feat: mvp (#1)

MVP including features:
* Detect IP change
* Configurable/generic external IP provider
* Configurable/generic DNS provider
* Impl. of plain external IP provider
* Impl. of Ionos DNS provider

Reviewed-on: #1
Co-authored-by: Timo Behrendt <t.behrendt@t00n.de>
Co-committed-by: Timo Behrendt <t.behrendt@t00n.de>

pkg/externalIpProvider/plain/plain_test.go

@@ -0,0 +1,150 @@
+package externalIpProvider
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestNew(t *testing.T) {
+	t.Run("returns external ip provider", testNew())
+	t.Run("returns error when url is empty", testNewEmptyUrl())
+}
+
+func testNew() func(t *testing.T) {
+	return func(t *testing.T) {
+		provider, err := New(PlainExternalIpProviderConfig{
+			Url: "http://localhost",
+		})
+		if err != nil {
+			t.Fatalf("NewPlain() returned unexpected error: %v", err)
+		}
+
+		if provider == nil {
+			t.Fatalf("NewPlain() returned nil provider")
+		}
+	}
+}
+
+func testNewEmptyUrl() func(t *testing.T) {
+	return func(t *testing.T) {
+		_, err := New(PlainExternalIpProviderConfig{})
+		if err == nil {
+			t.Fatalf("NewPlain() returned unexpected error: %v", err)
+		}
+	}
+}
+
+func TestGetExternal(t *testing.T) {
+	t.Run("returns external ip", testGetExternalIp())
+	t.Run("returns error when unable to parse ip", testGetExternalIpUnparsableIp())
+	t.Run("returns error when unexpected status code", testGetExternalIpUnexpectedStatusCode())
+	t.Run("returns error when unable to parse url", testGetExternalIpUnableToParseUrl())
+	t.Run("returns error when unable to get", testGetExternalIpUnableToGet())
+}
+
+func testGetExternalIp() func(t *testing.T) {
+	return func(t *testing.T) {
+		mockServer := httptest.NewServer(http.HandlerFunc(
+			func(w http.ResponseWriter, r *http.Request) {
+				w.Write([]byte("127.0.0.1"))
+			},
+		))
+		defer mockServer.Close()
+
+		provider, err := New(PlainExternalIpProviderConfig{
+			Url: mockServer.URL,
+		})
+		if err != nil {
+			t.Fatalf("NewPlain() returned unexpected error: %v", err)
+		}
+
+		ip, err := provider.GetExternalIp()
+		if err != nil {
+			t.Fatalf("GetExternalIp() returned unexpected error: %v", err)
+		}
+
+		if ip.String() != "127.0.0.1" {
+			t.Fatalf("GetExternalIp() returned unexpected ip: %v instead of 127.0.0.1", ip)
+		}
+	}
+}
+
+func testGetExternalIpUnparsableIp() func(t *testing.T) {
+	return func(t *testing.T) {
+		mockServer := httptest.NewServer(http.HandlerFunc(
+			func(w http.ResponseWriter, r *http.Request) {
+				w.Write([]byte("not an ip"))
+			},
+		))
+		defer mockServer.Close()
+
+		provider, err := New(PlainExternalIpProviderConfig{
+			Url: mockServer.URL,
+		})
+		if err != nil {
+			t.Fatalf("NewPlain() returned unexpected error: %v", err)
+		}
+
+		_, err = provider.GetExternalIp()
+		if err == nil {
+			t.Fatalf("GetExternalIp() returned unexpected error: %v", err)
+		}
+	}
+}
+
+func testGetExternalIpUnexpectedStatusCode() func(t *testing.T) {
+	return func(t *testing.T) {
+		mockServer := httptest.NewServer(http.HandlerFunc(
+			func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(500)
+			},
+		))
+		defer mockServer.Close()
+
+		provider, err := New(PlainExternalIpProviderConfig{
+			Url: mockServer.URL,
+		})
+		if err != nil {
+			t.Fatalf("NewPlain() returned unexpected error: %v", err)
+		}
+
+		_, err = provider.GetExternalIp()
+		if err == nil {
+			t.Fatalf("GetExternalIp() returned unexpected error: %v", err)
+		}
+	}
+}
+
+func testGetExternalIpUnableToParseUrl() func(t *testing.T) {
+	return func(t *testing.T) {
+		provider, err := New(PlainExternalIpProviderConfig{
+			Url: "not a url !'§%&",
+		})
+		if err != nil {
+			t.Fatalf("NewPlain() returned unexpected error: %v", err)
+		}
+
+		_, err = provider.GetExternalIp()
+		if err == nil {
+			t.Fatalf("GetExternalIp() returned unexpected error: %v", err)
+		}
+	}
+}
+
+func testGetExternalIpUnableToGet() func(t *testing.T) {
+	return func(t *testing.T) {
+		// force error by using a non-responding url, beware of side effects
+		provider, err := New(PlainExternalIpProviderConfig{
+			Url: "http://localhost:1234",
+		})
+		if err != nil {
+			t.Fatalf("NewPlain() returned unexpected error: %v", err)
+		}
+
+		_, err = provider.GetExternalIp()
+		if err == nil {
+			t.Fatalf("GetExternalIp() returned unexpected error: %v", err)
+		}
+	}
+}