            }
        } else {
            if ( !is_array( $args ) ) {
                $args = [ $args ];
            }

            $value = $computeFunction( ...$args );

            if ( $this->cacheEnabled ) {
                if ( is_null( $key ) ) {
                    $this->cachedChunks[] = $value;
                } else {
                    $this->cachedChunks[$key] = $value;
                }
            }
        }

        return $value;
    }

    public function saveCache() {
        if ( $this->cacheEnabled && $this->hasCached === false && !empty( $this->cachedChunks ) ) {
            wfGetCache( CACHE_ANYTHING )->set(
                $this->getCacheKeyString(),
                $this->cachedChunks,
                $this->cacheExpiry
            );
        }
    }

    public function setExpiry( $cacheExpiry ) {
        $this->cacheExpiry = $cacheExpiry;
    }

    protected function getCacheKeyString() {
        if ( $this->cacheKey === [] ) {
            throw new MWException( 'No cache key set, so cannot obtain or save the CacheHelper values.' );
        }

        return ObjectCache::getLocalClusterInstance()->makeKey(
            ...array_values( $this->cacheKey )
        );
    }

    public function setCacheKey( array $cacheKey ) {
        $this->cacheKey = $cacheKey;
    }

    public function rebuildOnDemand() {
        $this->hasCached = false;
    }

    public function setOnInitializedHandler( $handlerFunction ) {
        $this->onInitHandler = $handlerFunction;
    }
}