GODT-1932: frontend is instantiated before bridge.

WIP: introduced frontend.Type.
WIP: frontend is create before bridge is instantiated.
WIP: filtering of internet stastus event in gRPC event queue.

internal/frontend/grpc/event_utils.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+package grpc
+
+import "github.com/bradenaw/juniper/xslices"
+
+// isInternetStatus returns true iff the event is InternetStatus.
+func (x *StreamEvent) isInternetStatus() bool {
+	appEvent := x.GetApp()
+
+	return (appEvent != nil) && (appEvent.GetInternetStatus() != nil)
+}
+
+// filterOutInternetStatusEvents return a copy of the events list where all internet connection events have been removed.
+func filterOutInternetStatusEvents(events []*StreamEvent) []*StreamEvent {
+	return xslices.Filter(events, func(event *StreamEvent) bool { return !event.isInternetStatus() })
+}