/*
 * Copyright 2018-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"
	"errors"
	"github.com/golang-collections/go-datastructures/queue"
	"github.com/golang/protobuf/ptypes/empty"
	da "github.com/opencord/voltha-go/common/core/northbound/grpc"
	"github.com/opencord/voltha-go/common/log"
	"github.com/opencord/voltha-go/protos/common"
	"github.com/opencord/voltha-go/protos/openflow_13"
	"github.com/opencord/voltha-go/protos/voltha"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/status"
	"io"
	"time"
)

//TODO:  Move this Tag into the proto file
const OF_CONTROLLER_TAG= "voltha_backend_name"

const MAX_RESPONSE_TIME = int64(500) // milliseconds

const (
	IMAGE_DOWNLOAD = iota
	CANCEL_IMAGE_DOWNLOAD     = iota
	ACTIVATE_IMAGE = iota
	REVERT_IMAGE = iota
)

type APIHandler struct {
	deviceMgr        *DeviceManager
	logicalDeviceMgr *LogicalDeviceManager
	packetInQueue    *queue.Queue
	coreInCompetingMode bool
	da.DefaultAPIHandler
}

func NewAPIHandler(deviceMgr *DeviceManager, lDeviceMgr *LogicalDeviceManager, inCompetingMode bool) *APIHandler {
	handler := &APIHandler{
		deviceMgr:        deviceMgr,
		logicalDeviceMgr: lDeviceMgr,
		coreInCompetingMode:inCompetingMode,
		// TODO: Figure out what the 'hint' parameter to queue.New does
		packetInQueue: queue.New(10),
	}
	return handler
}

// isTestMode is a helper function to determine a function is invoked for testing only
func isTestMode(ctx context.Context) bool {
	md, _ := metadata.FromIncomingContext(ctx)
	_, exist := md[common.TestModeKeys_api_test.String()]
	return exist
}

// This function attempts to extract the serial number from the request metadata
// and create a KV transaction for that serial number for the current core.
func (handler *APIHandler) createKvTransaction(ctx context.Context) (*KVTransaction, error) {
	var (
		err    error
		ok     bool
		md     metadata.MD
		serNum []string
	)
	if md, ok = metadata.FromIncomingContext(ctx); !ok {
		err = errors.New("metadata-not-found")
	} else if serNum, ok = md["voltha_serial_number"]; !ok {
		err = errors.New("serial-number-not-found")
	}
	if !ok {
		log.Error(err)
		return nil, err
	}
	// Create KV transaction
	txn := NewKVTransaction(serNum[0])
	return txn, nil
}

// isOFControllerRequest is a helper function to determine if a request was initiated
// from the OpenFlow controller (or its proxy, e.g. OFAgent)
func isOFControllerRequest(ctx context.Context) bool {
	if md, ok := metadata.FromIncomingContext(ctx); ok {
		// Metadata in context
		if _, ok = md[OF_CONTROLLER_TAG]; ok {
			// OFAgent field in metadata
			return true
		}
	}
	return false
}

// competeForTransaction is a helper function to determine whether every request needs to compete with another
// Core to execute the request
func (handler *APIHandler) competeForTransaction() bool {
	return handler.coreInCompetingMode
}

func (handler *APIHandler) acquireTransaction(ctx context.Context, maxTimeout ...int64) (*KVTransaction, error) {
	timeout := MAX_RESPONSE_TIME
	if len(maxTimeout) > 0 {
		timeout = maxTimeout[0]
	}
	txn, err := handler.createKvTransaction(ctx)
	if txn == nil {
		return nil,  err
	} else if txn.Acquired(timeout) {
		return txn, nil
	} else {
		return nil, errors.New("failed-to-seize-request")
	}
}

// waitForNilResponseOnSuccess is a helper function to wait for a response on channel ch where an nil
// response is expected in a successful scenario
func waitForNilResponseOnSuccess(ctx context.Context, ch chan interface{}) (*empty.Empty, error) {
	select {
	case res := <-ch:
		if res == nil {
			return new(empty.Empty), nil
		} else if err, ok := res.(error); ok {
			return new(empty.Empty), err
		} else {
			log.Warnw("unexpected-return-type", log.Fields{"result": res})
			err = status.Errorf(codes.Internal, "%s", res)
			return new(empty.Empty), err
		}
	case <-ctx.Done():
		log.Debug("client-timeout")
		return nil, ctx.Err()
	}
}

func (handler *APIHandler) UpdateLogLevel(ctx context.Context, logging *voltha.Logging) (*empty.Empty, error) {
	log.Debugw("UpdateLogLevel-request", log.Fields{"package": logging.PackageName, "intval": int(logging.Level)})
	out := new(empty.Empty)
	if logging.PackageName == "" {
		log.SetAllLogLevel(int(logging.Level))
	} else {
		log.SetPackageLogLevel(logging.PackageName, int(logging.Level))
	}
	return out, nil
}

func (handler *APIHandler) EnableLogicalDevicePort(ctx context.Context, id *voltha.LogicalPortId) (*empty.Empty, error) {
	log.Debugw("EnableLogicalDevicePort-request", log.Fields{"id": id, "test": common.TestModeKeys_api_test.String()})
	if isTestMode(ctx) {
		out := new(empty.Empty)
		return out, nil
	}

	if handler.competeForTransaction() {
		if txn, err := handler.acquireTransaction(ctx); err != nil {
			return new(empty.Empty), err
		} else {
			defer txn.Close()
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.logicalDeviceMgr.enableLogicalPort(ctx, id, ch)
	return waitForNilResponseOnSuccess(ctx, ch)
}

func (handler *APIHandler) DisableLogicalDevicePort(ctx context.Context, id *voltha.LogicalPortId) (*empty.Empty, error) {
	log.Debugw("DisableLogicalDevicePort-request", log.Fields{"id": id, "test": common.TestModeKeys_api_test.String()})
	if isTestMode(ctx) {
		out := new(empty.Empty)
		return out, nil
	}

	if handler.competeForTransaction() {
		if txn, err := handler.acquireTransaction(ctx); err != nil {
			return new(empty.Empty), err
		} else {
			defer txn.Close()
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.logicalDeviceMgr.disableLogicalPort(ctx, id, ch)
	return waitForNilResponseOnSuccess(ctx, ch)
}

func (handler *APIHandler) UpdateLogicalDeviceFlowTable(ctx context.Context, flow *openflow_13.FlowTableUpdate) (*empty.Empty, error) {
	log.Debugw("UpdateLogicalDeviceFlowTable-request", log.Fields{"flow": flow, "test": common.TestModeKeys_api_test.String()})
	if isTestMode(ctx) {
		out := new(empty.Empty)
		return out, nil
	}

	if handler.competeForTransaction() {
		if !isOFControllerRequest(ctx) { // No need to acquire the transaction as request is sent to one core only
			if txn, err := handler.acquireTransaction(ctx); err != nil {
				return new(empty.Empty), err
			} else {
				defer txn.Close()
			}
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.logicalDeviceMgr.updateFlowTable(ctx, flow.Id, flow.FlowMod, ch)
	return waitForNilResponseOnSuccess(ctx, ch)
}

func (handler *APIHandler) UpdateLogicalDeviceFlowGroupTable(ctx context.Context, flow *openflow_13.FlowGroupTableUpdate) (*empty.Empty, error) {
	log.Debugw("UpdateLogicalDeviceFlowGroupTable-request", log.Fields{"flow": flow, "test": common.TestModeKeys_api_test.String()})
	if isTestMode(ctx) {
		out := new(empty.Empty)
		return out, nil
	}

	if handler.competeForTransaction() {
		if !isOFControllerRequest(ctx) { // No need to acquire the transaction as request is sent to one core only
			if txn, err := handler.acquireTransaction(ctx); err != nil {
				return new(empty.Empty), err
			} else {
				defer txn.Close()
			}
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.logicalDeviceMgr.updateGroupTable(ctx, flow.Id, flow.GroupMod, ch)
	return waitForNilResponseOnSuccess(ctx, ch)
}

// GetDevice must be implemented in the read-only containers - should it also be implemented here?
func (handler *APIHandler) GetDevice(ctx context.Context, id *voltha.ID) (*voltha.Device, error) {
	log.Debugw("GetDevice-request", log.Fields{"id": id})
	return handler.deviceMgr.GetDevice(id.Id)
}

// GetDevice must be implemented in the read-only containers - should it also be implemented here?
func (handler *APIHandler) ListDevices(ctx context.Context, empty *empty.Empty) (*voltha.Devices, error) {
	log.Debug("ListDevices")
	return handler.deviceMgr.ListDevices()
}

// ListDeviceIds returns the list of device ids managed by a voltha core
func (handler *APIHandler) ListDeviceIds(ctx context.Context, empty *empty.Empty) (*voltha.IDs, error) {
	log.Debug("ListDeviceIDs")
	if isTestMode(ctx) {
		out := &voltha.IDs{Items: make([]*voltha.ID, 0)}
		return out, nil
	}
	return handler.deviceMgr.ListDeviceIds()
}

//ReconcileDevices is a request to a voltha core to managed a list of devices  based on their IDs
func (handler *APIHandler) ReconcileDevices(ctx context.Context, ids *voltha.IDs) (*empty.Empty, error) {
	log.Debug("ReconcileDevices")
	if isTestMode(ctx) {
		out := new(empty.Empty)
		return out, nil
	}

	// No need to grab a transaction as this request is core specific

	ch := make(chan interface{})
	defer close(ch)
	go handler.deviceMgr.ReconcileDevices(ctx, ids, ch)
	return waitForNilResponseOnSuccess(ctx, ch)
}

// GetLogicalDevice must be implemented in the read-only containers - should it also be implemented here?
func (handler *APIHandler) GetLogicalDevice(ctx context.Context, id *voltha.ID) (*voltha.LogicalDevice, error) {
	log.Debugw("GetLogicalDevice-request", log.Fields{"id": id})
	return handler.logicalDeviceMgr.getLogicalDevice(id.Id)
}

// ListLogicalDevices must be implemented in the read-only containers - should it also be implemented here?
func (handler *APIHandler) ListLogicalDevices(ctx context.Context, empty *empty.Empty) (*voltha.LogicalDevices, error) {
	log.Debug("ListLogicalDevices")
	return handler.logicalDeviceMgr.listLogicalDevices()
}

// ListLogicalDevicePorts must be implemented in the read-only containers - should it also be implemented here?
func (handler *APIHandler) ListLogicalDevicePorts(ctx context.Context, id *voltha.ID) (*voltha.LogicalPorts, error) {
	log.Debugw("ListLogicalDevicePorts", log.Fields{"logicaldeviceid": id})
	return handler.logicalDeviceMgr.ListLogicalDevicePorts(ctx, id.Id)
}

// CreateDevice creates a new parent device in the data model
func (handler *APIHandler) CreateDevice(ctx context.Context, device *voltha.Device) (*voltha.Device, error) {
	log.Debugw("createdevice", log.Fields{"device": *device})
	if isTestMode(ctx) {
		return &voltha.Device{Id: device.Id}, nil
	}

	if handler.competeForTransaction() {
		if txn, err := handler.acquireTransaction(ctx); err != nil {
			return &voltha.Device{}, err
		} else {
			defer txn.Close()
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.deviceMgr.createDevice(ctx, device, ch)
	select {
	case res := <-ch:
		if res != nil {
			if err, ok := res.(error); ok {
				return &voltha.Device{}, err
			}
			if d, ok := res.(*voltha.Device); ok {
				return d, nil
			}
		}
		log.Warnw("create-device-unexpected-return-type", log.Fields{"result": res})
		err := status.Errorf(codes.Internal, "%s", res)
		return &voltha.Device{}, err
	case <-ctx.Done():
		log.Debug("createdevice-client-timeout")
		return nil, ctx.Err()
	}
}

// EnableDevice activates a device by invoking the adopt_device API on the appropriate adapter
func (handler *APIHandler) EnableDevice(ctx context.Context, id *voltha.ID) (*empty.Empty, error) {
	log.Debugw("enabledevice", log.Fields{"id": id})
	if isTestMode(ctx) {
		return new(empty.Empty), nil
	}

	if handler.competeForTransaction() {
		if txn, err := handler.acquireTransaction(ctx); err != nil {
			return new(empty.Empty), err
		} else {
			defer txn.Close()
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.deviceMgr.enableDevice(ctx, id, ch)
	return waitForNilResponseOnSuccess(ctx, ch)
}

// DisableDevice disables a device along with any child device it may have
func (handler *APIHandler) DisableDevice(ctx context.Context, id *voltha.ID) (*empty.Empty, error) {
	log.Debugw("disabledevice-request", log.Fields{"id": id})
	if isTestMode(ctx) {
		return new(empty.Empty), nil
	}

	if handler.competeForTransaction() {
		if txn, err := handler.acquireTransaction(ctx); err != nil {
			return new(empty.Empty), err
		} else {
			defer txn.Close()
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.deviceMgr.disableDevice(ctx, id, ch)
	return waitForNilResponseOnSuccess(ctx, ch)
}

//RebootDevice invoked the reboot API to the corresponding adapter
func (handler *APIHandler) RebootDevice(ctx context.Context, id *voltha.ID) (*empty.Empty, error) {
	log.Debugw("rebootDevice-request", log.Fields{"id": id})
	if isTestMode(ctx) {
		return new(empty.Empty), nil
	}

	if handler.competeForTransaction() {
		if txn, err := handler.acquireTransaction(ctx); err != nil {
			return new(empty.Empty), err
		} else {
			defer txn.Close()
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.deviceMgr.rebootDevice(ctx, id, ch)
	return waitForNilResponseOnSuccess(ctx, ch)
}

// DeleteDevice removes a device from the data model
func (handler *APIHandler) DeleteDevice(ctx context.Context, id *voltha.ID) (*empty.Empty, error) {
	log.Debugw("deletedevice-request", log.Fields{"id": id})
	if isTestMode(ctx) {
		return new(empty.Empty), nil
	}

	if handler.competeForTransaction() {
		if txn, err := handler.acquireTransaction(ctx); err != nil {
			return new(empty.Empty), err
		} else {
			defer txn.Close()
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.deviceMgr.deleteDevice(ctx, id, ch)
	return waitForNilResponseOnSuccess(ctx, ch)
}

// processImageRequest is a helper method to execute an image download request
func (handler *APIHandler) processImageRequest(ctx context.Context, img *voltha.ImageDownload, requestType int) (*common.OperationResp, error) {
	log.Debugw("processImageDownload", log.Fields{"img": *img, "requestType": requestType})
	if isTestMode(ctx) {
		resp := &common.OperationResp{Code: common.OperationResp_OPERATION_SUCCESS}
		return resp, nil
	}

	if handler.competeForTransaction() {
		if txn, err := handler.acquireTransaction(ctx); err != nil {
			return &common.OperationResp{}, err
		} else {
			defer txn.Close()
		}
	}

	failedresponse := &common.OperationResp{Code:voltha.OperationResp_OPERATION_FAILURE}

	ch := make(chan interface{})
	defer close(ch)
	switch requestType {
	case IMAGE_DOWNLOAD:
		go handler.deviceMgr.downloadImage(ctx, img, ch)
	case CANCEL_IMAGE_DOWNLOAD:
		go handler.deviceMgr.cancelImageDownload(ctx, img, ch)
	case ACTIVATE_IMAGE:
		go handler.deviceMgr.activateImage(ctx, img, ch)
	case REVERT_IMAGE:
		go handler.deviceMgr.revertImage(ctx, img, ch)
	default:
		log.Warn("invalid-request-type", log.Fields{"requestType": requestType})
		return failedresponse, status.Errorf(codes.InvalidArgument, "%d", requestType)
	}
	select {
	case res := <-ch:
		if res != nil {
			if err, ok := res.(error); ok {
				return failedresponse, err
			}
			if opResp, ok := res.(*common.OperationResp); ok {
				return opResp, nil
			}
		}
		log.Warnw("download-image-unexpected-return-type", log.Fields{"result": res})
		return failedresponse, status.Errorf(codes.Internal, "%s", res)
	case <-ctx.Done():
		log.Debug("downloadImage-client-timeout")
		return nil, ctx.Err()
	}
}

func (handler *APIHandler) DownloadImage(ctx context.Context, img *voltha.ImageDownload) (*common.OperationResp, error) {
	log.Debugw("DownloadImage-request", log.Fields{"img": *img})
	if isTestMode(ctx) {
		resp := &common.OperationResp{Code: common.OperationResp_OPERATION_SUCCESS}
		return resp, nil
	}

	return handler.processImageRequest(ctx, img, IMAGE_DOWNLOAD)
}

func (handler *APIHandler) CancelImageDownload(ctx context.Context, img *voltha.ImageDownload) (*common.OperationResp, error) {
	log.Debugw("cancelImageDownload-request", log.Fields{"img": *img})
	if isTestMode(ctx) {
		resp := &common.OperationResp{Code: common.OperationResp_OPERATION_SUCCESS}
		return resp, nil
	}
	return handler.processImageRequest(ctx, img, CANCEL_IMAGE_DOWNLOAD)
}

func (handler *APIHandler) ActivateImageUpdate(ctx context.Context, img *voltha.ImageDownload) (*common.OperationResp, error) {
	log.Debugw("activateImageUpdate-request", log.Fields{"img": *img})
	if isTestMode(ctx) {
		resp := &common.OperationResp{Code: common.OperationResp_OPERATION_SUCCESS}
		return resp, nil
	}

	return handler.processImageRequest(ctx, img, ACTIVATE_IMAGE)
}

func (handler *APIHandler) RevertImageUpdate(ctx context.Context, img *voltha.ImageDownload) (*common.OperationResp, error) {
	log.Debugw("revertImageUpdate-request", log.Fields{"img": *img})
	if isTestMode(ctx) {
		resp := &common.OperationResp{Code: common.OperationResp_OPERATION_SUCCESS}
		return resp, nil
	}

	return handler.processImageRequest(ctx, img, REVERT_IMAGE)
}

func (handler *APIHandler) GetImageDownloadStatus(ctx context.Context, img *voltha.ImageDownload) (*voltha.ImageDownload, error) {
	log.Debugw("getImageDownloadStatus-request", log.Fields{"img": *img})
	if isTestMode(ctx) {
		resp := &voltha.ImageDownload{State: voltha.ImageDownload_DOWNLOAD_SUCCEEDED}
		return resp, nil
	}

	failedresponse := &voltha.ImageDownload{State: voltha.ImageDownload_DOWNLOAD_UNKNOWN}

	if handler.competeForTransaction() {
		if txn, err := handler.acquireTransaction(ctx); err != nil {
			return failedresponse, err
		} else {
			defer txn.Close()
		}
	}

	ch := make(chan interface{})
	defer close(ch)
	go handler.deviceMgr.getImageDownloadStatus(ctx, img, ch)

	select {
	case res := <-ch:
		if res != nil {
			if err, ok := res.(error); ok {
				return failedresponse, err
			}
			if downloadResp, ok := res.(*voltha.ImageDownload); ok {
				return downloadResp, nil
			}
		}
		log.Warnw("download-image-status", log.Fields{"result": res})
		return failedresponse, status.Errorf(codes.Internal, "%s", res)
	case <-ctx.Done():
		log.Debug("downloadImage-client-timeout")
		return failedresponse, ctx.Err()
	}
}

func (handler *APIHandler) GetImageDownload(ctx context.Context, img *voltha.ImageDownload) (*voltha.ImageDownload, error) {
	log.Debugw("GetImageDownload-request", log.Fields{"img": *img})
	if isTestMode(ctx) {
		resp := &voltha.ImageDownload{State: voltha.ImageDownload_DOWNLOAD_SUCCEEDED}
		return resp, nil
	}

	if download, err := handler.deviceMgr.getImageDownload(ctx, img); err != nil {
		return &voltha.ImageDownload{State: voltha.ImageDownload_DOWNLOAD_UNKNOWN}, err
	} else {
		return download, nil
	}
}

func (handler *APIHandler) ListImageDownloads(ctx context.Context, id *voltha.ID) (*voltha.ImageDownloads, error) {
	log.Debugw("ListImageDownloads-request", log.Fields{"deviceId": id.Id})
	if isTestMode(ctx) {
		resp := &voltha.ImageDownloads{Items:[]*voltha.ImageDownload{}}
		return resp, nil
	}

	if downloads, err := handler.deviceMgr.listImageDownloads(ctx, id.Id); err != nil {
		failedResp := &voltha.ImageDownloads{
			Items:[]*voltha.ImageDownload{
				&voltha.ImageDownload{State: voltha.ImageDownload_DOWNLOAD_UNKNOWN},
		},
		}
		return failedResp, err
	} else {
		return downloads, nil
	}
}


func (handler *APIHandler) UpdateDevicePmConfigs(ctx context.Context, configs *voltha.PmConfigs) (*empty.Empty, error) {
	log.Debugw("UpdateDevicePmConfigs-request", log.Fields{"configs": *configs})
	if isTestMode(ctx) {
		out := new(empty.Empty)
		return out, nil
	}
	return nil, errors.New("UnImplemented")
}

func (handler *APIHandler) CreateAlarmFilter(ctx context.Context, filter *voltha.AlarmFilter) (*voltha.AlarmFilter, error) {
	log.Debugw("CreateAlarmFilter-request", log.Fields{"filter": *filter})
	if isTestMode(ctx) {
		f := &voltha.AlarmFilter{Id: filter.Id}
		return f, nil
	}
	return nil, errors.New("UnImplemented")
}

func (handler *APIHandler) UpdateAlarmFilter(ctx context.Context, filter *voltha.AlarmFilter) (*voltha.AlarmFilter, error) {
	log.Debugw("UpdateAlarmFilter-request", log.Fields{"filter": *filter})
	if isTestMode(ctx) {
		f := &voltha.AlarmFilter{Id: filter.Id}
		return f, nil
	}
	return nil, errors.New("UnImplemented")
}

func (handler *APIHandler) DeleteAlarmFilter(ctx context.Context, id *voltha.ID) (*empty.Empty, error) {
	log.Debugw("DeleteAlarmFilter-request", log.Fields{"id": *id})
	if isTestMode(ctx) {
		out := new(empty.Empty)
		return out, nil
	}
	return nil, errors.New("UnImplemented")
}

func (handler *APIHandler) SelfTest(ctx context.Context, id *voltha.ID) (*voltha.SelfTestResponse, error) {
	log.Debugw("SelfTest-request", log.Fields{"id": id})
	if isTestMode(ctx) {
		resp := &voltha.SelfTestResponse{Result: voltha.SelfTestResponse_SUCCESS}
		return resp, nil
	}
	return nil, errors.New("UnImplemented")
}

func (handler *APIHandler) forwardPacketOut(packet *openflow_13.PacketOut) {
	log.Debugw("forwardPacketOut-request", log.Fields{"packet": packet})
	agent := handler.logicalDeviceMgr.getLogicalDeviceAgent(packet.Id)
	agent.packetOut(packet.PacketOut)
}
func (handler *APIHandler) StreamPacketsOut(
	packets voltha.VolthaService_StreamPacketsOutServer,
) error {
	log.Debugw("StreamPacketsOut-request", log.Fields{"packets": packets})
	for {
		packet, err := packets.Recv()

		if err == io.EOF {
			break
		} else if err != nil {
			log.Errorw("Failed to receive packet", log.Fields{"error": err})
		}

		handler.forwardPacketOut(packet)
	}

	log.Debugw("StreamPacketsOut-request-done", log.Fields{"packets": packets})
	return nil
}

func (handler *APIHandler) sendPacketIn(deviceId string, packet *openflow_13.OfpPacketIn) {
	packetIn := openflow_13.PacketIn{Id: deviceId, PacketIn: packet}
	log.Debugw("sendPacketIn", log.Fields{"packetIn": packetIn})
	// Enqueue the packet
	if err := handler.packetInQueue.Put(packetIn); err != nil {
		log.Errorw("failed-to-enqueue-packet", log.Fields{"error": err})
	}
}

func (handler *APIHandler) ReceivePacketsIn(
	empty *empty.Empty,
	packetsIn voltha.VolthaService_ReceivePacketsInServer,
) error {
	log.Debugw("ReceivePacketsIn-request", log.Fields{"packetsIn": packetsIn})

	for {
		// Dequeue a packet
		if packets, err := handler.packetInQueue.Get(1); err == nil {
			log.Debugw("dequeued-packet", log.Fields{"packet": packets[0]})
			if packet, ok := packets[0].(openflow_13.PacketIn); ok {
				log.Debugw("sending-packet-in", log.Fields{"packet": packet})
				if err := packetsIn.Send(&packet); err != nil {
					log.Errorw("failed-to-send-packet", log.Fields{"error": err})
				}
			}
		}
	}
	//TODO: FInd an elegant way to get out of the above loop when the Core is stopped
}

func (handler *APIHandler) sendChangeEvent(deviceId string, portStatus *openflow_13.OfpPortStatus) {
	// TODO: validate the type of portStatus parameter
	//if _, ok := portStatus.(*openflow_13.OfpPortStatus); ok {
	//}
	event := openflow_13.ChangeEvent{Id: deviceId, Event: &openflow_13.ChangeEvent_PortStatus{PortStatus: portStatus}}
	log.Debugw("sendChangeEvent", log.Fields{"event": event})
	// TODO: put the packet in the queue
}

func (handler *APIHandler) ReceiveChangeEvents(
	empty *empty.Empty,
	changeEvents voltha.VolthaService_ReceiveChangeEventsServer,
) error {
	log.Debugw("ReceiveChangeEvents-request", log.Fields{"changeEvents": changeEvents})
	for {
		// TODO: need to retrieve packet from queue
		event := &openflow_13.ChangeEvent{}
		time.Sleep(time.Duration(5) * time.Second)
		err := changeEvents.Send(event)
		if err != nil {
			log.Errorw("Failed to send change event", log.Fields{"error": err})
		}
	}
	// TODO: put the packet in the queue
	}

func (handler *APIHandler) Subscribe(
	ctx context.Context,
	ofAgent *voltha.OfAgentSubscriber,
) (*voltha.OfAgentSubscriber, error) {
	log.Debugw("Subscribe-request", log.Fields{"ofAgent": ofAgent})
	return &voltha.OfAgentSubscriber{OfagentId: ofAgent.OfagentId, VolthaId: ofAgent.VolthaId}, nil
}