// 省略
package helloworld;

// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
string name = 1;
}

// The response message containing the greetings
message HelloReply {
string message = 1;
}

// 省略
package helloworld;

// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply) {}
// 新しくSayHelloAgainメソッドを定義
rpc SayHelloAgain (HelloRequest) returns (HelloReply) {}
}

// The request message containing the user's name.
message HelloRequest {
string name = 1;
}

// The response message containing the greetings
message HelloReply {
string message = 1;
}

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"net"

	"google.golang.org/grpc"
	pb "google.golang.org/grpc/examples/helloworld/helloworld"
)

var (
	port = flag.Int("port", 50051, "The server port")
)

// server is used to implement helloworld.GreeterServer.
type server struct {
	pb.UnimplementedGreeterServer
}

// SayHello implements helloworld.GreeterServer
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	log.Printf("Received: %v", in.GetName())
	return &pb.HelloReply{Message: "Hello " + in.GetName()}, nil
}

// SayHelloAgainメソッドを追記
func (s *server) SayHelloAgain(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply,error) {
return &pb.HelloReply{Message: "Hello again " + in.GetName()},nil
}

func main() {
	flag.Parse()
	lis, err := net.Listen("tcp", fmt.Sprintf(":%d", *port))
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}
	s := grpc.NewServer()
	pb.RegisterGreeterServer(s, &server{})
	log.Printf("server listening at %v", lis.Addr())
	if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to serve: %v", err)
	}
}

package main

import (
	"context"
	"flag"
	"log"
	"time"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
	pb "google.golang.org/grpc/examples/helloworld/helloworld"
)

const (
	defaultName = "world"
)

var (
	addr = flag.String("addr", "localhost:50051", "the address to connect to")
	name = flag.String("name", defaultName, "Name to greet")
)

func main() {
	flag.Parse()
　 // Set up a connection to the server.
	conn, err := grpc.Dial(*addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer conn.Close()
	c := pb.NewGreeterClient(conn)

	// Contact the server and print out its response.
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	r, err := c.SayHello(ctx, &pb.HelloRequest{Name: *name})
	if err != nil {
		log.Fatalf("could not greet: %v", err)
	}
	log.Printf("Greeting: %s", r.GetMessage())
	// SayHelloAgainの呼び出しを追記
	r, err = c.SayHelloAgain(ctx, &pb.HelloRequest{Name: *name})
	if err != nil {
		log.Fatalf("could not greet: %v", err)
	}
	log.Printf("Greeting: %s", r.GetMessage())
}

// server is used to implement helloworld.GreeterServer.
type server struct {
	pb.UnimplementedGreeterServer
}

// UnimplementedGreeterServer must be embedded to have forward compatible implementations.
type UnimplementedGreeterServer struct {
}

func (UnimplementedGreeterServer) SayHello(context.Context, HelloRequest) (HelloReply, error) {
return nil, status.Errorf(codes.Unimplemented, "method SayHello not implemented")
}
func (UnimplementedGreeterServer) SayHelloAgain(context.Context, HelloRequest) (HelloReply, error) {
return nil, status.Errorf(codes.Unimplemented, "method SayHelloAgain not implemented")
}
func (UnimplementedGreeterServer) mustEmbedUnimplementedGreeterServer() {}

// GreeterServer is the server API for Greeter service.
// All implementations must embed UnimplementedGreeterServer
// for forward compatibility
type GreeterServer interface {
	SayHello(context.Context, *HelloRequest) (*HelloReply, error)
	SayHelloAgain(context.Context, *HelloRequest) (*HelloReply, error)
	mustEmbedUnimplementedGreeterServer()
}

// SayHelloメソッドとSayHelloAgainメソッドだけなら以下のような形で外部からでも満たすことができる
type sampleServer interface {
	SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error)
	SayHelloAgain(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error)
}

type server struct {
	sampleServer
}

type sampleServer interface {
	SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error)
	SayHelloAgain(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error)
	mustEmbedUnimplementedGreeterServer()
}

// 形だけmustEmbedUnimplementedGreeterServerを追記してもGreeterServerを満たしたことにはならない
type server struct {
	sampleServer
}

// GreeterServerを満たすにはUnimplementedGreeterServer埋め込むしかない
type server struct {
	pb.UnimplementedGreeterServer
}

func (UnimplementedGreeterServer) SayHello(context.Context, *HelloRequest) (*HelloReply, error) {
	return nil, status.Errorf(codes.Unimplemented, "method SayHello not implemented")
}
func (UnimplementedGreeterServer) SayHelloAgain(context.Context, *HelloRequest) (*HelloReply, error) {
	return nil, status.Errorf(codes.Unimplemented, "method SayHelloAgain not implemented")
}
func (UnimplementedGreeterServer) mustEmbedUnimplementedGreeterServer() {}

// SayHello implements helloworld.GreeterServer
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	log.Printf("Received: %v", in.GetName())
	return &pb.HelloReply{Message: "Hello " + in.GetName()}, nil
}

func (s *server) SayHelloAgain(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	return &pb.HelloReply{Message: "Hello again " + in.GetName()}, nil
}

flag.Parse()
lis, err := net.Listen("tcp", fmt.Sprintf(":%d", *port))
if err != nil {
log.Fatalf("failed to listen: %v", err)
}

s := grpc.NewServer()

// NewServer creates a gRPC server which has no service registered and has not
// started to accept requests yet.
func NewServer(opt ...ServerOption) *Server {
// 省略

// A ServerOption sets options such as credentials, codec and keepalive parameters, etc.
type ServerOption interface {
	apply(*serverOptions)
}

type serverOptions struct {
	creds                 credentials.TransportCredentials
	codec                 baseCodec
	cp                    Compressor
	dc                    Decompressor
	unaryInt              UnaryServerInterceptor
	streamInt             StreamServerInterceptor
	chainUnaryInts        []UnaryServerInterceptor
	chainStreamInts       []StreamServerInterceptor
	inTapHandle           tap.ServerInHandle
	statsHandlers         []stats.Handler
	maxConcurrentStreams  uint32
	maxReceiveMessageSize int
	maxSendMessageSize    int
	unknownStreamDesc     *StreamDesc
	keepaliveParams       keepalive.ServerParameters
	keepalivePolicy       keepalive.EnforcementPolicy
	initialWindowSize     int32
	initialConnWindowSize int32
	writeBufferSize       int
	readBufferSize        int
	connectionTimeout     time.Duration
	maxHeaderListSize     *uint32
	headerTableSize       *uint32
	numServerWorkers      uint32
}

// サーバーのkeepalive実施ポリシーを設定するServerOptionを返します。
func KeepaliveEnforcementPolicy(kep keepalive.EnforcementPolicy) ServerOption {
	return newFuncServerOption(func(o *serverOptions) {
		o.keepalivePolicy = kep
	})
}

//　メッセージのマーシャルとアンマーシャルにCodecを設定するServerOptionを返します。
func CustomCodec(codec Codec) ServerOption {
	return newFuncServerOption(func(o *serverOptions) {
		o.codec = codec
	})
}

// Stream通信を実装するために必要なStreamServerInterceptor（Middalewareのようなもの）を設定するServerOptionを返します。　
func StreamInterceptor(i StreamServerInterceptor) ServerOption {
	return newFuncServerOption(func(o *serverOptions) {
		if o.streamInt != nil {
			panic("The stream server interceptor was already set and may not be reset.")
		}
		o.streamInt = i
	})
}

// Server is a gRPC server to serve RPC requests.
type Server struct {
	opts serverOptions

	mu  sync.Mutex // guards following
	lis map[net.Listener]bool
	// conns contains all active server transports. It is a map keyed on a
	// listener address with the value being the set of active transports
	// belonging to that listener.
	conns    map[string]map[transport.ServerTransport]bool
	serve    bool
	drain    bool
	cv       *sync.Cond              // signaled when connections close for GracefulStop
	services map[string]*serviceInfo // service name -> service info
	events   trace.EventLog

	quit               *grpcsync.Event
	done               *grpcsync.Event
	channelzRemoveOnce sync.Once
	serveWG            sync.WaitGroup // counts active Serve goroutines for GracefulStop

	channelzID *channelz.Identifier
	czData     *channelzData

	serverWorkerChannels []chan *serverWorkerData
}

func NewServer(opt ...ServerOption) *Server {
	opts := defaultServerOptions
	for _, o := range extraServerOptions {
		o.apply(&opts)
	}
	for _, o := range opt {
		o.apply(&opts)
	}
	s := &Server{
		lis:      make(map[net.Listener]bool),
		opts:     opts,
		conns:    make(map[string]map[transport.ServerTransport]bool),
		services: make(map[string]*serviceInfo),
		quit:     grpcsync.NewEvent(),
		done:     grpcsync.NewEvent(),
		czData:   new(channelzData),
	}
	chainUnaryServerInterceptors(s)
	chainStreamServerInterceptors(s)
	s.cv = sync.NewCond(&s.mu)
	if EnableTracing {
		_, file, line, _ := runtime.Caller(1)
		s.events = trace.NewEventLog("grpc.Server", fmt.Sprintf("%s:%d", file, line))
	}

	if s.opts.numServerWorkers > 0 {
		s.initServerWorkers()
	}

	s.channelzID = channelz.RegisterServer(&channelzServer{s}, "")
	channelz.Info(logger, s.channelzID, "Server created")
	return s
}

// 省略
func main() {
	grpc.EnableTracing = false
// 省略

pb.RegisterGreeterServer(s, &server{})

func RegisterGreeterServer(s grpc.ServiceRegistrar, srv GreeterServer) {
	s.RegisterService(&Greeter_ServiceDesc, srv)
}

// ServiceDesc represents an RPC service's specification.
type ServiceDesc struct {
	ServiceName string
	// The pointer to the service interface. Used to check whether the user
	// provided implementation satisfies the interface requirements.
	HandlerType interface{}
	Methods     []MethodDesc
	Streams     []StreamDesc
	Metadata    interface{}
}

// RegisterService registers a service and its implementation to the gRPC
// server. It is called from the IDL generated code. This must be called before
// invoking Serve. If ss is non-nil (for legacy code), its type is checked to
// ensure it implements sd.HandlerType.
func (s *Server) RegisterService(sd *ServiceDesc, ss interface{}) {
	if ss != nil {
		ht := reflect.TypeOf(sd.HandlerType).Elem()
		st := reflect.TypeOf(ss)
		if !st.Implements(ht) {
			logger.Fatalf("grpc: Server.RegisterService found the handler of type %v that does not satisfy %v", st, ht)
		}
	}
	s.register(sd, ss)
}

func (s *Server) register(sd *ServiceDesc, ss interface{}) {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.printf("RegisterService(%q)", sd.ServiceName)
	if s.serve {
		logger.Fatalf("grpc: Server.RegisterService after Server.Serve for %q", sd.ServiceName)
	}
	if _, ok := s.services[sd.ServiceName]; ok {
		logger.Fatalf("grpc: Server.RegisterService found duplicate service registration for %q", sd.ServiceName)
	}
	info := &serviceInfo{
		serviceImpl: ss,
		methods:     make(map[string]*MethodDesc),
		streams:     make(map[string]*StreamDesc),
		mdata:       sd.Metadata,
	}
	for i := range sd.Methods {
		d := &sd.Methods[i]
		info.methods[d.MethodName] = d
	}
	for i := range sd.Streams {
		d := &sd.Streams[i]
		info.streams[d.StreamName] = d
	}
	s.services[sd.ServiceName] = info
}

log.Printf("server listening at %v", lis.Addr())
if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to serve: %v", err)
	}

// Serve accepts incoming connections on the listener lis, creating a new
// ServerTransport and service goroutine for each. The service goroutines
// read gRPC requests and then call the registered handlers to reply to them.
// Serve returns when lis.Accept fails with fatal errors.  lis will be closed when
// this method returns.
// Serve will return a non-nil error unless Stop or GracefulStop is called.
func (s *Server) Serve(lis net.Listener) error {
	s.mu.Lock()
	s.printf("serving")
	s.serve = true
	if s.lis == nil {
		// Serve called after Stop or GracefulStop.
		s.mu.Unlock()
		lis.Close()
		return ErrServerStopped
	}

	s.serveWG.Add(1)
	defer func() {
		s.serveWG.Done()
		if s.quit.HasFired() {
			// Stop or GracefulStop called; block until done and return nil.
			<-s.done.Done()
		}
	}()

	ls := &listenSocket{Listener: lis}
	s.lis[ls] = true

	defer func() {
		s.mu.Lock()
		if s.lis != nil && s.lis[ls] {
			ls.Close()
			delete(s.lis, ls)
		}
		s.mu.Unlock()
	}()

	var err error
	ls.channelzID, err = channelz.RegisterListenSocket(ls, s.channelzID, lis.Addr().String())
	if err != nil {
		s.mu.Unlock()
		return err
	}
	s.mu.Unlock()
	channelz.Info(logger, ls.channelzID, "ListenSocket created")

	var tempDelay time.Duration // how long to sleep on accept failure
	for {
		rawConn, err := lis.Accept()
		if err != nil {
			if ne, ok := err.(interface {
				Temporary() bool
			}); ok && ne.Temporary() {
				if tempDelay == 0 {
					tempDelay = 5 * time.Millisecond
				} else {
					tempDelay *= 2
				}
				if max := 1 * time.Second; tempDelay > max {
					tempDelay = max
				}
				s.mu.Lock()
				s.printf("Accept error: %v; retrying in %v", err, tempDelay)
				s.mu.Unlock()
				timer := time.NewTimer(tempDelay)
				select {
				case <-timer.C:
				case <-s.quit.Done():
					timer.Stop()
					return nil
				}
				continue
			}
			s.mu.Lock()
			s.printf("done serving; Accept = %v", err)
			s.mu.Unlock()

			if s.quit.HasFired() {
				return nil
			}
			return err
		}
		tempDelay = 0
		// Start a new goroutine to deal with rawConn so we don't stall this Accept
		// loop goroutine.
		//
		// Make sure we account for the goroutine so GracefulStop doesn't nil out
		// s.conns before this conn can be added.
		s.serveWG.Add(1)
		go func() {
			s.handleRawConn(lis.Addr().String(), rawConn)
			s.serveWG.Done()
		}()
	}
}