<?php

/**
 * Validates the HTML attribute lang, effectively a language code.
 * @note Built according to RFC 3066, which obsoleted RFC 1766
 */
class HTMLPurifier_AttrDef_Lang extends HTMLPurifier_AttrDef {
	
	/**
	 *
	 * @param string $string        	
	 * @param HTMLPurifier_Config $config        	
	 * @param HTMLPurifier_Context $context        	
	 * @return bool|string
	 */
	public function validate($string, $config, $context) {
		$string = trim ( $string );
		if (! $string) {
			return false;
		}
		
		$subtags = explode ( '-', $string );
		$num_subtags = count ( $subtags );
		
		if ($num_subtags == 0) { // sanity check
			return false;
		}
		
		// process primary subtag : $subtags[0]
		$length = strlen ( $subtags [0] );
		switch ($length) {
			case 0 :
				return false;
			case 1 :
				if (! ($subtags [0] == 'x' || $subtags [0] == 'i')) {
					return false;
				}
				break;
			case 2 :
			case 3 :
				if (! ctype_alpha ( $subtags [0] )) {
					return false;
				} elseif (! ctype_lower ( $subtags [0] )) {
					$subtags [0] = strtolower ( $subtags [0] );
				}
				break;
			default :
				return false;
		}
		
		$new_string = $subtags [0];
		if ($num_subtags == 1) {
			return $new_string;
		}
		
		// process second subtag : $subtags[1]
		$length = strlen ( $subtags [1] );
		if ($length == 0 || ($length == 1 && $subtags [1] != 'x') || $length > 8 || ! ctype_alnum ( $subtags [1] )) {
			return $new_string;
		}
		if (! ctype_lower ( $subtags [1] )) {
			$subtags [1] = strtolower ( $subtags [1] );
		}
		
		$new_string .= '-' . $subtags [1];
		if ($num_subtags == 2) {
			return $new_string;
		}
		
		// process all other subtags, index 2 and up
		for($i = 2; $i < $num_subtags; $i ++) {
			$length = strlen ( $subtags [$i] );
			if ($length == 0 || $length > 8 || ! ctype_alnum ( $subtags [$i] )) {
				return $new_string;
			}
			if (! ctype_lower ( $subtags [$i] )) {
				$subtags [$i] = strtolower ( $subtags [$i] );
			}
			$new_string .= '-' . $subtags [$i];
		}
		return $new_string;
	}
}

// vim: et sw=4 sts=4