github.com/cloudwego/kitex@v0.9.0/pkg/endpoint/endpoint.go (about)

     1  /*
     2   * Copyright 2021 CloudWeGo Authors
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package endpoint
    18  
    19  import "context"
    20  
    21  // Endpoint represent one method for calling from remote.
    22  type Endpoint func(ctx context.Context, req, resp interface{}) (err error)
    23  
    24  // Middleware deal with input Endpoint and output Endpoint.
    25  type Middleware func(Endpoint) Endpoint
    26  
    27  // MiddlewareBuilder builds a middleware with information from a context.
    28  type MiddlewareBuilder func(ctx context.Context) Middleware
    29  
    30  // Chain connect middlewares into one middleware.
    31  func Chain(mws ...Middleware) Middleware {
    32  	return func(next Endpoint) Endpoint {
    33  		for i := len(mws) - 1; i >= 0; i-- {
    34  			next = mws[i](next)
    35  		}
    36  		return next
    37  	}
    38  }
    39  
    40  // Build builds the given middlewares into one middleware.
    41  func Build(mws []Middleware) Middleware {
    42  	if len(mws) == 0 {
    43  		return DummyMiddleware
    44  	}
    45  	return func(next Endpoint) Endpoint {
    46  		return mws[0](Build(mws[1:])(next))
    47  	}
    48  }
    49  
    50  // DummyMiddleware is a dummy middleware.
    51  func DummyMiddleware(next Endpoint) Endpoint {
    52  	return next
    53  }
    54  
    55  // DummyEndpoint is a dummy endpoint.
    56  func DummyEndpoint(ctx context.Context, req, resp interface{}) (err error) {
    57  	return nil
    58  }
    59  
    60  type mwCtxKeyType int
    61  
    62  // Keys for components attached to the context for a middleware builder.
    63  const (
    64  	CtxEventBusKey mwCtxKeyType = iota
    65  	CtxEventQueueKey
    66  )