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client_hooks.go
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client_hooks.go
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// Copyright 2018 Twitch Interactive, Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"). You may not
// use this file except in compliance with the License. A copy of the License is
// located at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// or in the "license" file accompanying this file. This file 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 twirp
import (
"context"
"net/http"
)
// ClientOption is a functional option for extending a Twirp client.
type ClientOption func(*ClientOptions)
// ClientOptions encapsulate the configurable parameters on a Twirp client.
type ClientOptions struct {
Hooks *ClientHooks
}
// ClientHooks is a container for callbacks that can instrument a
// Twirp-generated client. These callbacks all accept a context and some return
// a context. They can use this to add to the context, appending values or
// deadlines to it.
//
// The RequestPrepared hook is special because it can return errors. If it
// returns non-nil error, handling for that request will be stopped at that
// point. The Error hook will then be triggered.
//
// The RequestPrepaared hook will always be called first and will be called for
// each outgoing request from the Twirp client. The last hook to be called
// will either be Error or ResponseReceived, so be sure to handle both cases in
// your hooks.
type ClientHooks struct {
// RequestPrepared is called as soon as a request has been created and before it has been sent
// to the Twirp server.
RequestPrepared func(context.Context, *http.Request) (context.Context, error)
// ResponseReceived is called after a request has finished sending. Since this
// is terminal, the context is not returned. ResponseReceived will not be
// called in the case of an error being returned from the request.
ResponseReceived func(context.Context)
// Error hook is called whenever an error occurs during the sending of a
// request. The Error is passed as an argument to the hook.
Error func(context.Context, Error)
}
// WithClientHooks defines the hooks for a Twirp client.
func WithClientHooks(hooks *ClientHooks) ClientOption {
return func(o *ClientOptions) {
o.Hooks = hooks
}
}
// ChainClientHooks creates a new *ClientHooks which chains the callbacks in
// each of the constituent hooks passed in. Each hook function will be
// called in the order of the ClientHooks values passed in.
//
// For the erroring hook, RequestPrepared, any returned
// errors prevent processing by later hooks.
func ChainClientHooks(hooks ...*ClientHooks) *ClientHooks {
if len(hooks) == 0 {
return nil
}
if len(hooks) == 1 {
return hooks[0]
}
return &ClientHooks{
RequestPrepared: func(ctx context.Context, req *http.Request) (context.Context, error) {
for _, h := range hooks {
if h != nil && h.RequestPrepared != nil {
var err error
ctx, err = h.RequestPrepared(ctx, req)
if err != nil {
return ctx, err
}
}
}
return ctx, nil
},
ResponseReceived: func(ctx context.Context) {
for _, h := range hooks {
if h != nil && h.ResponseReceived != nil {
h.ResponseReceived(ctx)
}
}
},
Error: func(ctx context.Context, twerr Error) {
for _, h := range hooks {
if h != nil && h.Error != nil {
h.Error(ctx, twerr)
}
}
},
}
}