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<?php

/**

 * Takes tokens makes them well-formed (balance end tags, etc.)

 *

 * Specification of the armor attributes this strategy uses:

 *

 *      - MakeWellFormed_TagClosedError: This armor field is used to

 *        suppress tag closed errors for certain tokens [TagClosedSuppress],

 *        in particular, if a tag was generated automatically by HTML

 *        Purifier, we may rely on our infrastructure to close it for us

 *        and shouldn't report an error to the user [TagClosedAuto].

 */

class HTMLPurifier_Strategy_MakeWellFormed extends HTMLPurifier_Strategy

{

    /**

     * Array stream of tokens being processed.

     * @type HTMLPurifier_Token[]

     */

    protected $tokens;

    /**

     * Current token.

     * @type HTMLPurifier_Token

     */

    protected $token;

    /**

     * Zipper managing the true state.

     * @type HTMLPurifier_Zipper

     */

    protected $zipper;

    /**

     * Current nesting of elements.

     * @type array

     */

    protected $stack;

    /**

     * Injectors active in this stream processing.

     * @type HTMLPurifier_Injector[]

     */

    protected $injectors;

    /**

     * Current instance of HTMLPurifier_Config.

     * @type HTMLPurifier_Config

     */

    protected $config;

    /**

     * Current instance of HTMLPurifier_Context.

     * @type HTMLPurifier_Context

     */

    protected $context;

    /**

     * @param HTMLPurifier_Token[] $tokens

     * @param HTMLPurifier_Config $config

     * @param HTMLPurifier_Context $context

     * @return HTMLPurifier_Token[]

     * @throws HTMLPurifier_Exception

     */

    public function execute($tokens, $config, $context)

    {

        $definition = $config->getHTMLDefinition();

        // local variables

        $generator = new HTMLPurifier_Generator($config, $context);

        $escape_invalid_tags = $config->get('Core.EscapeInvalidTags');

        // used for autoclose early abortion

        $global_parent_allowed_elements = $definition->info_parent_def->child->getAllowedElements($config);

        $e = $context->get('ErrorCollector', true);

        $i = false; // injector index

        list($zipper, $token) = HTMLPurifier_Zipper::fromArray($tokens);

        if ($token === NULL) {

            return array();

        }

        $reprocess = false; // whether or not to reprocess the same token

        $stack = array();

        // member variables

        $this->stack =& $stack;

        $this->tokens =& $tokens;

        $this->token =& $token;

        $this->zipper =& $zipper;

        $this->config = $config;

        $this->context = $context;

        // context variables

        $context->register('CurrentNesting', $stack);

        $context->register('InputZipper', $zipper);

        $context->register('CurrentToken', $token);

        // -- begin INJECTOR --

        $this->injectors = array();

        $injectors = $config->getBatch('AutoFormat');

        $def_injectors = $definition->info_injector;

        $custom_injectors = $injectors['Custom'];

        unset($injectors['Custom']); // special case

        foreach ($injectors as $injector => $b) {

            // XXX: Fix with a legitimate lookup table of enabled filters

            if (strpos($injector, '.') !== false) {

                continue;

            }

            $injector = "HTMLPurifier_Injector_$injector";

            if (!$b) {

                continue;

            }

            $this->injectors[] = new $injector;

        }

        foreach ($def_injectors as $injector) {

            // assumed to be objects

            $this->injectors[] = $injector;

        }

        foreach ($custom_injectors as $injector) {

            if (!$injector) {

                continue;

            }

            if (is_string($injector)) {

                $injector = "HTMLPurifier_Injector_$injector";

                $injector = new $injector;

            }

            $this->injectors[] = $injector;

        }

        // give the injectors references to the definition and context

        // variables for performance reasons

        foreach ($this->injectors as $ix => $injector) {

            $error = $injector->prepare($config, $context);

            if (!$error) {

                continue;

            }

            array_splice($this->injectors, $ix, 1); // rm the injector

            trigger_error("Cannot enable {$injector->name} injector because $error is not allowed", E_USER_WARNING);

        }

        // -- end INJECTOR --

        // a note on reprocessing:

        //      In order to reduce code duplication, whenever some code needs

        //      to make HTML changes in order to make things "correct", the

        //      new HTML gets sent through the purifier, regardless of its

        //      status. This means that if we add a start token, because it

        //      was totally necessary, we don't have to update nesting; we just

        //      punt ($reprocess = true; continue;) and it does that for us.

        // isset is in loop because $tokens size changes during loop exec

        for (;;

             // only increment if we don't need to reprocess

             $reprocess ? $reprocess = false : $token = $zipper->next($token)) {

            // check for a rewind

            if (is_int($i)) {

                // possibility: disable rewinding if the current token has a

                // rewind set on it already. This would offer protection from

                // infinite loop, but might hinder some advanced rewinding.

                $rewind_offset = $this->injectors[$i]->getRewindOffset();

                if (is_int($rewind_offset)) {

                    for ($j = 0; $j < $rewind_offset; $j++) {

                        if (empty($zipper->front)) break;

                        $token = $zipper->prev($token);

                        // indicate that other injectors should not process this token,

                        // but we need to reprocess it.  See Note [Injector skips]

                        unset($token->skip[$i]);

                        $token->rewind = $i;

                        if ($token instanceof HTMLPurifier_Token_Start) {

                            array_pop($this->stack);

                        } elseif ($token instanceof HTMLPurifier_Token_End) {

                            $this->stack[] = $token->start;

                        }

                    }

                }

                $i = false;

            }

            // handle case of document end

            if ($token === NULL) {

                // kill processing if stack is empty

                if (empty($this->stack)) {

                    break;

                }

                // peek

                $top_nesting = array_pop($this->stack);

                $this->stack[] = $top_nesting;

                // send error [TagClosedSuppress]

                if ($e && !isset($top_nesting->armor['MakeWellFormed_TagClosedError'])) {

                    $e->send(E_NOTICE, 'Strategy_MakeWellFormed: Tag closed by document end', $top_nesting);

                }

                // append, don't splice, since this is the end

                $token = new HTMLPurifier_Token_End($top_nesting->name);

                // punt!

                $reprocess = true;

                continue;

            }

            //echo '<br>'; printZipper($zipper, $token);//printTokens($this->stack);

            //flush();

            // quick-check: if it's not a tag, no need to process

            if (empty($token->is_tag)) {

                if ($token instanceof HTMLPurifier_Token_Text) {

                    foreach ($this->injectors as $i => $injector) {

                        if (isset($token->skip[$i])) {

                            // See Note [Injector skips]

                            continue;

                        }

                        if ($token->rewind !== null && $token->rewind !== $i) {

                            continue;

                        }

                        // XXX fuckup

                        $r = $token;

                        $injector->handleText($r);

                        $token = $this->processToken($r, $i);

                        $reprocess = true;

                        break;

                    }

                }

                // another possibility is a comment

                continue;

            }

            if (isset($definition->info[$token->name])) {

                $type = $definition->info[$token->name]->child->type;

            } else {

                $type = false; // Type is unknown, treat accordingly

            }

            // quick tag checks: anything that's *not* an end tag

            $ok = false;

            if ($type === 'empty' && $token instanceof HTMLPurifier_Token_Start) {

                // claims to be a start tag but is empty

                $token = new HTMLPurifier_Token_Empty(

                    $token->name,

                    $token->attr,

                    $token->line,

                    $token->col,

                    $token->armor

                );

                $ok = true;

            } elseif ($type && $type !== 'empty' && $token instanceof HTMLPurifier_Token_Empty) {

                // claims to be empty but really is a start tag

                // NB: this assignment is required

                $old_token = $token;

                $token = new HTMLPurifier_Token_End($token->name);

                $token = $this->insertBefore(

                    new HTMLPurifier_Token_Start($old_token->name, $old_token->attr, $old_token->line, $old_token->col, $old_token->armor)

                );

                // punt (since we had to modify the input stream in a non-trivial way)

                $reprocess = true;

                continue;

            } elseif ($token instanceof HTMLPurifier_Token_Empty) {

                // real empty token

                $ok = true;

            } elseif ($token instanceof HTMLPurifier_Token_Start) {

                // start tag

                // ...unless they also have to close their parent

                if (!empty($this->stack)) {

                    // Performance note: you might think that it's rather

                    // inefficient, recalculating the autoclose information

                    // for every tag that a token closes (since when we

                    // do an autoclose, we push a new token into the

                    // stream and then /process/ that, before

                    // re-processing this token.)  But this is

                    // necessary, because an injector can make an

                    // arbitrary transformations to the autoclosing

                    // tokens we introduce, so things may have changed

                    // in the meantime.  Also, doing the inefficient thing is

                    // "easy" to reason about (for certain perverse definitions

                    // of "easy")

                    $parent = array_pop($this->stack);

                    $this->stack[] = $parent;

                    $parent_def = null;

                    $parent_elements = null;

                    $autoclose = false;

                    if (isset($definition->info[$parent->name])) {

                        $parent_def = $definition->info[$parent->name];

                        $parent_elements = $parent_def->child->getAllowedElements($config);

                        $autoclose = !isset($parent_elements[$token->name]);

                    }

                    if ($autoclose && $definition->info[$token->name]->wrap) {

                        // Check if an element can be wrapped by another

                        // element to make it valid in a context (for

                        // example, <ul><ul> needs a <li> in between)

                        $wrapname = $definition->info[$token->name]->wrap;

                        $wrapdef = $definition->info[$wrapname];

                        $elements = $wrapdef->child->getAllowedElements($config);

                        if (isset($elements[$token->name]) && isset($parent_elements[$wrapname])) {

                            $newtoken = new HTMLPurifier_Token_Start($wrapname);

                            $token = $this->insertBefore($newtoken);

                            $reprocess = true;

                            continue;

                        }

                    }

                    $carryover = false;

                    if ($autoclose && $parent_def->formatting) {

                        $carryover = true;

                    }

                    if ($autoclose) {

                        // check if this autoclose is doomed to fail

                        // (this rechecks $parent, which his harmless)

                        $autoclose_ok = isset($global_parent_allowed_elements[$token->name]);

                        if (!$autoclose_ok) {

                            foreach ($this->stack as $ancestor) {

                                $elements = $definition->info[$ancestor->name]->child->getAllowedElements($config);

                                if (isset($elements[$token->name])) {

                                    $autoclose_ok = true;

                                    break;

                                }

                                if ($definition->info[$token->name]->wrap) {

                                    $wrapname = $definition->info[$token->name]->wrap;

                                    $wrapdef = $definition->info[$wrapname];

                                    $wrap_elements = $wrapdef->child->getAllowedElements($config);

                                    if (isset($wrap_elements[$token->name]) && isset($elements[$wrapname])) {

                                        $autoclose_ok = true;

                                        break;

                                    }

                                }

                            }

                        }

                        if ($autoclose_ok) {

                            // errors need to be updated

                            $new_token = new HTMLPurifier_Token_End($parent->name);

                            $new_token->start = $parent;

                            // [TagClosedSuppress]

                            if ($e && !isset($parent->armor['MakeWellFormed_TagClosedError'])) {

                                if (!$carryover) {

                                    $e->send(E_NOTICE, 'Strategy_MakeWellFormed: Tag auto closed', $parent);

                                } else {

                                    $e->send(E_NOTICE, 'Strategy_MakeWellFormed: Tag carryover', $parent);

                                }

                            }

                            if ($carryover) {

                                $element = clone $parent;

                                // [TagClosedAuto]

                                $element->armor['MakeWellFormed_TagClosedError'] = true;

                                $element->carryover = true;

                                $token = $this->processToken(array($new_token, $token, $element));

                            } else {

                                $token = $this->insertBefore($new_token);

                            }

                        } else {

                            $token = $this->remove();

                        }

                        $reprocess = true;

                        continue;

                    }

                }

                $ok = true;

            }

            if ($ok) {

                foreach ($this->injectors as $i => $injector) {

                    if (isset($token->skip[$i])) {

                        // See Note [Injector skips]

                        continue;

                    }

                    if ($token->rewind !== null && $token->rewind !== $i) {

                        continue;

                    }

                    $r = $token;

                    $injector->handleElement($r);

                    $token = $this->processToken($r, $i);

                    $reprocess = true;

                    break;

                }

                if (!$reprocess) {

                    // ah, nothing interesting happened; do normal processing

                    if ($token instanceof HTMLPurifier_Token_Start) {

                        $this->stack[] = $token;

                    } elseif ($token instanceof HTMLPurifier_Token_End) {

                        throw new HTMLPurifier_Exception(

                            'Improper handling of end tag in start code; possible error in MakeWellFormed'

                        );

                    }

                }

                continue;

            }

            // sanity check: we should be dealing with a closing tag

            if (!$token instanceof HTMLPurifier_Token_End) {

                throw new HTMLPurifier_Exception('Unaccounted for tag token in input stream, bug in HTML Purifier');

            }

            // make sure that we have something open

            if (empty($this->stack)) {

                if ($escape_invalid_tags) {

                    if ($e) {

                        $e->send(E_WARNING, 'Strategy_MakeWellFormed: Unnecessary end tag to text');

                    }

                    $token = new HTMLPurifier_Token_Text($generator->generateFromToken($token));

                } else {

                    if ($e) {

                        $e->send(E_WARNING, 'Strategy_MakeWellFormed: Unnecessary end tag removed');

                    }

                    $token = $this->remove();

                }

                $reprocess = true;

                continue;

            }

            // first, check for the simplest case: everything closes neatly.

            // Eventually, everything passes through here; if there are problems

            // we modify the input stream accordingly and then punt, so that

            // the tokens get processed again.

            $current_parent = array_pop($this->stack);

            if ($current_parent->name == $token->name) {

                $token->start = $current_parent;

                foreach ($this->injectors as $i => $injector) {

                    if (isset($token->skip[$i])) {

                        // See Note [Injector skips]

                        continue;

                    }

                    if ($token->rewind !== null && $token->rewind !== $i) {

                        continue;

                    }

                    $r = $token;

                    $injector->handleEnd($r);

                    $token = $this->processToken($r, $i);

                    $this->stack[] = $current_parent;

                    $reprocess = true;

                    break;

                }

                continue;

            }

            // okay, so we're trying to close the wrong tag

            // undo the pop previous pop

            $this->stack[] = $current_parent;

            // scroll back the entire nest, trying to find our tag.

            // (feature could be to specify how far you'd like to go)

            $size = count($this->stack);

            // -2 because -1 is the last element, but we already checked that

            $skipped_tags = false;

            for ($j = $size - 2; $j >= 0; $j--) {

                if ($this->stack[$j]->name == $token->name) {

                    $skipped_tags = array_slice($this->stack, $j);

                    break;

                }

            }

            // we didn't find the tag, so remove

            if ($skipped_tags === false) {

                if ($escape_invalid_tags) {

                    if ($e) {

                        $e->send(E_WARNING, 'Strategy_MakeWellFormed: Stray end tag to text');

                    }

                    $token = new HTMLPurifier_Token_Text($generator->generateFromToken($token));

                } else {

                    if ($e) {

                        $e->send(E_WARNING, 'Strategy_MakeWellFormed: Stray end tag removed');

                    }

                    $token = $this->remove();

                }

                $reprocess = true;

                continue;

            }

            // do errors, in REVERSE $j order: a,b,c with </a></b></c>

            $c = count($skipped_tags);

            if ($e) {

                for ($j = $c - 1; $j > 0; $j--) {

                    // notice we exclude $j == 0, i.e. the current ending tag, from

                    // the errors... [TagClosedSuppress]

                    if (!isset($skipped_tags[$j]->armor['MakeWellFormed_TagClosedError'])) {

                        $e->send(E_NOTICE, 'Strategy_MakeWellFormed: Tag closed by element end', $skipped_tags[$j]);

                    }

                }

            }

            // insert tags, in FORWARD $j order: c,b,a with </a></b></c>

            $replace = array($token);

            for ($j = 1; $j < $c; $j++) {

                // ...as well as from the insertions

                $new_token = new HTMLPurifier_Token_End($skipped_tags[$j]->name);

                $new_token->start = $skipped_tags[$j];

                array_unshift($replace, $new_token);

                if (isset($definition->info[$new_token->name]) && $definition->info[$new_token->name]->formatting) {

                    // [TagClosedAuto]

                    $element = clone $skipped_tags[$j];

                    $element->carryover = true;

                    $element->armor['MakeWellFormed_TagClosedError'] = true;

                    $replace[] = $element;

                }

            }

            $token = $this->processToken($replace);

            $reprocess = true;

            continue;

        }

        $context->destroy('CurrentToken');

        $context->destroy('CurrentNesting');

        $context->destroy('InputZipper');

        unset($this->injectors, $this->stack, $this->tokens);

        return $zipper->toArray($token);

    }

    /**

     * Processes arbitrary token values for complicated substitution patterns.

     * In general:

     *

     * If $token is an array, it is a list of tokens to substitute for the

     * current token. These tokens then get individually processed. If there

     * is a leading integer in the list, that integer determines how many

     * tokens from the stream should be removed.

     *

     * If $token is a regular token, it is swapped with the current token.

     *

     * If $token is false, the current token is deleted.

     *

     * If $token is an integer, that number of tokens (with the first token

     * being the current one) will be deleted.

     *

     * @param HTMLPurifier_Token|array|int|bool $token Token substitution value

     * @param HTMLPurifier_Injector|int $injector Injector that performed the substitution; default is if

     *        this is not an injector related operation.

     * @throws HTMLPurifier_Exception

     */

    protected function processToken($token, $injector = -1)

    {

        // Zend OpCache miscompiles $token = array($token), so

        // avoid this pattern.  See: https://github.com/ezyang/htmlpurifier/issues/108

        // normalize forms of token

        if (is_object($token)) {

            $tmp = $token;

            $token = array(1, $tmp);

        }

        if (is_int($token)) {

            $tmp = $token;

            $token = array($tmp);

        }

        if ($token === false) {

            $token = array(1);

        }

        if (!is_array($token)) {

            throw new HTMLPurifier_Exception('Invalid token type from injector');

        }

        if (!is_int($token[0])) {

            array_unshift($token, 1);

        }

        if ($token[0] === 0) {

            throw new HTMLPurifier_Exception('Deleting zero tokens is not valid');

        }

        // $token is now an array with the following form:

        // array(number nodes to delete, new node 1, new node 2, ...)

        $delete = array_shift($token);

        list($old, $r) = $this->zipper->splice($this->token, $delete, $token);

        if ($injector > -1) {

            // See Note [Injector skips]

            // Determine appropriate skips.  Here's what the code does:

            //  *If* we deleted one or more tokens, copy the skips

            //  of those tokens into the skips of the new tokens (in $token).

            //  Also, mark the newly inserted tokens as having come from

            //  $injector.

            $oldskip = isset($old[0]) ? $old[0]->skip : array();

            foreach ($token as $object) {

                $object->skip = $oldskip;

                $object->skip[$injector] = true;

            }

        }

        return $r;

    }

    /**

     * Inserts a token before the current token. Cursor now points to

     * this token.  You must reprocess after this.

     * @param HTMLPurifier_Token $token

     */

    private function insertBefore($token)

    {

        // NB not $this->zipper->insertBefore(), due to positioning

        // differences

        $splice = $this->zipper->splice($this->token, 0, array($token));

        return $splice[1];

    }

    /**

     * Removes current token. Cursor now points to new token occupying previously

     * occupied space.  You must reprocess after this.

     */

    private function remove()

    {

        return $this->zipper->delete();

    }

}

// Note [Injector skips]

// ~~~~~~~~~~~~~~~~~~~~~

// When I originally designed this class, the idea behind the 'skip'

// property of HTMLPurifier_Token was to help avoid infinite loops

// in injector processing.  For example, suppose you wrote an injector

// that bolded swear words.  Naively, you might write it so that

// whenever you saw ****, you replaced it with <strong>****</strong>.

//

// When this happens, we will reprocess all of the tokens with the

// other injectors.  Now there is an opportunity for infinite loop:

// if we rerun the swear-word injector on these tokens, we might

// see **** and then reprocess again to get

// <strong><strong>****</strong></strong> ad infinitum.

//

// Thus, the idea of a skip is that once we process a token with

// an injector, we mark all of those tokens as having "come from"

// the injector, and we never run the injector again on these

// tokens.

//

// There were two more complications, however:

//

//  - With HTMLPurifier_Injector_RemoveEmpty, we noticed that if

//    you had <b><i></i></b>, after you removed the <i></i>, you

//    really would like this injector to go back and reprocess

//    the <b> tag, discovering that it is now empty and can be

//    removed.  So we reintroduced the possibility of infinite looping

//    by adding a "rewind" function, which let you go back to an

//    earlier point in the token stream and reprocess it with injectors.

//    Needless to say, we need to UN-skip the token so it gets

//    reprocessed.

//

//  - Suppose that you successfuly process a token, replace it with

//    one with your skip mark, but now another injector wants to

//    process the skipped token with another token.  Should you continue

//    to skip that new token, or reprocess it?  If you reprocess,

//    you can end up with an infinite loop where one injector converts

//    <a> to <b>, and then another injector converts it back.  So

//    we inherit the skips, but for some reason, I thought that we

//    should inherit the skip from the first token of the token

//    that we deleted.  Why?  Well, it seems to work OK.

//

// If I were to redesign this functionality, I would absolutely not

// go about doing it this way: the semantics are just not very well

// defined, and in any case you probably wanted to operate on trees,

// not token streams.

// vim: et sw=4 sts=4