WIP - Suggesting changes (take2)

    This is not yet completed, still working on things. Eventually the plan
    is to provide the following changes

    - restructure repo to be more aligned with https://github.com/golang-standards/project-layout
    - add k8s probes
    - modifications (golang range loops, etc) to follow some golang
    practices

Change-Id: I6922cbc00b5ef17ceab183aba00a7fc59ab46480
diff --git a/internal/pkg/ofagent/refresh.go b/internal/pkg/ofagent/refresh.go
new file mode 100644
index 0000000..8f68ef0
--- /dev/null
+++ b/internal/pkg/ofagent/refresh.go
@@ -0,0 +1,109 @@
+/*
+   Copyright 2020 the original author or authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+        http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package ofagent
+
+import (
+	"context"
+	"github.com/golang/protobuf/ptypes/empty"
+	"github.com/opencord/ofagent-go/internal/pkg/openflow"
+	"github.com/opencord/voltha-lib-go/v2/pkg/log"
+	"time"
+)
+
+func (ofa *OFAgent) synchronizeDeviceList(ctx context.Context) {
+	// Refresh once to get everything started
+	ofa.refreshDeviceList()
+
+	tick := time.NewTicker(ofa.DeviceListRefreshInterval)
+loop:
+	for {
+		select {
+		case <-ctx.Done():
+			break loop
+		case <-tick.C:
+			ofa.refreshDeviceList()
+		}
+	}
+	tick.Stop()
+}
+
+func (ofa *OFAgent) refreshDeviceList() {
+	deviceList, err := ofa.volthaClient.ListLogicalDevices(context.Background(), &empty.Empty{})
+	if err != nil {
+		logger.Errorw("ofagent failed to query device list from voltha",
+			log.Fields{"error": err})
+		return
+	}
+	devices := deviceList.GetItems()
+
+	var toAdd []string
+	var toDel []string
+	var deviceIDMap = make(map[string]string)
+	for i := 0; i < len(devices); i++ {
+		deviceID := devices[i].GetId()
+		deviceIDMap[deviceID] = deviceID
+		if ofa.clientMap[deviceID] == nil {
+			toAdd = append(toAdd, deviceID)
+		}
+	}
+	for key := range ofa.clientMap {
+		if deviceIDMap[key] == "" {
+			toDel = append(toDel, key)
+		}
+	}
+	logger.Debugw("GrpcClient refreshDeviceList", log.Fields{"ToAdd": toAdd, "ToDel": toDel})
+	for i := 0; i < len(toAdd); i++ {
+		var client = ofa.addOFClient(toAdd[i])
+		go client.Run(context.Background())
+	}
+	for i := 0; i < len(toDel); i++ {
+		ofa.clientMap[toDel[i]].Stop()
+		ofa.mapLock.Lock()
+		delete(ofa.clientMap, toDel[i])
+		ofa.mapLock.Unlock()
+	}
+}
+
+func (ofa *OFAgent) addOFClient(deviceID string) *openflow.OFClient {
+	logger.Debugw("GrpcClient addClient called ", log.Fields{"device-id": deviceID})
+	ofa.mapLock.Lock()
+	ofc := ofa.clientMap[deviceID]
+	if ofc == nil {
+		ofc = openflow.NewOFClient(&openflow.OFClient{
+			DeviceID:             deviceID,
+			OFControllerEndPoint: ofa.OFControllerEndPoint,
+			VolthaClient:         ofa.volthaClient,
+			PacketOutChannel:     ofa.packetOutChannel,
+			ConnectionMaxRetries: ofa.ConnectionMaxRetries,
+			ConnectionRetryDelay: ofa.ConnectionRetryDelay,
+			KeepRunning:          true,
+		})
+		go ofc.Run(context.Background())
+		ofa.clientMap[deviceID] = ofc
+	}
+	ofa.mapLock.Unlock()
+	logger.Debugw("Finished with addClient", log.Fields{"deviceID": deviceID})
+	return ofc
+}
+
+func (ofa *OFAgent) getOFClient(deviceID string) *openflow.OFClient {
+	ofc := ofa.clientMap[deviceID]
+	if ofc == nil {
+		ofc = ofa.addOFClient(deviceID)
+	}
+	return ofc
+}