1<?php
2
3/**
4 * Injects tokens into the document while parsing for well-formedness.
5 * This enables "formatter-like" functionality such as auto-paragraphing,
6 * smiley-ification and linkification to take place.
7 *
8 * A note on how handlers create changes; this is done by assigning a new
9 * value to the $token reference. These values can take a variety of forms and
10 * are best described HTMLPurifier_Strategy_MakeWellFormed->processToken()
11 * documentation.
12 *
13 * @todo Allow injectors to request a re-run on their output. This
14 *       would help if an operation is recursive.
15 */
16abstract class HTMLPurifier_Injector
17{
18
19    /**
20     * Advisory name of injector, this is for friendly error messages.
21     * @type string
22     */
23    public $name;
24
25    /**
26     * @type HTMLPurifier_HTMLDefinition
27     */
28    protected $htmlDefinition;
29
30    /**
31     * Reference to CurrentNesting variable in Context. This is an array
32     * list of tokens that we are currently "inside"
33     * @type array
34     */
35    protected $currentNesting;
36
37    /**
38     * Reference to current token.
39     * @type HTMLPurifier_Token
40     */
41    protected $currentToken;
42
43    /**
44     * Reference to InputZipper variable in Context.
45     * @type HTMLPurifier_Zipper
46     */
47    protected $inputZipper;
48
49    /**
50     * Array of elements and attributes this injector creates and therefore
51     * need to be allowed by the definition. Takes form of
52     * array('element' => array('attr', 'attr2'), 'element2')
53     * @type array
54     */
55    public $needed = array();
56
57    /**
58     * Number of elements to rewind backwards (relative).
59     * @type bool|int
60     */
61    protected $rewindOffset = false;
62
63    /**
64     * Rewind to a spot to re-perform processing. This is useful if you
65     * deleted a node, and now need to see if this change affected any
66     * earlier nodes. Rewinding does not affect other injectors, and can
67     * result in infinite loops if not used carefully.
68     * @param bool|int $offset
69     * @warning HTML Purifier will prevent you from fast-forwarding with this
70     *          function.
71     */
72    public function rewindOffset($offset)
73    {
74        $this->rewindOffset = $offset;
75    }
76
77    /**
78     * Retrieves rewind offset, and then unsets it.
79     * @return bool|int
80     */
81    public function getRewindOffset()
82    {
83        $r = $this->rewindOffset;
84        $this->rewindOffset = false;
85        return $r;
86    }
87
88    /**
89     * Prepares the injector by giving it the config and context objects:
90     * this allows references to important variables to be made within
91     * the injector. This function also checks if the HTML environment
92     * will work with the Injector (see checkNeeded()).
93     * @param HTMLPurifier_Config $config
94     * @param HTMLPurifier_Context $context
95     * @return bool|string Boolean false if success, string of missing needed element/attribute if failure
96     */
97    public function prepare($config, $context)
98    {
99        $this->htmlDefinition = $config->getHTMLDefinition();
100        // Even though this might fail, some unit tests ignore this and
101        // still test checkNeeded, so be careful. Maybe get rid of that
102        // dependency.
103        $result = $this->checkNeeded($config);
104        if ($result !== false) {
105            return $result;
106        }
107        $this->currentNesting =& $context->get('CurrentNesting');
108        $this->currentToken   =& $context->get('CurrentToken');
109        $this->inputZipper    =& $context->get('InputZipper');
110        return false;
111    }
112
113    /**
114     * This function checks if the HTML environment
115     * will work with the Injector: if p tags are not allowed, the
116     * Auto-Paragraphing injector should not be enabled.
117     * @param HTMLPurifier_Config $config
118     * @return bool|string Boolean false if success, string of missing needed element/attribute if failure
119     */
120    public function checkNeeded($config)
121    {
122        $def = $config->getHTMLDefinition();
123        foreach ($this->needed as $element => $attributes) {
124            if (is_int($element)) {
125                $element = $attributes;
126            }
127            if (!isset($def->info[$element])) {
128                return $element;
129            }
130            if (!is_array($attributes)) {
131                continue;
132            }
133            foreach ($attributes as $name) {
134                if (!isset($def->info[$element]->attr[$name])) {
135                    return "$element.$name";
136                }
137            }
138        }
139        return false;
140    }
141
142    /**
143     * Tests if the context node allows a certain element
144     * @param string $name Name of element to test for
145     * @return bool True if element is allowed, false if it is not
146     */
147    public function allowsElement($name)
148    {
149        if (!empty($this->currentNesting)) {
150            $parent_token = array_pop($this->currentNesting);
151            $this->currentNesting[] = $parent_token;
152            $parent = $this->htmlDefinition->info[$parent_token->name];
153        } else {
154            $parent = $this->htmlDefinition->info_parent_def;
155        }
156        if (!isset($parent->child->elements[$name]) || isset($parent->excludes[$name])) {
157            return false;
158        }
159        // check for exclusion
160        if (!empty($this->currentNesting)) {
161            for ($i = count($this->currentNesting) - 2; $i >= 0; $i--) {
162                $node = $this->currentNesting[$i];
163                $def  = $this->htmlDefinition->info[$node->name];
164                if (isset($def->excludes[$name])) {
165                    return false;
166                }
167            }
168        }
169        return true;
170    }
171
172    /**
173     * Iterator function, which starts with the next token and continues until
174     * you reach the end of the input tokens.
175     * @warning Please prevent previous references from interfering with this
176     *          functions by setting $i = null beforehand!
177     * @param int $i Current integer index variable for inputTokens
178     * @param HTMLPurifier_Token $current Current token variable.
179     *          Do NOT use $token, as that variable is also a reference
180     * @return bool
181     */
182    protected function forward(&$i, &$current)
183    {
184        if ($i === null) {
185            $i = count($this->inputZipper->back) - 1;
186        } else {
187            $i--;
188        }
189        if ($i < 0) {
190            return false;
191        }
192        $current = $this->inputZipper->back[$i];
193        return true;
194    }
195
196    /**
197     * Similar to _forward, but accepts a third parameter $nesting (which
198     * should be initialized at 0) and stops when we hit the end tag
199     * for the node $this->inputIndex starts in.
200     * @param int $i Current integer index variable for inputTokens
201     * @param HTMLPurifier_Token $current Current token variable.
202     *          Do NOT use $token, as that variable is also a reference
203     * @param int $nesting
204     * @return bool
205     */
206    protected function forwardUntilEndToken(&$i, &$current, &$nesting)
207    {
208        $result = $this->forward($i, $current);
209        if (!$result) {
210            return false;
211        }
212        if ($nesting === null) {
213            $nesting = 0;
214        }
215        if ($current instanceof HTMLPurifier_Token_Start) {
216            $nesting++;
217        } elseif ($current instanceof HTMLPurifier_Token_End) {
218            if ($nesting <= 0) {
219                return false;
220            }
221            $nesting--;
222        }
223        return true;
224    }
225
226    /**
227     * Iterator function, starts with the previous token and continues until
228     * you reach the beginning of input tokens.
229     * @warning Please prevent previous references from interfering with this
230     *          functions by setting $i = null beforehand!
231     * @param int $i Current integer index variable for inputTokens
232     * @param HTMLPurifier_Token $current Current token variable.
233     *          Do NOT use $token, as that variable is also a reference
234     * @return bool
235     */
236    protected function backward(&$i, &$current)
237    {
238        if ($i === null) {
239            $i = count($this->inputZipper->front) - 1;
240        } else {
241            $i--;
242        }
243        if ($i < 0) {
244            return false;
245        }
246        $current = $this->inputZipper->front[$i];
247        return true;
248    }
249
250    /**
251     * Handler that is called when a text token is processed
252     */
253    public function handleText(&$token)
254    {
255    }
256
257    /**
258     * Handler that is called when a start or empty token is processed
259     */
260    public function handleElement(&$token)
261    {
262    }
263
264    /**
265     * Handler that is called when an end token is processed
266     */
267    public function handleEnd(&$token)
268    {
269        $this->notifyEnd($token);
270    }
271
272    /**
273     * Notifier that is called when an end token is processed
274     * @param HTMLPurifier_Token $token Current token variable.
275     * @note This differs from handlers in that the token is read-only
276     * @deprecated
277     */
278    public function notifyEnd($token)
279    {
280    }
281}
282
283// vim: et sw=4 sts=4
284