DiffFormatter.php

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<?php
abstract class DiffFormatter {

    protected $leadingContextLines = 0;

    protected $trailingContextLines = 0;

    public function format( $diff ) {
        wfProfileIn( __METHOD__ );

        $xi = $yi = 1;
        $block = false;
        $context = array();

        $nlead = $this->leadingContextLines;
        $ntrail = $this->trailingContextLines;

        $this->startDiff();

        // Initialize $x0 and $y0 to prevent IDEs from getting confused.
        $x0 = $y0 = 0;
        foreach ( $diff->edits as $edit ) {
            if ( $edit->type == 'copy' ) {
                if ( is_array( $block ) ) {
                    if ( count( $edit->orig ) <= $nlead + $ntrail ) {
                        $block[] = $edit;
                    } else {
                        if ( $ntrail ) {
                            $context = array_slice( $edit->orig, 0, $ntrail );
                            $block[] = new DiffOpCopy( $context );
                        }
                        $this->block( $x0, $ntrail + $xi - $x0,
                            $y0, $ntrail + $yi - $y0,
                            $block );
                        $block = false;
                    }
                }
                $context = $edit->orig;
            } else {
                if ( !is_array( $block ) ) {
                    $context = array_slice( $context, count( $context ) - $nlead );
                    $x0 = $xi - count( $context );
                    $y0 = $yi - count( $context );
                    $block = array();
                    if ( $context ) {
                        $block[] = new DiffOpCopy( $context );
                    }
                }
                $block[] = $edit;
            }

            if ( $edit->orig ) {
                $xi += count( $edit->orig );
            }
            if ( $edit->closing ) {
                $yi += count( $edit->closing );
            }
        }

        if ( is_array( $block ) ) {
            $this->block( $x0, $xi - $x0,
                $y0, $yi - $y0,
                $block );
        }

        $end = $this->endDiff();
        wfProfileOut( __METHOD__ );

        return $end;
    }

    protected function block( $xbeg, $xlen, $ybeg, $ylen, &$edits ) {
        wfProfileIn( __METHOD__ );
        $this->startBlock( $this->blockHeader( $xbeg, $xlen, $ybeg, $ylen ) );
        foreach ( $edits as $edit ) {
            if ( $edit->type == 'copy' ) {
                $this->context( $edit->orig );
            } elseif ( $edit->type == 'add' ) {
                $this->added( $edit->closing );
            } elseif ( $edit->type == 'delete' ) {
                $this->deleted( $edit->orig );
            } elseif ( $edit->type == 'change' ) {
                $this->changed( $edit->orig, $edit->closing );
            } else {
                throw new MWException( "Unknown edit type: {$edit->type}" );
            }
        }
        $this->endBlock();
        wfProfileOut( __METHOD__ );
    }

    protected function startDiff() {
        ob_start();
    }

    protected function endDiff() {
        $val = ob_get_contents();
        ob_end_clean();

        return $val;
    }

    protected function blockHeader( $xbeg, $xlen, $ybeg, $ylen ) {
        if ( $xlen > 1 ) {
            $xbeg .= ',' . ( $xbeg + $xlen - 1 );
        }
        if ( $ylen > 1 ) {
            $ybeg .= ',' . ( $ybeg + $ylen - 1 );
        }

        return $xbeg . ( $xlen ? ( $ylen ? 'c' : 'd' ) : 'a' ) . $ybeg;
    }

    protected function startBlock( $header ) {
        echo $header . "\n";
    }

    protected function endBlock() {
    }

    protected function lines( $lines, $prefix = ' ' ) {
        foreach ( $lines as $line ) {
            echo "$prefix $line\n";
        }
    }

    protected function context( $lines ) {
        $this->lines( $lines );
    }

    protected function added( $lines ) {
        $this->lines( $lines, '>' );
    }

    protected function deleted( $lines ) {
        $this->lines( $lines, '<' );
    }

    protected function changed( $orig, $closing ) {
        $this->deleted( $orig );
        echo "---\n";
        $this->added( $closing );
    }

}