update-dns/ip/ip.go

package ip

import (
	"encoding/json"
	"net/http"

	"github.com/pkg/errors"
)

// IP address results
type IP struct {
	IP      string `json:"ip"`
	Version string `json:"version"`
}

// Client for getting IP address
type Client struct {
	URLv4 string
	URLv6 string
}

// GetIPv6 returns an IPv6 IP address
func (c *Client) GetIPv6() (string, error) {
	return c.getIP(c.URLv6, "v6")
}

// GetIPv4 returns an IPv6 IP address
func (c *Client) GetIPv4() (string, error) {
	return c.getIP(c.URLv4, "v4")
}

// GetIPv6 returns an IPv6 IP address
func (c *Client) getIP(host, version string) (string, error) {
	ip, err := c.fetchIP(host)
	if err != nil {
		return "", errors.Wrap(err, "could not get ip address")
	}
	if ip.Version != version {
		return "", errors.New("did not get " + version + " result")
	}
	return ip.IP, nil
}

func (c *Client) fetchIP(host string) (*IP, error) {
	result, err := http.Get(host)
	if err != nil {
		return nil, errors.Wrap(err, "could not get url "+host)
	}
	defer result.Body.Close()
	ipResult := &IP{}
	if err := json.NewDecoder(result.Body).Decode(ipResult); err != nil {
		return nil, errors.Wrap(err, "could parse json from url "+host)
	}
	return ipResult, nil
}