// 2019 Rackspace, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"): you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.

package tsip

// FindNextHop method will take a ip address as a string input and do a route lookup across
// Rackspace infrastructure to gather the next-hop address by pulling the most specific
// route.
// Return data will be the next-hop address or the self address if not found.
func (c *Client) FindNextHop(ipAddr string) (string, error) {
	s, err := c.u.GetStaticRouteByIP(ipAddr, nil)
	if err != nil {
		return ipAddr, err
	}
	// If we cannot find any routing information for this address,
	// return the self address.
	if s.Count == 0 {
		return ipAddr, nil
	}

	// Return data from Unipede is sorted most specific route first.  Because of this, we only
	// need to return the first iteration that had a next-hop address assigned.
	for _, dev := range s.Data {
		if dev.NextHopAddress != "" {
			return dev.NextHopAddress, nil
		}
	}
	return ipAddr, nil
}