73 lines
2.6 KiB
Go
73 lines
2.6 KiB
Go
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// Copyright 2018 Twitch Interactive, Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"). You may not
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// use this file except in compliance with the License. A copy of the License is
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// located at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// or in the "license" file accompanying this file. This file is distributed on
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// an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
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// express or implied. See the License for the specific language governing
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// permissions and limitations under the License.
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package twirp
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import (
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"context"
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)
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// Interceptor is a form of middleware for Twirp requests, that can be installed on both
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// clients and servers. To intercept RPC calls in the client, use the option
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// `twirp.WithClientInterceptors` on the client constructor. To intercept RPC calls in the server,
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// use the option `twirp.WithServerInterceptors` on the server constructor.
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//
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// Just like http middleware, interceptors can mutate requests and responses.
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// This can enable some powerful integrations, but it should be used with much care
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// becuase it may result in code that is very hard to debug.
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//
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// Example of an interceptor that logs every request and response:
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//
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// func LogInterceptor(l *log.Logger) twirp.Interceptor {
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// return func(next twirp.Method) twirp.Method {
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// return func(ctx context.Context, req interface{}) (interface{}, error) {
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// l.Printf("Service: %s, Method: %s, Request: %v",
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// twirp.ServiceName(ctx), twirp.MethodName(ctx), req)
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// resp, err := next(ctx, req)
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// l.Printf("Response: %v, Error: %v", resp)
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// return resp, err
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// }
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// }
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// }
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//
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type Interceptor func(Method) Method
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// Method is a generic representation of a Twirp-generated RPC method.
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// It is used to define Interceptors.
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type Method func(ctx context.Context, request interface{}) (interface{}, error)
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// ChainInterceptors chains multiple Interceptors into a single Interceptor.
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// The first interceptor wraps the second one, and so on.
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// Returns nil if interceptors is empty. Nil interceptors are ignored.
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func ChainInterceptors(interceptors ...Interceptor) Interceptor {
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filtered := make([]Interceptor, 0, len(interceptors))
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for _, interceptor := range interceptors {
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if interceptor != nil {
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filtered = append(filtered, interceptor)
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}
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}
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switch n := len(filtered); n {
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case 0:
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return nil
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case 1:
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return filtered[0]
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default:
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first := filtered[0]
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return func(next Method) Method {
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for i := len(filtered) - 1; i > 0; i-- {
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next = filtered[i](next)
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}
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return first(next)
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}
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}
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}
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