silverstripe-framework/src/View/Parsers/Diff.php

<?php

namespace SilverStripe\View\Parsers;


use InvalidArgumentException;
use SilverStripe\Core\Convert;
use SilverStripe\Core\Injector\Injector;

require_once 'difflib/difflib.php';

/**
 * Class representing a 'diff' between two sequences of strings.
 */
class Diff extends \Diff
{
	public static $html_cleaner_class = null;

	/**
	 *  Attempt to clean invalid HTML, which messes up diffs.
	 *  This cleans code if possible, using an instance of HTMLCleaner
	 *
	 *  NB: By default, only extremely simple tidying is performed,
	 *  by passing through DomDocument::loadHTML and saveXML
	 *
	 * @param string $content HTML content
	 * @param HTMLCleaner $cleaner Optional instance of a HTMLCleaner class to
	 *    use, overriding self::$html_cleaner_class
	 * @return mixed|string
	 */
	public static function cleanHTML($content, $cleaner = null) {
		if (!$cleaner) {
			if (self::$html_cleaner_class && class_exists(self::$html_cleaner_class)) {
				$cleaner = Injector::inst()->create(self::$html_cleaner_class);
			} else {
				//load cleaner if the dependent class is available
				$cleaner = HTMLCleaner::inst();
			}
		}

		if ($cleaner) {
			$content = $cleaner->cleanHTML($content);
		} else {
			// At most basic level of cleaning, use DOMDocument to save valid XML.
			$doc = Injector::inst()->create('HTMLValue', $content);
			$content = $doc->getContent();
		}

		// Remove empty <ins /> and <del /> tags because browsers hate them
		$content = preg_replace('/<(ins|del)[^>]*\/>/','', $content);

		return $content;
	}

	/**
	 * @param string $from
	 * @param string $to
	 * @param bool $escape
	 * @return string
	 */
	public static function compareHTML($from, $to, $escape = false) {
		// First split up the content into words and tags
		$set1 = self::getHTMLChunks($from);
		$set2 = self::getHTMLChunks($to);

		// Diff that
		$diff = new Diff($set1, $set2);

		$tagStack[1] = $tagStack[2] = 0;
		$rechunked[1] = $rechunked[2] = array();

		// Go through everything, converting edited tags (and their content) into single chunks.  Otherwise
		// the generated HTML gets crusty
		foreach($diff->edits as $edit) {
			$lookForTag = false;
			$stuffFor = [];
			switch($edit->type) {
				case 'copy':
					$lookForTag = false;
					$stuffFor[1] = $edit->orig;
					$stuffFor[2] = $edit->orig;
					break;

				case 'change':
					$lookForTag = true;
					$stuffFor[1] = $edit->orig;
					$stuffFor[2] = $edit->final;
					break;

				case 'add':
					$lookForTag = true;
					$stuffFor[1] = null;
					$stuffFor[2] = $edit->final;
					break;

				case 'delete':
					$lookForTag = true;
					$stuffFor[1] = $edit->orig;
					$stuffFor[2] = null;
					break;
			}

			foreach($stuffFor as $listName => $chunks) {
				if($chunks) {
					foreach($chunks as $item) {
						// $tagStack > 0 indicates that we should be tag-building
						if ($tagStack[$listName]) {
							$rechunked[$listName][sizeof($rechunked[$listName])-1] .= ' ' . $item;
						} else {
							$rechunked[$listName][] = $item;
						}

						if ($lookForTag
							&& !$tagStack[$listName]
							&& isset($item[0])
							&& $item[0] == "<"
							&& substr($item,0,2) != "</"
						) {
							$tagStack[$listName] = 1;
						} else if($tagStack[$listName]) {
							if(substr($item,0,2) == "</") {
								$tagStack[$listName]--;
							} else if(isset($item[0]) && $item[0] == "<") {
								$tagStack[$listName]++;
							}
						}
					}
				}
			}
		}

		// Diff the re-chunked data, turning it into maked up HTML
		$diff = new Diff($rechunked[1], $rechunked[2]);
		$content = '';
		foreach($diff->edits as $edit) {
			$orig = ($escape) ? Convert::raw2xml($edit->orig) : $edit->orig;
			$final = ($escape) ? Convert::raw2xml($edit->final) : $edit->final;

			switch($edit->type) {
				case 'copy':
					$content .= " " . implode(" ", $orig) . " ";
					break;

				case 'change':
					$content .= " <ins>" . implode(" ", $final) . "</ins> ";
					$content .= " <del>" . implode(" ", $orig) . "</del> ";
					break;

				case 'add':
					$content .= " <ins>" . implode(" ", $final) . "</ins> ";
					break;

				case 'delete':
					$content .= " <del>" . implode(" ", $orig) . "</del> ";
					break;
			}
		}

		return self::cleanHTML($content);
	}

	/**
	 * @param string|array $content If passed as an array, values will be concatenated with a comma.
	 * @return array
	 */
	public static function getHTMLChunks($content) {
		if($content && !is_string($content) && !is_array($content) && !is_numeric($content)) {
			throw new InvalidArgumentException('$content parameter needs to be a string or array');
		}
		if(is_array($content)) {
			$content = implode(',', $content);
		}

		$content = str_replace(array("&nbsp;", "<", ">"), array(" "," <", "> "), $content);
		$candidateChunks = preg_split("/[\t\r\n ]+/", $content);
		$chunks = [];
		while($chunk = each($candidateChunks)) {
			$item = $chunk['value'];
			if(isset($item[0]) && $item[0] == "<") {
				$newChunk = $item;
				while($item[strlen($item)-1] != ">") {
					$chunk = each($candidateChunks);
					$item = $chunk['value'];
					$newChunk .= ' ' . $item;
				}
				$chunks[] = $newChunk;
			} else {
				$chunks[] = $item;
			}
		}
		return $chunks;
	}

}