Add grpc client skeleton

Signed-off-by: Darko Draskovic <darko.draskovic@gmail.com>

manager/api/manager/grpc/client.go

@@ -1 +1,79 @@
 package grpc
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/go-kit/kit/endpoint"
+	kitot "github.com/go-kit/kit/tracing/opentracing"
+	kitgrpc "github.com/go-kit/kit/transport/grpc"
+	"github.com/opentracing/opentracing-go"
+	"github.com/ultravioletrs/manager/manager"
+	"google.golang.org/grpc"
+)
+
+const (
+	svcName = "manager.ManagerService"
+)
+
+type grpcClient struct {
+	createDomain endpoint.Endpoint
+	timeout      time.Duration
+}
+
+// NewClient returns new gRPC client instance.
+func NewClient(tracer opentracing.Tracer, conn *grpc.ClientConn, timeout time.Duration) manager.ManagerServiceClient {
+	return &grpcClient{
+		createDomain: kitot.TraceClient(tracer, "createDomain")(kitgrpc.NewClient(
+			conn,
+			svcName,
+			"CreateDomain",
+			encodeCreateDomainRequest,
+			decodeCreateDomainResponse,
+			nil,
+		).Endpoint()),
+
+		timeout: timeout,
+	}
+}
+
+func (client grpcClient) CreateDomain(ctx context.Context, req *manager.CreateDomainRequest, _ ...grpc.CallOption) (*manager.CreateDomainResponse, error) {
+	ctx, close := context.WithTimeout(ctx, client.timeout)
+	defer close()
+
+	res, err := client.createDomain(ctx, createDomainReq{Pool: req.GetPool(),
+		Volume: req.GetVolume(), Domain: req.GetDomain()})
+	if err != nil {
+		return nil, err
+	}
+
+	cdr := res.(createDomainRes)
+	return &manager.CreateDomainResponse{Name: cdr.Name}, nil
+}
+
+// encodeCreateDomainRequest is a transport/grpc.EncodeRequestFunc that
+// converts a user-domain CreateDomainRequest to a gRPC request.
+func encodeCreateDomainRequest(_ context.Context, request interface{}) (interface{}, error) {
+	req, ok := request.(createDomainReq)
+	if !ok {
+		return nil, fmt.Errorf("invalid request type: %T", request)
+	}
+	return &manager.CreateDomainRequest{
+		Pool:   req.Pool,
+		Volume: req.Volume,
+		Domain: req.Domain,
+	}, nil
+}
+
+// decodeCreateDomainResponse is a transport/grpc.DecodeResponseFunc that
+// converts a gRPC CreateDomainResponse to a user-domain response.
+func decodeCreateDomainResponse(_ context.Context, grpcResponse interface{}) (interface{}, error) {
+	response, ok := grpcResponse.(*manager.CreateDomainResponse)
+	if !ok {
+		return nil, fmt.Errorf("invalid response type: %T", grpcResponse)
+	}
+	return createDomainRes{
+		Name: response.Name,
+	}, nil
+}