ConditionalHeaderUtil.php

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<?php
 
namespace MediaWiki\Rest;
 
use MediaWiki\Rest\HeaderParser\HttpDate;
use MediaWiki\Rest\HeaderParser\IfNoneMatch;
use RuntimeException;
use Wikimedia\Timestamp\ConvertibleTimestamp;
 
class ConditionalHeaderUtil {
    private $varnishETagHack = true;
    private $eTag;
    private $lastModified;
    private $hasRepresentation;
 
    public function setValidators( $eTag, $lastModified, $hasRepresentation ) {
        $this->eTag = $eTag;
        if ( $lastModified === null ) {
            $this->lastModified = null;
        } else {
            $this->lastModified = (int)ConvertibleTimestamp::convert( TS_UNIX, $lastModified );
        }
        $this->hasRepresentation = $hasRepresentation ?? ( $eTag !== null );
    }
 
    public function setVarnishETagHack( $hack ) {
        $this->varnishETagHack = $hack;
    }
 
    public function checkPreconditions( RequestInterface $request ) {
        $parser = new IfNoneMatch;
        if ( $this->eTag !== null ) {
            $resourceTag = $parser->parseETag( $this->eTag );
            if ( !$resourceTag ) {
                throw new RuntimeException( 'Invalid ETag returned by handler: `' .
                    $parser->getLastError() . '`' );
            }
        } else {
            $resourceTag = null;
        }
        $getOrHead = in_array( $request->getMethod(), [ 'GET', 'HEAD' ] );
        if ( $request->hasHeader( 'If-Match' ) ) {
            $im = $request->getHeader( 'If-Match' );
            $match = false;
            foreach ( $parser->parseHeaderList( $im ) as $tag ) {
                if ( $tag['whole'] === '*' && $this->hasRepresentation ) {
                    $match = true;
                    break;
                }
 
                if ( $this->strongCompare( $resourceTag, $tag ) ) {
                    $match = true;
                    break;
                }
            }
            if ( !$match ) {
                return 412;
            }
        } elseif ( $request->hasHeader( 'If-Unmodified-Since' ) ) {
            $requestDate = HttpDate::parse( $request->getHeader( 'If-Unmodified-Since' )[0] );
            if ( $requestDate !== null
                && ( $this->lastModified === null || $this->lastModified > $requestDate )
            ) {
                return 412;
            }
        }
        if ( $request->hasHeader( 'If-None-Match' ) ) {
            $inm = $request->getHeader( 'If-None-Match' );
            foreach ( $parser->parseHeaderList( $inm ) as $tag ) {
                if ( $tag['whole'] === '*' && $this->hasRepresentation ) {
                    return $getOrHead ? 304 : 412;
                }
                if ( $this->weakCompare( $resourceTag, $tag ) ) {
                    if ( $getOrHead ) {
                        return 304;
                    } else {
                        return 412;
                    }
                }
            }
        } elseif ( $getOrHead && $request->hasHeader( 'If-Modified-Since' ) ) {
            $requestDate = HttpDate::parse( $request->getHeader( 'If-Modified-Since' )[0] );
            if ( $requestDate !== null && $this->lastModified !== null
                && $this->lastModified <= $requestDate
            ) {
                return 304;
            }
        }
        // RFC 7232 states that If-Range should be evaluated here. However, the
        // purpose of If-Range is to cause the Range request header to be
        // conditionally ignored, not to immediately send a response, so it
        // doesn't fit here. RFC 7232 only requires that If-Range be checked
        // after the other conditional header fields, a requirement that is
        // satisfied if it is processed in Handler::execute().
        return null;
    }
 
    public function applyResponseHeaders( ResponseInterface $response ) {
        if ( $this->lastModified !== null && !$response->hasHeader( 'Last-Modified' ) ) {
            $response->setHeader( 'Last-Modified', HttpDate::format( $this->lastModified ) );
        }
        if ( $this->eTag !== null && !$response->hasHeader( 'ETag' ) ) {
            $response->setHeader( 'ETag', $this->eTag );
        }
    }
 
    private function weakCompare( $resourceETag, $headerETag ) {
        if ( $resourceETag === null || $headerETag === null ) {
            return false;
        }
        return $resourceETag['contents'] === $headerETag['contents'];
    }
 
    private function strongCompare( $resourceETag, $headerETag ) {
        if ( $resourceETag === null || $headerETag === null ) {
            return false;
        }
 
        return !$resourceETag['weak']
            && ( $this->varnishETagHack || !$headerETag['weak'] )
            && $resourceETag['contents'] === $headerETag['contents'];
    }
 
}