<?php

/**
 * Registry for retrieving specific URI scheme validator objects.
 */
class HTMLPurifier_URISchemeRegistry {
	
	/**
	 * Retrieve sole instance of the registry.
	 * 
	 * @param HTMLPurifier_URISchemeRegistry $prototype
	 *        	Optional prototype to overload sole instance with,
	 *        	or bool true to reset to default registry.
	 * @return HTMLPurifier_URISchemeRegistry @note Pass a registry object $prototype with a compatible interface and
	 *         the function will copy it and return it all further times.
	 */
	public static function instance($prototype = null) {
		static $instance = null;
		if ($prototype !== null) {
			$instance = $prototype;
		} elseif ($instance === null || $prototype == true) {
			$instance = new HTMLPurifier_URISchemeRegistry ();
		}
		return $instance;
	}
	
	/**
	 * Cache of retrieved schemes.
	 * @type HTMLPurifier_URIScheme[]
	 */
	protected $schemes = array ();
	
	/**
	 * Retrieves a scheme validator object
	 * 
	 * @param string $scheme
	 *        	String scheme name like http or mailto
	 * @param HTMLPurifier_Config $config        	
	 * @param HTMLPurifier_Context $context        	
	 * @return HTMLPurifier_URIScheme
	 */
	public function getScheme($scheme, $config, $context) {
		if (! $config) {
			$config = HTMLPurifier_Config::createDefault ();
		}
		
		// important, otherwise attacker could include arbitrary file
		$allowed_schemes = $config->get ( 'URI.AllowedSchemes' );
		if (! $config->get ( 'URI.OverrideAllowedSchemes' ) && ! isset ( $allowed_schemes [$scheme] )) {
			return;
		}
		
		if (isset ( $this->schemes [$scheme] )) {
			return $this->schemes [$scheme];
		}
		if (! isset ( $allowed_schemes [$scheme] )) {
			return;
		}
		
		$class = 'HTMLPurifier_URIScheme_' . $scheme;
		if (! class_exists ( $class )) {
			return;
		}
		$this->schemes [$scheme] = new $class ();
		return $this->schemes [$scheme];
	}
	
	/**
	 * Registers a custom scheme to the cache, bypassing reflection.
	 * 
	 * @param string $scheme
	 *        	Scheme name
	 * @param HTMLPurifier_URIScheme $scheme_obj        	
	 */
	public function register($scheme, $scheme_obj) {
		$this->schemes [$scheme] = $scheme_obj;
	}
}

// vim: et sw=4 sts=4