Add client and server unary interceptors

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

client.go

@@ -42,11 +42,12 @@ type Client struct {
 	channel *channel
 	calls   chan *callRequest
 
-	closed    chan struct{}
-	closeOnce sync.Once
-	closeFunc func()
-	done      chan struct{}
-	err       error
+	closed      chan struct{}
+	closeOnce   sync.Once
+	closeFunc   func()
+	done        chan struct{}
+	err         error
+	interceptor UnaryClientInterceptor
 }
 
 type ClientOpts func(c *Client)
@@ -57,15 +58,22 @@ func WithOnClose(onClose func()) ClientOpts {
 	}
 }
 
+func WithUnaryClientInterceptor(i UnaryClientInterceptor) ClientOpts {
+	return func(c *Client) {
+		c.interceptor = i
+	}
+}
+
 func NewClient(conn net.Conn, opts ...ClientOpts) *Client {
 	c := &Client{
-		codec:     codec{},
-		conn:      conn,
-		channel:   newChannel(conn),
-		calls:     make(chan *callRequest),
-		closed:    make(chan struct{}),
-		done:      make(chan struct{}),
-		closeFunc: func() {},
+		codec:       codec{},
+		conn:        conn,
+		channel:     newChannel(conn),
+		calls:       make(chan *callRequest),
+		closed:      make(chan struct{}),
+		done:        make(chan struct{}),
+		closeFunc:   func() {},
+		interceptor: defaultClientInterceptor,
 	}
 
 	for _, o := range opts {
@@ -107,7 +115,7 @@ func (c *Client) Call(ctx context.Context, service, method string, req, resp int
 		creq.TimeoutNano = dl.Sub(time.Now()).Nanoseconds()
 	}
 
-	if err := c.dispatch(ctx, creq, cresp); err != nil {
+	if err := c.interceptor(ctx, creq, cresp, c.dispatch); err != nil {
 		return err
 	}
 

config.go

@@ -19,7 +19,8 @@ package ttrpc
 import "github.com/pkg/errors"
 
 type serverConfig struct {
-	handshaker Handshaker
+	handshaker  Handshaker
+	interceptor UnaryServerInterceptor
 }
 
 type ServerOpt func(*serverConfig) error
@@ -37,3 +38,13 @@ func WithServerHandshaker(handshaker Handshaker) ServerOpt {
 		return nil
 	}
 }
+
+func WithUnaryServerInterceptor(i UnaryServerInterceptor) ServerOpt {
+	return func(c *serverConfig) error {
+		if c.interceptor != nil {
+			return errors.New("only one interceptor allowed per server")
+		}
+		c.interceptor = i
+		return nil
+	}
+}

interceptor.go

@@ -0,0 +1,39 @@
+/*
+   Copyright The containerd 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 ttrpc
+
+import "context"
+
+type UnaryServerInfo struct {
+	FullMethod string
+}
+
+type Unmarshaler func(interface{}) error
+
+type Invoker func(context.Context, *Request, *Response) error
+
+type UnaryServerInterceptor func(context.Context, Unmarshaler, *UnaryServerInfo, Method) (interface{}, error)
+
+type UnaryClientInterceptor func(context.Context, *Request, *Response, Invoker) error
+
+func defaultServerInterceptor(ctx context.Context, unmarshal Unmarshaler, info *UnaryServerInfo, method Method) (interface{}, error) {
+	return method(ctx, unmarshal)
+}
+
+func defaultClientInterceptor(ctx context.Context, req *Request, resp *Response, invoker Invoker) error {
+	return invoker(ctx, req, resp)
+}

server.go

@@ -53,10 +53,13 @@ func NewServer(opts ...ServerOpt) (*Server, error) {
 			return nil, err
 		}
 	}
+	if config.interceptor == nil {
+		config.interceptor = defaultServerInterceptor
+	}
 
 	return &Server{
 		config:      config,
-		services:    newServiceSet(),
+		services:    newServiceSet(config.interceptor),
 		done:        make(chan struct{}),
 		listeners:   make(map[net.Listener]struct{}),
 		connections: make(map[*serverConn]struct{}),

services.go

@@ -37,12 +37,14 @@ type ServiceDesc struct {
 }
 
 type serviceSet struct {
-	services map[string]ServiceDesc
+	services    map[string]ServiceDesc
+	interceptor UnaryServerInterceptor
 }
 
-func newServiceSet() *serviceSet {
+func newServiceSet(interceptor UnaryServerInterceptor) *serviceSet {
 	return &serviceSet{
-		services: make(map[string]ServiceDesc),
+		services:    make(map[string]ServiceDesc),
+		interceptor: interceptor,
 	}
 }
 
@@ -84,7 +86,11 @@ func (s *serviceSet) dispatch(ctx context.Context, serviceName, methodName strin
 		return nil
 	}
 
-	resp, err := method(ctx, unmarshal)
+	info := &UnaryServerInfo{
+		FullMethod: fullPath(serviceName, methodName),
+	}
+
+	resp, err := s.interceptor(ctx, unmarshal, info, method)
 	if err != nil {
 		return nil, err
 	}