Initial QSfera import

Server/vendor/github.com/crewjam/httperr/client.go

@@ -0,0 +1,120 @@
+package httperr
+
+import (
+	"bytes"
+	"encoding/json"
+	"io/ioutil"
+	"net/http"
+	"reflect"
+)
+
+// ClientArg is an argument to Client
+type ClientArg func(xport *Transport)
+
+// Client returns an http.Client that wraps client with
+// an error handling transport.
+func Client(next *http.Client, args ...ClientArg) *http.Client {
+	xport := Transport{Next: next.Transport}
+	for _, arg := range args {
+		arg(&xport)
+	}
+
+	rv := *next
+	rv.Transport = xport
+	return &rv
+}
+
+// DefaultClient returns an http.Client that wraps the default
+// http.Client with an error handling transport.
+func DefaultClient() *http.Client {
+	return Client(http.DefaultClient)
+}
+
+var _ http.RoundTripper = Transport{}
+
+// Transport is an http.RoundTripper that intercepts responses where
+// the StatusCode >= 400 and returns a Response{}.
+//
+// If ErrorFactory is specified it should return an error that can be used
+// to unmarshal a JSON error response. This is useful when a web service
+// offers structured error information. If the error structure cannot be
+// unmarshalled, then a regular Response error is returned.
+//
+//    type APIError struct {
+//      Code string `json:"code"`
+//      Message string `json:"message"`
+//    }
+//
+//    func (a APIError) Error() string {
+//       return fmt.Sprintf("%s (%d)", a.Message, a.Code)
+//    }
+//
+//    t := Transport{
+//        ErrorFactory: func() error {
+//            return &APIError{}
+//        },
+//    }
+//
+type Transport struct {
+	Next    http.RoundTripper
+	OnError func(req *http.Request, resp *http.Response) error
+}
+
+// RoundTrip implements http.RoundTripper.
+func (t Transport) RoundTrip(req *http.Request) (*http.Response, error) {
+	next := t.Next
+	if next == nil {
+		next = http.DefaultTransport
+	}
+
+	resp, err := next.RoundTrip(req)
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode < 400 {
+		return resp, nil
+	}
+
+	if t.OnError != nil {
+		if err := t.OnError(req, resp); err != nil {
+			return nil, err
+		}
+	}
+
+	return nil, Response(*resp)
+}
+
+// JSON returns a ClientArg that specifies a function that
+// handles errors structured as a JSON object.
+func JSON(errStruct error) ClientArg {
+	typ := reflect.TypeOf(errStruct)
+	if typ.Kind() != reflect.Struct {
+		panic("JSON() argument must be a structure")
+	}
+
+	e := reflect.New(typ).Interface()
+	_ = e.(error) // panic if errStruct
+
+	return func(xport *Transport) {
+		xport.OnError = func(req *http.Request, resp *http.Response) error {
+			defer resp.Body.Close()
+			body, err := ioutil.ReadAll(resp.Body)
+			if err != nil {
+				return err
+			}
+			resp.Body = ioutil.NopCloser(bytes.NewReader(body))
+
+			jsonErrValue := reflect.New(typ)
+
+			unmarshalErr := json.Unmarshal(body, jsonErrValue.Interface())
+			if unmarshalErr == nil {
+				// jsonErrValue is a *Foo if errStruct == Foo{}
+				return jsonErrValue.Elem().Interface().(error)
+			}
+
+			// we failed to unmarshal the response body, so ignore the
+			// JSON error and proceed as if ErrorFactory was not provided.
+			return Response(*resp)
+		}
+	}
+}