Preprocessor_DOM.php

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<?php
// @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps
class Preprocessor_DOM extends Preprocessor {
    // @codingStandardsIgnoreEnd

    public $parser;

    public $memoryLimit;

    const CACHE_PREFIX = 'preprocess-xml';

    public function __construct( $parser ) {
        $this->parser = $parser;
        $mem = ini_get( 'memory_limit' );
        $this->memoryLimit = false;
        if ( strval( $mem ) !== '' && $mem != -1 ) {
            if ( preg_match( '/^\d+$/', $mem ) ) {
                $this->memoryLimit = $mem;
            } elseif ( preg_match( '/^(\d+)M$/i', $mem, $m ) ) {
                $this->memoryLimit = $m[1] * 1048576;
            }
        }
    }

    public function newFrame() {
        return new PPFrame_DOM( $this );
    }

    public function newCustomFrame( $args ) {
        return new PPCustomFrame_DOM( $this, $args );
    }

    public function newPartNodeArray( $values ) {
        // NOTE: DOM manipulation is slower than building & parsing XML! (or so Tim sais)
        $xml = "<list>";

        foreach ( $values as $k => $val ) {
            if ( is_int( $k ) ) {
                $xml .= "<part><name index=\"$k\"/><value>"
                    . htmlspecialchars( $val ) . "</value></part>";
            } else {
                $xml .= "<part><name>" . htmlspecialchars( $k )
                    . "</name>=<value>" . htmlspecialchars( $val ) . "</value></part>";
            }
        }

        $xml .= "</list>";

        $dom = new DOMDocument();
        MediaWiki\suppressWarnings();
        $result = $dom->loadXML( $xml );
        MediaWiki\restoreWarnings();
        if ( !$result ) {
            // Try running the XML through UtfNormal to get rid of invalid characters
            $xml = UtfNormal\Validator::cleanUp( $xml );
            // 1 << 19 == XML_PARSE_HUGE, needed so newer versions of libxml2
            // don't barf when the XML is >256 levels deep
            $result = $dom->loadXML( $xml, 1 << 19 );
        }

        if ( !$result ) {
            throw new MWException( 'Parameters passed to ' . __METHOD__ . ' result in invalid XML' );
        }

        $root = $dom->documentElement;
        $node = new PPNode_DOM( $root->childNodes );
        return $node;
    }

    public function memCheck() {
        if ( $this->memoryLimit === false ) {
            return true;
        }
        $usage = memory_get_usage();
        if ( $usage > $this->memoryLimit * 0.9 ) {
            $limit = intval( $this->memoryLimit * 0.9 / 1048576 + 0.5 );
            throw new MWException( "Preprocessor hit 90% memory limit ($limit MB)" );
        }
        return $usage <= $this->memoryLimit * 0.8;
    }

    public function preprocessToObj( $text, $flags = 0 ) {

        $xml = $this->cacheGetTree( $text, $flags );
        if ( $xml === false ) {
            $xml = $this->preprocessToXml( $text, $flags );
            $this->cacheSetTree( $text, $flags, $xml );
        }

        // Fail if the number of elements exceeds acceptable limits
        // Do not attempt to generate the DOM
        $this->parser->mGeneratedPPNodeCount += substr_count( $xml, '<' );
        $max = $this->parser->mOptions->getMaxGeneratedPPNodeCount();
        if ( $this->parser->mGeneratedPPNodeCount > $max ) {
            // if ( $cacheable ) { ... }
            throw new MWException( __METHOD__ . ': generated node count limit exceeded' );
        }

        $dom = new DOMDocument;
        MediaWiki\suppressWarnings();
        $result = $dom->loadXML( $xml );
        MediaWiki\restoreWarnings();
        if ( !$result ) {
            // Try running the XML through UtfNormal to get rid of invalid characters
            $xml = UtfNormal\Validator::cleanUp( $xml );
            // 1 << 19 == XML_PARSE_HUGE, needed so newer versions of libxml2
            // don't barf when the XML is >256 levels deep.
            $result = $dom->loadXML( $xml, 1 << 19 );
        }
        if ( $result ) {
            $obj = new PPNode_DOM( $dom->documentElement );
        }

        // if ( $cacheable ) { ... }

        if ( !$result ) {
            throw new MWException( __METHOD__ . ' generated invalid XML' );
        }
        return $obj;
    }

    public function preprocessToXml( $text, $flags = 0 ) {
        $forInclusion = $flags & Parser::PTD_FOR_INCLUSION;

        $xmlishElements = $this->parser->getStripList();
        $xmlishAllowMissingEndTag = [ 'includeonly', 'noinclude', 'onlyinclude' ];
        $enableOnlyinclude = false;
        if ( $forInclusion ) {
            $ignoredTags = [ 'includeonly', '/includeonly' ];
            $ignoredElements = [ 'noinclude' ];
            $xmlishElements[] = 'noinclude';
            if ( strpos( $text, '<onlyinclude>' ) !== false
                && strpos( $text, '</onlyinclude>' ) !== false
            ) {
                $enableOnlyinclude = true;
            }
        } else {
            $ignoredTags = [ 'noinclude', '/noinclude', 'onlyinclude', '/onlyinclude' ];
            $ignoredElements = [ 'includeonly' ];
            $xmlishElements[] = 'includeonly';
        }
        $xmlishRegex = implode( '|', array_merge( $xmlishElements, $ignoredTags ) );

        // Use "A" modifier (anchored) instead of "^", because ^ doesn't work with an offset
        $elementsRegex = "~($xmlishRegex)(?:\s|\/>|>)|(!--)~iA";

        $stack = new PPDStack;

        $searchBase = "[{<\n"; # }
        // For fast reverse searches
        $revText = strrev( $text );
        $lengthText = strlen( $text );

        // Input pointer, starts out pointing to a pseudo-newline before the start
        $i = 0;
        // Current accumulator
        $accum =& $stack->getAccum();
        $accum = '<root>';
        // True to find equals signs in arguments
        $findEquals = false;
        // True to take notice of pipe characters
        $findPipe = false;
        $headingIndex = 1;
        // True if $i is inside a possible heading
        $inHeading = false;
        // True if there are no more greater-than (>) signs right of $i
        $noMoreGT = false;
        // Map of tag name => true if there are no more closing tags of given type right of $i
        $noMoreClosingTag = [];
        // True to ignore all input up to the next <onlyinclude>
        $findOnlyinclude = $enableOnlyinclude;
        // Do a line-start run without outputting an LF character
        $fakeLineStart = true;

        while ( true ) {
            // $this->memCheck();

            if ( $findOnlyinclude ) {
                // Ignore all input up to the next <onlyinclude>
                $startPos = strpos( $text, '<onlyinclude>', $i );
                if ( $startPos === false ) {
                    // Ignored section runs to the end
                    $accum .= '<ignore>' . htmlspecialchars( substr( $text, $i ) ) . '</ignore>';
                    break;
                }
                $tagEndPos = $startPos + strlen( '<onlyinclude>' ); // past-the-end
                $accum .= '<ignore>' . htmlspecialchars( substr( $text, $i, $tagEndPos - $i ) ) . '</ignore>';
                $i = $tagEndPos;
                $findOnlyinclude = false;
            }

            if ( $fakeLineStart ) {
                $found = 'line-start';
                $curChar = '';
            } else {
                # Find next opening brace, closing brace or pipe
                $search = $searchBase;
                if ( $stack->top === false ) {
                    $currentClosing = '';
                } else {
                    $currentClosing = $stack->top->close;
                    $search .= $currentClosing;
                }
                if ( $findPipe ) {
                    $search .= '|';
                }
                if ( $findEquals ) {
                    // First equals will be for the template
                    $search .= '=';
                }
                $rule = null;
                # Output literal section, advance input counter
                $literalLength = strcspn( $text, $search, $i );
                if ( $literalLength > 0 ) {
                    $accum .= htmlspecialchars( substr( $text, $i, $literalLength ) );
                    $i += $literalLength;
                }
                if ( $i >= $lengthText ) {
                    if ( $currentClosing == "\n" ) {
                        // Do a past-the-end run to finish off the heading
                        $curChar = '';
                        $found = 'line-end';
                    } else {
                        # All done
                        break;
                    }
                } else {
                    $curChar = $text[$i];
                    if ( $curChar == '|' ) {
                        $found = 'pipe';
                    } elseif ( $curChar == '=' ) {
                        $found = 'equals';
                    } elseif ( $curChar == '<' ) {
                        $found = 'angle';
                    } elseif ( $curChar == "\n" ) {
                        if ( $inHeading ) {
                            $found = 'line-end';
                        } else {
                            $found = 'line-start';
                        }
                    } elseif ( $curChar == $currentClosing ) {
                        $found = 'close';
                    } elseif ( isset( $this->rules[$curChar] ) ) {
                        $found = 'open';
                        $rule = $this->rules[$curChar];
                    } else {
                        # Some versions of PHP have a strcspn which stops on null characters
                        # Ignore and continue
                        ++$i;
                        continue;
                    }
                }
            }

            if ( $found == 'angle' ) {
                $matches = false;
                // Handle </onlyinclude>
                if ( $enableOnlyinclude
                    && substr( $text, $i, strlen( '</onlyinclude>' ) ) == '</onlyinclude>'
                ) {
                    $findOnlyinclude = true;
                    continue;
                }

                // Determine element name
                if ( !preg_match( $elementsRegex, $text, $matches, 0, $i + 1 ) ) {
                    // Element name missing or not listed
                    $accum .= '&lt;';
                    ++$i;
                    continue;
                }
                // Handle comments
                if ( isset( $matches[2] ) && $matches[2] == '!--' ) {

                    // To avoid leaving blank lines, when a sequence of
                    // space-separated comments is both preceded and followed by
                    // a newline (ignoring spaces), then
                    // trim leading and trailing spaces and the trailing newline.

                    // Find the end
                    $endPos = strpos( $text, '-->', $i + 4 );
                    if ( $endPos === false ) {
                        // Unclosed comment in input, runs to end
                        $inner = substr( $text, $i );
                        $accum .= '<comment>' . htmlspecialchars( $inner ) . '</comment>';
                        $i = $lengthText;
                    } else {
                        // Search backwards for leading whitespace
                        $wsStart = $i ? ( $i - strspn( $revText, " \t", $lengthText - $i ) ) : 0;

                        // Search forwards for trailing whitespace
                        // $wsEnd will be the position of the last space (or the '>' if there's none)
                        $wsEnd = $endPos + 2 + strspn( $text, " \t", $endPos + 3 );

                        // Keep looking forward as long as we're finding more
                        // comments.
                        $comments = [ [ $wsStart, $wsEnd ] ];
                        while ( substr( $text, $wsEnd + 1, 4 ) == '<!--' ) {
                            $c = strpos( $text, '-->', $wsEnd + 4 );
                            if ( $c === false ) {
                                break;
                            }
                            $c = $c + 2 + strspn( $text, " \t", $c + 3 );
                            $comments[] = [ $wsEnd + 1, $c ];
                            $wsEnd = $c;
                        }

                        // Eat the line if possible
                        // TODO: This could theoretically be done if $wsStart == 0, i.e. for comments at
                        // the overall start. That's not how Sanitizer::removeHTMLcomments() did it, but
                        // it's a possible beneficial b/c break.
                        if ( $wsStart > 0 && substr( $text, $wsStart - 1, 1 ) == "\n"
                            && substr( $text, $wsEnd + 1, 1 ) == "\n"
                        ) {
                            // Remove leading whitespace from the end of the accumulator
                            // Sanity check first though
                            $wsLength = $i - $wsStart;
                            if ( $wsLength > 0
                                && strspn( $accum, " \t", -$wsLength ) === $wsLength
                            ) {
                                $accum = substr( $accum, 0, -$wsLength );
                            }

                            // Dump all but the last comment to the accumulator
                            foreach ( $comments as $j => $com ) {
                                $startPos = $com[0];
                                $endPos = $com[1] + 1;
                                if ( $j == ( count( $comments ) - 1 ) ) {
                                    break;
                                }
                                $inner = substr( $text, $startPos, $endPos - $startPos );
                                $accum .= '<comment>' . htmlspecialchars( $inner ) . '</comment>';
                            }

                            // Do a line-start run next time to look for headings after the comment
                            $fakeLineStart = true;
                        } else {
                            // No line to eat, just take the comment itself
                            $startPos = $i;
                            $endPos += 2;
                        }

                        if ( $stack->top ) {
                            $part = $stack->top->getCurrentPart();
                            if ( !( isset( $part->commentEnd ) && $part->commentEnd == $wsStart - 1 ) ) {
                                $part->visualEnd = $wsStart;
                            }
                            // Else comments abutting, no change in visual end
                            $part->commentEnd = $endPos;
                        }
                        $i = $endPos + 1;
                        $inner = substr( $text, $startPos, $endPos - $startPos + 1 );
                        $accum .= '<comment>' . htmlspecialchars( $inner ) . '</comment>';
                    }
                    continue;
                }
                $name = $matches[1];
                $lowerName = strtolower( $name );
                $attrStart = $i + strlen( $name ) + 1;

                // Find end of tag
                $tagEndPos = $noMoreGT ? false : strpos( $text, '>', $attrStart );
                if ( $tagEndPos === false ) {
                    // Infinite backtrack
                    // Disable tag search to prevent worst-case O(N^2) performance
                    $noMoreGT = true;
                    $accum .= '&lt;';
                    ++$i;
                    continue;
                }

                // Handle ignored tags
                if ( in_array( $lowerName, $ignoredTags ) ) {
                    $accum .= '<ignore>'
                        . htmlspecialchars( substr( $text, $i, $tagEndPos - $i + 1 ) )
                        . '</ignore>';
                    $i = $tagEndPos + 1;
                    continue;
                }

                $tagStartPos = $i;
                if ( $text[$tagEndPos - 1] == '/' ) {
                    $attrEnd = $tagEndPos - 1;
                    $inner = null;
                    $i = $tagEndPos + 1;
                    $close = '';
                } else {
                    $attrEnd = $tagEndPos;
                    // Find closing tag
                    if (
                        !isset( $noMoreClosingTag[$name] ) &&
                        preg_match( "/<\/" . preg_quote( $name, '/' ) . "\s*>/i",
                            $text, $matches, PREG_OFFSET_CAPTURE, $tagEndPos + 1 )
                    ) {
                        $inner = substr( $text, $tagEndPos + 1, $matches[0][1] - $tagEndPos - 1 );
                        $i = $matches[0][1] + strlen( $matches[0][0] );
                        $close = '<close>' . htmlspecialchars( $matches[0][0] ) . '</close>';
                    } else {
                        // No end tag
                        if ( in_array( $name, $xmlishAllowMissingEndTag ) ) {
                            // Let it run out to the end of the text.
                            $inner = substr( $text, $tagEndPos + 1 );
                            $i = $lengthText;
                            $close = '';
                        } else {
                            // Don't match the tag, treat opening tag as literal and resume parsing.
                            $i = $tagEndPos + 1;
                            $accum .= htmlspecialchars( substr( $text, $tagStartPos, $tagEndPos + 1 - $tagStartPos ) );
                            // Cache results, otherwise we have O(N^2) performance for input like <foo><foo><foo>...
                            $noMoreClosingTag[$name] = true;
                            continue;
                        }
                    }
                }
                // <includeonly> and <noinclude> just become <ignore> tags
                if ( in_array( $lowerName, $ignoredElements ) ) {
                    $accum .= '<ignore>' . htmlspecialchars( substr( $text, $tagStartPos, $i - $tagStartPos ) )
                        . '</ignore>';
                    continue;
                }

                $accum .= '<ext>';
                if ( $attrEnd <= $attrStart ) {
                    $attr = '';
                } else {
                    $attr = substr( $text, $attrStart, $attrEnd - $attrStart );
                }
                $accum .= '<name>' . htmlspecialchars( $name ) . '</name>' .
                    // Note that the attr element contains the whitespace between name and attribute,
                    // this is necessary for precise reconstruction during pre-save transform.
                    '<attr>' . htmlspecialchars( $attr ) . '</attr>';
                if ( $inner !== null ) {
                    $accum .= '<inner>' . htmlspecialchars( $inner ) . '</inner>';
                }
                $accum .= $close . '</ext>';
            } elseif ( $found == 'line-start' ) {
                // Is this the start of a heading?
                // Line break belongs before the heading element in any case
                if ( $fakeLineStart ) {
                    $fakeLineStart = false;
                } else {
                    $accum .= $curChar;
                    $i++;
                }

                $count = strspn( $text, '=', $i, 6 );
                if ( $count == 1 && $findEquals ) {
                    // DWIM: This looks kind of like a name/value separator.
                    // Let's let the equals handler have it and break the
                    // potential heading. This is heuristic, but AFAICT the
                    // methods for completely correct disambiguation are very
                    // complex.
                } elseif ( $count > 0 ) {
                    $piece = [
                        'open' => "\n",
                        'close' => "\n",
                        'parts' => [ new PPDPart( str_repeat( '=', $count ) ) ],
                        'startPos' => $i,
                        'count' => $count ];
                    $stack->push( $piece );
                    $accum =& $stack->getAccum();
                    $flags = $stack->getFlags();
                    extract( $flags );
                    $i += $count;
                }
            } elseif ( $found == 'line-end' ) {
                $piece = $stack->top;
                // A heading must be open, otherwise \n wouldn't have been in the search list
                assert( $piece->open === "\n" );
                $part = $piece->getCurrentPart();
                // Search back through the input to see if it has a proper close.
                // Do this using the reversed string since the other solutions
                // (end anchor, etc.) are inefficient.
                $wsLength = strspn( $revText, " \t", $lengthText - $i );
                $searchStart = $i - $wsLength;
                if ( isset( $part->commentEnd ) && $searchStart - 1 == $part->commentEnd ) {
                    // Comment found at line end
                    // Search for equals signs before the comment
                    $searchStart = $part->visualEnd;
                    $searchStart -= strspn( $revText, " \t", $lengthText - $searchStart );
                }
                $count = $piece->count;
                $equalsLength = strspn( $revText, '=', $lengthText - $searchStart );
                if ( $equalsLength > 0 ) {
                    if ( $searchStart - $equalsLength == $piece->startPos ) {
                        // This is just a single string of equals signs on its own line
                        // Replicate the doHeadings behavior /={count}(.+)={count}/
                        // First find out how many equals signs there really are (don't stop at 6)
                        $count = $equalsLength;
                        if ( $count < 3 ) {
                            $count = 0;
                        } else {
                            $count = min( 6, intval( ( $count - 1 ) / 2 ) );
                        }
                    } else {
                        $count = min( $equalsLength, $count );
                    }
                    if ( $count > 0 ) {
                        // Normal match, output <h>
                        $element = "<h level=\"$count\" i=\"$headingIndex\">$accum</h>";
                        $headingIndex++;
                    } else {
                        // Single equals sign on its own line, count=0
                        $element = $accum;
                    }
                } else {
                    // No match, no <h>, just pass down the inner text
                    $element = $accum;
                }
                // Unwind the stack
                $stack->pop();
                $accum =& $stack->getAccum();
                $flags = $stack->getFlags();
                extract( $flags );

                // Append the result to the enclosing accumulator
                $accum .= $element;
                // Note that we do NOT increment the input pointer.
                // This is because the closing linebreak could be the opening linebreak of
                // another heading. Infinite loops are avoided because the next iteration MUST
                // hit the heading open case above, which unconditionally increments the
                // input pointer.
            } elseif ( $found == 'open' ) {
                # count opening brace characters
                $count = strspn( $text, $curChar, $i );

                # we need to add to stack only if opening brace count is enough for one of the rules
                if ( $count >= $rule['min'] ) {
                    # Add it to the stack
                    $piece = [
                        'open' => $curChar,
                        'close' => $rule['end'],
                        'count' => $count,
                        'lineStart' => ( $i > 0 && $text[$i - 1] == "\n" ),
                    ];

                    $stack->push( $piece );
                    $accum =& $stack->getAccum();
                    $flags = $stack->getFlags();
                    extract( $flags );
                } else {
                    # Add literal brace(s)
                    $accum .= htmlspecialchars( str_repeat( $curChar, $count ) );
                }
                $i += $count;
            } elseif ( $found == 'close' ) {
                $piece = $stack->top;
                # lets check if there are enough characters for closing brace
                $maxCount = $piece->count;
                $count = strspn( $text, $curChar, $i, $maxCount );

                # check for maximum matching characters (if there are 5 closing
                # characters, we will probably need only 3 - depending on the rules)
                $rule = $this->rules[$piece->open];
                if ( $count > $rule['max'] ) {
                    # The specified maximum exists in the callback array, unless the caller
                    # has made an error
                    $matchingCount = $rule['max'];
                } else {
                    # Count is less than the maximum
                    # Skip any gaps in the callback array to find the true largest match
                    # Need to use array_key_exists not isset because the callback can be null
                    $matchingCount = $count;
                    while ( $matchingCount > 0 && !array_key_exists( $matchingCount, $rule['names'] ) ) {
                        --$matchingCount;
                    }
                }

                if ( $matchingCount <= 0 ) {
                    # No matching element found in callback array
                    # Output a literal closing brace and continue
                    $accum .= htmlspecialchars( str_repeat( $curChar, $count ) );
                    $i += $count;
                    continue;
                }
                $name = $rule['names'][$matchingCount];
                if ( $name === null ) {
                    // No element, just literal text
                    $element = $piece->breakSyntax( $matchingCount ) . str_repeat( $rule['end'], $matchingCount );
                } else {
                    # Create XML element
                    # Note: $parts is already XML, does not need to be encoded further
                    $parts = $piece->parts;
                    $title = $parts[0]->out;
                    unset( $parts[0] );

                    # The invocation is at the start of the line if lineStart is set in
                    # the stack, and all opening brackets are used up.
                    if ( $maxCount == $matchingCount && !empty( $piece->lineStart ) ) {
                        $attr = ' lineStart="1"';
                    } else {
                        $attr = '';
                    }

                    $element = "<$name$attr>";
                    $element .= "<title>$title</title>";
                    $argIndex = 1;
                    foreach ( $parts as $part ) {
                        if ( isset( $part->eqpos ) ) {
                            $argName = substr( $part->out, 0, $part->eqpos );
                            $argValue = substr( $part->out, $part->eqpos + 1 );
                            $element .= "<part><name>$argName</name>=<value>$argValue</value></part>";
                        } else {
                            $element .= "<part><name index=\"$argIndex\" /><value>{$part->out}</value></part>";
                            $argIndex++;
                        }
                    }
                    $element .= "</$name>";
                }

                # Advance input pointer
                $i += $matchingCount;

                # Unwind the stack
                $stack->pop();
                $accum =& $stack->getAccum();

                # Re-add the old stack element if it still has unmatched opening characters remaining
                if ( $matchingCount < $piece->count ) {
                    $piece->parts = [ new PPDPart ];
                    $piece->count -= $matchingCount;
                    # do we still qualify for any callback with remaining count?
                    $min = $this->rules[$piece->open]['min'];
                    if ( $piece->count >= $min ) {
                        $stack->push( $piece );
                        $accum =& $stack->getAccum();
                    } else {
                        $accum .= str_repeat( $piece->open, $piece->count );
                    }
                }
                $flags = $stack->getFlags();
                extract( $flags );

                # Add XML element to the enclosing accumulator
                $accum .= $element;
            } elseif ( $found == 'pipe' ) {
                $findEquals = true; // shortcut for getFlags()
                $stack->addPart();
                $accum =& $stack->getAccum();
                ++$i;
            } elseif ( $found == 'equals' ) {
                $findEquals = false; // shortcut for getFlags()
                $stack->getCurrentPart()->eqpos = strlen( $accum );
                $accum .= '=';
                ++$i;
            }
        }

        # Output any remaining unclosed brackets
        foreach ( $stack->stack as $piece ) {
            $stack->rootAccum .= $piece->breakSyntax();
        }
        $stack->rootAccum .= '</root>';
        $xml = $stack->rootAccum;

        return $xml;
    }
}

class PPDStack {
    public $stack, $rootAccum;

    public $top;
    public $out;
    public $elementClass = 'PPDStackElement';

    public static $false = false;

    public function __construct() {
        $this->stack = [];
        $this->top = false;
        $this->rootAccum = '';
        $this->accum =& $this->rootAccum;
    }

    public function count() {
        return count( $this->stack );
    }

    public function &getAccum() {
        return $this->accum;
    }

    public function getCurrentPart() {
        if ( $this->top === false ) {
            return false;
        } else {
            return $this->top->getCurrentPart();
        }
    }

    public function push( $data ) {
        if ( $data instanceof $this->elementClass ) {
            $this->stack[] = $data;
        } else {
            $class = $this->elementClass;
            $this->stack[] = new $class( $data );
        }
        $this->top = $this->stack[count( $this->stack ) - 1];
        $this->accum =& $this->top->getAccum();
    }

    public function pop() {
        if ( !count( $this->stack ) ) {
            throw new MWException( __METHOD__ . ': no elements remaining' );
        }
        $temp = array_pop( $this->stack );

        if ( count( $this->stack ) ) {
            $this->top = $this->stack[count( $this->stack ) - 1];
            $this->accum =& $this->top->getAccum();
        } else {
            $this->top = self::$false;
            $this->accum =& $this->rootAccum;
        }
        return $temp;
    }

    public function addPart( $s = '' ) {
        $this->top->addPart( $s );
        $this->accum =& $this->top->getAccum();
    }

    public function getFlags() {
        if ( !count( $this->stack ) ) {
            return [
                'findEquals' => false,
                'findPipe' => false,
                'inHeading' => false,
            ];
        } else {
            return $this->top->getFlags();
        }
    }
}

class PPDStackElement {
    public $open;

    public $close;

    public $count;

    public $parts;

    public $lineStart;

    public $partClass = 'PPDPart';

    public function __construct( $data = [] ) {
        $class = $this->partClass;
        $this->parts = [ new $class ];

        foreach ( $data as $name => $value ) {
            $this->$name = $value;
        }
    }

    public function &getAccum() {
        return $this->parts[count( $this->parts ) - 1]->out;
    }

    public function addPart( $s = '' ) {
        $class = $this->partClass;
        $this->parts[] = new $class( $s );
    }

    public function getCurrentPart() {
        return $this->parts[count( $this->parts ) - 1];
    }

    public function getFlags() {
        $partCount = count( $this->parts );
        $findPipe = $this->open != "\n" && $this->open != '[';
        return [
            'findPipe' => $findPipe,
            'findEquals' => $findPipe && $partCount > 1 && !isset( $this->parts[$partCount - 1]->eqpos ),
            'inHeading' => $this->open == "\n",
        ];
    }

    public function breakSyntax( $openingCount = false ) {
        if ( $this->open == "\n" ) {
            $s = $this->parts[0]->out;
        } else {
            if ( $openingCount === false ) {
                $openingCount = $this->count;
            }
            $s = str_repeat( $this->open, $openingCount );
            $first = true;
            foreach ( $this->parts as $part ) {
                if ( $first ) {
                    $first = false;
                } else {
                    $s .= '|';
                }
                $s .= $part->out;
            }
        }
        return $s;
    }
}

class PPDPart {
    public $out;

    // Optional member variables:
    //   eqpos        Position of equals sign in output accumulator
    //   commentEnd   Past-the-end input pointer for the last comment encountered
    //   visualEnd    Past-the-end input pointer for the end of the accumulator minus comments

    public function __construct( $out = '' ) {
        $this->out = $out;
    }
}

// @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps
class PPFrame_DOM implements PPFrame {
    // @codingStandardsIgnoreEnd

    public $preprocessor;

    public $parser;

    public $title;
    public $titleCache;

    public $loopCheckHash;

    public $depth;

    private $volatile = false;
    private $ttl = null;

    protected $childExpansionCache;

    public function __construct( $preprocessor ) {
        $this->preprocessor = $preprocessor;
        $this->parser = $preprocessor->parser;
        $this->title = $this->parser->mTitle;
        $this->titleCache = [ $this->title ? $this->title->getPrefixedDBkey() : false ];
        $this->loopCheckHash = [];
        $this->depth = 0;
        $this->childExpansionCache = [];
    }

    public function newChild( $args = false, $title = false, $indexOffset = 0 ) {
        $namedArgs = [];
        $numberedArgs = [];
        if ( $title === false ) {
            $title = $this->title;
        }
        if ( $args !== false ) {
            $xpath = false;
            if ( $args instanceof PPNode ) {
                $args = $args->node;
            }
            foreach ( $args as $arg ) {
                if ( $arg instanceof PPNode ) {
                    $arg = $arg->node;
                }
                if ( !$xpath || $xpath->document !== $arg->ownerDocument ) {
                    $xpath = new DOMXPath( $arg->ownerDocument );
                }

                $nameNodes = $xpath->query( 'name', $arg );
                $value = $xpath->query( 'value', $arg );
                if ( $nameNodes->item( 0 )->hasAttributes() ) {
                    // Numbered parameter
                    $index = $nameNodes->item( 0 )->attributes->getNamedItem( 'index' )->textContent;
                    $index = $index - $indexOffset;
                    if ( isset( $namedArgs[$index] ) || isset( $numberedArgs[$index] ) ) {
                        $this->parser->getOutput()->addWarning( wfMessage( 'duplicate-args-warning',
                            wfEscapeWikiText( $this->title ),
                            wfEscapeWikiText( $title ),
                            wfEscapeWikiText( $index ) )->text() );
                        $this->parser->addTrackingCategory( 'duplicate-args-category' );
                    }
                    $numberedArgs[$index] = $value->item( 0 );
                    unset( $namedArgs[$index] );
                } else {
                    // Named parameter
                    $name = trim( $this->expand( $nameNodes->item( 0 ), PPFrame::STRIP_COMMENTS ) );
                    if ( isset( $namedArgs[$name] ) || isset( $numberedArgs[$name] ) ) {
                        $this->parser->getOutput()->addWarning( wfMessage( 'duplicate-args-warning',
                            wfEscapeWikiText( $this->title ),
                            wfEscapeWikiText( $title ),
                            wfEscapeWikiText( $name ) )->text() );
                        $this->parser->addTrackingCategory( 'duplicate-args-category' );
                    }
                    $namedArgs[$name] = $value->item( 0 );
                    unset( $numberedArgs[$name] );
                }
            }
        }
        return new PPTemplateFrame_DOM( $this->preprocessor, $this, $numberedArgs, $namedArgs, $title );
    }

    public function cachedExpand( $key, $root, $flags = 0 ) {
        // we don't have a parent, so we don't have a cache
        return $this->expand( $root, $flags );
    }

    public function expand( $root, $flags = 0 ) {
        static $expansionDepth = 0;
        if ( is_string( $root ) ) {
            return $root;
        }

        if ( ++$this->parser->mPPNodeCount > $this->parser->mOptions->getMaxPPNodeCount() ) {
            $this->parser->limitationWarn( 'node-count-exceeded',
                $this->parser->mPPNodeCount,
                $this->parser->mOptions->getMaxPPNodeCount()
            );
            return '<span class="error">Node-count limit exceeded</span>';
        }

        if ( $expansionDepth > $this->parser->mOptions->getMaxPPExpandDepth() ) {
            $this->parser->limitationWarn( 'expansion-depth-exceeded',
                $expansionDepth,
                $this->parser->mOptions->getMaxPPExpandDepth()
            );
            return '<span class="error">Expansion depth limit exceeded</span>';
        }
        ++$expansionDepth;
        if ( $expansionDepth > $this->parser->mHighestExpansionDepth ) {
            $this->parser->mHighestExpansionDepth = $expansionDepth;
        }

        if ( $root instanceof PPNode_DOM ) {
            $root = $root->node;
        }
        if ( $root instanceof DOMDocument ) {
            $root = $root->documentElement;
        }

        $outStack = [ '', '' ];
        $iteratorStack = [ false, $root ];
        $indexStack = [ 0, 0 ];

        while ( count( $iteratorStack ) > 1 ) {
            $level = count( $outStack ) - 1;
            $iteratorNode =& $iteratorStack[$level];
            $out =& $outStack[$level];
            $index =& $indexStack[$level];

            if ( $iteratorNode instanceof PPNode_DOM ) {
                $iteratorNode = $iteratorNode->node;
            }

            if ( is_array( $iteratorNode ) ) {
                if ( $index >= count( $iteratorNode ) ) {
                    // All done with this iterator
                    $iteratorStack[$level] = false;
                    $contextNode = false;
                } else {
                    $contextNode = $iteratorNode[$index];
                    $index++;
                }
            } elseif ( $iteratorNode instanceof DOMNodeList ) {
                if ( $index >= $iteratorNode->length ) {
                    // All done with this iterator
                    $iteratorStack[$level] = false;
                    $contextNode = false;
                } else {
                    $contextNode = $iteratorNode->item( $index );
                    $index++;
                }
            } else {
                // Copy to $contextNode and then delete from iterator stack,
                // because this is not an iterator but we do have to execute it once
                $contextNode = $iteratorStack[$level];
                $iteratorStack[$level] = false;
            }

            if ( $contextNode instanceof PPNode_DOM ) {
                $contextNode = $contextNode->node;
            }

            $newIterator = false;

            if ( $contextNode === false ) {
                // nothing to do
            } elseif ( is_string( $contextNode ) ) {
                $out .= $contextNode;
            } elseif ( is_array( $contextNode ) || $contextNode instanceof DOMNodeList ) {
                $newIterator = $contextNode;
            } elseif ( $contextNode instanceof DOMNode ) {
                if ( $contextNode->nodeType == XML_TEXT_NODE ) {
                    $out .= $contextNode->nodeValue;
                } elseif ( $contextNode->nodeName == 'template' ) {
                    # Double-brace expansion
                    $xpath = new DOMXPath( $contextNode->ownerDocument );
                    $titles = $xpath->query( 'title', $contextNode );
                    $title = $titles->item( 0 );
                    $parts = $xpath->query( 'part', $contextNode );
                    if ( $flags & PPFrame::NO_TEMPLATES ) {
                        $newIterator = $this->virtualBracketedImplode( '{{', '|', '}}', $title, $parts );
                    } else {
                        $lineStart = $contextNode->getAttribute( 'lineStart' );
                        $params = [
                            'title' => new PPNode_DOM( $title ),
                            'parts' => new PPNode_DOM( $parts ),
                            'lineStart' => $lineStart ];
                        $ret = $this->parser->braceSubstitution( $params, $this );
                        if ( isset( $ret['object'] ) ) {
                            $newIterator = $ret['object'];
                        } else {
                            $out .= $ret['text'];
                        }
                    }
                } elseif ( $contextNode->nodeName == 'tplarg' ) {
                    # Triple-brace expansion
                    $xpath = new DOMXPath( $contextNode->ownerDocument );
                    $titles = $xpath->query( 'title', $contextNode );
                    $title = $titles->item( 0 );
                    $parts = $xpath->query( 'part', $contextNode );
                    if ( $flags & PPFrame::NO_ARGS ) {
                        $newIterator = $this->virtualBracketedImplode( '{{{', '|', '}}}', $title, $parts );
                    } else {
                        $params = [
                            'title' => new PPNode_DOM( $title ),
                            'parts' => new PPNode_DOM( $parts ) ];
                        $ret = $this->parser->argSubstitution( $params, $this );
                        if ( isset( $ret['object'] ) ) {
                            $newIterator = $ret['object'];
                        } else {
                            $out .= $ret['text'];
                        }
                    }
                } elseif ( $contextNode->nodeName == 'comment' ) {
                    # HTML-style comment
                    # Remove it in HTML, pre+remove and STRIP_COMMENTS modes
                    # Not in RECOVER_COMMENTS mode (msgnw) though.
                    if ( ( $this->parser->ot['html']
                        || ( $this->parser->ot['pre'] && $this->parser->mOptions->getRemoveComments() )
                        || ( $flags & PPFrame::STRIP_COMMENTS )
                        ) && !( $flags & PPFrame::RECOVER_COMMENTS )
                    ) {
                        $out .= '';
                    } elseif ( $this->parser->ot['wiki'] && !( $flags & PPFrame::RECOVER_COMMENTS ) ) {
                        # Add a strip marker in PST mode so that pstPass2() can
                        # run some old-fashioned regexes on the result.
                        # Not in RECOVER_COMMENTS mode (extractSections) though.
                        $out .= $this->parser->insertStripItem( $contextNode->textContent );
                    } else {
                        # Recover the literal comment in RECOVER_COMMENTS and pre+no-remove
                        $out .= $contextNode->textContent;
                    }
                } elseif ( $contextNode->nodeName == 'ignore' ) {
                    # Output suppression used by <includeonly> etc.
                    # OT_WIKI will only respect <ignore> in substed templates.
                    # The other output types respect it unless NO_IGNORE is set.
                    # extractSections() sets NO_IGNORE and so never respects it.
                    if ( ( !isset( $this->parent ) && $this->parser->ot['wiki'] )
                        || ( $flags & PPFrame::NO_IGNORE )
                    ) {
                        $out .= $contextNode->textContent;
                    } else {
                        $out .= '';
                    }
                } elseif ( $contextNode->nodeName == 'ext' ) {
                    # Extension tag
                    $xpath = new DOMXPath( $contextNode->ownerDocument );
                    $names = $xpath->query( 'name', $contextNode );
                    $attrs = $xpath->query( 'attr', $contextNode );
                    $inners = $xpath->query( 'inner', $contextNode );
                    $closes = $xpath->query( 'close', $contextNode );
                    if ( $flags & PPFrame::NO_TAGS ) {
                        $s = '<' . $this->expand( $names->item( 0 ), $flags );
                        if ( $attrs->length > 0 ) {
                            $s .= $this->expand( $attrs->item( 0 ), $flags );
                        }
                        if ( $inners->length > 0 ) {
                            $s .= '>' . $this->expand( $inners->item( 0 ), $flags );
                            if ( $closes->length > 0 ) {
                                $s .= $this->expand( $closes->item( 0 ), $flags );
                            }
                        } else {
                            $s .= '/>';
                        }
                        $out .= $s;
                    } else {
                        $params = [
                            'name' => new PPNode_DOM( $names->item( 0 ) ),
                            'attr' => $attrs->length > 0 ? new PPNode_DOM( $attrs->item( 0 ) ) : null,
                            'inner' => $inners->length > 0 ? new PPNode_DOM( $inners->item( 0 ) ) : null,
                            'close' => $closes->length > 0 ? new PPNode_DOM( $closes->item( 0 ) ) : null,
                        ];
                        $out .= $this->parser->extensionSubstitution( $params, $this );
                    }
                } elseif ( $contextNode->nodeName == 'h' ) {
                    # Heading
                    $s = $this->expand( $contextNode->childNodes, $flags );

                    # Insert a heading marker only for <h> children of <root>
                    # This is to stop extractSections from going over multiple tree levels
                    if ( $contextNode->parentNode->nodeName == 'root' && $this->parser->ot['html'] ) {
                        # Insert heading index marker
                        $headingIndex = $contextNode->getAttribute( 'i' );
                        $titleText = $this->title->getPrefixedDBkey();
                        $this->parser->mHeadings[] = [ $titleText, $headingIndex ];
                        $serial = count( $this->parser->mHeadings ) - 1;
                        $marker = Parser::MARKER_PREFIX . "-h-$serial-" . Parser::MARKER_SUFFIX;
                        $count = $contextNode->getAttribute( 'level' );
                        $s = substr( $s, 0, $count ) . $marker . substr( $s, $count );
                        $this->parser->mStripState->addGeneral( $marker, '' );
                    }
                    $out .= $s;
                } else {
                    # Generic recursive expansion
                    $newIterator = $contextNode->childNodes;
                }
            } else {
                throw new MWException( __METHOD__ . ': Invalid parameter type' );
            }

            if ( $newIterator !== false ) {
                if ( $newIterator instanceof PPNode_DOM ) {
                    $newIterator = $newIterator->node;
                }
                $outStack[] = '';
                $iteratorStack[] = $newIterator;
                $indexStack[] = 0;
            } elseif ( $iteratorStack[$level] === false ) {
                // Return accumulated value to parent
                // With tail recursion
                while ( $iteratorStack[$level] === false && $level > 0 ) {
                    $outStack[$level - 1] .= $out;
                    array_pop( $outStack );
                    array_pop( $iteratorStack );
                    array_pop( $indexStack );
                    $level--;
                }
            }
        }
        --$expansionDepth;
        return $outStack[0];
    }

    public function implodeWithFlags( $sep, $flags /*, ... */ ) {
        $args = array_slice( func_get_args(), 2 );

        $first = true;
        $s = '';
        foreach ( $args as $root ) {
            if ( $root instanceof PPNode_DOM ) {
                $root = $root->node;
            }
            if ( !is_array( $root ) && !( $root instanceof DOMNodeList ) ) {
                $root = [ $root ];
            }
            foreach ( $root as $node ) {
                if ( $first ) {
                    $first = false;
                } else {
                    $s .= $sep;
                }
                $s .= $this->expand( $node, $flags );
            }
        }
        return $s;
    }

    public function implode( $sep /*, ... */ ) {
        $args = array_slice( func_get_args(), 1 );

        $first = true;
        $s = '';
        foreach ( $args as $root ) {
            if ( $root instanceof PPNode_DOM ) {
                $root = $root->node;
            }
            if ( !is_array( $root ) && !( $root instanceof DOMNodeList ) ) {
                $root = [ $root ];
            }
            foreach ( $root as $node ) {
                if ( $first ) {
                    $first = false;
                } else {
                    $s .= $sep;
                }
                $s .= $this->expand( $node );
            }
        }
        return $s;
    }

    public function virtualImplode( $sep /*, ... */ ) {
        $args = array_slice( func_get_args(), 1 );
        $out = [];
        $first = true;

        foreach ( $args as $root ) {
            if ( $root instanceof PPNode_DOM ) {
                $root = $root->node;
            }
            if ( !is_array( $root ) && !( $root instanceof DOMNodeList ) ) {
                $root = [ $root ];
            }
            foreach ( $root as $node ) {
                if ( $first ) {
                    $first = false;
                } else {
                    $out[] = $sep;
                }
                $out[] = $node;
            }
        }
        return $out;
    }

    public function virtualBracketedImplode( $start, $sep, $end /*, ... */ ) {
        $args = array_slice( func_get_args(), 3 );
        $out = [ $start ];
        $first = true;

        foreach ( $args as $root ) {
            if ( $root instanceof PPNode_DOM ) {
                $root = $root->node;
            }
            if ( !is_array( $root ) && !( $root instanceof DOMNodeList ) ) {
                $root = [ $root ];
            }
            foreach ( $root as $node ) {
                if ( $first ) {
                    $first = false;
                } else {
                    $out[] = $sep;
                }
                $out[] = $node;
            }
        }
        $out[] = $end;
        return $out;
    }

    public function __toString() {
        return 'frame{}';
    }

    public function getPDBK( $level = false ) {
        if ( $level === false ) {
            return $this->title->getPrefixedDBkey();
        } else {
            return isset( $this->titleCache[$level] ) ? $this->titleCache[$level] : false;
        }
    }

    public function getArguments() {
        return [];
    }

    public function getNumberedArguments() {
        return [];
    }

    public function getNamedArguments() {
        return [];
    }

    public function isEmpty() {
        return true;
    }

    public function getArgument( $name ) {
        return false;
    }

    public function loopCheck( $title ) {
        return !isset( $this->loopCheckHash[$title->getPrefixedDBkey()] );
    }

    public function isTemplate() {
        return false;
    }

    public function getTitle() {
        return $this->title;
    }

    public function setVolatile( $flag = true ) {
        $this->volatile = $flag;
    }

    public function isVolatile() {
        return $this->volatile;
    }

    public function setTTL( $ttl ) {
        if ( $ttl !== null && ( $this->ttl === null || $ttl < $this->ttl ) ) {
            $this->ttl = $ttl;
        }
    }

    public function getTTL() {
        return $this->ttl;
    }
}

// @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps
class PPTemplateFrame_DOM extends PPFrame_DOM {
    // @codingStandardsIgnoreEnd

    public $numberedArgs, $namedArgs;

    public $parent;
    public $numberedExpansionCache, $namedExpansionCache;

    public function __construct( $preprocessor, $parent = false, $numberedArgs = [],
        $namedArgs = [], $title = false
    ) {
        parent::__construct( $preprocessor );

        $this->parent = $parent;
        $this->numberedArgs = $numberedArgs;
        $this->namedArgs = $namedArgs;
        $this->title = $title;
        $pdbk = $title ? $title->getPrefixedDBkey() : false;
        $this->titleCache = $parent->titleCache;
        $this->titleCache[] = $pdbk;
        $this->loopCheckHash = /*clone*/ $parent->loopCheckHash;
        if ( $pdbk !== false ) {
            $this->loopCheckHash[$pdbk] = true;
        }
        $this->depth = $parent->depth + 1;
        $this->numberedExpansionCache = $this->namedExpansionCache = [];
    }

    public function __toString() {
        $s = 'tplframe{';
        $first = true;
        $args = $this->numberedArgs + $this->namedArgs;
        foreach ( $args as $name => $value ) {
            if ( $first ) {
                $first = false;
            } else {
                $s .= ', ';
            }
            $s .= "\"$name\":\"" .
                str_replace( '"', '\\"', $value->ownerDocument->saveXML( $value ) ) . '"';
        }
        $s .= '}';
        return $s;
    }

    public function cachedExpand( $key, $root, $flags = 0 ) {
        if ( isset( $this->parent->childExpansionCache[$key] ) ) {
            return $this->parent->childExpansionCache[$key];
        }
        $retval = $this->expand( $root, $flags );
        if ( !$this->isVolatile() ) {
            $this->parent->childExpansionCache[$key] = $retval;
        }
        return $retval;
    }

    public function isEmpty() {
        return !count( $this->numberedArgs ) && !count( $this->namedArgs );
    }

    public function getArguments() {
        $arguments = [];
        foreach ( array_merge(
                array_keys( $this->numberedArgs ),
                array_keys( $this->namedArgs ) ) as $key ) {
            $arguments[$key] = $this->getArgument( $key );
        }
        return $arguments;
    }

    public function getNumberedArguments() {
        $arguments = [];
        foreach ( array_keys( $this->numberedArgs ) as $key ) {
            $arguments[$key] = $this->getArgument( $key );
        }
        return $arguments;
    }

    public function getNamedArguments() {
        $arguments = [];
        foreach ( array_keys( $this->namedArgs ) as $key ) {
            $arguments[$key] = $this->getArgument( $key );
        }
        return $arguments;
    }

    public function getNumberedArgument( $index ) {
        if ( !isset( $this->numberedArgs[$index] ) ) {
            return false;
        }
        if ( !isset( $this->numberedExpansionCache[$index] ) ) {
            # No trimming for unnamed arguments
            $this->numberedExpansionCache[$index] = $this->parent->expand(
                $this->numberedArgs[$index],
                PPFrame::STRIP_COMMENTS
            );
        }
        return $this->numberedExpansionCache[$index];
    }

    public function getNamedArgument( $name ) {
        if ( !isset( $this->namedArgs[$name] ) ) {
            return false;
        }
        if ( !isset( $this->namedExpansionCache[$name] ) ) {
            # Trim named arguments post-expand, for backwards compatibility
            $this->namedExpansionCache[$name] = trim(
                $this->parent->expand( $this->namedArgs[$name], PPFrame::STRIP_COMMENTS ) );
        }
        return $this->namedExpansionCache[$name];
    }

    public function getArgument( $name ) {
        $text = $this->getNumberedArgument( $name );
        if ( $text === false ) {
            $text = $this->getNamedArgument( $name );
        }
        return $text;
    }

    public function isTemplate() {
        return true;
    }

    public function setVolatile( $flag = true ) {
        parent::setVolatile( $flag );
        $this->parent->setVolatile( $flag );
    }

    public function setTTL( $ttl ) {
        parent::setTTL( $ttl );
        $this->parent->setTTL( $ttl );
    }
}

// @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps
class PPCustomFrame_DOM extends PPFrame_DOM {
    // @codingStandardsIgnoreEnd

    public $args;

    public function __construct( $preprocessor, $args ) {
        parent::__construct( $preprocessor );
        $this->args = $args;
    }

    public function __toString() {
        $s = 'cstmframe{';
        $first = true;
        foreach ( $this->args as $name => $value ) {
            if ( $first ) {
                $first = false;
            } else {
                $s .= ', ';
            }
            $s .= "\"$name\":\"" .
                str_replace( '"', '\\"', $value->__toString() ) . '"';
        }
        $s .= '}';
        return $s;
    }

    public function isEmpty() {
        return !count( $this->args );
    }

    public function getArgument( $index ) {
        if ( !isset( $this->args[$index] ) ) {
            return false;
        }
        return $this->args[$index];
    }

    public function getArguments() {
        return $this->args;
    }
}

// @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps
class PPNode_DOM implements PPNode {
    // @codingStandardsIgnoreEnd

    public $node;
    public $xpath;

    public function __construct( $node, $xpath = false ) {
        $this->node = $node;
    }

    public function getXPath() {
        if ( $this->xpath === null ) {
            $this->xpath = new DOMXPath( $this->node->ownerDocument );
        }
        return $this->xpath;
    }

    public function __toString() {
        if ( $this->node instanceof DOMNodeList ) {
            $s = '';
            foreach ( $this->node as $node ) {
                $s .= $node->ownerDocument->saveXML( $node );
            }
        } else {
            $s = $this->node->ownerDocument->saveXML( $this->node );
        }
        return $s;
    }

    public function getChildren() {
        return $this->node->childNodes ? new self( $this->node->childNodes ) : false;
    }

    public function getFirstChild() {
        return $this->node->firstChild ? new self( $this->node->firstChild ) : false;
    }

    public function getNextSibling() {
        return $this->node->nextSibling ? new self( $this->node->nextSibling ) : false;
    }

    public function getChildrenOfType( $type ) {
        return new self( $this->getXPath()->query( $type, $this->node ) );
    }

    public function getLength() {
        if ( $this->node instanceof DOMNodeList ) {
            return $this->node->length;
        } else {
            return false;
        }
    }

    public function item( $i ) {
        $item = $this->node->item( $i );
        return $item ? new self( $item ) : false;
    }

    public function getName() {
        if ( $this->node instanceof DOMNodeList ) {
            return '#nodelist';
        } else {
            return $this->node->nodeName;
        }
    }

    public function splitArg() {
        $xpath = $this->getXPath();
        $names = $xpath->query( 'name', $this->node );
        $values = $xpath->query( 'value', $this->node );
        if ( !$names->length || !$values->length ) {
            throw new MWException( 'Invalid brace node passed to ' . __METHOD__ );
        }
        $name = $names->item( 0 );
        $index = $name->getAttribute( 'index' );
        return [
            'name' => new self( $name ),
            'index' => $index,
            'value' => new self( $values->item( 0 ) ) ];
    }

    public function splitExt() {
        $xpath = $this->getXPath();
        $names = $xpath->query( 'name', $this->node );
        $attrs = $xpath->query( 'attr', $this->node );
        $inners = $xpath->query( 'inner', $this->node );
        $closes = $xpath->query( 'close', $this->node );
        if ( !$names->length || !$attrs->length ) {
            throw new MWException( 'Invalid ext node passed to ' . __METHOD__ );
        }
        $parts = [
            'name' => new self( $names->item( 0 ) ),
            'attr' => new self( $attrs->item( 0 ) ) ];
        if ( $inners->length ) {
            $parts['inner'] = new self( $inners->item( 0 ) );
        }
        if ( $closes->length ) {
            $parts['close'] = new self( $closes->item( 0 ) );
        }
        return $parts;
    }

    public function splitHeading() {
        if ( $this->getName() !== 'h' ) {
            throw new MWException( 'Invalid h node passed to ' . __METHOD__ );
        }
        return [
            'i' => $this->node->getAttribute( 'i' ),
            'level' => $this->node->getAttribute( 'level' ),
            'contents' => $this->getChildren()
        ];
    }
}