Add basic polling functionality for NDF

io/poll.go

+///////////////////////////////////////////////////////////////////////////////
+// Copyright © 2020 xx network SEZC                                          //
+//                                                                           //
+// Use of this source code is governed by a license that can be found in the //
+// LICENSE file                                                              //
+///////////////////////////////////////////////////////////////////////////////
+
+// Poll the network for the NDF. Users should create an ndf Poller with:
+//     poller := NewNdfPoller(Protocom object, permissioning host)
+// and subsequently call poller.GetNdf() to get a new copy of the NDF.
+//
+// Use the "PollingConn" interface in functions so you can mock the NDF for
+// testing.
+
+package io
+
+import (
+	"github.com/golang/protobuf/ptypes"
+	"github.com/golang/protobuf/ptypes/any"
+	"github.com/pkg/errors"
+	jww "github.com/spf13/jwalterweatherman"
+	pb "gitlab.com/elixxir/comms/mixmessages"
+	"gitlab.com/xx_network/comms/connect"
+	"google.golang.org/grpc"
+)
+
+// PollingConn is an object that implements the PollNdf Function
+// and allows it to be mocked for testing.
+type PollingConn interface {
+	PollNdf() (*pb.NDF, error)
+}
+
+// NdfPoller is a regular connection to the permissioning server, created
+// with a protocomms object.
+type NdfPoller struct {
+	permHost *connect.Host
+	pc       *connect.ProtoComms
+}
+
+// NewNdfPoller creates a new permconn object with a host and protocomms id.
+func NewNdfPoller(pc *connect.ProtoComms, permHost *connect.Host) NdfPoller {
+	return NdfPoller{
+		pc:       pc,
+		permHost: permHost,
+	}
+}
+
+// PollNdf gets the NDF from the Permissioning server.
+func (p NdfPoller) PollNdf() (*pb.NDF, error) {
+	permHost := p.permHost
+	// Create the Send Function
+	f := func(conn *grpc.ClientConn) (*any.Any, error) {
+		// Set up the context
+		ctx, cancel := connect.MessagingContext()
+		defer cancel()
+
+		// We use an empty NDF Hash to request an NDF
+		ndfRequest := &pb.NDFHash{Hash: make([]byte, 0)}
+
+		// Send the message
+		clientConn := pb.NewRegistrationClient(conn)
+		resultMsg, err := clientConn.PollNdf(ctx, ndfRequest)
+		if err != nil {
+			return nil, errors.New(err.Error())
+		}
+		return ptypes.MarshalAny(resultMsg)
+	}
+
+	// Execute the Send function
+	jww.TRACE.Printf("Sending Request Ndf message...")
+	resultMsg, err := p.pc.Send(permHost, f)
+	if err != nil {
+		return nil, err
+	}
+
+	result := &pb.NDF{}
+	err = ptypes.UnmarshalAny(resultMsg, result)
+	return result, err
+}