CommentParser.php: Use tree walking instead of XPath

This is similar to what the JS version does.

The TreeWalker and NodeFilter classes are adapted from
https://github.com/Krinkle/dom-TreeWalker-polyfill
(MIT license).

This makes #getComments twice as fast on en-big-oldparser.html

Change-Id: I2441f33e6e7bad753ac830d277e6a2e81ee8c93d

includes/CommentParser.php

@@ -103,21 +103,16 @@ class CommentParser {
 	 * @return DOMNode
 	 */
 	private function nextInterestingLeafNode( DOMNode $node, DOMElement $rootNode ) : DOMNode {
-		$n = $node;
-		do {
-			if ( $n->firstChild && ( $node === $rootNode || $n !== $node ) ) {
-				$n = $n->firstChild;
-			} elseif ( $n->nextSibling ) {
-				$n = $n->nextSibling;
-			} else {
-				while ( $n && $n !== $rootNode && !$n->nextSibling ) {
-					$n = $n->parentNode;
+		$treeWalker = new TreeWalker(
+			$rootNode,
+			NodeFilter::SHOW_ELEMENT | NodeFilter::SHOW_TEXT,
+			function ( $n ) use ( $node, $rootNode ) {
+				// Ignore this node and its descendants
+				// (unless it's the root node, this is a special case for "fakeHeading" handling)
+				if ( $node !== $rootNode && ( $n === $node || $n->parentNode === $node ) ) {
+					return NodeFilter::FILTER_REJECT;
 				}
-				$n = $n->nextSibling;
-			}
-
-			if (
-				$n && (
+				if (
 					(
 						$n->nodeType === XML_TEXT_NODE &&
 						CommentUtils::htmlTrim( $n->nodeValue ) !== ''
@@ -127,12 +122,18 @@ class CommentParser {
 						CommentUtils::htmlTrim( $n->nodeValue ) !== ''
 					) ||
 					( $n->nodeType === XML_ELEMENT_NODE && !$n->firstChild )
-				)
-			) {
-				return $n;
+				) {
+					return NodeFilter::FILTER_ACCEPT;
+				}
+				return NodeFilter::FILTER_SKIP;
 			}
-		} while ( $n && $n !== $rootNode );
-		throw new MWException( 'nextInterestingLeafNode not found' );
+		);
+		$treeWalker->currentNode = $node;
+		$treeWalker->nextNode();
+		if ( !$treeWalker->currentNode ) {
+			throw new MWException( 'nextInterestingLeafNode not found' );
+		}
+		return $treeWalker->currentNode;
 	}
 
 	/**
@@ -618,6 +619,21 @@ class CommentParser {
 		return [ $sigNodes, $sigUsername ];
 	}
 
+	/**
+	 * Callback for TreeWalker that will skip over nodes where we don't want to detect
+	 * comments (or section headings).
+	 *
+	 * @param DOMNode $node
+	 * @return int Appropriate NodeFilter constant
+	 */
+	public static function acceptOnlyNodesAllowingComments( DOMNode $node ) {
+		// The table of contents has a heading that gets erroneously detected as a section
+		if ( $node instanceof DOMElement && $node->getAttribute( 'id' ) === 'toc' ) {
+			return NodeFilter::FILTER_REJECT;
+		}
+		return NodeFilter::FILTER_ACCEPT;
+	}
+
 	/**
 	 * Find all timestamps within a DOM subtree.
 	 *
@@ -710,9 +726,6 @@ class CommentParser {
 	public function getComments( DOMElement $rootNode ) : array {
 		$timestamps = $this->findTimestamps( $rootNode );
 
-		$xpath = new DOMXPath( $rootNode->ownerDocument );
-		$allNodes = $xpath->query( '//text()|//node()', $rootNode );
-		$tocNode = $rootNode->ownerDocument->getElementById( 'toc' );
 		$comments = [];
 		$dfParser = $this->getLocalTimestampParser();
 
@@ -723,17 +736,20 @@ class CommentParser {
 		$curComment = $fakeHeading;
 
 		$nextTimestamp = 0;
-		foreach ( $allNodes as $node ) {
-			// Skip nodes inside <div id="toc">
-			if ( $tocNode && CommentUtils::contains( $tocNode, $node ) ) {
-				continue;
-			}
-
+		$treeWalker = new TreeWalker(
+			$rootNode,
+			NodeFilter::SHOW_ELEMENT | NodeFilter::SHOW_TEXT,
+			[ self::class, 'acceptOnlyNodesAllowingComments' ]
+		);
+		while ( $node = $treeWalker->nextNode() ) {
 			if ( $node->nodeType === XML_ELEMENT_NODE && preg_match( '/^h[1-6]$/i', $node->nodeName ) ) {
 				$range = new ImmutableRange( $node, 0, $node, $node->childNodes->length );
 				$curComment = new HeadingItem( $range );
 				$comments[] = $curComment;
-			} elseif ( isset( $timestamps[$nextTimestamp] ) && $node === $timestamps[$nextTimestamp][0] ) {
+			} elseif (
+				$node instanceof DOMText &&
+				isset( $timestamps[$nextTimestamp] ) && $node === $timestamps[$nextTimestamp][0]
+			) {
 				$warnings = [];
 				$foundSignature = $this->findSignature( $node, $curComment->getRange()->endContainer );
 				$author = $foundSignature[1];

includes/NodeFilter.php

@@ -0,0 +1,60 @@
+<?php
+
+namespace MediaWiki\Extension\DiscussionTools;
+
+use DOMNode;
+use Exception;
+
+/**
+ * Partial implementation of W3 DOM4 NodeFilter interface.
+ *
+ * See also:
+ * - https://dom.spec.whatwg.org/#interface-nodefilter
+ *
+ * Adapted from https://github.com/Krinkle/dom-TreeWalker-polyfill/blob/master/src/TreeWalker-polyfill.js
+ */
+class NodeFilter {
+
+	// Constants for acceptNode()
+	public const FILTER_ACCEPT = 1;
+	public const FILTER_REJECT = 2;
+	public const FILTER_SKIP = 3;
+
+	// Constants for whatToShow
+	public const SHOW_ALL = 0xFFFFFFFF;
+	public const SHOW_ELEMENT = 0x1;
+	public const SHOW_ATTRIBUTE = 0x2;
+	public const SHOW_TEXT = 0x4;
+	public const SHOW_CDATA_SECTION = 0x8;
+	public const SHOW_ENTITY_REFERENCE = 0x10;
+	public const SHOW_ENTITY = 0x20;
+	public const SHOW_PROCESSING_INSTRUCTION = 0x40;
+	public const SHOW_COMMENT = 0x80;
+	public const SHOW_DOCUMENT = 0x100;
+	public const SHOW_DOCUMENT_TYPE = 0x200;
+	public const SHOW_DOCUMENT_FRAGMENT = 0x400;
+	public const SHOW_NOTATION = 0x800;
+
+	public $filter;
+
+	private $active = false;
+
+	/**
+	 * See https://dom.spec.whatwg.org/#dom-nodefilter-acceptnode
+	 *
+	 * @param DOMNode $node
+	 * @return int Constant NodeFilter::FILTER_ACCEPT,
+	 *  NodeFilter::FILTER_REJECT or NodeFilter::FILTER_SKIP.
+	 */
+	public function acceptNode( $node ) {
+		if ( $this->active ) {
+			throw new Exception( 'DOMException: INVALID_STATE_ERR' );
+		}
+
+		$this->active = true;
+		$result = call_user_func( $this->filter, $node );
+		$this->active = false;
+
+		return $result;
+	}
+}

includes/TreeWalker.php

@@ -0,0 +1,133 @@
+<?php
+
+namespace MediaWiki\Extension\DiscussionTools;
+
+use DOMNode;
+use Exception;
+
+/**
+ * Partial implementation of W3 DOM4 TreeWalker interface.
+ *
+ * See also:
+ * - https://dom.spec.whatwg.org/#interface-treewalker
+ *
+ * Adapted from https://github.com/Krinkle/dom-TreeWalker-polyfill/blob/master/src/TreeWalker-polyfill.js
+ */
+class TreeWalker {
+
+	public $root;
+	public $whatToShow;
+	public $currentNode;
+	public $filter;
+
+	/**
+	 * See https://dom.spec.whatwg.org/#concept-node-filter
+	 *
+	 * @param TreeWalker $tw
+	 * @param DOMNode $node
+	 * @return int Constant NodeFilter::FILTER_ACCEPT,
+	 *  NodeFilter::FILTER_REJECT or NodeFilter::FILTER_SKIP.
+	 */
+	private function nodeFilter( TreeWalker $tw, DOMNode $node ) {
+		// Maps nodeType to whatToShow
+		if ( !( ( ( 1 << ( $node->nodeType - 1 ) ) & $tw->whatToShow ) ) ) {
+			return NodeFilter::FILTER_SKIP;
+		}
+
+		if ( $tw->filter === null ) {
+			return NodeFilter::FILTER_ACCEPT;
+		}
+
+		return $tw->filter->acceptNode( $node );
+	}
+
+	/**
+	 * Based on WebKit's NodeTraversal::nextSkippingChildren
+	 * https://trac.webkit.org/browser/trunk/Source/WebCore/dom/NodeTraversal.h?rev=137221#L103
+	 *
+	 * @param DOMNode $node
+	 * @param DOMNode $stayWithin
+	 * @return DOMNode|null
+	 */
+	private function nextSkippingChildren( DOMNode $node, DOMNode $stayWithin ) : ?DOMNode {
+		if ( $node === $stayWithin ) {
+			return null;
+		}
+		if ( $node->nextSibling !== null ) {
+			return $node->nextSibling;
+		}
+
+		/**
+		 * Based on WebKit's NodeTraversal::nextAncestorSibling
+		 * https://trac.webkit.org/browser/trunk/Source/WebCore/dom/NodeTraversal.cpp?rev=137221#L43
+		 */
+		while ( $node->parentNode !== null ) {
+			$node = $node->parentNode;
+			if ( $node === $stayWithin ) {
+				return null;
+			}
+			if ( $node->nextSibling !== null ) {
+				return $node->nextSibling;
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * See https://dom.spec.whatwg.org/#interface-treewalker
+	 *
+	 * @param DOMNode $root
+	 * @param int|null $whatToShow
+	 * @param callable|null $filter
+	 * @throws Exception
+	 */
+	public function __construct( DOMNode $root, $whatToShow = null, callable $filter = null ) {
+		if ( !$root->nodeType ) {
+			throw new Exception( 'DOMException: NOT_SUPPORTED_ERR' );
+		}
+
+		$this->root = $root;
+		$this->whatToShow = (int)$whatToShow ?: 0;
+
+		$this->currentNode = $root;
+
+		if ( !$filter ) {
+			$this->filter = null;
+		} else {
+			$this->filter = new NodeFilter();
+			$this->filter->filter = $filter;
+		}
+	}
+
+	/**
+	 * See https://dom.spec.whatwg.org/#dom-treewalker-nextnode
+	 *
+	 * @return DOMNode|null The current node
+	 */
+	public function nextNode() : ?DOMNode {
+		$node = $this->currentNode;
+		$result = NodeFilter::FILTER_ACCEPT;
+
+		while ( true ) {
+			while ( $result !== NodeFilter::FILTER_REJECT && $node->firstChild !== null ) {
+				$node = $node->firstChild;
+				$result = $this->nodeFilter( $this, $node );
+				if ( $result === NodeFilter::FILTER_ACCEPT ) {
+					$this->currentNode = $node;
+					return $node;
+				}
+			}
+			$following = $this->nextSkippingChildren( $node, $this->root );
+			if ( $following !== null ) {
+				$node = $following;
+			} else {
+				return null;
+			}
+			$result = $this->nodeFilter( $this, $node );
+			if ( $result === NodeFilter::FILTER_ACCEPT ) {
+				$this->currentNode = $node;
+				return $node;
+			}
+		}
+	}
+}