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-<?php
-
-/**
- * Takes a well formed list of tokens and fixes their nesting.
- *
- * HTML elements dictate which elements are allowed to be their children,
- * for example, you can't have a p tag in a span tag. Other elements have
- * much more rigorous definitions: tables, for instance, require a specific
- * order for their elements. There are also constraints not expressible by
- * document type definitions, such as the chameleon nature of ins/del
- * tags and global child exclusions.
- *
- * The first major objective of this strategy is to iterate through all the
- * nodes (not tokens) of the list of tokens and determine whether or not
- * their children conform to the element's definition. If they do not, the
- * child definition may optionally supply an amended list of elements that
- * is valid or require that the entire node be deleted (and the previous
- * node rescanned).
- *
- * The second objective is to ensure that explicitly excluded elements of
- * an element do not appear in its children. Code that accomplishes this
- * task is pervasive through the strategy, though the two are distinct tasks
- * and could, theoretically, be seperated (although it's not recommended).
- *
- * @note Whether or not unrecognized children are silently dropped or
- * translated into text depends on the child definitions.
- *
- * @todo Enable nodes to be bubbled out of the structure.
- */
-
-class HTMLPurifier_Strategy_FixNesting extends HTMLPurifier_Strategy
-{
-
- public function execute($tokens, $config, $context) {
- //####################################################################//
- // Pre-processing
-
- // get a copy of the HTML definition
- $definition = $config->getHTMLDefinition();
-
- // insert implicit "parent" node, will be removed at end.
- // DEFINITION CALL
- $parent_name = $definition->info_parent;
- array_unshift($tokens, new HTMLPurifier_Token_Start($parent_name));
- $tokens[] = new HTMLPurifier_Token_End($parent_name);
-
- // setup the context variable 'IsInline', for chameleon processing
- // is 'false' when we are not inline, 'true' when it must always
- // be inline, and an integer when it is inline for a certain
- // branch of the document tree
- $is_inline = $definition->info_parent_def->descendants_are_inline;
- $context->register('IsInline', $is_inline);
-
- // setup error collector
- $e =& $context->get('ErrorCollector', true);
-
- //####################################################################//
- // Loop initialization
-
- // stack that contains the indexes of all parents,
- // $stack[count($stack)-1] being the current parent
- $stack = array();
-
- // stack that contains all elements that are excluded
- // it is organized by parent elements, similar to $stack,
- // but it is only populated when an element with exclusions is
- // processed, i.e. there won't be empty exclusions.
- $exclude_stack = array();
-
- // variable that contains the start token while we are processing
- // nodes. This enables error reporting to do its job
- $start_token = false;
- $context->register('CurrentToken', $start_token);
-
- //####################################################################//
- // Loop
-
- // iterate through all start nodes. Determining the start node
- // is complicated so it has been omitted from the loop construct
- for ($i = 0, $size = count($tokens) ; $i < $size; ) {
-
- //################################################################//
- // Gather information on children
-
- // child token accumulator
- $child_tokens = array();
-
- // scroll to the end of this node, report number, and collect
- // all children
- for ($j = $i, $depth = 0; ; $j++) {
- if ($tokens[$j] instanceof HTMLPurifier_Token_Start) {
- $depth++;
- // skip token assignment on first iteration, this is the
- // token we currently are on
- if ($depth == 1) continue;
- } elseif ($tokens[$j] instanceof HTMLPurifier_Token_End) {
- $depth--;
- // skip token assignment on last iteration, this is the
- // end token of the token we're currently on
- if ($depth == 0) break;
- }
- $child_tokens[] = $tokens[$j];
- }
-
- // $i is index of start token
- // $j is index of end token
-
- $start_token = $tokens[$i]; // to make token available via CurrentToken
-
- //################################################################//
- // Gather information on parent
-
- // calculate parent information
- if ($count = count($stack)) {
- $parent_index = $stack[$count-1];
- $parent_name = $tokens[$parent_index]->name;
- if ($parent_index == 0) {
- $parent_def = $definition->info_parent_def;
- } else {
- $parent_def = $definition->info[$parent_name];
- }
- } else {
- // processing as if the parent were the "root" node
- // unknown info, it won't be used anyway, in the future,
- // we may want to enforce one element only (this is
- // necessary for HTML Purifier to clean entire documents
- $parent_index = $parent_name = $parent_def = null;
- }
-
- // calculate context
- if ($is_inline === false) {
- // check if conditions make it inline
- if (!empty($parent_def) && $parent_def->descendants_are_inline) {
- $is_inline = $count - 1;
- }
- } else {
- // check if we're out of inline
- if ($count === $is_inline) {
- $is_inline = false;
- }
- }
-
- //################################################################//
- // Determine whether element is explicitly excluded SGML-style
-
- // determine whether or not element is excluded by checking all
- // parent exclusions. The array should not be very large, two
- // elements at most.
- $excluded = false;
- if (!empty($exclude_stack)) {
- foreach ($exclude_stack as $lookup) {
- if (isset($lookup[$tokens[$i]->name])) {
- $excluded = true;
- // no need to continue processing
- break;
- }
- }
- }
-
- //################################################################//
- // Perform child validation
-
- if ($excluded) {
- // there is an exclusion, remove the entire node
- $result = false;
- $excludes = array(); // not used, but good to initialize anyway
- } else {
- // DEFINITION CALL
- if ($i === 0) {
- // special processing for the first node
- $def = $definition->info_parent_def;
- } else {
- $def = $definition->info[$tokens[$i]->name];
-
- }
-
- if (!empty($def->child)) {
- // have DTD child def validate children
- $result = $def->child->validateChildren(
- $child_tokens, $config, $context);
- } else {
- // weird, no child definition, get rid of everything
- $result = false;
- }
-
- // determine whether or not this element has any exclusions
- $excludes = $def->excludes;
- }
-
- // $result is now a bool or array
-
- //################################################################//
- // Process result by interpreting $result
-
- if ($result === true || $child_tokens === $result) {
- // leave the node as is
-
- // register start token as a parental node start
- $stack[] = $i;
-
- // register exclusions if there are any
- if (!empty($excludes)) $exclude_stack[] = $excludes;
-
- // move cursor to next possible start node
- $i++;
-
- } elseif($result === false) {
- // remove entire node
-
- if ($e) {
- if ($excluded) {
- $e->send(E_ERROR, 'Strategy_FixNesting: Node excluded');
- } else {
- $e->send(E_ERROR, 'Strategy_FixNesting: Node removed');
- }
- }
-
- // calculate length of inner tokens and current tokens
- $length = $j - $i + 1;
-
- // perform removal
- array_splice($tokens, $i, $length);
-
- // update size
- $size -= $length;
-
- // there is no start token to register,
- // current node is now the next possible start node
- // unless it turns out that we need to do a double-check
-
- // this is a rought heuristic that covers 100% of HTML's
- // cases and 99% of all other cases. A child definition
- // that would be tricked by this would be something like:
- // ( | a b c) where it's all or nothing. Fortunately,
- // our current implementation claims that that case would
- // not allow empty, even if it did
- if (!$parent_def->child->allow_empty) {
- // we need to do a double-check
- $i = $parent_index;
- array_pop($stack);
- }
-
- // PROJECTED OPTIMIZATION: Process all children elements before
- // reprocessing parent node.
-
- } else {
- // replace node with $result
-
- // calculate length of inner tokens
- $length = $j - $i - 1;
-
- if ($e) {
- if (empty($result) && $length) {
- $e->send(E_ERROR, 'Strategy_FixNesting: Node contents removed');
- } else {
- $e->send(E_WARNING, 'Strategy_FixNesting: Node reorganized');
- }
- }
-
- // perform replacement
- array_splice($tokens, $i + 1, $length, $result);
-
- // update size
- $size -= $length;
- $size += count($result);
-
- // register start token as a parental node start
- $stack[] = $i;
-
- // register exclusions if there are any
- if (!empty($excludes)) $exclude_stack[] = $excludes;
-
- // move cursor to next possible start node
- $i++;
-
- }
-
- //################################################################//
- // Scroll to next start node
-
- // We assume, at this point, that $i is the index of the token
- // that is the first possible new start point for a node.
-
- // Test if the token indeed is a start tag, if not, move forward
- // and test again.
- $size = count($tokens);
- while ($i < $size and !$tokens[$i] instanceof HTMLPurifier_Token_Start) {
- if ($tokens[$i] instanceof HTMLPurifier_Token_End) {
- // pop a token index off the stack if we ended a node
- array_pop($stack);
- // pop an exclusion lookup off exclusion stack if
- // we ended node and that node had exclusions
- if ($i == 0 || $i == $size - 1) {
- // use specialized var if it's the super-parent
- $s_excludes = $definition->info_parent_def->excludes;
- } else {
- $s_excludes = $definition->info[$tokens[$i]->name]->excludes;
- }
- if ($s_excludes) {
- array_pop($exclude_stack);
- }
- }
- $i++;
- }
-
- }
-
- //####################################################################//
- // Post-processing
-
- // remove implicit parent tokens at the beginning and end
- array_shift($tokens);
- array_pop($tokens);
-
- // remove context variables
- $context->destroy('IsInline');
- $context->destroy('CurrentToken');
-
- //####################################################################//
- // Return
-
- return $tokens;
-
- }
-
-}
-
-// vim: et sw=4 sts=4