<?php

/**
 * Proof-of-concept lexer that uses the PEAR package XML_HTMLSax3 to parse HTML.
 * 
 * PEAR, not suprisingly, also has a SAX parser for HTML.  I don't know
 * very much about implementation, but it's fairly well written.  However, that
 * abstraction comes at a price: performance. You need to have it installed,
 * and if the API changes, it might break our adapter. Not sure whether or not
 * it's UTF-8 aware, but it has some entity parsing trouble (in all areas,
 * text and attributes).
 * 
 * Quite personally, I don't recommend using the PEAR class, and the defaults
 * don't use it. The unit tests do perform the tests on the SAX parser too, but
 * whatever it does for poorly formed HTML is up to it.
 * 
 * @todo Generalize so that XML_HTMLSax is also supported.
 * 
 * @warning Entity-resolution inside attributes is broken.
 */

class HTMLPurifier_Lexer_PEARSax3 extends HTMLPurifier_Lexer
{
    
    /**
     * Internal accumulator array for SAX parsers.
     */
    protected $tokens = array();
    
    public function tokenizeHTML($string, $config, $context) {
        
        $this->tokens = array();
        
        $string = $this->normalize($string, $config, $context);
        
        $parser = new XML_HTMLSax3();
        $parser->set_object($this);
        $parser->set_element_handler('openHandler','closeHandler');
        $parser->set_data_handler('dataHandler');
        $parser->set_escape_handler('escapeHandler');
        
        // doesn't seem to work correctly for attributes
        $parser->set_option('XML_OPTION_ENTITIES_PARSED', 1);
        
        $parser->parse($string);
        
        return $this->tokens;
        
    }
    
    /**
     * Open tag event handler, interface is defined by PEAR package.
     */
    public function openHandler(&$parser, $name, $attrs, $closed) {
        // entities are not resolved in attrs
        foreach ($attrs as $key => $attr) {
            $attrs[$key] = $this->parseData($attr);
        }
        if ($closed) {
            $this->tokens[] = new HTMLPurifier_Token_Empty($name, $attrs);
        } else {
            $this->tokens[] = new HTMLPurifier_Token_Start($name, $attrs);
        }
        return true;
    }
    
    /**
     * Close tag event handler, interface is defined by PEAR package.
     */
    public function closeHandler(&$parser, $name) {
        // HTMLSax3 seems to always send empty tags an extra close tag
        // check and ignore if you see it:
        // [TESTME] to make sure it doesn't overreach
        if ($this->tokens[count($this->tokens)-1] instanceof HTMLPurifier_Token_Empty) {
            return true;
        }
        $this->tokens[] = new HTMLPurifier_Token_End($name);
        return true;
    }
    
    /**
     * Data event handler, interface is defined by PEAR package.
     */
    public function dataHandler(&$parser, $data) {
        $this->tokens[] = new HTMLPurifier_Token_Text($data);
        return true;
    }
    
    /**
     * Escaped text handler, interface is defined by PEAR package.
     */
    public function escapeHandler(&$parser, $data) {
        if (strpos($data, '--') === 0) {
            $this->tokens[] = new HTMLPurifier_Token_Comment($data);
        }
        // CDATA is handled elsewhere, but if it was handled here:
        //if (strpos($data, '[CDATA[') === 0) {
        //    $this->tokens[] = new HTMLPurifier_Token_Text(
        //        substr($data, 7, strlen($data) - 9) );
        //}
        return true;
    }
    
}

