add_action( 'init', 'custom_remove_add_filters' );

function custom_remove_add_filters(){
	global $woocommerce_auctions;
	remove_filter( 'woocommerce_is_purchasable', array( $woocommerce_auctions, 'auction_is_purchasable' ), 10 );
	add_filter( 'woocommerce_is_purchasable', 'custom_auction_is_purchasable' , 10, 2 );
}

function custom_auction_is_purchasable( $is_purchasable, $object ) {

	$object_type = method_exists( $object, 'get_type' ) ? $object->get_type() : $object->product_type;
	if ( $object_type == 'auction' ) {

		if ( get_option( 'simple_auctions_alow_buy_now', 'yes' ) == 'no' && $object->get_auction_bid_count() != '0' && $object->get_auction_closed() != '2' ) {
			return false;
		}
		if ( ! $object->get_auction_closed() && ! $object->get_auction_closed() && $object->get_price() !== '' ) {

			return true;
		}

		if ( ! is_user_logged_in() ) {
			return false;
		}

		$current_user = wp_get_current_user();
		if ( $current_user->ID != $object->get_auction_current_bider() ) {
			return false;
		}

		if ( ! $object->get_auction_closed() ) {
			return false;
		}
		if ( $object->get_auction_closed() != '2' ) {
			return false;
		}
		if ( $object->get_auction_type() == 'reverse' && get_option( 'simple_auctions_remove_pay_reverse' ) == 'yes' ) {
			return false;
		}

		return true;
	}
	return $is_purchasable;
}