wikimedia/mediawiki-core

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includes/tidy/RemexCompatMunger.php

Summary

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5 days
Test Coverage
<?php

namespace MediaWiki\Tidy;

use RemexHtml\HTMLData;
use RemexHtml\Serializer\Serializer;
use RemexHtml\Serializer\SerializerNode;
use RemexHtml\Tokenizer\Attributes;
use RemexHtml\Tokenizer\PlainAttributes;
use RemexHtml\TreeBuilder\Element;
use RemexHtml\TreeBuilder\TreeBuilder;
use RemexHtml\TreeBuilder\TreeHandler;

/**
 * @internal
 */
class RemexCompatMunger implements TreeHandler {
    private static $onlyInlineElements = [
        "a" => true,
        "abbr" => true,
        "acronym" => true,
        "applet" => true,
        "b" => true,
        "basefont" => true,
        "bdo" => true,
        "big" => true,
        "br" => true,
        "button" => true,
        "cite" => true,
        "code" => true,
        "del" => true,
        "dfn" => true,
        "em" => true,
        "font" => true,
        "i" => true,
        "iframe" => true,
        "img" => true,
        "input" => true,
        "ins" => true,
        "kbd" => true,
        "label" => true,
        "legend" => true,
        "map" => true,
        "object" => true,
        "param" => true,
        "q" => true,
        "rb" => true,
        "rbc" => true,
        "rp" => true,
        "rt" => true,
        "rtc" => true,
        "ruby" => true,
        "s" => true,
        "samp" => true,
        "select" => true,
        "small" => true,
        "span" => true,
        "strike" => true,
        "strong" => true,
        "sub" => true,
        "sup" => true,
        "textarea" => true,
        "tt" => true,
        "u" => true,
        "var" => true,
        // Those defined in tidy.conf
        "video" => true,
        "audio" => true,
        "bdi" => true,
        "data" => true,
        "time" => true,
        "mark" => true,
    ];

    /**
     * For the purposes of this class, "metadata" elements are those that
     * should neither trigger p-wrapping nor stop an outer p-wrapping,
     * typically those that are themselves invisible in a browser's rendering.
     * This isn't a complete list, it's just the tags that we're likely to
     * encounter in practice.
     * @var array
     */
    private static $metadataElements = [
        'style' => true,
        'script' => true,
        'link' => true,
        'meta' => true,
    ];

    private static $formattingElements = [
        'a' => true,
        'b' => true,
        'big' => true,
        'code' => true,
        'em' => true,
        'font' => true,
        'i' => true,
        'nobr' => true,
        's' => true,
        'small' => true,
        'strike' => true,
        'strong' => true,
        'tt' => true,
        'u' => true,
    ];

    /** @var Serializer */
    private $serializer;

    /** @var bool */
    private $trace;

    /**
     * @param Serializer $serializer
     * @param bool $trace
     */
    public function __construct( Serializer $serializer, $trace = false ) {
        $this->serializer = $serializer;
        $this->trace = $trace;
    }

    public function startDocument( $fragmentNamespace, $fragmentName ) {
        $this->serializer->startDocument( $fragmentNamespace, $fragmentName );
        $root = $this->serializer->getRootNode();
        $root->snData = new RemexMungerData;
        $root->snData->needsPWrapping = true;
    }

    public function endDocument( $pos ) {
        $this->serializer->endDocument( $pos );
    }

    private function getParentForInsert( $preposition, $refElement ) {
        if ( $preposition === TreeBuilder::ROOT ) {
            return [ $this->serializer->getRootNode(), null ];
        } elseif ( $preposition === TreeBuilder::BEFORE ) {
            $refNode = $refElement->userData;
            return [ $this->serializer->getParentNode( $refNode ), $refNode ];
        } else {
            $refNode = $refElement->userData;
            $refData = $refNode->snData;
            if ( $refData->currentCloneElement ) {
                // Follow a chain of clone links if necessary
                $origRefData = $refData;
                while ( $refData->currentCloneElement ) {
                    $refElement = $refData->currentCloneElement;
                    $refNode = $refElement->userData;
                    $refData = $refNode->snData;
                }
                // Cache the end of the chain in the requested element
                $origRefData->currentCloneElement = $refElement;
            } elseif ( $refData->childPElement ) {
                $refElement = $refData->childPElement;
                $refNode = $refElement->userData;
            }
            return [ $refNode, $refNode ];
        }
    }

    /**
     * Insert a p-wrapper
     *
     * @param SerializerNode $parent
     * @param int $sourceStart
     * @return SerializerNode
     */
    private function insertPWrapper( SerializerNode $parent, $sourceStart ) {
        $pWrap = new Element( HTMLData::NS_HTML, 'mw:p-wrap', new PlainAttributes );
        $this->serializer->insertElement( TreeBuilder::UNDER, $parent, $pWrap, false,
            $sourceStart, 0 );
        $data = new RemexMungerData;
        $data->isPWrapper = true;
        $data->wrapBaseNode = $parent;
        $pWrap->userData->snData = $data;
        $parent->snData->childPElement = $pWrap;
        return $pWrap->userData;
    }

    public function characters( $preposition, $refElement, $text, $start, $length,
        $sourceStart, $sourceLength
    ) {
        $isBlank = strspn( $text, "\t\n\f\r ", $start, $length ) === $length;

        list( $parent, $refNode ) = $this->getParentForInsert( $preposition, $refElement );
        $parentData = $parent->snData;

        if ( $preposition === TreeBuilder::UNDER ) {
            if ( $parentData->needsPWrapping && !$isBlank ) {
                // Add a p-wrapper for bare text under body/blockquote
                $refNode = $this->insertPWrapper( $refNode, $sourceStart );
                $parent = $refNode;
                $parentData = $parent->snData;
            } elseif ( $parentData->isSplittable && !$parentData->ancestorPNode ) {
                // The parent is splittable and in block mode, so split the tag stack
                $refNode = $this->splitTagStack( $refNode, true, $sourceStart );
                $parent = $refNode;
                $parentData = $parent->snData;
            }
        }

        if ( !$isBlank ) {
            // Non-whitespace characters detected
            $parentData->nonblankNodeCount++;
        }
        $this->serializer->characters( $preposition, $refNode, $text, $start,
            $length, $sourceStart, $sourceLength );
    }

    private function trace( $msg ) {
        if ( $this->trace ) {
            wfDebug( "[RCM] $msg" );
        }
    }

    /**
     * Insert or reparent an element. Create p-wrappers or split the tag stack
     * as necessary.
     *
     * Consider the following insertion locations. The parent may be:
     *
     *   - A: A body or blockquote (!!needsPWrapping)
     *   - B: A p-wrapper (!!isPWrapper)
     *   - C: A descendant of a p-wrapper (!!ancestorPNode)
     *     - CS: With splittable formatting elements in the stack region up to
     *       the p-wrapper
     *     - CU: With one or more unsplittable elements in the stack region up
     *       to the p-wrapper
     *   - D: Not a descendant of a p-wrapper (!ancestorNode)
     *     - DS: With splittable formatting elements in the stack region up to
     *       the body or blockquote
     *     - DU: With one or more unsplittable elements in the stack region up
     *       to the body or blockquote
     *
     * And consider that we may insert two types of element:
     *   - b: block
     *   - i: inline
     *
     * We handle the insertion as follows:
     *
     *   - A/i: Create a p-wrapper, insert under it
     *   - A/b: Insert as normal
     *   - B/i: Insert as normal
     *   - B/b: Close the p-wrapper, insert under the body/blockquote (wrap
     *     base) instead)
     *   - C/i: Insert as normal
     *   - CS/b: Split the tag stack, insert the block under cloned formatting
     *     elements which have the wrap base (the parent of the p-wrap) as
     *     their ultimate parent.
     *   - CU/b: Disable the p-wrap, by reparenting the currently open child
     *     of the p-wrap under the p-wrap's parent. Then insert the block as
     *     normal.
     *   - D/b: Insert as normal
     *   - DS/i: Split the tag stack, creating a new p-wrapper as the ultimate
     *     parent of the formatting elements thus cloned. The parent of the
     *     p-wrapper is the body or blockquote.
     *   - DU/i: Insert as normal
     *
     * FIXME: fostering ($preposition == BEFORE) is mostly done by inserting as
     * normal, the full algorithm is not followed.
     *
     * @param int $preposition
     * @param Element|SerializerNode|null $refElement
     * @param Element $element
     * @param bool $void
     * @param int $sourceStart
     * @param int $sourceLength
     */
    public function insertElement( $preposition, $refElement, Element $element, $void,
        $sourceStart, $sourceLength
    ) {
        list( $parent, $newRef ) = $this->getParentForInsert( $preposition, $refElement );
        $parentData = $parent->snData;
        $elementName = $element->htmlName;

        $inline = isset( self::$onlyInlineElements[$elementName] );
        $under = $preposition === TreeBuilder::UNDER;
        $elementToEnd = null;

        if ( isset( self::$metadataElements[$elementName] ) ) {
            // The element is a metadata element, that we allow to appear in
            // both inline and block contexts.
            $this->trace( 'insert metadata' );
        } elseif ( $under && $parentData->isPWrapper && !$inline ) {
            // [B/b] The element is non-inline and the parent is a p-wrapper,
            // close the parent and insert into its parent instead
            $this->trace( 'insert B/b' );
            $newParent = $this->serializer->getParentNode( $parent );
            $parent = $newParent;
            $parentData = $parent->snData;
            $parentData->childPElement = null;
            $newRef = $refElement->userData;
        } elseif ( $under && $parentData->isSplittable
            && (bool)$parentData->ancestorPNode !== $inline
        ) {
            // [CS/b, DS/i] The parent is splittable and the current element is
            // inline in block context, or if the current element is a block
            // under a p-wrapper, split the tag stack.
            $this->trace( $inline ? 'insert DS/i' : 'insert CS/b' );
            $newRef = $this->splitTagStack( $newRef, $inline, $sourceStart );
            $parent = $newRef;
            $parentData = $parent->snData;
        } elseif ( $under && $parentData->needsPWrapping && $inline ) {
            // [A/i] If the element is inline and we are in body/blockquote,
            // we need to create a p-wrapper
            $this->trace( 'insert A/i' );
            $newRef = $this->insertPWrapper( $newRef, $sourceStart );
            $parent = $newRef;
            $parentData = $parent->snData;
        } elseif ( $parentData->ancestorPNode && !$inline ) {
            // [CU/b] If the element is non-inline and (despite attempting to
            // split above) there is still an ancestor p-wrap, disable that
            // p-wrap
            $this->trace( 'insert CU/b' );
            $this->disablePWrapper( $parent, $sourceStart );
        } else {
            // [A/b, B/i, C/i, D/b, DU/i] insert as normal
            $this->trace( 'insert normal' );
        }

        // An element with element children is a non-blank element
        $parentData->nonblankNodeCount++;

        // Insert the element downstream and so initialise its userData
        $this->serializer->insertElement( $preposition, $newRef,
            $element, $void, $sourceStart, $sourceLength );

        // Initialise snData
        if ( !$element->userData->snData ) {
            $elementData = $element->userData->snData = new RemexMungerData;
        } else {
            $elementData = $element->userData->snData;
        }
        if ( ( $parentData->isPWrapper || $parentData->isSplittable )
            && isset( self::$formattingElements[$elementName] )
        ) {
            $elementData->isSplittable = true;
        }
        if ( $parentData->isPWrapper ) {
            $elementData->ancestorPNode = $parent;
        } elseif ( $parentData->ancestorPNode ) {
            $elementData->ancestorPNode = $parentData->ancestorPNode;
        }
        if ( $parentData->wrapBaseNode ) {
            $elementData->wrapBaseNode = $parentData->wrapBaseNode;
        } elseif ( $parentData->needsPWrapping ) {
            $elementData->wrapBaseNode = $parent;
        }
        if ( $elementName === 'body'
            || $elementName === 'blockquote'
            || $elementName === 'html'
        ) {
            $elementData->needsPWrapping = true;
        }
    }

    /**
     * Clone nodes in a stack range and return the new parent
     *
     * @param SerializerNode $parentNode
     * @param bool $inline
     * @param int $pos The source position
     * @return SerializerNode
     */
    private function splitTagStack( SerializerNode $parentNode, $inline, $pos ) {
        $parentData = $parentNode->snData;
        $wrapBase = $parentData->wrapBaseNode;
        $pWrap = $parentData->ancestorPNode;
        if ( !$pWrap ) {
            $cloneEnd = $wrapBase;
        } else {
            $cloneEnd = $parentData->ancestorPNode;
        }

        $serializer = $this->serializer;
        $node = $parentNode;
        $root = $serializer->getRootNode();
        $nodes = [];
        $removableNodes = [];
        while ( $node !== $cloneEnd ) {
            $nextParent = $serializer->getParentNode( $node );
            if ( $nextParent === $root ) {
                throw new \Exception( 'Did not find end of clone range' );
            }
            $nodes[] = $node;
            if ( $node->snData->nonblankNodeCount === 0 ) {
                $removableNodes[] = $node;
                $nextParent->snData->nonblankNodeCount--;
            }
            $node = $nextParent;
        }

        if ( $inline ) {
            $pWrap = $this->insertPWrapper( $wrapBase, $pos );
            $node = $pWrap;
        } else {
            if ( $pWrap ) {
                // End the p-wrap which was open, cancel the diversion
                $wrapBase->snData->childPElement = null;
            }
            $pWrap = null;
            $node = $wrapBase;
        }

        for ( $i = count( $nodes ) - 1; $i >= 0; $i-- ) {
            $oldNode = $nodes[$i];
            $oldData = $oldNode->snData;
            $nodeParent = $node;
            $element = new Element( $oldNode->namespace, $oldNode->name, $oldNode->attrs );
            $this->serializer->insertElement( TreeBuilder::UNDER, $nodeParent,
                $element, false, $pos, 0 );
            $oldData->currentCloneElement = $element;

            $newNode = $element->userData;
            $newData = $newNode->snData = new RemexMungerData;
            if ( $pWrap ) {
                $newData->ancestorPNode = $pWrap;
            }
            $newData->isSplittable = true;
            $newData->wrapBaseNode = $wrapBase;
            $newData->isPWrapper = $oldData->isPWrapper;

            $nodeParent->snData->nonblankNodeCount++;

            $node = $newNode;
        }
        foreach ( $removableNodes as $rNode ) {
            $fakeElement = new Element( $rNode->namespace, $rNode->name, $rNode->attrs );
            $fakeElement->userData = $rNode;
            $this->serializer->removeNode( $fakeElement, $pos );
        }
        return $node;
    }

    /**
     * Find the ancestor of $node which is a child of a p-wrapper, and
     * reparent that node so that it is placed after the end of the p-wrapper
     * @param SerializerNode $node
     * @param int $sourceStart
     */
    private function disablePWrapper( SerializerNode $node, $sourceStart ) {
        $nodeData = $node->snData;
        $pWrapNode = $nodeData->ancestorPNode;
        $newParent = $this->serializer->getParentNode( $pWrapNode );
        if ( $pWrapNode !== $this->serializer->getLastChild( $newParent ) ) {
            // Fostering or something? Abort!
            return;
        }

        $nextParent = $node;
        do {
            $victim = $nextParent;
            $victim->snData->ancestorPNode = null;
            $nextParent = $this->serializer->getParentNode( $victim );
        } while ( $nextParent !== $pWrapNode );

        // Make a fake Element to use in a reparenting operation
        $victimElement = new Element( $victim->namespace, $victim->name, $victim->attrs );
        $victimElement->userData = $victim;

        // Reparent
        $this->serializer->insertElement( TreeBuilder::UNDER, $newParent, $victimElement,
            false, $sourceStart, 0 );

        // Decrement nonblank node count
        $pWrapNode->snData->nonblankNodeCount--;

        // Cancel the diversion so that no more elements are inserted under this p-wrap
        $newParent->snData->childPElement = null;
    }

    public function endTag( Element $element, $sourceStart, $sourceLength ) {
        $data = $element->userData->snData;
        if ( $data->childPElement ) {
            $this->endTag( $data->childPElement, $sourceStart, 0 );
        }
        $this->serializer->endTag( $element, $sourceStart, $sourceLength );
        $element->userData->snData = null;
        $element->userData = null;
    }

    public function doctype( $name, $public, $system, $quirks, $sourceStart, $sourceLength ) {
        $this->serializer->doctype( $name, $public, $system, $quirks,
            $sourceStart, $sourceLength );
    }

    public function comment( $preposition, $refElement, $text, $sourceStart, $sourceLength ) {
        list( , $refNode ) = $this->getParentForInsert( $preposition, $refElement );
        $this->serializer->comment( $preposition, $refNode, $text, $sourceStart, $sourceLength );
    }

    public function error( $text, $pos ) {
        $this->serializer->error( $text, $pos );
    }

    public function mergeAttributes( Element $element, Attributes $attrs, $sourceStart ) {
        $this->serializer->mergeAttributes( $element, $attrs, $sourceStart );
    }

    public function removeNode( Element $element, $sourceStart ) {
        $this->serializer->removeNode( $element, $sourceStart );
    }

    public function reparentChildren( Element $element, Element $newParent, $sourceStart ) {
        $self = $element->userData;
        if ( $self->snData->childPElement ) {
            // Reparent under the p-wrapper instead, so that e.g.
            //   <blockquote><mw:p-wrap>...</mw:p-wrap></blockquote>
            // becomes
            //   <blockquote><mw:p-wrap><i>...</i></mw:p-wrap></blockquote>

            // The formatting element should not be the parent of the p-wrap.
            // Without this special case, the insertElement() of the <i> below
            // would be diverted into the p-wrapper, causing infinite recursion
            // (T178632)
            $this->reparentChildren( $self->snData->childPElement, $newParent, $sourceStart );
            return;
        }

        $children = $self->children;
        $self->children = [];
        $this->insertElement( TreeBuilder::UNDER, $element, $newParent, false, $sourceStart, 0 );
        $newParentNode = $newParent->userData;
        $newParentId = $newParentNode->id;
        foreach ( $children as $child ) {
            if ( is_object( $child ) ) {
                $this->trace( "reparent <{$child->name}>" );
                $child->parentId = $newParentId;
            }
        }
        $newParentNode->children = $children;
    }
}