Merge "API: Add show=unread to ApiQueryWatchlist"

[mediawiki.git] / includes / parser / Preprocessor_DOM.php

<?php
/**
 * Preprocessor using PHP's dom extension
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Parser
 */

/**
 * @ingroup Parser
 */
class Preprocessor_DOM implements Preprocessor {

        /**
         * @var Parser
         */
        var $parser;

        var $memoryLimit;

        const CACHE_VERSION = 1;

        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;
                        }
                }
        }

        /**
         * @return PPFrame_DOM
         */
        function newFrame() {
                return new PPFrame_DOM( $this );
        }

        /**
         * @param array $args
         * @return PPCustomFrame_DOM
         */
        function newCustomFrame( $args ) {
                return new PPCustomFrame_DOM( $this, $args );
        }

        /**
         * @param array $values
         * @return PPNode_DOM
         */
        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>";

                wfProfileIn( __METHOD__ . '-loadXML' );
                $dom = new DOMDocument();
                wfSuppressWarnings();
                $result = $dom->loadXML( $xml );
                wfRestoreWarnings();
                if ( !$result ) {
                        // Try running the XML through UtfNormal to get rid of invalid characters
                        $xml = UtfNormal::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 );
                }
                wfProfileOut( __METHOD__ . '-loadXML' );

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

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

        /**
         * @throws MWException
         * @return bool
         */
        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;
        }

        /**
         * Preprocess some wikitext and return the document tree.
         * This is the ghost of Parser::replace_variables().
         *
         * @param string $text The text to parse
         * @param int $flags Bitwise combination of:
         *     Parser::PTD_FOR_INCLUSION  Handle "<noinclude>" and "<includeonly>"
         *                                as if the text is being included. Default
         *                                is to assume a direct page view.
         *
         * The generated DOM tree must depend only on the input text and the flags.
         * The DOM tree must be the same in OT_HTML and OT_WIKI mode, to avoid a regression of bug 4899.
         *
         * Any flag added to the $flags parameter here, or any other parameter liable to cause a
         * change in the DOM tree for a given text, must be passed through the section identifier
         * in the section edit link and thus back to extractSections().
         *
         * The output of this function is currently only cached in process memory, but a persistent
         * cache may be implemented at a later date which takes further advantage of these strict
         * dependency requirements.
         *
         * @throws MWException
         * @return PPNode_DOM
         */
        function preprocessToObj( $text, $flags = 0 ) {
                wfProfileIn( __METHOD__ );
                global $wgMemc, $wgPreprocessorCacheThreshold;

                $xml = false;
                $cacheable = ( $wgPreprocessorCacheThreshold !== false
                        && strlen( $text ) > $wgPreprocessorCacheThreshold );
                if ( $cacheable ) {
                        wfProfileIn( __METHOD__ . '-cacheable' );

                        $cacheKey = wfMemcKey( 'preprocess-xml', md5( $text ), $flags );
                        $cacheValue = $wgMemc->get( $cacheKey );
                        if ( $cacheValue ) {
                                $version = substr( $cacheValue, 0, 8 );
                                if ( intval( $version ) == self::CACHE_VERSION ) {
                                        $xml = substr( $cacheValue, 8 );
                                        // From the cache
                                        wfDebugLog( "Preprocessor", "Loaded preprocessor XML from memcached (key $cacheKey)" );
                                }
                        }
                        if ( $xml === false ) {
                                wfProfileIn( __METHOD__ . '-cache-miss' );
                                $xml = $this->preprocessToXml( $text, $flags );
                                $cacheValue = sprintf( "%08d", self::CACHE_VERSION ) . $xml;
                                $wgMemc->set( $cacheKey, $cacheValue, 86400 );
                                wfProfileOut( __METHOD__ . '-cache-miss' );
                                wfDebugLog( "Preprocessor", "Saved preprocessor XML to memcached (key $cacheKey)" );
                        }
                } else {
                        $xml = $this->preprocessToXml( $text, $flags );
                }

                // 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 ) {
                                wfProfileOut( __METHOD__ . '-cacheable' );
                        }
                        wfProfileOut( __METHOD__ );
                        throw new MWException( __METHOD__ . ': generated node count limit exceeded' );
                }

                wfProfileIn( __METHOD__ . '-loadXML' );
                $dom = new DOMDocument;
                wfSuppressWarnings();
                $result = $dom->loadXML( $xml );
                wfRestoreWarnings();
                if ( !$result ) {
                        // Try running the XML through UtfNormal to get rid of invalid characters
                        $xml = UtfNormal::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 );
                }
                wfProfileOut( __METHOD__ . '-loadXML' );

                if ( $cacheable ) {
                        wfProfileOut( __METHOD__ . '-cacheable' );
                }

                wfProfileOut( __METHOD__ );

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

        /**
         * @param string $text
         * @param int $flags
         * @return string
         */
        function preprocessToXml( $text, $flags = 0 ) {
                wfProfileIn( __METHOD__ );
                $rules = array(
                        '{' => array(
                                'end' => '}',
                                'names' => array(
                                        2 => 'template',
                                        3 => 'tplarg',
                                ),
                                'min' => 2,
                                'max' => 3,
                        ),
                        '[' => array(
                                'end' => ']',
                                'names' => array( 2 => null ),
                                'min' => 2,
                                'max' => 2,
                        )
                );

                $forInclusion = $flags & Parser::PTD_FOR_INCLUSION;

                $xmlishElements = $this->parser->getStripList();
                $enableOnlyinclude = false;
                if ( $forInclusion ) {
                        $ignoredTags = array( 'includeonly', '/includeonly' );
                        $ignoredElements = array( 'noinclude' );
                        $xmlishElements[] = 'noinclude';
                        if ( strpos( $text, '<onlyinclude>' ) !== false
                                && strpos( $text, '</onlyinclude>' ) !== false
                        ) {
                                $enableOnlyinclude = true;
                        }
                } else {
                        $ignoredTags = array( 'noinclude', '/noinclude', 'onlyinclude', '/onlyinclude' );
                        $ignoredElements = array( '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;
                // 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( $rules[$curChar] ) ) {
                                                $found = 'open';
                                                $rule = $rules[$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 = array( array( $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[] = array( $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 ( 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 -- let it run out to the end of the text.
                                                $inner = substr( $text, $tagEndPos + 1 );
                                                $i = $lengthText;
                                                $close = '';
                                        }
                                }
                                // <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 = array(
                                                'open' => "\n",
                                                'close' => "\n",
                                                'parts' => array( 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 = array(
                                                '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 = $rules[$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 = array( new PPDPart );
                                        $piece->count -= $matchingCount;
                                        # do we still qualify for any callback with remaining count?
                                        $min = $rules[$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;

                wfProfileOut( __METHOD__ );

                return $xml;
        }
}

/**
 * Stack class to help Preprocessor::preprocessToObj()
 * @ingroup Parser
 */
class PPDStack {
        var $stack, $rootAccum;

        /**
         * @var PPDStack
         */
        var $top;
        var $out;
        var $elementClass = 'PPDStackElement';

        static $false = false;

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

        /**
         * @return int
         */
        function count() {
                return count( $this->stack );
        }

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

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

        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();
        }

        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;
        }

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

        /**
         * @return array
         */
        function getFlags() {
                if ( !count( $this->stack ) ) {
                        return array(
                                'findEquals' => false,
                                'findPipe' => false,
                                'inHeading' => false,
                        );
                } else {
                        return $this->top->getFlags();
                }
        }
}

/**
 * @ingroup Parser
 */
class PPDStackElement {
        var     $open,              // Opening character (\n for heading)
                $close,             // Matching closing character
                $count,             // Number of opening characters found (number of "=" for heading)
                $parts,             // Array of PPDPart objects describing pipe-separated parts.
                $lineStart;         // True if the open char appeared at the start of the input line. Not set for headings.

        var $partClass = 'PPDPart';

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

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

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

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

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

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

        /**
         * Get the output string that would result if the close is not found.
         *
         * @param bool|int $openingCount
         * @return string
         */
        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;
        }
}

/**
 * @ingroup Parser
 */
class PPDPart {
        var $out; // Output accumulator string

        // 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

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

/**
 * An expansion frame, used as a context to expand the result of preprocessToObj()
 * @ingroup Parser
 */
class PPFrame_DOM implements PPFrame {

        /**
         * @var Preprocessor
         */
        var $preprocessor;

        /**
         * @var Parser
         */
        var $parser;

        /**
         * @var Title
         */
        var $title;
        var $titleCache;

        /**
         * Hashtable listing templates which are disallowed for expansion in this frame,
         * having been encountered previously in parent frames.
         */
        var $loopCheckHash;

        /**
         * Recursion depth of this frame, top = 0
         * Note that this is NOT the same as expansion depth in expand()
         */
        var $depth;

        private $volatile = false;

        /**
         * @var array
         */
        protected $childExpansionCache;

        /**
         * Construct a new preprocessor frame.
         * @param Preprocessor $preprocessor The parent preprocessor
         */
        function __construct( $preprocessor ) {
                $this->preprocessor = $preprocessor;
                $this->parser = $preprocessor->parser;
                $this->title = $this->parser->mTitle;
                $this->titleCache = array( $this->title ? $this->title->getPrefixedDBkey() : false );
                $this->loopCheckHash = array();
                $this->depth = 0;
                $this->childExpansionCache = array();
        }

        /**
         * Create a new child frame
         * $args is optionally a multi-root PPNode or array containing the template arguments
         *
         * @param bool|array $args
         * @param Title|bool $title
         * @param int $indexOffset
         * @return PPTemplateFrame_DOM
         */
        function newChild( $args = false, $title = false, $indexOffset = 0 ) {
                $namedArgs = array();
                $numberedArgs = array();
                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 = 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;
                                        $numberedArgs[$index] = $value->item( 0 );
                                        unset( $namedArgs[$index] );
                                } else {
                                        // Named parameter
                                        $name = trim( $this->expand( $nameNodes->item( 0 ), PPFrame::STRIP_COMMENTS ) );
                                        $namedArgs[$name] = $value->item( 0 );
                                        unset( $numberedArgs[$name] );
                                }
                        }
                }
                return new PPTemplateFrame_DOM( $this->preprocessor, $this, $numberedArgs, $namedArgs, $title );
        }

        /**
         * @throws MWException
         * @param string|int $key
         * @param string|PPNode_DOM|DOMDocument $root
         * @param int $flags
         * @return string
         */
        function cachedExpand( $key, $root, $flags = 0 ) {
                // we don't have a parent, so we don't have a cache
                return $this->expand( $root, $flags );
        }

        /**
         * @throws MWException
         * @param string|PPNode_DOM|DOMDocument $root
         * @param int $flags
         * @return string
         */
        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,
                                $this->parser->mOptions->getMaxPPExpandDepth()
                        );
                        return '<span class="error">Expansion depth limit exceeded</span>';
                }
                wfProfileIn( __METHOD__ );
                ++$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 = array( '', '' );
                $iteratorStack = array( false, $root );
                $indexStack = array( 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 = array(
                                                        '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 = array(
                                                        '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
                                        if ( $this->parser->ot['html']
                                                || ( $this->parser->ot['pre'] && $this->parser->mOptions->getRemoveComments() )
                                                || ( $flags & PPFrame::STRIP_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 );
                                        $params = array(
                                                '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[] = array( $titleText, $headingIndex );
                                                $serial = count( $this->parser->mHeadings ) - 1;
                                                $marker = "{$this->parser->mUniqPrefix}-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 {
                                wfProfileOut( __METHOD__ );
                                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;
                wfProfileOut( __METHOD__ );
                return $outStack[0];
        }

        /**
         * @param string $sep
         * @param int $flags
         * @return string
         */
        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 = array( $root );
                        }
                        foreach ( $root as $node ) {
                                if ( $first ) {
                                        $first = false;
                                } else {
                                        $s .= $sep;
                                }
                                $s .= $this->expand( $node, $flags );
                        }
                }
                return $s;
        }

        /**
         * Implode with no flags specified
         * This previously called implodeWithFlags but has now been inlined to reduce stack depth
         *
         * @param string $sep
         * @return string
         */
        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 = array( $root );
                        }
                        foreach ( $root as $node ) {
                                if ( $first ) {
                                        $first = false;
                                } else {
                                        $s .= $sep;
                                }
                                $s .= $this->expand( $node );
                        }
                }
                return $s;
        }

        /**
         * Makes an object that, when expand()ed, will be the same as one obtained
         * with implode()
         *
         * @param string $sep
         * @return array
         */
        function virtualImplode( $sep /*, ... */ ) {
                $args = array_slice( func_get_args(), 1 );
                $out = array();
                $first = true;

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

        /**
         * Virtual implode with brackets
         * @param string $start
         * @param string $sep
         * @param string $end
         * @return array
         */
        function virtualBracketedImplode( $start, $sep, $end /*, ... */ ) {
                $args = array_slice( func_get_args(), 3 );
                $out = array( $start );
                $first = true;

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

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

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

        /**
         * @return array
         */
        function getArguments() {
                return array();
        }

        /**
         * @return array
         */
        function getNumberedArguments() {
                return array();
        }

        /**
         * @return array
         */
        function getNamedArguments() {
                return array();
        }

        /**
         * Returns true if there are no arguments in this frame
         *
         * @return bool
         */
        function isEmpty() {
                return true;
        }

        function getArgument( $name ) {
                return false;
        }

        /**
         * Returns true if the infinite loop check is OK, false if a loop is detected
         *
         * @param Title $title
         * @return bool
         */
        function loopCheck( $title ) {
                return !isset( $this->loopCheckHash[$title->getPrefixedDBkey()] );
        }

        /**
         * Return true if the frame is a template frame
         *
         * @return bool
         */
        function isTemplate() {
                return false;
        }

        /**
         * Get a title of frame
         *
         * @return Title
         */
        function getTitle() {
                return $this->title;
        }

        /**
         * Set the volatile flag
         *
         * @param bool $flag
         */
        function setVolatile( $flag = true ) {
                $this->volatile = $flag;
        }

        /**
         * Get the volatile flag
         *
         * @return bool
         */
        function isVolatile() {
                return $this->volatile;
        }
}

/**
 * Expansion frame with template arguments
 * @ingroup Parser
 */
class PPTemplateFrame_DOM extends PPFrame_DOM {
        var $numberedArgs, $namedArgs;

        /**
         * @var PPFrame_DOM
         */
        var $parent;
        var $numberedExpansionCache, $namedExpansionCache;

        /**
         * @param Preprocessor $preprocessor
         * @param bool|PPFrame_DOM $parent
         * @param array $numberedArgs
         * @param array $namedArgs
         * @param bool|Title $title
         */
        function __construct( $preprocessor, $parent = false, $numberedArgs = array(),
                $namedArgs = array(), $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 = array();
        }

        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;
        }

        /**
         * @throws MWException
         * @param string|int $key
         * @param string|PPNode_DOM|DOMDocument $root
         * @param int $flags
         * @return string
         */
        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;
        }

        /**
         * Returns true if there are no arguments in this frame
         *
         * @return bool
         */
        function isEmpty() {
                return !count( $this->numberedArgs ) && !count( $this->namedArgs );
        }

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

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

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

        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];
        }

        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];
        }

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

        /**
         * Return true if the frame is a template frame
         *
         * @return bool
         */
        function isTemplate() {
                return true;
        }

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

/**
 * Expansion frame with custom arguments
 * @ingroup Parser
 */
class PPCustomFrame_DOM extends PPFrame_DOM {
        var $args;

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

        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;
        }

        /**
         * @return bool
         */
        function isEmpty() {
                return !count( $this->args );
        }

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

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

/**
 * @ingroup Parser
 */
class PPNode_DOM implements PPNode {

        /**
         * @var DOMElement
         */
        var $node;
        var $xpath;

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

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

        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;
        }

        /**
         * @return bool|PPNode_DOM
         */
        function getChildren() {
                return $this->node->childNodes ? new self( $this->node->childNodes ) : false;
        }

        /**
         * @return bool|PPNode_DOM
         */
        function getFirstChild() {
                return $this->node->firstChild ? new self( $this->node->firstChild ) : false;
        }

        /**
         * @return bool|PPNode_DOM
         */
        function getNextSibling() {
                return $this->node->nextSibling ? new self( $this->node->nextSibling ) : false;
        }

        /**
         * @param string $type
         *
         * @return bool|PPNode_DOM
         */
        function getChildrenOfType( $type ) {
                return new self( $this->getXPath()->query( $type, $this->node ) );
        }

        /**
         * @return int
         */
        function getLength() {
                if ( $this->node instanceof DOMNodeList ) {
                        return $this->node->length;
                } else {
                        return false;
                }
        }

        /**
         * @param int $i
         * @return bool|PPNode_DOM
         */
        function item( $i ) {
                $item = $this->node->item( $i );
                return $item ? new self( $item ) : false;
        }

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

        /**
         * Split a "<part>" node into an associative array containing:
         *  - name          PPNode name
         *  - index         String index
         *  - value         PPNode value
         *
         * @throws MWException
         * @return array
         */
        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 array(
                        'name' => new self( $name ),
                        'index' => $index,
                        'value' => new self( $values->item( 0 ) ) );
        }

        /**
         * Split an "<ext>" node into an associative array containing name, attr, inner and close
         * All values in the resulting array are PPNodes. Inner and close are optional.
         *
         * @throws MWException
         * @return array
         */
        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 = array(
                        '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;
        }

        /**
         * Split a "<h>" node
         * @throws MWException
         * @return array
         */
        function splitHeading() {
                if ( $this->getName() !== 'h' ) {
                        throw new MWException( 'Invalid h node passed to ' . __METHOD__ );
                }
                return array(
                        'i' => $this->node->getAttribute( 'i' ),
                        'level' => $this->node->getAttribute( 'level' ),
                        'contents' => $this->getChildren()
                );
        }
}