node/pkg/publicrpc: add GetCurrentGuardianSet RPC call

This is required for network explorers to know about missing guardians
(the GetLastHeartbeats call won't contain those nodes at all).

Change-Id: I28d8621023d79e6fa94c40f36a239c34aa12f1b0

bridge/pkg/publicrpc/publicrpcserver.go

@@ -113,3 +113,23 @@ func (s *PublicrpcServer) GetSignedVAA(ctx context.Context, req *publicrpcv1.Get
 		VaaBytes: b,
 	}, nil
 }
+
+func (s *PublicrpcServer) GetCurrentGuardianSet(ctx context.Context, req *publicrpcv1.GetCurrentGuardianSetRequest) (*publicrpcv1.GetCurrentGuardianSetResponse, error) {
+	gs := s.gst.Get()
+	if gs == nil {
+		return nil, status.Error(codes.Unavailable, "guardian set not fetched from chain yet")
+	}
+
+	resp := &publicrpcv1.GetCurrentGuardianSetResponse{
+		GuardianSet: &publicrpcv1.GuardianSet{
+			Index:     gs.Index,
+			Addresses: make([]string, len(gs.Keys)),
+		},
+	}
+
+	for i, v := range gs.Keys {
+		resp.GuardianSet.Addresses[i] = v.Hex()
+	}
+
+	return resp, nil
+}

proto/publicrpc/v1/publicrpc.proto

@@ -50,6 +50,13 @@ service Publicrpc {
       get: "/v1/signed_vaa/{message_id.emitter_chain}/{message_id.emitter_address}/{message_id.sequence}"
     };
   }
+
+  rpc GetCurrentGuardianSet (GetCurrentGuardianSetRequest) returns (GetCurrentGuardianSetResponse) {
+    option (google.api.http) = {
+      get: "/v1/guardianset/current"
+    };
+  }
+
 }
 
 message GetRawHeartbeatsRequest {
@@ -84,3 +91,17 @@ message GetLastHeartbeatResponse {
 
   repeated Entry entries = 1;
 }
+
+message GetCurrentGuardianSetRequest {
+}
+
+message GetCurrentGuardianSetResponse {
+  GuardianSet guardian_set = 1;
+}
+
+message GuardianSet {
+  // Guardian set index
+  uint32 index = 1;
+  // List of guardian addresses as human-readable hex-encoded (leading 0x) addresses.
+  repeated string addresses = 2;
+}