<?php

/**
 * Represents an XHTML 1.1 module, with information on elements, tags
 * and attributes.
 * @note Even though this is technically XHTML 1.1, it is also used for
 *       regular HTML parsing. We are using modulization as a convenient
 *       way to represent the internals of HTMLDefinition, and our
 *       implementation is by no means conforming and does not directly
 *       use the normative DTDs or XML schemas.
 * @note The public variables in a module should almost directly
 *       correspond to the variables in HTMLPurifier_HTMLDefinition.
 *       However, the prefix info carries no special meaning in these
 *       objects (include it anyway if that's the correspondence though).
 * @todo Consider making some member functions protected
 */

class HTMLPurifier_HTMLModule
{
    
    // -- Overloadable ----------------------------------------------------
    
    /**
     * Short unique string identifier of the module
     */
    public $name;
    
    /**
     * Informally, a list of elements this module changes. Not used in
     * any significant way.
     */
    public $elements = array();
    
    /**
     * Associative array of element names to element definitions.
     * Some definitions may be incomplete, to be merged in later
     * with the full definition.
     */
    public $info = array();
    
    /**
     * Associative array of content set names to content set additions.
     * This is commonly used to, say, add an A element to the Inline
     * content set. This corresponds to an internal variable $content_sets
     * and NOT info_content_sets member variable of HTMLDefinition.
     */
    public $content_sets = array();
    
    /**
     * Associative array of attribute collection names to attribute
     * collection additions. More rarely used for adding attributes to
     * the global collections. Example is the StyleAttribute module adding
     * the style attribute to the Core. Corresponds to HTMLDefinition's
     * attr_collections->info, since the object's data is only info,
     * with extra behavior associated with it.
     */
    public $attr_collections = array();
    
    /**
     * Associative array of deprecated tag name to HTMLPurifier_TagTransform
     */
    public $info_tag_transform = array();
    
    /**
     * List of HTMLPurifier_AttrTransform to be performed before validation.
     */
    public $info_attr_transform_pre = array();
    
    /**
     * List of HTMLPurifier_AttrTransform to be performed after validation.
     */
    public $info_attr_transform_post = array();
    
    /**
     * Boolean flag that indicates whether or not getChildDef is implemented.
     * For optimization reasons: may save a call to a function. Be sure
     * to set it if you do implement getChildDef(), otherwise it will have
     * no effect!
     */
    public $defines_child_def = false;
    
    /**
     * Boolean flag whether or not this module is safe. If it is not safe, all
     * of its members are unsafe. Modules are safe by default (this might be
     * slightly dangerous, but it doesn't make much sense to force HTML Purifier,
     * which is based off of safe HTML, to explicitly say, "This is safe," even
     * though there are modules which are "unsafe")
     * 
     * @note Previously, safety could be applied at an element level granularity.
     *       We've removed this ability, so in order to add "unsafe" elements
     *       or attributes, a dedicated module with this property set to false
     *       must be used.
     */
    public $safe = true;
    
    /**
     * Retrieves a proper HTMLPurifier_ChildDef subclass based on 
     * content_model and content_model_type member variables of
     * the HTMLPurifier_ElementDef class. There is a similar function
     * in HTMLPurifier_HTMLDefinition.
     * @param $def HTMLPurifier_ElementDef instance
     * @return HTMLPurifier_ChildDef subclass
     */
    public function getChildDef($def) {return false;}
    
    // -- Convenience -----------------------------------------------------
    
    /**
     * Convenience function that sets up a new element
     * @param $element Name of element to add
     * @param $type What content set should element be registered to?
     *              Set as false to skip this step.
     * @param $contents Allowed children in form of:
     *              "$content_model_type: $content_model"
     * @param $attr_includes What attribute collections to register to
     *              element?
     * @param $attr What unique attributes does the element define?
     * @note See ElementDef for in-depth descriptions of these parameters.
     * @return Created element definition object, so you 
     *         can set advanced parameters
     */
    public function addElement($element, $type, $contents, $attr_includes = array(), $attr = array()) {
        $this->elements[] = $element;
        // parse content_model
        list($content_model_type, $content_model) = $this->parseContents($contents);
        // merge in attribute inclusions
        $this->mergeInAttrIncludes($attr, $attr_includes);
        // add element to content sets
        if ($type) $this->addElementToContentSet($element, $type);
        // create element
        $this->info[$element] = HTMLPurifier_ElementDef::create(
            $content_model, $content_model_type, $attr
        );
        // literal object $contents means direct child manipulation
        if (!is_string($contents)) $this->info[$element]->child = $contents;
        return $this->info[$element];
    }
    
    /**
     * Convenience function that creates a totally blank, non-standalone
     * element.
     * @param $element Name of element to create
     * @return Created element
     */
    public function addBlankElement($element) {
        if (!isset($this->info[$element])) {
            $this->elements[] = $element;
            $this->info[$element] = new HTMLPurifier_ElementDef();
            $this->info[$element]->standalone = false;
        } else {
            trigger_error("Definition for $element already exists in module, cannot redefine");
        }
        return $this->info[$element];
    }
    
    /**
     * Convenience function that registers an element to a content set
     * @param Element to register
     * @param Name content set (warning: case sensitive, usually upper-case
     *        first letter)
     */
    public function addElementToContentSet($element, $type) {
        if (!isset($this->content_sets[$type])) $this->content_sets[$type] = '';
        else $this->content_sets[$type] .= ' | ';
        $this->content_sets[$type] .= $element;
    }
    
    /**
     * Convenience function that transforms single-string contents
     * into separate content model and content model type
     * @param $contents Allowed children in form of:
     *                  "$content_model_type: $content_model"
     * @note If contents is an object, an array of two nulls will be
     *       returned, and the callee needs to take the original $contents
     *       and use it directly.
     */
    public function parseContents($contents) {
        if (!is_string($contents)) return array(null, null); // defer
        switch ($contents) {
            // check for shorthand content model forms
            case 'Empty':
                return array('empty', '');
            case 'Inline':
                return array('optional', 'Inline | #PCDATA');
            case 'Flow':
                return array('optional', 'Flow | #PCDATA');
        }
        list($content_model_type, $content_model) = explode(':', $contents);
        $content_model_type = strtolower(trim($content_model_type));
        $content_model = trim($content_model);
        return array($content_model_type, $content_model);
    }
    
    /**
     * Convenience function that merges a list of attribute includes into
     * an attribute array.
     * @param $attr Reference to attr array to modify
     * @param $attr_includes Array of includes / string include to merge in
     */
    public function mergeInAttrIncludes(&$attr, $attr_includes) {
        if (!is_array($attr_includes)) {
            if (empty($attr_includes)) $attr_includes = array();
            else $attr_includes = array($attr_includes);
        }
        $attr[0] = $attr_includes;
    }
    
    /**
     * Convenience function that generates a lookup table with boolean
     * true as value.
     * @param $list List of values to turn into a lookup
     * @note You can also pass an arbitrary number of arguments in
     *       place of the regular argument
     * @return Lookup array equivalent of list
     */
    public function makeLookup($list) {
        if (is_string($list)) $list = func_get_args();
        $ret = array();
        foreach ($list as $value) {
            if (is_null($value)) continue;
            $ret[$value] = true;
        }
        return $ret;
    }
    
    /**
     * Lazy load construction of the module after determining whether
     * or not it's needed, and also when a finalized configuration object
     * is available.
     * @param $config Instance of HTMLPurifier_Config
     */
    public function setup($config) {}
    
}