Add HTTP status code and error type conversion

Signed-off-by: Derek McGowan <derek@mcg.dev>

grpc_test.go

@@ -88,6 +88,11 @@ func TestGRPCRoundTrip(t *testing.T) {
 			cause: ErrNotModified,
 			str:   "everything is the same: not modified",
 		},
+		{
+			input: fmt.Errorf("odd HTTP response: %w", FromHTTP(418)),
+			cause: errUnexpectedStatus{418},
+			str:   "odd HTTP response: unexpected status 418",
+		},
 	} {
 		t.Run(testcase.input.Error(), func(t *testing.T) {
 			t.Logf("input: %v", testcase.input)

http.go

@@ -0,0 +1,88 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package errdefs
+
+import (
+	"errors"
+	"net/http"
+)
+
+// FromHTTP returns the error best matching the HTTP status code
+func FromHTTP(statusCode int) error {
+	switch statusCode {
+	case http.StatusNotFound:
+		return ErrNotFound
+	case http.StatusBadRequest:
+		return ErrInvalidArgument
+	case http.StatusConflict:
+		return ErrConflict
+	case http.StatusPreconditionFailed:
+		return ErrFailedPrecondition
+	case http.StatusUnauthorized:
+		return ErrUnauthenticated
+	case http.StatusForbidden:
+		return ErrPermissionDenied
+	case http.StatusNotModified:
+		return ErrNotModified
+	case http.StatusTooManyRequests:
+		return ErrResourceExhausted
+	case http.StatusInternalServerError:
+		return ErrInternal
+	case http.StatusNotImplemented:
+		return ErrNotImplemented
+	case http.StatusServiceUnavailable:
+		return ErrUnavailable
+	default:
+		return errUnexpectedStatus{statusCode}
+	}
+}
+
+// ToHTTP returns the best status code for the given error
+func ToHTTP(err error) int {
+	switch {
+	case IsNotFound(err):
+		return http.StatusNotFound
+	case IsInvalidArgument(err):
+		return http.StatusBadRequest
+	case IsConflict(err):
+		return http.StatusConflict
+	case IsNotModified(err):
+		return http.StatusNotModified
+	case IsFailedPrecondition(err):
+		return http.StatusPreconditionFailed
+	case IsUnauthorized(err):
+		return http.StatusUnauthorized
+	case IsPermissionDenied(err):
+		return http.StatusForbidden
+	case IsResourceExhausted(err):
+		return http.StatusTooManyRequests
+	case IsInternal(err):
+		return http.StatusInternalServerError
+	case IsNotImplemented(err):
+		return http.StatusNotImplemented
+	case IsUnavailable(err):
+		return http.StatusServiceUnavailable
+	case IsUnknown(err):
+		var unexpected errUnexpectedStatus
+		if errors.As(err, &unexpected) && unexpected.status >= 200 && unexpected.status < 600 {
+			return unexpected.status
+		}
+		return http.StatusInternalServerError
+	default:
+		return http.StatusInternalServerError
+	}
+}