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<?php
/**
* 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
*/
/**
* 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 origional diff output and the previous diff
* parsing code.
*/
class EchoDiffParser {
/**
* @var integer $prefixLength The number of characters the diff prefixes a line with
*/
protected $prefixLength = 1;
/**
* @var array $left The text of the left side of the diff operation
*/
protected $left;
/**
* @var integer $leftPos The current position within the left text
*/
protected $leftPos;
/**
* @var array $right The text of the right side of the diff operation
*/
protected $right;
/**
* @var integer $rightPos The current position within the right text
*/
protected $rightPos;
/**
* @var array[] $changeSet 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 ) . "\n";
$right = trim( $rightText ) . "\n";
$diff = wfDiff( $left, $right, '-u -w' );
return $this->parse( $diff, $left, $right );
}
/**
* Duplicates the check from the global wfDiff function to determine
* if we are using internal or external diff utilities
*/
protected static function usingInternalDiff() {
global $wgDiff;
wfSuppressWarnings();
$haveDiff = $wgDiff && file_exists( $wgDiff );
wfRestoreWarnings();
return !$haveDiff;
}
/**
* 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 = array(
'_info' => array(
'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;
} else {
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 EchoDiffGroup $change Changes the the immediately previous lines
*
* @throws MWException
* @return EchoDiffGroup Changes to this line and any changed lines immediately previous
*/
protected function parseLine( $line, EchoDiffGroup $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 @@
list( , $left, $right ) = explode( ' ', $line );
list( $this->leftPos ) = explode( ',', substr( $left, 1 ) );
list( $this->rightPos ) = explode( ',', substr( $right, 1 ) );
// -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 MWException( 'Positional error: left' );
}
if ( $change === null ) {
$change = new EchoDiffGroup( $this->leftPos, $this->rightPos );
}
$change->subtract( $line );
$this->leftPos++;
break;
case '+': // add
if ( $this->right[$this->rightPos] !== $line ) {
throw new MWException( 'Positional error: right' );
}
if ( $change === null ) {
$change = new EchoDiffGroup( $this->leftPos, $this->rightPos );
}
$change->add( $line );
$this->rightPos++;
break;
default:
throw new MWException( 'Unknown Diff Operation: ' . $op );
}
return $change;
}
}
/**
* Represents a single set of changes all effecting neighboring lines
*/
class EchoDiffGroup {
/**
* @var array The left and right position this change starts at
*/
protected $position;
/**
* @var array The lines that have been added
*/
protected $new = array();
/**
* @var array The lines that have been removed
*/
protected $old = array();
/**
* @param integer $leftPos The starting line number in the left text
* @param integer $rightPos The starting line number in the right text
*/
public function __construct( $leftPos, $rightPos ) {
// +1 due to the origional code use 1 indexing for this result
$this->position = array(
'right-pos' => $rightPos + 1,
'left-pos' => $leftPos + 1,
);
}
/**
* @param string $line Line in the right text but not in the left
*/
public function add( $line ) {
$this->new[] = $line;
}
/**
* @param string $line Line in the left text but not in the right
*/
public function subtract( $line ) {
$this->old[] = $line;
}
/**
* @return array[] set of changes
* 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() {
$old = implode( "\n", $this->old );
$new = implode( "\n", $this->new );
$position = $this->position;
$changeSet = array();
// The implodes must come first because we consider array( '' ) to also be false
// meaning a blank link replaced with content is an addition
if ( $old && $new ) {
$min = min( count( $this->old ), count( $this->new ) );
$changeSet[] = $position + array(
'action' => 'change',
'old_content' => implode( "\n", array_slice( $this->old, 0, $min ) ),
'new_content' => implode( "\n", array_slice( $this->new, 0, $min ) ),
);
$position['left-pos'] += $min;
$position['right-pos'] += $min;
$old = implode( "\n", array_slice( $this->old, $min ) );
$new = implode( "\n", array_slice( $this->new, $min ) );
}
if ( $new ) {
$changeSet[] = $position + array(
'action' => 'add',
'content' => $new,
);
} elseif ( $old ) {
$changeSet[] = $position + array(
'action' => 'subtract',
'content' => $old,
);
}
return $changeSet;
}
}