Preprocessor_Hash.php

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

    public $parser;

    const CACHE_PREFIX = 'preprocess-hash';
    const CACHE_VERSION = 2;

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

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

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

    public function newPartNodeArray( $values ) {
        $list = [];

        foreach ( $values as $k => $val ) {
            if ( is_int( $k ) ) {
                $store = [ [ 'part', [
                    [ 'name', [ [ '@index', [ $k ] ] ] ],
                    [ 'value', [ strval( $val ) ] ],
                ] ] ];
            } else {
                $store = [ [ 'part', [
                    [ 'name', [ strval( $k ) ] ],
                    '=',
                    [ 'value', [ strval( $val ) ] ],
                ] ] ];
            }

            $list[] = new PPNode_Hash_Tree( $store, 0 );
        }

        $node = new PPNode_Hash_Array( $list );
        return $node;
    }

    public function preprocessToObj( $text, $flags = 0 ) {
        $tree = $this->cacheGetTree( $text, $flags );
        if ( $tree !== false ) {
            $store = json_decode( $tree );
            if ( is_array( $store ) ) {
                return new PPNode_Hash_Tree( $store, 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_Hash;

        $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. See the doc comment for Preprocessor_Hash for the format.
        $accum =& $stack->getAccum();
        // 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', [ substr( $text, $i ) ] ];
                    break;
                }
                $tagEndPos = $startPos + strlen( '<onlyinclude>' ); // past-the-end
                $accum[] = [ 'ignore', [ substr( $text, $i, $tagEndPos - $i ) ] ];
                $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 ) {
                    self::addLiteral( $accum, 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
                    self::addLiteral( $accum, '<' );
                    ++$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', [ $inner ] ];
                        $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
                            $wsLength = $i - $wsStart;
                            $endIndex = count( $accum ) - 1;

                            // Sanity check
                            if ( $wsLength > 0
                                && $endIndex >= 0
                                && is_string( $accum[$endIndex] )
                                && strspn( $accum[$endIndex], " \t", -$wsLength ) === $wsLength
                            ) {
                                $accum[$endIndex] = substr( $accum[$endIndex], 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', [ $inner ] ];
                            }

                            // 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', [ $inner ] ];
                    }
                    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;
                    self::addLiteral( $accum, '<' );
                    ++$i;
                    continue;
                }

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

                $tagStartPos = $i;
                if ( $text[$tagEndPos - 1] == '/' ) {
                    // Short end tag
                    $attrEnd = $tagEndPos - 1;
                    $inner = null;
                    $i = $tagEndPos + 1;
                    $close = null;
                } 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 = $matches[0][0];
                    } 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 = null;
                        } else {
                            // Don't match the tag, treat opening tag as literal and resume parsing.
                            $i = $tagEndPos + 1;
                            self::addLiteral( $accum,
                                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', [ substr( $text, $tagStartPos, $i - $tagStartPos ) ] ];
                    continue;
                }

                if ( $attrEnd <= $attrStart ) {
                    $attr = '';
                } else {
                    // Note that the attr element contains the whitespace between name and attribute,
                    // this is necessary for precise reconstruction during pre-save transform.
                    $attr = substr( $text, $attrStart, $attrEnd - $attrStart );
                }

                $children = [
                    [ 'name', [ $name ] ],
                    [ 'attr', [ $attr ] ] ];
                if ( $inner !== null ) {
                    $children[] = [ 'inner', [ $inner ] ];
                }
                if ( $close !== null ) {
                    $children[] = [ 'close', [ $close ] ];
                }
                $accum[] = [ 'ext', $children ];
            } 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 {
                    self::addLiteral( $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_Hash( str_repeat( '=', $count ) ) ],
                        'startPos' => $i,
                        'count' => $count ];
                    $stack->push( $piece );
                    $accum =& $stack->getAccum();
                    extract( $stack->getFlags() );
                    $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 = [ [ 'possible-h',
                            array_merge(
                                [
                                    [ '@level', [ $count ] ],
                                    [ '@i', [ $headingIndex++ ] ]
                                ],
                                $accum
                            )
                        ] ];
                    } 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();
                extract( $stack->getFlags() );

                // Append the result to the enclosing accumulator
                array_splice( $accum, count( $accum ), 0, $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();
                    extract( $stack->getFlags() );
                } else {
                    # Add literal brace(s)
                    self::addLiteral( $accum, 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
                    self::addLiteral( $accum, str_repeat( $curChar, $count ) );
                    $i += $count;
                    continue;
                }
                $name = $rule['names'][$matchingCount];
                if ( $name === null ) {
                    // No element, just literal text
                    $element = $piece->breakSyntax( $matchingCount );
                    self::addLiteral( $element, str_repeat( $rule['end'], $matchingCount ) );
                } else {
                    # Create XML element
                    $parts = $piece->parts;
                    $titleAccum = $parts[0]->out;
                    unset( $parts[0] );

                    $children = [];

                    # 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 ) ) {
                        $children[] = [ '@lineStart', [ 1 ] ];
                    }
                    $titleNode = [ 'title', $titleAccum ];
                    $children[] = $titleNode;
                    $argIndex = 1;
                    foreach ( $parts as $part ) {
                        if ( isset( $part->eqpos ) ) {
                            $equalsNode = $part->out[$part->eqpos];
                            $nameNode = [ 'name', array_slice( $part->out, 0, $part->eqpos ) ];
                            $valueNode = [ 'value', array_slice( $part->out, $part->eqpos + 1 ) ];
                            $partNode = [ 'part', [ $nameNode, $equalsNode, $valueNode ] ];
                            $children[] = $partNode;
                        } else {
                            $nameNode = [ 'name', [ [ '@index', [ $argIndex++ ] ] ] ];
                            $valueNode = [ 'value', $part->out ];
                            $partNode = [ 'part', [ $nameNode, $valueNode ] ];
                            $children[] = $partNode;
                        }
                    }
                    $element = [ [ $name, $children ] ];
                }

                # 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_Hash ];
                    $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 {
                        self::addLiteral( $accum, str_repeat( $piece->open, $piece->count ) );
                    }
                }

                extract( $stack->getFlags() );

                # Add XML element to the enclosing accumulator
                array_splice( $accum, count( $accum ), 0, $element );
            } elseif ( $found == 'pipe' ) {
                $findEquals = true; // shortcut for getFlags()
                $stack->addPart();
                $accum =& $stack->getAccum();
                ++$i;
            } elseif ( $found == 'equals' ) {
                $findEquals = false; // shortcut for getFlags()
                $accum[] = [ 'equals', [ '=' ] ];
                $stack->getCurrentPart()->eqpos = count( $accum ) - 1;
                ++$i;
            }
        }

        # Output any remaining unclosed brackets
        foreach ( $stack->stack as $piece ) {
            array_splice( $stack->rootAccum, count( $stack->rootAccum ), 0, $piece->breakSyntax() );
        }

        # Enable top-level headings
        foreach ( $stack->rootAccum as &$node ) {
            if ( is_array( $node ) && $node[PPNode_Hash_Tree::NAME] === 'possible-h' ) {
                $node[PPNode_Hash_Tree::NAME] = 'h';
            }
        }

        $rootStore = [ [ 'root', $stack->rootAccum ] ];
        $rootNode = new PPNode_Hash_Tree( $rootStore, 0 );

        // Cache
        $tree = json_encode( $rootStore, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE );
        if ( $tree !== false ) {
            $this->cacheSetTree( $text, $flags, $tree );
        }

        return $rootNode;
    }

    private static function addLiteral( array &$accum, $text ) {
        $n = count( $accum );
        if ( $n && is_string( $accum[$n - 1] ) ) {
            $accum[$n - 1] .= $text;
        } else {
            $accum[] = $text;
        }
    }
}

// @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps
class PPDStack_Hash extends PPDStack {
    // @codingStandardsIgnoreEnd

    public function __construct() {
        $this->elementClass = 'PPDStackElement_Hash';
        parent::__construct();
        $this->rootAccum = [];
    }
}

// @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps
class PPDStackElement_Hash extends PPDStackElement {
    // @codingStandardsIgnoreEnd

    public function __construct( $data = [] ) {
        $this->partClass = 'PPDPart_Hash';
        parent::__construct( $data );
    }

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

// @codingStandardsIgnoreStart Squiz.Classes.ValidClassName.NotCamelCaps
class PPDPart_Hash extends PPDPart {
    // @codingStandardsIgnoreEnd

    public function __construct( $out = '' ) {
        if ( $out !== '' ) {
            $accum = [ $out ];
        } else {
            $accum = [];
        }
        parent::__construct( $accum );
    }
}

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

    public $parser;

    public $preprocessor;

    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 ) {
            if ( $args instanceof PPNode_Hash_Array ) {
                $args = $args->value;
            } elseif ( !is_array( $args ) ) {
                throw new MWException( __METHOD__ . ': $args must be array or PPNode_Hash_Array' );
            }
            foreach ( $args as $arg ) {
                $bits = $arg->splitArg();
                if ( $bits['index'] !== '' ) {
                    // Numbered parameter
                    $index = $bits['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] = $bits['value'];
                    unset( $namedArgs[$index] );
                } else {
                    // Named parameter
                    $name = trim( $this->expand( $bits['name'], 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] = $bits['value'];
                    unset( $numberedArgs[$name] );
                }
            }
        }
        return new PPTemplateFrame_Hash( $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;
        }

        $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 ( 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 PPNode_Hash_Array ) {
                if ( $index >= $iteratorNode->getLength() ) {
                    // 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;
            }

            $newIterator = false;
            $contextName = false;
            $contextChildren = false;

            if ( $contextNode === false ) {
                // nothing to do
            } elseif ( is_string( $contextNode ) ) {
                $out .= $contextNode;
            } elseif ( $contextNode instanceof PPNode_Hash_Array ) {
                $newIterator = $contextNode;
            } elseif ( $contextNode instanceof PPNode_Hash_Attr ) {
                // No output
            } elseif ( $contextNode instanceof PPNode_Hash_Text ) {
                $out .= $contextNode->value;
            } elseif ( $contextNode instanceof PPNode_Hash_Tree ) {
                $contextName = $contextNode->name;
                $contextChildren = $contextNode->getRawChildren();
            } elseif ( is_array( $contextNode ) ) {
                // Node descriptor array
                if ( count( $contextNode ) !== 2 ) {
                    throw new MWException( __METHOD__.
                        ': found an array where a node descriptor should be' );
                }
                list( $contextName, $contextChildren ) = $contextNode;
            } else {
                throw new MWException( __METHOD__ . ': Invalid parameter type' );
            }

            // Handle node descriptor array or tree object
            if ( $contextName === false ) {
                // Not a node, already handled above
            } elseif ( $contextName[0] === '@' ) {
                // Attribute: no output
            } elseif ( $contextName === 'template' ) {
                # Double-brace expansion
                $bits = PPNode_Hash_Tree::splitRawTemplate( $contextChildren );
                if ( $flags & PPFrame::NO_TEMPLATES ) {
                    $newIterator = $this->virtualBracketedImplode(
                        '{{', '|', '}}',
                        $bits['title'],
                        $bits['parts']
                    );
                } else {
                    $ret = $this->parser->braceSubstitution( $bits, $this );
                    if ( isset( $ret['object'] ) ) {
                        $newIterator = $ret['object'];
                    } else {
                        $out .= $ret['text'];
                    }
                }
            } elseif ( $contextName === 'tplarg' ) {
                # Triple-brace expansion
                $bits = PPNode_Hash_Tree::splitRawTemplate( $contextChildren );
                if ( $flags & PPFrame::NO_ARGS ) {
                    $newIterator = $this->virtualBracketedImplode(
                        '{{{', '|', '}}}',
                        $bits['title'],
                        $bits['parts']
                    );
                } else {
                    $ret = $this->parser->argSubstitution( $bits, $this );
                    if ( isset( $ret['object'] ) ) {
                        $newIterator = $ret['object'];
                    } else {
                        $out .= $ret['text'];
                    }
                }
            } elseif ( $contextName === '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( $contextChildren[0] );
                } else {
                    # Recover the literal comment in RECOVER_COMMENTS and pre+no-remove
                    $out .= $contextChildren[0];
                }
            } elseif ( $contextName === '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 .= $contextChildren[0];
                } else {
                    // $out .= '';
                }
            } elseif ( $contextName === 'ext' ) {
                # Extension tag
                $bits = PPNode_Hash_Tree::splitRawExt( $contextChildren ) +
                    [ 'attr' => null, 'inner' => null, 'close' => null ];
                if ( $flags & PPFrame::NO_TAGS ) {
                    $s = '<' . $bits['name']->getFirstChild()->value;
                    if ( $bits['attr'] ) {
                        $s .= $bits['attr']->getFirstChild()->value;
                    }
                    if ( $bits['inner'] ) {
                        $s .= '>' . $bits['inner']->getFirstChild()->value;
                        if ( $bits['close'] ) {
                            $s .= $bits['close']->getFirstChild()->value;
                        }
                    } else {
                        $s .= '/>';
                    }
                    $out .= $s;
                } else {
                    $out .= $this->parser->extensionSubstitution( $bits, $this );
                }
            } elseif ( $contextName === 'h' ) {
                # Heading
                if ( $this->parser->ot['html'] ) {
                    # Expand immediately and insert heading index marker
                    $s = $this->expand( $contextChildren, $flags );
                    $bits = PPNode_Hash_Tree::splitRawHeading( $contextChildren );
                    $titleText = $this->title->getPrefixedDBkey();
                    $this->parser->mHeadings[] = [ $titleText, $bits['i'] ];
                    $serial = count( $this->parser->mHeadings ) - 1;
                    $marker = Parser::MARKER_PREFIX . "-h-$serial-" . Parser::MARKER_SUFFIX;
                    $s = substr( $s, 0, $bits['level'] ) . $marker . substr( $s, $bits['level'] );
                    $this->parser->mStripState->addGeneral( $marker, '' );
                    $out .= $s;
                } else {
                    # Expand in virtual stack
                    $newIterator = $contextChildren;
                }
            } else {
                # Generic recursive expansion
                $newIterator = $contextChildren;
            }

            if ( $newIterator !== false ) {
                $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_Hash_Array ) {
                $root = $root->value;
            }
            if ( !is_array( $root ) ) {
                $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_Hash_Array ) {
                $root = $root->value;
            }
            if ( !is_array( $root ) ) {
                $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_Hash_Array ) {
                $root = $root->value;
            }
            if ( !is_array( $root ) ) {
                $root = [ $root ];
            }
            foreach ( $root as $node ) {
                if ( $first ) {
                    $first = false;
                } else {
                    $out[] = $sep;
                }
                $out[] = $node;
            }
        }
        return new PPNode_Hash_Array( $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_Hash_Array ) {
                $root = $root->value;
            }
            if ( !is_array( $root ) ) {
                $root = [ $root ];
            }
            foreach ( $root as $node ) {
                if ( $first ) {
                    $first = false;
                } else {
                    $out[] = $sep;
                }
                $out[] = $node;
            }
        }
        $out[] = $end;
        return new PPNode_Hash_Array( $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_Hash extends PPFrame_Hash {
    // @codingStandardsIgnoreEnd

    public $numberedArgs, $namedArgs, $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->__toString() ) . '"';
        }
        $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_Hash extends PPFrame_Hash {
    // @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_Hash_Tree implements PPNode {
    // @codingStandardsIgnoreEnd

    public $name;

    private $rawChildren;

    private $store;

    private $index;

    const NAME = 0;

    const CHILDREN = 1;

    public function __construct( array $store, $index ) {
        $this->store = $store;
        $this->index = $index;
        list( $this->name, $this->rawChildren ) = $this->store[$index];
    }

    public static function factory( array $store, $index ) {
        if ( !isset( $store[$index] ) ) {
            return false;
        }

        $descriptor = $store[$index];
        if ( is_string( $descriptor ) ) {
            $class = 'PPNode_Hash_Text';
        } elseif ( is_array( $descriptor ) ) {
            if ( $descriptor[self::NAME][0] === '@' ) {
                $class = 'PPNode_Hash_Attr';
            } else {
                $class = 'PPNode_Hash_Tree';
            }
        } else {
            throw new MWException( __METHOD__.': invalid node descriptor' );
        }
        return new $class( $store, $index );
    }

    public function __toString() {
        $inner = '';
        $attribs = '';
        for ( $node = $this->getFirstChild(); $node; $node = $node->getNextSibling() ) {
            if ( $node instanceof PPNode_Hash_Attr ) {
                $attribs .= ' ' . $node->name . '="' . htmlspecialchars( $node->value ) . '"';
            } else {
                $inner .= $node->__toString();
            }
        }
        if ( $inner === '' ) {
            return "<{$this->name}$attribs/>";
        } else {
            return "<{$this->name}$attribs>$inner</{$this->name}>";
        }
    }

    public function getChildren() {
        $children = [];
        foreach ( $this->rawChildren as $i => $child ) {
            $children[] = self::factory( $this->rawChildren, $i );
        }
        return new PPNode_Hash_Array( $children );
    }

    public function getFirstChild() {
        if ( !isset( $this->rawChildren[0] ) ) {
            return false;
        } else {
            return self::factory( $this->rawChildren, 0 );
        }
    }

    public function getNextSibling() {
        return self::factory( $this->store, $this->index + 1 );
    }

    public function getChildrenOfType( $name ) {
        $children = [];
        foreach ( $this->rawChildren as $i => $child ) {
            if ( is_array( $child ) && $child[self::NAME] === $name ) {
                $children[] = self::factory( $this->rawChildren, $i );
            }
        }
        return new PPNode_Hash_Array( $children );
    }

    public function getRawChildren() {
        return $this->rawChildren;
    }

    public function getLength() {
        return false;
    }

    public function item( $i ) {
        return false;
    }

    public function getName() {
        return $this->name;
    }

    public function splitArg() {
        return self::splitRawArg( $this->rawChildren );
    }

    public static function splitRawArg( array $children ) {
        $bits = [];
        foreach ( $children as $i => $child ) {
            if ( !is_array( $child ) ) {
                continue;
            }
            if ( $child[self::NAME] === 'name' ) {
                $bits['name'] = new self( $children, $i );
                if ( isset( $child[self::CHILDREN][0][self::NAME] )
                    && $child[self::CHILDREN][0][self::NAME] === '@index'
                ) {
                    $bits['index'] = $child[self::CHILDREN][0][self::CHILDREN][0];
                }
            } elseif ( $child[self::NAME] === 'value' ) {
                $bits['value'] = new self( $children, $i );
            }
        }

        if ( !isset( $bits['name'] ) ) {
            throw new MWException( 'Invalid brace node passed to ' . __METHOD__ );
        }
        if ( !isset( $bits['index'] ) ) {
            $bits['index'] = '';
        }
        return $bits;
    }

    public function splitExt() {
        return self::splitRawExt( $this->rawChildren );
    }

    public static function splitRawExt( array $children ) {
        $bits = [];
        foreach ( $children as $i => $child ) {
            if ( !is_array( $child ) ) {
                continue;
            }
            switch ( $child[self::NAME] ) {
            case 'name':
                $bits['name'] = new self( $children, $i );
                break;
            case 'attr':
                $bits['attr'] = new self( $children, $i );
                break;
            case 'inner':
                $bits['inner'] = new self( $children, $i );
                break;
            case 'close':
                $bits['close'] = new self( $children, $i );
                break;
            }
        }
        if ( !isset( $bits['name'] ) ) {
            throw new MWException( 'Invalid ext node passed to ' . __METHOD__ );
        }
        return $bits;
    }

    public function splitHeading() {
        if ( $this->name !== 'h' ) {
            throw new MWException( 'Invalid h node passed to ' . __METHOD__ );
        }
        return self::splitRawHeading( $this->rawChildren );
    }

    public static function splitRawHeading( array $children ) {
        $bits = [];
        foreach ( $children as $i => $child ) {
            if ( !is_array( $child ) ) {
                continue;
            }
            if ( $child[self::NAME] === '@i' ) {
                $bits['i'] = $child[self::CHILDREN][0];
            } elseif ( $child[self::NAME] === '@level' ) {
                $bits['level'] = $child[self::CHILDREN][0];
            }
        }
        if ( !isset( $bits['i'] ) ) {
            throw new MWException( 'Invalid h node passed to ' . __METHOD__ );
        }
        return $bits;
    }

    public function splitTemplate() {
        return self::splitRawTemplate( $this->rawChildren );
    }

    public static function splitRawTemplate( array $children ) {
        $parts = [];
        $bits = [ 'lineStart' => '' ];
        foreach ( $children as $i => $child ) {
            if ( !is_array( $child ) ) {
                continue;
            }
            switch ( $child[self::NAME] ) {
            case 'title':
                $bits['title'] = new self( $children, $i );
                break;
            case 'part':
                $parts[] = new self( $children, $i );
                break;
            case '@lineStart':
                $bits['lineStart'] = '1';
                break;
            }
        }
        if ( !isset( $bits['title'] ) ) {
            throw new MWException( 'Invalid node passed to ' . __METHOD__ );
        }
        $bits['parts'] = new PPNode_Hash_Array( $parts );
        return $bits;
    }
}

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

    public $value;
    private $store, $index;

    public function __construct( array $store, $index ) {
        $this->value = $store[$index];
        if ( !is_scalar( $this->value ) ) {
            throw new MWException( __CLASS__ . ' given object instead of string' );
        }
        $this->store = $store;
        $this->index = $index;
    }

    public function __toString() {
        return htmlspecialchars( $this->value );
    }

    public function getNextSibling() {
        return PPNode_Hash_Tree::factory( $this->store, $this->index + 1 );
    }

    public function getChildren() {
        return false;
    }

    public function getFirstChild() {
        return false;
    }

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

    public function getLength() {
        return false;
    }

    public function item( $i ) {
        return false;
    }

    public function getName() {
        return '#text';
    }

    public function splitArg() {
        throw new MWException( __METHOD__ . ': not supported' );
    }

    public function splitExt() {
        throw new MWException( __METHOD__ . ': not supported' );
    }

    public function splitHeading() {
        throw new MWException( __METHOD__ . ': not supported' );
    }
}

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

    public $value;

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

    public function __toString() {
        return var_export( $this, true );
    }

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

    public function item( $i ) {
        return $this->value[$i];
    }

    public function getName() {
        return '#nodelist';
    }

    public function getNextSibling() {
        return false;
    }

    public function getChildren() {
        return false;
    }

    public function getFirstChild() {
        return false;
    }

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

    public function splitArg() {
        throw new MWException( __METHOD__ . ': not supported' );
    }

    public function splitExt() {
        throw new MWException( __METHOD__ . ': not supported' );
    }

    public function splitHeading() {
        throw new MWException( __METHOD__ . ': not supported' );
    }
}

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

    public $name, $value;
    private $store, $index;

    public function __construct( array $store, $index ) {
        $descriptor = $store[$index];
        if ( $descriptor[PPNode_Hash_Tree::NAME][0] !== '@' ) {
            throw new MWException( __METHOD__.': invalid name in attribute descriptor' );
        }
        $this->name = substr( $descriptor[PPNode_Hash_Tree::NAME], 1 );
        $this->value = $descriptor[PPNode_Hash_Tree::CHILDREN][0];
        $this->store = $store;
        $this->index = $index;
    }

    public function __toString() {
        return "<@{$this->name}>" . htmlspecialchars( $this->value ) . "</@{$this->name}>";
    }

    public function getName() {
        return $this->name;
    }

    public function getNextSibling() {
        return PPNode_Hash_Tree::factory( $this->store, $this->index + 1 );
    }

    public function getChildren() {
        return false;
    }

    public function getFirstChild() {
        return false;
    }

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

    public function getLength() {
        return false;
    }

    public function item( $i ) {
        return false;
    }

    public function splitArg() {
        throw new MWException( __METHOD__ . ': not supported' );
    }

    public function splitExt() {
        throw new MWException( __METHOD__ . ': not supported' );
    }

    public function splitHeading() {
        throw new MWException( __METHOD__ . ': not supported' );
    }
}