1// Copyright 2016 The Go Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style 3// license that can be found in the LICENSE file. 4 5package gensupport 6 7import ( 8 "context" 9 "encoding/json" 10 "errors" 11 "net/http" 12) 13 14// Hook is the type of a function that is called once before each HTTP request 15// that is sent by a generated API. It returns a function that is called after 16// the request returns. 17// Hooks are not called if the context is nil. 18type Hook func(ctx context.Context, req *http.Request) func(resp *http.Response) 19 20var hooks []Hook 21 22// RegisterHook registers a Hook to be called before each HTTP request by a 23// generated API. Hooks are called in the order they are registered. Each 24// hook can return a function; if it is non-nil, it is called after the HTTP 25// request returns. These functions are called in the reverse order. 26// RegisterHook should not be called concurrently with itself or SendRequest. 27func RegisterHook(h Hook) { 28 hooks = append(hooks, h) 29} 30 31// SendRequest sends a single HTTP request using the given client. 32// If ctx is non-nil, it calls all hooks, then sends the request with 33// req.WithContext, then calls any functions returned by the hooks in 34// reverse order. 35func SendRequest(ctx context.Context, client *http.Client, req *http.Request) (*http.Response, error) { 36 // Disallow Accept-Encoding because it interferes with the automatic gzip handling 37 // done by the default http.Transport. See https://github.com/google/google-api-go-client/issues/219. 38 if _, ok := req.Header["Accept-Encoding"]; ok { 39 return nil, errors.New("google api: custom Accept-Encoding headers not allowed") 40 } 41 if ctx == nil { 42 return client.Do(req) 43 } 44 // Call hooks in order of registration, store returned funcs. 45 post := make([]func(resp *http.Response), len(hooks)) 46 for i, h := range hooks { 47 fn := h(ctx, req) 48 post[i] = fn 49 } 50 51 // Send request. 52 resp, err := send(ctx, client, req) 53 54 // Call returned funcs in reverse order. 55 for i := len(post) - 1; i >= 0; i-- { 56 if fn := post[i]; fn != nil { 57 fn(resp) 58 } 59 } 60 return resp, err 61} 62 63func send(ctx context.Context, client *http.Client, req *http.Request) (*http.Response, error) { 64 if client == nil { 65 client = http.DefaultClient 66 } 67 resp, err := client.Do(req.WithContext(ctx)) 68 // If we got an error, and the context has been canceled, 69 // the context's error is probably more useful. 70 if err != nil { 71 select { 72 case <-ctx.Done(): 73 err = ctx.Err() 74 default: 75 } 76 } 77 return resp, err 78} 79 80// DecodeResponse decodes the body of res into target. If there is no body, 81// target is unchanged. 82func DecodeResponse(target interface{}, res *http.Response) error { 83 if res.StatusCode == http.StatusNoContent { 84 return nil 85 } 86 return json.NewDecoder(res.Body).Decode(target) 87} 88