feat: external ip provider plain

pkg/externalIpProvider/plain/plain.go

@@ -0,0 +1,56 @@
+package externalIpProvider
+
+import (
+	"errors"
+	"net"
+	"net/http"
+	"net/url"
+	externalIpProvider "realdnydns/pkg/externalIpProvider"
+)
+
+type ExternalIpProviderImplPlain struct {
+	IPProviderURL string
+	HTTPClient    *http.Client
+}
+
+type PlainExternalIpProviderConfig struct {
+	Url string `yaml:"url"`
+}
+
+func New(config PlainExternalIpProviderConfig) (externalIpProvider.ExternalIpProvider, error) {
+	if config.Url == "" {
+		return nil, errors.New("url is required")
+	}
+
+	return &ExternalIpProviderImplPlain{
+		config.Url,
+		&http.Client{},
+	}, nil
+}
+
+func (p *ExternalIpProviderImplPlain) GetExternalIp() (net.IP, error) {
+	parsedUrl, err := url.Parse(p.IPProviderURL)
+	if err != nil {
+		return nil, err
+	}
+
+	res, err := p.HTTPClient.Get(parsedUrl.String())
+	if err != nil {
+		return nil, err
+	}
+
+	if res.StatusCode != 200 {
+		return nil, errors.New("unexpected status code")
+	}
+
+	responseBody := make([]byte, res.ContentLength)
+	res.Body.Read(responseBody)
+	defer res.Body.Close()
+
+	parsedIp := net.ParseIP(string(responseBody))
+	if parsedIp == nil {
+		return nil, errors.New("unable to parse ip")
+	}
+
+	return parsedIp, nil
+}