Add api err type (#24)

* Add api err type

* Shush linter

Author: Nesze

client.go

@@ -21,6 +21,15 @@ type Castle struct {
 	apiSecret string
 }
 
+type APIError struct {
+	StatusCode int    `json:"status_code"`
+	Message    string `json:"message"`
+}
+
+func (e *APIError) Error() string {
+	return fmt.Sprintf("status code: %d, message: %s", e.StatusCode, e.Message)
+}
+
 // New creates a new castle client with default http client
 func New(secret string) (*Castle, error) {
 	return NewWithHTTPClient(secret, http.DefaultClient)
@@ -95,7 +104,11 @@ func (c *Castle) sendCall(ctx context.Context, r *castleAPIRequest, url string)
 	defer res.Body.Close() // nolint: gosec
 	if res.StatusCode != http.StatusCreated {
 		b, _ := io.ReadAll(res.Body) // nolint: errcheck
-		return RecommendedActionNone, fmt.Errorf("expected 201 status but got %d: %s", res.StatusCode, string(b))
+
+		return RecommendedActionNone, &APIError{
+			StatusCode: res.StatusCode,
+			Message:    string(b),
+		}
 	}
 
 	resp := &castleAPIResponse{}

client_test.go

@@ -63,12 +63,15 @@ func TestCastle_SendFilterCall(t *testing.T) {
 		fs := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			w.Header().Set("content-type", "application/json")
 			w.WriteHeader(400)
+			w.Write([]byte(`foo`)) // nolint: errcheck
 		}))
 
 		castle.FilterEndpoint = fs.URL
 
 		res, err := cstl.Filter(ctx, req)
 		assert.Error(t, err)
+		assert.IsType(t, &castle.APIError{}, err)
+		assert.Equal(t, &castle.APIError{StatusCode: 400, Message: "foo"}, err)
 		assert.Equal(t, castle.RecommendedActionNone, res)
 	})
 
@@ -303,13 +306,16 @@ func TestCastle_SendRiskCall(t *testing.T) {
 		ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			w.Header().Set("content-type", "application/json")
 			w.WriteHeader(400)
+			w.Write([]byte(`foo`)) // nolint: errcheck
 		}))
 		t.Cleanup(ts.Close)
 
 		castle.RiskEndpoint = ts.URL
 
 		res, err := cstl.Risk(ctx, req)
 		assert.Error(t, err)
+		assert.IsType(t, &castle.APIError{}, err)
+		assert.Equal(t, &castle.APIError{StatusCode: 400, Message: "foo"}, err)
 		assert.Equal(t, castle.RecommendedActionNone, res)
 	})