VOL-1405 : First submission for read-only core

- Most of the logic was copied from the read-write implementation
- Added missing Get/List calls
- Added necessary targets in Makefile
- Added docker and k8s manifests

Amendments:

- Removed more unecessary code.
- Removed refs to kafka
- Adjustements to reflect comments
- Removed refs to kafka in manifests

Change-Id: Ife2ca13d3ae428923825f7c19d42359d60406839
diff --git a/ro_core/core/model_proxy_manager.go b/ro_core/core/model_proxy_manager.go
new file mode 100644
index 0000000..d5f7ace
--- /dev/null
+++ b/ro_core/core/model_proxy_manager.go
@@ -0,0 +1,252 @@
+/*
+ * Copyright 2019-present Open Networking Foundation
+
+ * 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 core
+
+import (
+	"context"
+	"github.com/opencord/voltha-go/common/log"
+	"github.com/opencord/voltha-go/db/model"
+	"github.com/opencord/voltha-go/protos/voltha"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// Enumerated type to keep track of miscellaneous data path agents
+type DataModelType int
+
+// Enumerated list of data path agents
+const (
+	Adapters DataModelType = 1 + iota
+	AlarmFilters
+	CoreInstances
+	DeviceTypes
+	DeviceGroups
+	Voltha
+)
+
+// String equivalent for data path agents
+var commonTypes = []string {
+	"Adapters",
+	"AlarmFilters",
+	"CoreInstances",
+	"DeviceTypes",
+	"DeviceGroups",
+	"Voltha",
+}
+
+// String converts the enumerated data path agent value to its string equivalent
+func (t DataModelType) String() string {
+	return commonTypes[t-1]
+}
+
+// ModelProxyManager controls requests made to the miscellaneous data path agents
+type ModelProxyManager struct {
+	modelProxy       map[string]*ModelProxy
+	clusterDataProxy *model.Proxy
+}
+
+func newModelProxyManager(cdProxy *model.Proxy) *ModelProxyManager {
+	var mgr ModelProxyManager
+	mgr.modelProxy = make(map[string]*ModelProxy)
+	mgr.clusterDataProxy = cdProxy
+	return &mgr
+}
+
+// GetDeviceType returns the device type associated to the provided id
+func (mpMgr *ModelProxyManager) GetVoltha(ctx context.Context) (*voltha.Voltha, error) {
+	log.Debug("GetVoltha")
+
+	var agent *ModelProxy
+	var exists bool
+
+	if agent, exists = mpMgr.modelProxy[Voltha.String()]; !exists {
+		agent = newModelProxy("", mpMgr.clusterDataProxy)
+		mpMgr.modelProxy[Voltha.String()] = agent
+	}
+
+	if instance, _ := agent.Get(); instance != nil {
+		return instance.(*voltha.Voltha), nil
+	}
+
+	return &voltha.Voltha{}, status.Errorf(codes.NotFound, "no-voltha-instance")
+}
+
+// ListCoreInstances returns all the core instances known to the system
+func (mpMgr *ModelProxyManager) ListCoreInstances(ctx context.Context) (*voltha.CoreInstances, error) {
+	log.Debug("ListCoreInstances")
+
+	// TODO: Need to retrieve the list of registered cores
+
+	return &voltha.CoreInstances{}, status.Errorf(codes.NotFound, "no-core-instances")
+}
+
+// GetCoreInstance returns the core instance associated to the provided id
+func (mpMgr *ModelProxyManager) GetCoreInstance(ctx context.Context, id string) (*voltha.CoreInstance, error) {
+	log.Debugw("GetCoreInstance", log.Fields{"id": id})
+
+	// TODO: Need to retrieve the list of registered cores
+
+	return &voltha.CoreInstance{}, status.Errorf(codes.NotFound, "core-instance-%s", id)
+}
+
+// ListAdapters returns all the device types known to the system
+func (mpMgr *ModelProxyManager) ListAdapters(ctx context.Context) (*voltha.Adapters, error) {
+	log.Debug("ListAdapters")
+
+	var agent *ModelProxy
+	var exists bool
+
+	if agent, exists = mpMgr.modelProxy[Adapters.String()]; !exists {
+		agent = newModelProxy("adapters", mpMgr.clusterDataProxy)
+		mpMgr.modelProxy[Adapters.String()] = agent
+	}
+
+	adapters := &voltha.Adapters{}
+	if items, _ := agent.Get(); items != nil {
+		for _, item := range items.([]interface{}) {
+			adapters.Items = append(adapters.Items, item.(*voltha.Adapter))
+		}
+		log.Debugw("retrieved-adapters", log.Fields{"adapters": adapters})
+		return adapters, nil
+	}
+
+	return adapters, status.Errorf(codes.NotFound, "no-adapters")
+}
+
+// ListDeviceTypes returns all the device types known to the system
+func (mpMgr *ModelProxyManager) ListDeviceTypes(ctx context.Context) (*voltha.DeviceTypes, error) {
+	log.Debug("ListDeviceTypes")
+
+	var agent *ModelProxy
+	var exists bool
+
+	if agent, exists = mpMgr.modelProxy[DeviceTypes.String()]; !exists {
+		agent = newModelProxy("device_types", mpMgr.clusterDataProxy)
+		mpMgr.modelProxy[DeviceTypes.String()] = agent
+	}
+
+	deviceTypes := &voltha.DeviceTypes{}
+	if items, _ := agent.Get(); items != nil {
+		for _, item := range items.([]interface{}) {
+			deviceTypes.Items = append(deviceTypes.Items, item.(*voltha.DeviceType))
+		}
+		return deviceTypes, nil
+	}
+
+	return deviceTypes, status.Errorf(codes.NotFound, "no-device-types")
+}
+
+// GetDeviceType returns the device type associated to the provided id
+func (mpMgr *ModelProxyManager) GetDeviceType(ctx context.Context, id string) (*voltha.DeviceType, error) {
+	log.Debugw("GetDeviceType", log.Fields{"id": id})
+
+	var agent *ModelProxy
+	var exists bool
+
+	if agent, exists = mpMgr.modelProxy[DeviceTypes.String()]; !exists {
+		agent = newModelProxy("device_types", mpMgr.clusterDataProxy)
+		mpMgr.modelProxy[DeviceTypes.String()] = agent
+	}
+
+	if deviceType, _ := agent.Get(id); deviceType != nil {
+		return deviceType.(*voltha.DeviceType), nil
+	}
+
+	return &voltha.DeviceType{}, status.Errorf(codes.NotFound, "device-type-%s", id)
+}
+
+// ListDeviceGroups returns all the device groups known to the system
+func (mpMgr *ModelProxyManager) ListDeviceGroups(ctx context.Context) (*voltha.DeviceGroups, error) {
+	log.Debug("ListDeviceGroups")
+
+	var agent *ModelProxy
+	var exists bool
+
+	if agent, exists = mpMgr.modelProxy[DeviceGroups.String()]; !exists {
+		agent = newModelProxy("device_groups", mpMgr.clusterDataProxy)
+		mpMgr.modelProxy[DeviceGroups.String()] = agent
+	}
+
+	deviceGroups := &voltha.DeviceGroups{}
+	if items, _ := agent.Get(); items != nil {
+		for _, item := range items.([]interface{}) {
+			deviceGroups.Items = append(deviceGroups.Items, item.(*voltha.DeviceGroup))
+		}
+		return deviceGroups, nil
+	}
+
+	return deviceGroups, status.Errorf(codes.NotFound, "no-device-groups")
+}
+
+// GetDeviceGroup returns the device group associated to the provided id
+func (mpMgr *ModelProxyManager) GetDeviceGroup(ctx context.Context, id string) (*voltha.DeviceGroup, error) {
+	log.Debugw("GetDeviceGroup", log.Fields{"id": id})
+
+	var agent *ModelProxy
+	var exists bool
+
+	if agent, exists = mpMgr.modelProxy[DeviceGroups.String()]; !exists {
+		agent = newModelProxy("device_groups", mpMgr.clusterDataProxy)
+		mpMgr.modelProxy[DeviceGroups.String()] = agent
+	}
+
+	if deviceGroup, _ := agent.Get(id); deviceGroup != nil {
+		return deviceGroup.(*voltha.DeviceGroup), nil
+	}
+
+	return &voltha.DeviceGroup{}, status.Errorf(codes.NotFound, "device-group-%s", id)
+}
+
+// ListAlarmFilters returns all the alarm filters known to the system
+func (mpMgr *ModelProxyManager) ListAlarmFilters(ctx context.Context) (*voltha.AlarmFilters, error) {
+	log.Debug("ListAlarmFilters")
+
+	var agent *ModelProxy
+	var exists bool
+
+	if agent, exists = mpMgr.modelProxy[AlarmFilters.String()]; !exists {
+		agent = newModelProxy("alarm_filters", mpMgr.clusterDataProxy)
+		mpMgr.modelProxy[AlarmFilters.String()] = agent
+	}
+
+	alarmFilters := &voltha.AlarmFilters{}
+	if items, _ := agent.Get(); items != nil {
+		for _, item := range items.([]interface{}) {
+			alarmFilters.Filters = append(alarmFilters.Filters, item.(*voltha.AlarmFilter))
+		}
+		return alarmFilters, nil
+	}
+
+	return alarmFilters, status.Errorf(codes.NotFound, "no-alarm-filters")
+}
+
+// GetAlarmFilter returns the alarm filter associated to the provided id
+func (mpMgr *ModelProxyManager) GetAlarmFilter(ctx context.Context, id string) (*voltha.AlarmFilter, error) {
+	log.Debugw("GetAlarmFilter", log.Fields{"id": id})
+
+	var agent *ModelProxy
+	var exists bool
+
+	if agent, exists = mpMgr.modelProxy[AlarmFilters.String()]; !exists {
+		agent = newModelProxy("alarm_filters", mpMgr.clusterDataProxy)
+		mpMgr.modelProxy[AlarmFilters.String()] = agent
+	}
+
+	if alarmFilter, _ := agent.Get(id); alarmFilter != nil {
+		return alarmFilter.(*voltha.AlarmFilter), nil
+	}
+	return &voltha.AlarmFilter{}, status.Errorf(codes.NotFound, "alarm-filter-%s", id)
+}