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package autorest
// Copyright 2017 Microsoft Corporation
//
// 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.
import (
"bytes"
"encoding/json"
"encoding/xml"
"fmt"
"io"
"io/ioutil"
"net/http"
"strings"
)
// Responder is the interface that wraps the Respond method.
//
// Respond accepts and reacts to an http.Response. Implementations must ensure to not share or hold
// state since Responders may be shared and re-used.
type Responder interface {
Respond(*http.Response) error
}
// ResponderFunc is a method that implements the Responder interface.
type ResponderFunc func(*http.Response) error
// Respond implements the Responder interface on ResponderFunc.
func (rf ResponderFunc) Respond(r *http.Response) error {
return rf(r)
}
// RespondDecorator takes and possibly decorates, by wrapping, a Responder. Decorators may react to
// the http.Response and pass it along or, first, pass the http.Response along then react.
type RespondDecorator func(Responder) Responder
// CreateResponder creates, decorates, and returns a Responder. Without decorators, the returned
// Responder returns the passed http.Response unmodified. Responders may or may not be safe to share
// and re-used: It depends on the applied decorators. For example, a standard decorator that closes
// the response body is fine to share whereas a decorator that reads the body into a passed struct
// is not.
//
// To prevent memory leaks, ensure that at least one Responder closes the response body.
func CreateResponder(decorators ...RespondDecorator) Responder {
return DecorateResponder(
Responder(ResponderFunc(func(r *http.Response) error { return nil })),
decorators...)
}
// DecorateResponder accepts a Responder and a, possibly empty, set of RespondDecorators, which it
// applies to the Responder. Decorators are applied in the order received, but their affect upon the
// request depends on whether they are a pre-decorator (react to the http.Response and then pass it
// along) or a post-decorator (pass the http.Response along and then react).
func DecorateResponder(r Responder, decorators ...RespondDecorator) Responder {
for _, decorate := range decorators {
r = decorate(r)
}
return r
}
// Respond accepts an http.Response and a, possibly empty, set of RespondDecorators.
// It creates a Responder from the decorators it then applies to the passed http.Response.
func Respond(r *http.Response, decorators ...RespondDecorator) error {
if r == nil {
return nil
}
return CreateResponder(decorators...).Respond(r)
}
// ByIgnoring returns a RespondDecorator that ignores the passed http.Response passing it unexamined
// to the next RespondDecorator.
func ByIgnoring() RespondDecorator {
return func(r Responder) Responder {
return ResponderFunc(func(resp *http.Response) error {
return r.Respond(resp)
})
}
}
// ByCopying copies the contents of the http.Response Body into the passed bytes.Buffer as
// the Body is read.
func ByCopying(b *bytes.Buffer) RespondDecorator {
return func(r Responder) Responder {
return ResponderFunc(func(resp *http.Response) error {
err := r.Respond(resp)
if err == nil && resp != nil && resp.Body != nil {
resp.Body = TeeReadCloser(resp.Body, b)
}
return err
})
}
}
// ByDiscardingBody returns a RespondDecorator that first invokes the passed Responder after which
// it copies the remaining bytes (if any) in the response body to ioutil.Discard. Since the passed
// Responder is invoked prior to discarding the response body, the decorator may occur anywhere
// within the set.
func ByDiscardingBody() RespondDecorator {
return func(r Responder) Responder {
return ResponderFunc(func(resp *http.Response) error {
err := r.Respond(resp)
if err == nil && resp != nil && resp.Body != nil {
if _, err := io.Copy(ioutil.Discard, resp.Body); err != nil {
return fmt.Errorf("Error discarding the response body: %v", err)
}
}
return err
})
}
}
// ByClosing returns a RespondDecorator that first invokes the passed Responder after which it
// closes the response body. Since the passed Responder is invoked prior to closing the response
// body, the decorator may occur anywhere within the set.
func ByClosing() RespondDecorator {
return func(r Responder) Responder {
return ResponderFunc(func(resp *http.Response) error {
err := r.Respond(resp)
if resp != nil && resp.Body != nil {
if err := resp.Body.Close(); err != nil {
return fmt.Errorf("Error closing the response body: %v", err)
}
}
return err
})
}
}
// ByClosingIfError returns a RespondDecorator that first invokes the passed Responder after which
// it closes the response if the passed Responder returns an error and the response body exists.
func ByClosingIfError() RespondDecorator {
return func(r Responder) Responder {
return ResponderFunc(func(resp *http.Response) error {
err := r.Respond(resp)
if err != nil && resp != nil && resp.Body != nil {
if err := resp.Body.Close(); err != nil {
return fmt.Errorf("Error closing the response body: %v", err)
}
}
return err
})
}
}
// ByUnmarshallingBytes returns a RespondDecorator that copies the Bytes returned in the
// response Body into the value pointed to by v.
func ByUnmarshallingBytes(v *[]byte) RespondDecorator {
return func(r Responder) Responder {
return ResponderFunc(func(resp *http.Response) error {
err := r.Respond(resp)
if err == nil {
bytes, errInner := ioutil.ReadAll(resp.Body)
if errInner != nil {
err = fmt.Errorf("Error occurred reading http.Response#Body - Error = '%v'", errInner)
} else {
*v = bytes
}
}
return err
})
}
}
// ByUnmarshallingJSON returns a RespondDecorator that decodes a JSON document returned in the
// response Body into the value pointed to by v.
func ByUnmarshallingJSON(v interface{}) RespondDecorator {
return func(r Responder) Responder {
return ResponderFunc(func(resp *http.Response) error {
err := r.Respond(resp)
if err == nil {
b, errInner := ioutil.ReadAll(resp.Body)
// Some responses might include a BOM, remove for successful unmarshalling
b = bytes.TrimPrefix(b, []byte("\xef\xbb\xbf"))
if errInner != nil {
err = fmt.Errorf("Error occurred reading http.Response#Body - Error = '%v'", errInner)
} else if len(strings.Trim(string(b), " ")) > 0 {
errInner = json.Unmarshal(b, v)
if errInner != nil {
err = fmt.Errorf("Error occurred unmarshalling JSON - Error = '%v' JSON = '%s'", errInner, string(b))
}
}
}
return err
})
}
}
// ByUnmarshallingXML returns a RespondDecorator that decodes a XML document returned in the
// response Body into the value pointed to by v.
func ByUnmarshallingXML(v interface{}) RespondDecorator {
return func(r Responder) Responder {
return ResponderFunc(func(resp *http.Response) error {
err := r.Respond(resp)
if err == nil {
b, errInner := ioutil.ReadAll(resp.Body)
if errInner != nil {
err = fmt.Errorf("Error occurred reading http.Response#Body - Error = '%v'", errInner)
} else {
errInner = xml.Unmarshal(b, v)
if errInner != nil {
err = fmt.Errorf("Error occurred unmarshalling Xml - Error = '%v' Xml = '%s'", errInner, string(b))
}
}
}
return err
})
}
}
// WithErrorUnlessStatusCode returns a RespondDecorator that emits an error unless the response
// StatusCode is among the set passed. On error, response body is fully read into a buffer and
// presented in the returned error, as well as in the response body.
func WithErrorUnlessStatusCode(codes ...int) RespondDecorator {
return func(r Responder) Responder {
return ResponderFunc(func(resp *http.Response) error {
err := r.Respond(resp)
if err == nil && !ResponseHasStatusCode(resp, codes...) {
derr := NewErrorWithResponse("autorest", "WithErrorUnlessStatusCode", resp, "%v %v failed with %s",
resp.Request.Method,
resp.Request.URL,
resp.Status)
if resp.Body != nil {
defer resp.Body.Close()
b, _ := ioutil.ReadAll(resp.Body)
derr.ServiceError = b
resp.Body = ioutil.NopCloser(bytes.NewReader(b))
}
err = derr
}
return err
})
}
}
// WithErrorUnlessOK returns a RespondDecorator that emits an error if the response StatusCode is
// anything other than HTTP 200.
func WithErrorUnlessOK() RespondDecorator {
return WithErrorUnlessStatusCode(http.StatusOK)
}
// ExtractHeader extracts all values of the specified header from the http.Response. It returns an
// empty string slice if the passed http.Response is nil or the header does not exist.
func ExtractHeader(header string, resp *http.Response) []string {
if resp != nil && resp.Header != nil {
return resp.Header[http.CanonicalHeaderKey(header)]
}
return nil
}
// ExtractHeaderValue extracts the first value of the specified header from the http.Response. It
// returns an empty string if the passed http.Response is nil or the header does not exist.
func ExtractHeaderValue(header string, resp *http.Response) string {
h := ExtractHeader(header, resp)
if len(h) > 0 {
return h[0]
}
return ""
}
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