/**
* Define a constant path to our single template folder
*/
define(SINGLE_PATH, TEMPLATEPATH . '/single');

/**
* Filter the single_template with our custom function
*/
add_filter('single_template', 'my_single_template');

/**
* Single template function which will choose our template
*/
function my_single_template($single) {
	global $wp_query, $post;

/**
	* Checks for single template by category
	* Check by category slug and ID
	*/
	foreach((array)get_the_category() as $cat) :

		if(file_exists(SINGLE_PATH . '/single-cat-' . $cat->slug . '.php'))
			return SINGLE_PATH . '/single-cat-' . $cat->slug . '.php';

		elseif(file_exists(SINGLE_PATH . '/single-cat-' . $cat->term_id . '.php'))
			return SINGLE_PATH . '/single-cat-' . $cat->term_id . '.php';

	endforeach;

/**
	* Checks for default single post files within the single folder
	*/
	if(file_exists(SINGLE_PATH . '/single.php'))
		return SINGLE_PATH . '/single.php';

	elseif(file_exists(SINGLE_PATH . '/default.php'))
		return SINGLE_PATH . '/default.php';

return $single;

}