From ffb1997902facb36b78a7cfa522f41f2b3d71cda Mon Sep 17 00:00:00 2001
From: Mike Macgirvin <mike@macgirvin.com>
Date: Wed, 8 Sep 2010 20:14:17 -0700
Subject: mistpark 2.0 infrasturcture lands

---
 library/HTMLPurifier/Strategy/FixNesting.php | 328 +++++++++++++++++++++++++++
 1 file changed, 328 insertions(+)
 create mode 100644 library/HTMLPurifier/Strategy/FixNesting.php

(limited to 'library/HTMLPurifier/Strategy/FixNesting.php')

diff --git a/library/HTMLPurifier/Strategy/FixNesting.php b/library/HTMLPurifier/Strategy/FixNesting.php
new file mode 100644
index 000000000..f81802391
--- /dev/null
+++ b/library/HTMLPurifier/Strategy/FixNesting.php
@@ -0,0 +1,328 @@
+<?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
-- 
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