TextSlotDiffRenderer.php

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<?php
use MediaWiki\Shell\Shell;
use Wikimedia\Assert\Assert;

class TextSlotDiffRenderer extends SlotDiffRenderer {

    const ENGINE_PHP = 'php';

    const ENGINE_WIKIDIFF2 = 'wikidiff2';

    const ENGINE_WIKIDIFF2_INLINE = 'wikidiff2inline';

    const ENGINE_EXTERNAL = 'external';

    private $statsdDataFactory;

    private $language;

    private $engine = self::ENGINE_PHP;

    private $externalEngine;

    public function getExtraCacheKeys() {
        // Tell DifferenceEngine this is a different variant from the standard wikidiff2 variant
        return $this->engine === self::ENGINE_WIKIDIFF2_INLINE ? [
            phpversion( 'wikidiff2' ), 'inline'
        ] : [];
    }

    public static function diff( $oldText, $newText ) {
        $slotDiffRenderer = ContentHandler::getForModelID( CONTENT_MODEL_TEXT )
            ->getSlotDiffRenderer( RequestContext::getMain() );
        '@phan-var TextSlotDiffRenderer $slotDiffRenderer';
        return $slotDiffRenderer->getTextDiff( $oldText, $newText );
    }

    public function setStatsdDataFactory( IBufferingStatsdDataFactory $statsdDataFactory ) {
        $this->statsdDataFactory = $statsdDataFactory;
    }

    public function setLanguage( Language $language ) {
        $this->language = $language;
    }

    public function setEngine( $type, $executable = null ) {
        $engines = [ self::ENGINE_PHP, self::ENGINE_WIKIDIFF2, self::ENGINE_EXTERNAL,
            self::ENGINE_WIKIDIFF2_INLINE ];
        Assert::parameter( in_array( $type, $engines, true ), '$type',
            'must be one of the TextSlotDiffRenderer::ENGINE_* constants' );
        if ( $type === self::ENGINE_EXTERNAL ) {
            Assert::parameter( is_string( $executable ) && is_executable( $executable ), '$executable',
                'must be a path to a valid executable' );
        } else {
            Assert::parameter( is_null( $executable ), '$executable',
                'must not be set unless $type is ENGINE_EXTERNAL' );
        }
        $this->engine = $type;
        $this->externalEngine = $executable;
    }

    public function getDiff( Content $oldContent = null, Content $newContent = null ) {
        $this->normalizeContents( $oldContent, $newContent, TextContent::class );

        $oldText = $oldContent->serialize();
        $newText = $newContent->serialize();

        return $this->getTextDiff( $oldText, $newText );
    }

    public function getTextDiff( $oldText, $newText ) {
        Assert::parameterType( 'string', $oldText, '$oldText' );
        Assert::parameterType( 'string', $newText, '$newText' );

        $diff = function () use ( $oldText, $newText ) {
            $time = microtime( true );

            $result = $this->getTextDiffInternal( $oldText, $newText );

            $time = intval( ( microtime( true ) - $time ) * 1000 );
            if ( $this->statsdDataFactory ) {
                $this->statsdDataFactory->timing( 'diff_time', $time );
            }

            // TODO reimplement this using T142313
            /*
            // Log requests slower than 99th percentile
            if ( $time > 100 && $this->mOldPage && $this->mNewPage ) {
                wfDebugLog( 'diff',
                    "$time ms diff: {$this->mOldid} -> {$this->mNewid} {$this->mNewPage}" );
            }
            */

            return $result;
        };

        $error = function ( $status ) {
            throw new FatalError( $status->getWikiText() );
        };

        // Use PoolCounter if the diff looks like it can be expensive
        if ( strlen( $oldText ) + strlen( $newText ) > 20000 ) {
            $work = new PoolCounterWorkViaCallback( 'diff',
                md5( $oldText ) . md5( $newText ),
                [ 'doWork' => $diff, 'error' => $error ]
            );
            return $work->execute();
        }

        return $diff();
    }

    protected function getTextDiffInternal( $oldText, $newText ) {
        // TODO move most of this into three parallel implementations of a text diff generator
        // class, choose which one to use via dependecy injection

        $oldText = str_replace( "\r\n", "\n", $oldText );
        $newText = str_replace( "\r\n", "\n", $newText );

        // Better external diff engine, the 2 may some day be dropped
        // This one does the escaping and segmenting itself
        if ( $this->engine === self::ENGINE_WIKIDIFF2 ) {
            $wikidiff2Version = phpversion( 'wikidiff2' );
            if (
                $wikidiff2Version !== false &&
                version_compare( $wikidiff2Version, '1.5.0', '>=' ) &&
                version_compare( $wikidiff2Version, '1.8.0', '<' )
            ) {
                $text = wikidiff2_do_diff(
                    $oldText,
                    $newText,
                    2,
                    0
                );
            } else {
                // Don't pass the 4th parameter introduced in version 1.5.0 and removed in version 1.8.0
                $text = wikidiff2_do_diff(
                    $oldText,
                    $newText,
                    2
                );
            }

            return $text;
        } elseif ( $this->engine === self::ENGINE_EXTERNAL ) {
            # Diff via the shell
            $tmpDir = wfTempDir();
            $tempName1 = tempnam( $tmpDir, 'diff_' );
            $tempName2 = tempnam( $tmpDir, 'diff_' );

            $tempFile1 = fopen( $tempName1, "w" );
            if ( !$tempFile1 ) {
                return false;
            }
            $tempFile2 = fopen( $tempName2, "w" );
            if ( !$tempFile2 ) {
                return false;
            }
            fwrite( $tempFile1, $oldText );
            fwrite( $tempFile2, $newText );
            fclose( $tempFile1 );
            fclose( $tempFile2 );
            $cmd = [ $this->externalEngine, $tempName1, $tempName2 ];
            $result = Shell::command( $cmd )
                ->execute();
            $exitCode = $result->getExitCode();
            if ( $exitCode !== 0 ) {
                throw new Exception( "External diff command returned code {$exitCode}. Stderr: "
                                     . wfEscapeWikiText( $result->getStderr() )
                );
            }
            $difftext = $result->getStdout();
            unlink( $tempName1 );
            unlink( $tempName2 );

            return $difftext;
        } elseif ( $this->engine === self::ENGINE_PHP ) {
            if ( $this->language ) {
                $oldText = $this->language->segmentForDiff( $oldText );
                $newText = $this->language->segmentForDiff( $newText );
            }
            $ota = explode( "\n", $oldText );
            $nta = explode( "\n", $newText );
            $diffs = new Diff( $ota, $nta );
            $formatter = new TableDiffFormatter();
            $difftext = $formatter->format( $diffs );
            if ( $this->language ) {
                $difftext = $this->language->unsegmentForDiff( $difftext );
            }

            return $difftext;
        } elseif ( $this->engine === self::ENGINE_WIKIDIFF2_INLINE ) {
            // Note wikidiff2_inline_diff returns an element sans table.
            // Due to the way other diffs work (return a table with before and after), we need to wrap
            // the output in a row that spans the 4 columns that are expected, so that our diff appears in
            // the correct place!
            return '<tr><td colspan="4">' . wikidiff2_inline_diff( $oldText, $newText, 2 ) . '</td></tr>';
        }
        throw new LogicException( 'Invalid engine: ' . $this->engine );
    }

}