HtmlDiff.php
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HtmlDiff.php
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	<?php

	namespace Caxy\HtmlDiff;

	class HtmlDiff
	{
	public static $defaultSpecialCaseTags = array('strong', 'b', 'i', 'big', 'small', 'u', 'sub', 'sup', 'strike', 's', 'p');
	public static $defaultSpecialCaseChars = array('.', ',', '(', ')', '\'');
	public static $defaultGroupDiffs = true;

	protected $content;
	protected $oldText;
	protected $newText;
	protected $oldWords = array();
	protected $newWords = array();
	protected $wordIndices;
	protected $encoding;
	protected $specialCaseOpeningTags = array();
	protected $specialCaseClosingTags = array();
	protected $specialCaseTags;
	protected $specialCaseChars;
	protected $groupDiffs;
	protected $insertSpaceInReplace = false;

	public function __construct($oldText, $newText, $encoding = 'UTF-8', $specialCaseTags = null, $groupDiffs = null)
	{
	if ($specialCaseTags === null) {
	$specialCaseTags = static::$defaultSpecialCaseTags;
	}

	if ($groupDiffs === null) {
	$groupDiffs = static::$defaultGroupDiffs;
	}

	$this->oldText = $this->purifyHtml(trim($oldText));
	$this->newText = $this->purifyHtml(trim($newText));
	$this->encoding = $encoding;
	$this->content = '';
	$this->groupDiffs = $groupDiffs;
	$this->setSpecialCaseTags($specialCaseTags);
	$this->setSpecialCaseChars(static::$defaultSpecialCaseChars);
	}

	/**
	* @param boolean $boolean
	* @return HtmlDiff
	*/
	public function setInsertSpaceInReplace($boolean)
	{
	$this->insertSpaceInReplace = $boolean;

	return $this;
	}

	/**
	* @return boolean
	*/
	public function getInsertSpaceInReplace()
	{
	return $this->insertSpaceInReplace;
	}

	public function setSpecialCaseChars(array $chars)
	{
	$this->specialCaseChars = $chars;
	}

	public function getSpecialCaseChars()
	{
	return $this->specialCaseChars;
	}

	public function addSpecialCaseChar($char)
	{
	if (!in_array($char, $this->specialCaseChars)) {
	$this->specialCaseChars[] = $char;
	}
	}

	public function removeSpecialCaseChar($char)
	{
	$key = array_search($char, $this->specialCaseChars);
	if ($key !== false) {
	unset($this->specialCaseChars[$key]);
	}
	}

	public function setSpecialCaseTags(array $tags = array())
	{
	$this->specialCaseTags = $tags;

	foreach ($this->specialCaseTags as $tag) {
	$this->addSpecialCaseTag($tag);
	}
	}

	public function addSpecialCaseTag($tag)
	{
	if (!in_array($tag, $this->specialCaseTags)) {
	$this->specialCaseTags[] = $tag;
	}

	$opening = $this->getOpeningTag($tag);
	$closing = $this->getClosingTag($tag);

	if (!in_array($opening, $this->specialCaseOpeningTags)) {
	$this->specialCaseOpeningTags[] = $opening;
	}
	if (!in_array($closing, $this->specialCaseClosingTags)) {
	$this->specialCaseClosingTags[] = $closing;
	}
	}

	public function removeSpecialCaseTag($tag)
	{
	if (($key = array_search($tag, $this->specialCaseTags)) !== false) {
	unset($this->specialCaseTags[$key]);

	$opening = $this->getOpeningTag($tag);
	$closing = $this->getClosingTag($tag);

	if (($key = array_search($opening, $this->specialCaseOpeningTags)) !== false) {
	unset($this->specialCaseOpeningTags[$key]);
	}
	if (($key = array_search($closing, $this->specialCaseClosingTags)) !== false) {
	unset($this->specialCaseClosingTags[$key]);
	}
	}
	}

	public function getSpecialCaseTags()
	{
	return $this->specialCaseTags;
	}

	public function getOldHtml()
	{
	return $this->oldText;
	}

	public function getNewHtml()
	{
	return $this->newText;
	}

	public function getDifference()
	{
	return $this->content;
	}

	public function setGroupDiffs($boolean)
	{
	$this->groupDiffs = $boolean;
	}

	public function isGroupDiffs()
	{
	return $this->groupDiffs;
	}

	protected function getOpeningTag($tag)
	{
	return "/<".$tag."[^>]*/i";
	}

	protected function getClosingTag($tag)
	{
	return "</".$tag.">";
	}

	protected function getStringBetween($str, $start, $end)
	{
	$expStr = explode( $start, $str, 2 );
	if ( count( $expStr ) > 1 ) {
	$expStr = explode( $end, $expStr[ 1 ] );
	if ( count( $expStr ) > 1 ) {
	array_pop( $expStr );

	return implode( $end, $expStr );
	}
	}

	return '';
	}

	protected function purifyHtml($html, $tags = null)
	{
	if ( class_exists( 'Tidy' ) && false ) {
	$config = array( 'output-xhtml' => true, 'indent' => false );
	$tidy = new tidy;
	$tidy->parseString( $html, $config, 'utf8' );
	$html = (string) $tidy;

	return $this->getStringBetween( $html, '<body>' );
	}

	return $html;
	}

	public function build()
	{
	$this->splitInputsToWords();
	$this->indexNewWords();
	$operations = $this->operations();
	foreach ($operations as $item) {
	$this->performOperation( $item );
	}

	return $this->content;
	}

	protected function indexNewWords()
	{
	$this->wordIndices = array();
	foreach ($this->newWords as $i => $word) {
	if ( $this->isTag( $word ) ) {
	$word = $this->stripTagAttributes( $word );
	}
	if ( isset( $this->wordIndices[ $word ] ) ) {
	$this->wordIndices[ $word ][] = $i;
	} else {
	$this->wordIndices[ $word ] = array( $i );
	}
	}
	}

	protected function splitInputsToWords()
	{
	$this->oldWords = $this->convertHtmlToListOfWords( $this->explode( $this->oldText ) );
	$this->newWords = $this->convertHtmlToListOfWords( $this->explode( $this->newText ) );
	}

	protected function isPartOfWord($text)
	{
	return ctype_alnum(str_replace($this->specialCaseChars, '', $text));
	}

	protected function convertHtmlToListOfWords($characterString)
	{
	$mode = 'character';
	$current_word = '';
	$words = array();
	foreach ($characterString as $i => $character) {
	switch ($mode) {
	case 'character':
	if ( $this->isStartOfTag( $character ) ) {
	if ($current_word != '') {
	$words[] = $current_word;
	}
	$current_word = "<";
	$mode = 'tag';
	} elseif ( preg_match( "[^\s]", $character ) > 0 ) {
	if ($current_word != '') {
	$words[] = $current_word;
	}
	$current_word = $character;
	$mode = 'whitespace';
	} else {
	if (
	(ctype_alnum($character) && (strlen($current_word) == 0 \|\| $this->isPartOfWord($current_word))) \|\|
	(in_array($character, $this->specialCaseChars) && isset($characterString[$i+1]) && $this->isPartOfWord($characterString[$i+1]))
	) {
	$current_word .= $character;
	} else {
	$words[] = $current_word;
	$current_word = $character;
	}
	}
	break;
	case 'tag' :
	if ( $this->isEndOfTag( $character ) ) {
	$current_word .= ">";
	$words[] = $current_word;
	$current_word = "";

	if ( !preg_match('[^\s]', $character ) ) {
	$mode = 'whitespace';
	} else {
	$mode = 'character';
	}
	} else {
	$current_word .= $character;
	}
	break;
	case 'whitespace':
	if ( $this->isStartOfTag( $character ) ) {
	if ($current_word != '') {
	$words[] = $current_word;
	}
	$current_word = "<";
	$mode = 'tag';
	} elseif ( preg_match( "[^\s]", $character ) ) {
	$current_word .= $character;
	} else {
	if ($current_word != '') {
	$words[] = $current_word;
	}
	$current_word = $character;
	$mode = 'character';
	}
	break;
	default:
	break;
	}
	}
	if ($current_word != '') {
	$words[] = $current_word;
	}

	return $words;
	}

	protected function isStartOfTag($val)
	{
	return $val == "<";
	}

	protected function isEndOfTag($val)
	{
	return $val == ">";
	}

	protected function isWhiteSpace($value)
	{
	return !preg_match( '[^\s]', $value );
	}

	protected function explode($value)
	{
	// as suggested by @onassar
	return preg_split( '//u', $value );
	}

	protected function performOperation($operation)
	{
	switch ($operation->action) {
	case 'equal' :
	$this->processEqualOperation( $operation );
	break;
	case 'delete' :
	$this->processDeleteOperation( $operation, "diffdel" );
	break;
	case 'insert' :
	$this->processInsertOperation( $operation, "diffins");
	break;
	case 'replace':
	$this->processReplaceOperation( $operation );
	break;
	default:
	break;
	}
	}

	protected function processReplaceOperation($operation)
	{
	$processDelete = strlen($this->oldText) > 0;
	$processInsert = strlen($this->newText) > 0;

	if ($processDelete) {
	$this->processDeleteOperation( $operation, "diffmod" );
	}

	if ($this->insertSpaceInReplace && $processDelete && $processInsert) {
	$this->content .= ' ';
	}

	if ($processInsert) {
	$this->processInsertOperation( $operation, "diffmod" );
	}
	}

	protected function processInsertOperation($operation, $cssClass)
	{
	$text = array();
	foreach ($this->newWords as $pos => $s) {
	if ($pos >= $operation->startInNew && $pos < $operation->endInNew) {
	$text[] = $s;
	}
	}
	$this->insertTag( "ins", $cssClass, $text );
	}

	protected function processDeleteOperation($operation, $cssClass)
	{
	$text = array();
	foreach ($this->oldWords as $pos => $s) {
	if ($pos >= $operation->startInOld && $pos < $operation->endInOld) {
	$text[] = $s;
	}
	}
	$this->insertTag( "del", $cssClass, $text );
	}

	protected function processEqualOperation($operation)
	{
	$result = array();
	foreach ($this->newWords as $pos => $s) {
	if ($pos >= $operation->startInNew && $pos < $operation->endInNew) {
	$result[] = $s;
	}
	}
	$this->content .= implode( "", $result );
	}

	protected function insertTag($tag, $cssClass, &$words)
	{
	while (true) {
	if ( count( $words ) == 0 ) {
	break;
	}

	$nonTags = $this->extractConsecutiveWords( $words, 'noTag' );

	$specialCaseTagInjection = '';
	$specialCaseTagInjectionIsBefore = false;

	if ( count( $nonTags ) != 0 ) {
	$text = $this->wrapText( implode( "", $nonTags ), $tag, $cssClass );
	$this->content .= $text;
	} else {
	$firstOrDefault = false;
	foreach ($this->specialCaseOpeningTags as $x) {
	if ( preg_match( $x, $words[ 0 ] ) ) {
	$firstOrDefault = $x;
	break;
	}
	}
	if ($firstOrDefault) {
	$specialCaseTagInjection = '<ins class="mod">';
	if ($tag == "del") {
	unset( $words[ 0 ] );
	}
	} elseif ( array_search( $words[ 0 ], $this->specialCaseClosingTags ) !== false ) {
	$specialCaseTagInjection = "</ins>";
	$specialCaseTagInjectionIsBefore = true;
	if ($tag == "del") {
	unset( $words[ 0 ] );
	}
	}
	}
	if ( count( $words ) == 0 && count( $specialCaseTagInjection ) == 0 ) {
	break;
	}
	if ($specialCaseTagInjectionIsBefore) {
	$this->content .= $specialCaseTagInjection . implode( "", $this->extractConsecutiveWords( $words, 'tag' ) );
	} else {
	$workTag = $this->extractConsecutiveWords( $words, 'tag' );
	if ( isset( $workTag[ 0 ] ) && $this->isOpeningTag( $workTag[ 0 ] ) && !$this->isClosingTag( $workTag[ 0 ] ) ) {
	if ( strpos( $workTag[ 0 ], 'class=' ) ) {
	$workTag[ 0 ] = str_replace( 'class="', 'class="diffmod ', $workTag[ 0 ] );
	$workTag[ 0 ] = str_replace( "class='", 'class="diffmod ', $workTag[ 0 ] );
	} else {
	$workTag[ 0 ] = str_replace( ">", ' class="diffmod">', $workTag[ 0 ] );
	}
	}
	$this->content .= implode( "", $workTag ) . $specialCaseTagInjection;
	}
	}
	}

	protected function checkCondition($word, $condition)
	{
	return $condition == 'tag' ? $this->isTag( $word ) : !$this->isTag( $word );
	}

	protected function wrapText($text, $tagName, $cssClass)
	{
	return sprintf( '<%1$s class="%2$s">%3$s</%1$s>', $tagName, $cssClass, $text );
	}

	protected function extractConsecutiveWords(&$words, $condition)
	{
	$indexOfFirstTag = null;
	foreach ($words as $i => $word) {
	if ( !$this->checkCondition( $word, $condition ) ) {
	$indexOfFirstTag = $i;
	break;
	}
	}
	if ($indexOfFirstTag !== null) {
	$items = array();
	foreach ($words as $pos => $s) {
	if ($pos >= 0 && $pos < $indexOfFirstTag) {
	$items[] = $s;
	}
	}
	if ($indexOfFirstTag > 0) {
	array_splice( $words, 0, $indexOfFirstTag );
	}

	return $items;
	} else {
	$items = array();
	foreach ($words as $pos => $s) {
	if ( $pos >= 0 && $pos <= count( $words ) ) {
	$items[] = $s;
	}
	}
	array_splice( $words, 0, count( $words ) );

	return $items;
	}
	}

	protected function isTag($item)
	{
	return $this->isOpeningTag( $item ) \|\| $this->isClosingTag( $item );
	}

	protected function isOpeningTag($item)
	{
	return preg_match( "#<[^>]+>\\s*#iU", $item );
	}

	protected function isClosingTag($item)
	{
	return preg_match( "#</[^>]+>\\s*#iU", $item );
	}

	protected function operations()
	{
	$positionInOld = 0;
	$positionInNew = 0;
	$operations = array();
	$matches = $this->matchingBlocks();
	$matches[] = new Match( count( $this->oldWords ), count( $this->newWords ), 0 );
	foreach ($matches as $i => $match) {
	$matchStartsAtCurrentPositionInOld = ( $positionInOld == $match->startInOld );
	$matchStartsAtCurrentPositionInNew = ( $positionInNew == $match->startInNew );
	$action = 'none';

	if ($matchStartsAtCurrentPositionInOld == false && $matchStartsAtCurrentPositionInNew == false) {
	$action = 'replace';
	} elseif ($matchStartsAtCurrentPositionInOld == true && $matchStartsAtCurrentPositionInNew == false) {
	$action = 'insert';
	} elseif ($matchStartsAtCurrentPositionInOld == false && $matchStartsAtCurrentPositionInNew == true) {
	$action = 'delete';
	} else { // This occurs if the first few words are the same in both versions
	$action = 'none';
	}
	if ($action != 'none') {
	$operations[] = new Operation( $action, $positionInOld, $match->startInOld, $positionInNew, $match->startInNew );
	}
	if ( count( $match ) != 0 ) {
	$operations[] = new Operation( 'equal', $match->startInOld, $match->endInOld(), $match->startInNew, $match->endInNew() );
	}
	$positionInOld = $match->endInOld();
	$positionInNew = $match->endInNew();
	}

	return $operations;
	}

	protected function matchingBlocks()
	{
	$matchingBlocks = array();
	$this->findMatchingBlocks( 0, count( $this->oldWords ), 0, count( $this->newWords ), $matchingBlocks );

	return $matchingBlocks;
	}

	protected function findMatchingBlocks($startInOld, $endInOld, $startInNew, $endInNew, &$matchingBlocks)
	{
	$match = $this->findMatch( $startInOld, $endInOld, $startInNew, $endInNew );
	if ($match !== null) {
	if ($startInOld < $match->startInOld && $startInNew < $match->startInNew) {
	$this->findMatchingBlocks( $startInOld, $match->startInOld, $startInNew, $match->startInNew, $matchingBlocks );
	}
	$matchingBlocks[] = $match;
	if ( $match->endInOld() < $endInOld && $match->endInNew() < $endInNew ) {
	$this->findMatchingBlocks( $match->endInOld(), $endInOld, $match->endInNew(), $endInNew, $matchingBlocks );
	}
	}
	}

	protected function stripTagAttributes($word)
	{
	$word = explode( ' ', trim( $word, '<>' ) );

	return '<' . $word[ 0 ] . '>';
	}

	protected function findMatch($startInOld, $endInOld, $startInNew, $endInNew)
	{
	$bestMatchInOld = $startInOld;
	$bestMatchInNew = $startInNew;
	$bestMatchSize = 0;
	$matchLengthAt = array();
	for ($indexInOld = $startInOld; $indexInOld < $endInOld; $indexInOld++) {
	$newMatchLengthAt = array();
	$index = $this->oldWords[ $indexInOld ];
	if ( $this->isTag( $index ) ) {
	$index = $this->stripTagAttributes( $index );
	}
	if ( !isset( $this->wordIndices[ $index ] ) ) {
	$matchLengthAt = $newMatchLengthAt;
	continue;
	}
	foreach ($this->wordIndices[ $index ] as $indexInNew) {
	if ($indexInNew < $startInNew) {
	continue;
	}
	if ($indexInNew >= $endInNew) {
	break;
	}
	$newMatchLength = ( isset( $matchLengthAt[ $indexInNew - 1 ] ) ? $matchLengthAt[ $indexInNew - 1 ] : 0 ) + 1;
	$newMatchLengthAt[ $indexInNew ] = $newMatchLength;
	if ($newMatchLength > $bestMatchSize) {
	$bestMatchInOld = $indexInOld - $newMatchLength + 1;
	$bestMatchInNew = $indexInNew - $newMatchLength + 1;
	$bestMatchSize = $newMatchLength;
	}
	}
	$matchLengthAt = $newMatchLengthAt;
	}

	// Skip match if none found or match consists only of whitespace
	if ($bestMatchSize != 0 &&
	(
	!$this->isGroupDiffs() \|\|
	!preg_match('/^\s+$/', implode('', array_slice($this->oldWords, $bestMatchInOld, $bestMatchSize)))
	)
	) {
	return new Match($bestMatchInOld, $bestMatchInNew, $bestMatchSize);
	}

	return null;
	}
	}

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