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DiffParser.php
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DiffParser.php
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<?php
namespace MediaWiki\Extension\Notifications;
/**
* MediaWiki Extension: Echo
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* This program is distributed WITHOUT ANY WARRANTY.
*/
/**
* @file
* @ingroup Extensions
* @author Erik Bernhardson
*/
use UnexpectedValueException;
use Wikimedia\Diff\Diff;
use Wikimedia\Diff\UnifiedDiffFormatter;
/**
* Calculates the individual sets of differences between two pieces of text
* as individual groupings of add, subtract, and change actions. Internally
* uses 0-indexing for positions. All results from the class are 1 indexed
* to stay consistent with the original diff output and the previous diff
* parsing code.
*/
class DiffParser {
/**
* @var int The number of characters the diff prefixes a line with
*/
protected $prefixLength = 1;
/**
* @var string[] The text of the left side of the diff operation
*/
protected $left;
/**
* @var int The current position within the left text
*/
protected $leftPos;
/**
* @var string[] The text of the right side of the diff operation
*/
protected $right;
/**
* @var int The current position within the right text
*/
protected $rightPos;
/**
* @var array[] Set of add, subtract, or change operations within the diff
*/
protected $changeSet;
/**
* Get the set of add, subtract, and change operations required to transform leftText into rightText
*
* @param string $leftText The left, or old, revision of the text
* @param string $rightText The right, or new, revision of the text
* @return array[] Array of arrays containing changes to individual groups of lines within the text
* Each change consists of:
* An 'action', one of:
* - add
* - subtract
* - change
* 'content' that was added or removed, or in the case
* of a change, 'old_content' and 'new_content'
* 'left_pos' and 'right_pos' (in 1-indexed lines) of the change.
*/
public function getChangeSet( $leftText, $rightText ) {
$left = trim( $leftText );
$right = trim( $rightText );
if ( $left === '' ) {
// fixes T155998
return $this->getChangeSetFromEmptyLeft( $right );
}
$diffs = new Diff( explode( "\n", $left ), explode( "\n", $right ) );
$format = new UnifiedDiffFormatter();
$diff = $format->format( $diffs );
return $this->parse( $diff, $left, $right );
}
/**
* If we add content to an empty page the changeSet can be composed straightaway
*
* @param string $right
* @return array[] See {@see getChangeSet}
*/
private function getChangeSetFromEmptyLeft( $right ) {
$rightLines = explode( "\n", $right );
return [
'_info' => [
'lhs-length' => 1,
'rhs-length' => count( $rightLines ),
'lhs' => [ '' ],
'rhs' => $rightLines
],
[
'right-pos' => 1,
'left-pos' => 1,
'action' => 'add',
'content' => $right,
]
];
}
/**
* Duplicates the check from the global wfDiff function to determine
* if we are using internal or external diff utilities
*
* @deprecated since 1.29, the internal diff parser is always used
* @return bool
*/
protected static function usingInternalDiff() {
return true;
}
/**
* Parse the unified diff output into an array of changes to individual groups of the text
*
* @param string $diff The unified diff output
* @param string $left The left side of the diff used for sanity checks
* @param string $right The right side of the diff used for sanity checks
*
* @return array[]
*/
protected function parse( $diff, $left, $right ) {
$this->left = explode( "\n", $left );
$this->right = explode( "\n", $right );
$diff = explode( "\n", $diff );
$this->leftPos = 0;
$this->rightPos = 0;
$this->changeSet = [
'_info' => [
'lhs-length' => count( $this->left ),
'rhs-length' => count( $this->right ),
'lhs' => $this->left,
'rhs' => $this->right,
],
];
$change = null;
foreach ( $diff as $line ) {
$change = $this->parseLine( $line, $change );
}
if ( $change === null ) {
return $this->changeSet;
}
return array_merge( $this->changeSet, $change->getChangeSet() );
}
/**
* Parse the next line of the unified diff output
*
* @param string $line The next line of the unified diff
* @param DiffGroup|null $change Changes the immediately previous lines
*
* @return DiffGroup|null Changes to this line and any changed lines immediately previous
*/
protected function parseLine( $line, ?DiffGroup $change = null ) {
if ( $line ) {
$op = $line[0];
if ( strlen( $line ) > $this->prefixLength ) {
$line = substr( $line, $this->prefixLength );
} else {
$line = '';
}
} else {
$op = ' ';
}
switch ( $op ) {
case '@':
// metadata
if ( $change !== null ) {
$this->changeSet = array_merge( $this->changeSet, $change->getChangeSet() );
$change = null;
}
// @@ -start,numLines +start,numLines @@
[ , $left, $right ] = explode( ' ', $line, 3 );
[ $this->leftPos ] = explode( ',', substr( $left, 1 ), 2 );
[ $this->rightPos ] = explode( ',', substr( $right, 1 ), 2 );
$this->leftPos = (int)$this->leftPos;
$this->rightPos = (int)$this->rightPos;
// -1 because diff is 1 indexed, and we are 0 indexed
$this->leftPos--;
$this->rightPos--;
break;
case ' ':
// No changes
if ( $change !== null ) {
$this->changeSet = array_merge( $this->changeSet, $change->getChangeSet() );
$change = null;
}
$this->leftPos++;
$this->rightPos++;
break;
case '-':
// subtract
if ( $this->left[$this->leftPos] !== $line ) {
throw new UnexpectedValueException( 'Positional error: left' );
}
if ( $change === null ) {
// @phan-suppress-next-line PhanTypeMismatchArgument
$change = new DiffGroup( $this->leftPos, $this->rightPos );
}
$change->subtract( $line );
$this->leftPos++;
break;
case '+':
// add
if ( $this->right[$this->rightPos] !== $line ) {
throw new UnexpectedValueException( 'Positional error: right' );
}
if ( $change === null ) {
// @phan-suppress-next-line PhanTypeMismatchArgument
$change = new DiffGroup( $this->leftPos, $this->rightPos );
}
$change->add( $line );
$this->rightPos++;
break;
default:
throw new UnexpectedValueException( 'Unknown Diff Operation: ' . $op );
}
return $change;
}
}

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