Add grpc plugin (#2758)

* Add grpc plugin

* remove stale readmes

server/grpc/codec.go

@@ -0,0 +1,186 @@
+package grpc
+
+import (
+	"encoding/json"
+	"strings"
+
+	b "bytes"
+
+	"github.com/golang/protobuf/jsonpb"
+	"github.com/golang/protobuf/proto"
+	"go-micro.dev/v5/codec"
+	"go-micro.dev/v5/codec/bytes"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/encoding"
+	"google.golang.org/grpc/metadata"
+)
+
+type jsonCodec struct{}
+type bytesCodec struct{}
+type protoCodec struct{}
+type wrapCodec struct{ encoding.Codec }
+
+var jsonpbMarshaler = &jsonpb.Marshaler{
+	EnumsAsInts:  false,
+	EmitDefaults: false,
+	OrigName:     true,
+}
+
+var (
+	defaultGRPCCodecs = map[string]encoding.Codec{
+		"application/json":         jsonCodec{},
+		"application/proto":        protoCodec{},
+		"application/protobuf":     protoCodec{},
+		"application/octet-stream": protoCodec{},
+		"application/grpc":         protoCodec{},
+		"application/grpc+json":    jsonCodec{},
+		"application/grpc+proto":   protoCodec{},
+		"application/grpc+bytes":   bytesCodec{},
+	}
+)
+
+func (w wrapCodec) String() string {
+	return w.Codec.Name()
+}
+
+func (w wrapCodec) Marshal(v interface{}) ([]byte, error) {
+	b, ok := v.(*bytes.Frame)
+	if ok {
+		return b.Data, nil
+	}
+	return w.Codec.Marshal(v)
+}
+
+func (w wrapCodec) Unmarshal(data []byte, v interface{}) error {
+	b, ok := v.(*bytes.Frame)
+	if ok {
+		b.Data = data
+		return nil
+	}
+	if v == nil {
+		return nil
+	}
+	return w.Codec.Unmarshal(data, v)
+}
+
+func (protoCodec) Marshal(v interface{}) ([]byte, error) {
+	m, ok := v.(proto.Message)
+	if !ok {
+		return nil, codec.ErrInvalidMessage
+	}
+	return proto.Marshal(m)
+}
+
+func (protoCodec) Unmarshal(data []byte, v interface{}) error {
+	m, ok := v.(proto.Message)
+	if !ok {
+		return codec.ErrInvalidMessage
+	}
+	return proto.Unmarshal(data, m)
+}
+
+func (protoCodec) Name() string {
+	return "proto"
+}
+
+func (jsonCodec) Marshal(v interface{}) ([]byte, error) {
+	if pb, ok := v.(proto.Message); ok {
+		s, err := jsonpbMarshaler.MarshalToString(pb)
+		return []byte(s), err
+	}
+
+	return json.Marshal(v)
+}
+
+func (jsonCodec) Unmarshal(data []byte, v interface{}) error {
+	if len(data) == 0 {
+		return nil
+	}
+	if pb, ok := v.(proto.Message); ok {
+		return jsonpb.Unmarshal(b.NewReader(data), pb)
+	}
+	return json.Unmarshal(data, v)
+}
+
+func (jsonCodec) Name() string {
+	return "json"
+}
+
+func (bytesCodec) Marshal(v interface{}) ([]byte, error) {
+	b, ok := v.(*[]byte)
+	if !ok {
+		return nil, codec.ErrInvalidMessage
+	}
+	return *b, nil
+}
+
+func (bytesCodec) Unmarshal(data []byte, v interface{}) error {
+	b, ok := v.(*[]byte)
+	if !ok {
+		return codec.ErrInvalidMessage
+	}
+	*b = data
+	return nil
+}
+
+func (bytesCodec) Name() string {
+	return "bytes"
+}
+
+type grpcCodec struct {
+	// headers
+	id       string
+	target   string
+	method   string
+	endpoint string
+
+	s grpc.ServerStream
+	c encoding.Codec
+}
+
+func (g *grpcCodec) ReadHeader(m *codec.Message, mt codec.MessageType) error {
+	md, _ := metadata.FromIncomingContext(g.s.Context())
+	if m == nil {
+		m = new(codec.Message)
+	}
+	if m.Header == nil {
+		m.Header = make(map[string]string, len(md))
+	}
+	for k, v := range md {
+		m.Header[k] = strings.Join(v, ",")
+	}
+	m.Id = g.id
+	m.Target = g.target
+	m.Method = g.method
+	m.Endpoint = g.endpoint
+	return nil
+}
+
+func (g *grpcCodec) ReadBody(v interface{}) error {
+	// caller has requested a frame
+	if f, ok := v.(*bytes.Frame); ok {
+		return g.s.RecvMsg(f)
+	}
+	return g.s.RecvMsg(v)
+}
+
+func (g *grpcCodec) Write(m *codec.Message, v interface{}) error {
+	// if we don't have a body
+	if v != nil {
+		b, err := g.c.Marshal(v)
+		if err != nil {
+			return err
+		}
+		m.Body = b
+	}
+	// write the body using the framing codec
+	return g.s.SendMsg(&bytes.Frame{Data: m.Body})
+}
+
+func (g *grpcCodec) Close() error {
+	return nil
+}
+
+func (g *grpcCodec) String() string {
+	return "grpc"
+}