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// Copyright 2021-2023 The Connect 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 connect
import (
"context"
)
// UnaryFunc is the generic signature of a unary RPC. Interceptors may wrap
// Funcs.
//
// The type of the request and response structs depend on the codec being used.
// When using Protobuf, request.Any() and response.Any() will always be
// [proto.Message] implementations.
type UnaryFunc func(context.Context, AnyRequest) (AnyResponse, error)
// StreamingClientFunc is the generic signature of a streaming RPC from the client's
// perspective. Interceptors may wrap StreamingClientFuncs.
type StreamingClientFunc func(context.Context, Spec) StreamingClientConn
// StreamingHandlerFunc is the generic signature of a streaming RPC from the
// handler's perspective. Interceptors may wrap StreamingHandlerFuncs.
type StreamingHandlerFunc func(context.Context, StreamingHandlerConn) error
// An Interceptor adds logic to a generated handler or client, like the
// decorators or middleware you may have seen in other libraries. Interceptors
// may replace the context, mutate requests and responses, handle errors,
// retry, recover from panics, emit logs and metrics, or do nearly anything
// else.
//
// The returned functions must be safe to call concurrently.
type Interceptor interface {
WrapUnary(UnaryFunc) UnaryFunc
WrapStreamingClient(StreamingClientFunc) StreamingClientFunc
WrapStreamingHandler(StreamingHandlerFunc) StreamingHandlerFunc
}
// UnaryInterceptorFunc is a simple Interceptor implementation that only
// wraps unary RPCs. It has no effect on streaming RPCs.
type UnaryInterceptorFunc func(UnaryFunc) UnaryFunc
// WrapUnary implements [Interceptor] by applying the interceptor function.
func (f UnaryInterceptorFunc) WrapUnary(next UnaryFunc) UnaryFunc { return f(next) }
// WrapStreamingClient implements [Interceptor] with a no-op.
func (f UnaryInterceptorFunc) WrapStreamingClient(next StreamingClientFunc) StreamingClientFunc {
return next
}
// WrapStreamingHandler implements [Interceptor] with a no-op.
func (f UnaryInterceptorFunc) WrapStreamingHandler(next StreamingHandlerFunc) StreamingHandlerFunc {
return next
}
// A chain composes multiple interceptors into one.
type chain struct {
interceptors []Interceptor
}
// newChain composes multiple interceptors into one.
func newChain(interceptors []Interceptor) *chain {
// We usually wrap in reverse order to have the first interceptor from
// the slice act first. Rather than doing this dance repeatedly, reverse the
// interceptor order now.
var chain chain
for i := len(interceptors) - 1; i >= 0; i-- {
if interceptor := interceptors[i]; interceptor != nil {
chain.interceptors = append(chain.interceptors, interceptor)
}
}
return &chain
}
func (c *chain) WrapUnary(next UnaryFunc) UnaryFunc {
for _, interceptor := range c.interceptors {
next = interceptor.WrapUnary(next)
}
return next
}
func (c *chain) WrapStreamingClient(next StreamingClientFunc) StreamingClientFunc {
for _, interceptor := range c.interceptors {
next = interceptor.WrapStreamingClient(next)
}
return next
}
func (c *chain) WrapStreamingHandler(next StreamingHandlerFunc) StreamingHandlerFunc {
for _, interceptor := range c.interceptors {
next = interceptor.WrapStreamingHandler(next)
}
return next
}
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