/*
 * 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"
	"sync"
	"time"

	"github.com/opencord/voltha-go/db/model"
	"github.com/opencord/voltha-go/rw_core/config"
	"github.com/opencord/voltha-lib-go/v3/pkg/db"
	"github.com/opencord/voltha-lib-go/v3/pkg/db/kvstore"
	grpcserver "github.com/opencord/voltha-lib-go/v3/pkg/grpc"
	"github.com/opencord/voltha-lib-go/v3/pkg/kafka"
	"github.com/opencord/voltha-lib-go/v3/pkg/log"
	"github.com/opencord/voltha-lib-go/v3/pkg/probe"
	"github.com/opencord/voltha-protos/v3/go/voltha"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

// Core represent read,write core attributes
type Core struct {
	instanceID        string
	deviceMgr         *DeviceManager
	logicalDeviceMgr  *LogicalDeviceManager
	grpcServer        *grpcserver.GrpcServer
	grpcNBIAPIHandler *APIHandler
	adapterMgr        *AdapterManager
	config            *config.RWCoreFlags
	kmp               kafka.InterContainerProxy
	clusterDataProxy  *model.Proxy
	localDataProxy    *model.Proxy
	exitChannel       chan struct{}
	stopOnce          sync.Once
	kvClient          kvstore.Client
	backend           db.Backend
	kafkaClient       kafka.Client
}

// NewCore creates instance of rw core
func NewCore(ctx context.Context, id string, cf *config.RWCoreFlags, kvClient kvstore.Client, kafkaClient kafka.Client) *Core {
	var core Core
	core.instanceID = id
	core.exitChannel = make(chan struct{})
	core.config = cf
	core.kvClient = kvClient
	core.kafkaClient = kafkaClient

	// Configure backend to push Liveness Status at least every (cf.LiveProbeInterval / 2) seconds
	// so as to avoid trigger of Liveness check (due to Liveness timeout) when backend is alive
	livenessChannelInterval := cf.LiveProbeInterval / 2

	// Setup the KV store
	core.backend = db.Backend{
		Client:                  kvClient,
		StoreType:               cf.KVStoreType,
		Host:                    cf.KVStoreHost,
		Port:                    cf.KVStorePort,
		Timeout:                 cf.KVStoreTimeout,
		LivenessChannelInterval: livenessChannelInterval,
		PathPrefix:              cf.KVStoreDataPrefix}
	return &core
}

// Start brings up core services
func (core *Core) Start(ctx context.Context) error {

	// If the context has a probe then fetch it and register our services
	var p *probe.Probe
	if value := ctx.Value(probe.ProbeContextKey); value != nil {
		if _, ok := value.(*probe.Probe); ok {
			p = value.(*probe.Probe)
			p.RegisterService(
				"message-bus",
				"kv-store",
				"device-manager",
				"logical-device-manager",
				"adapter-manager",
				"grpc-service",
			)
		}
	}

	logger.Info("starting-core-services", log.Fields{"coreId": core.instanceID})

	// Wait until connection to KV Store is up
	if err := core.waitUntilKVStoreReachableOrMaxTries(ctx, core.config.MaxConnectionRetries, core.config.ConnectionRetryInterval); err != nil {
		logger.Fatal("Unable-to-connect-to-KV-store")
	}
	if p != nil {
		p.UpdateStatus("kv-store", probe.ServiceStatusRunning)
	}

	core.clusterDataProxy = model.NewProxy(&core.backend, "/")
	core.localDataProxy = model.NewProxy(&core.backend, "/")

	// core.kmp must be created before deviceMgr and adapterMgr, as they will make
	// private copies of the poiner to core.kmp.
	core.initKafkaManager(ctx)

	logger.Debugw("values", log.Fields{"kmp": core.kmp})
	core.deviceMgr = newDeviceManager(core)
	core.adapterMgr = newAdapterManager(core.clusterDataProxy, core.instanceID, core.kafkaClient, core.deviceMgr)
	core.deviceMgr.adapterMgr = core.adapterMgr
	core.logicalDeviceMgr = newLogicalDeviceManager(core, core.deviceMgr, core.kmp, core.clusterDataProxy, core.config.DefaultCoreTimeout)

	// Start the KafkaManager. This must be done after the deviceMgr, adapterMgr, and
	// logicalDeviceMgr have been created, as once the kmp is started, it will register
	// the above with the kmp.

	go core.startKafkaManager(ctx,
		core.config.ConnectionRetryInterval,
		core.config.LiveProbeInterval,
		core.config.NotLiveProbeInterval)

	go core.startDeviceManager(ctx)
	go core.startLogicalDeviceManager(ctx)
	go core.startGRPCService(ctx)
	go core.startAdapterManager(ctx)
	go core.monitorKvstoreLiveness(ctx)

	logger.Info("core-services-started")
	return nil
}

// Stop brings down core services
func (core *Core) Stop(ctx context.Context) {
	core.stopOnce.Do(func() {
		logger.Info("stopping-adaptercore")
		// Signal to the KVStoreMonitor that we are stopping.
		close(core.exitChannel)
		// Stop all the started services
		if core.grpcServer != nil {
			core.grpcServer.Stop()
		}
		if core.logicalDeviceMgr != nil {
			core.logicalDeviceMgr.stop(ctx)
		}
		if core.deviceMgr != nil {
			core.deviceMgr.stop(ctx)
		}
		if core.kmp != nil {
			core.kmp.Stop()
		}
		logger.Info("adaptercore-stopped")
	})
}

//startGRPCService creates the grpc service handlers, registers it to the grpc server and starts the server
func (core *Core) startGRPCService(ctx context.Context) {
	//	create an insecure gserver server
	core.grpcServer = grpcserver.NewGrpcServer(core.config.GrpcHost, core.config.GrpcPort, nil, false, probe.GetProbeFromContext(ctx))
	logger.Info("grpc-server-created")

	core.grpcNBIAPIHandler = NewAPIHandler(core)
	logger.Infow("grpc-handler", log.Fields{"core_binding_key": core.config.CoreBindingKey})
	core.logicalDeviceMgr.setGrpcNbiHandler(core.grpcNBIAPIHandler)
	//	Create a function to register the core GRPC service with the GRPC server
	f := func(gs *grpc.Server) {
		voltha.RegisterVolthaServiceServer(
			gs,
			core.grpcNBIAPIHandler,
		)
	}

	core.grpcServer.AddService(f)
	logger.Info("grpc-service-added")

	/*
	 * Start the GRPC server
	 *
	 * This is a bit sub-optimal here as the grpcServer.Start call does not return (blocks)
	 * until something fails, but we want to send a "start" status update. As written this
	 * means that we are actually sending the "start" status update before the server is
	 * started, which means it is possible that the status is "running" before it actually is.
	 *
	 * This means that there is a small window in which the core could return its status as
	 * ready, when it really isn't.
	 */
	probe.UpdateStatusFromContext(ctx, "grpc-service", probe.ServiceStatusRunning)
	logger.Info("grpc-server-started")
	core.grpcServer.Start(ctx)
	probe.UpdateStatusFromContext(ctx, "grpc-service", probe.ServiceStatusStopped)
}

// Initialize the kafka manager, but we will start it later
func (core *Core) initKafkaManager(ctx context.Context) {
	logger.Infow("initialize-kafka-manager", log.Fields{"host": core.config.KafkaAdapterHost,
		"port": core.config.KafkaAdapterPort, "topic": core.config.CoreTopic})

	probe.UpdateStatusFromContext(ctx, "message-bus", probe.ServiceStatusPreparing)

	// create the proxy
	core.kmp = kafka.NewInterContainerProxy(
		kafka.InterContainerHost(core.config.KafkaAdapterHost),
		kafka.InterContainerPort(core.config.KafkaAdapterPort),
		kafka.MsgClient(core.kafkaClient),
		kafka.DefaultTopic(&kafka.Topic{Name: core.config.CoreTopic}),
		kafka.DeviceDiscoveryTopic(&kafka.Topic{Name: core.config.AffinityRouterTopic}))

	probe.UpdateStatusFromContext(ctx, "message-bus", probe.ServiceStatusPrepared)
}

/*
 * KafkaMonitorThread
 *
 * Responsible for starting the Kafka Interadapter Proxy and monitoring its liveness
 * state.
 *
 * Any producer that fails to send will cause KafkaInterContainerProxy to
 * post a false event on its liveness channel. Any producer that succeeds in sending
 * will cause KafkaInterContainerProxy to post a true event on its liveness
 * channel. Group receivers also update liveness state, and a receiver will typically
 * indicate a loss of liveness within 3-5 seconds of Kafka going down. Receivers
 * only indicate restoration of liveness if a message is received. During normal
 * operation, messages will be routinely produced and received, automatically
 * indicating liveness state. These routine liveness indications are rate-limited
 * inside sarama_client.
 *
 * This thread monitors the status of KafkaInterContainerProxy's liveness and pushes
 * that state to the core's readiness probes. If no liveness event has been seen
 * within a timeout, then the thread will make an attempt to produce a "liveness"
 * message, which will in turn trigger a liveness event on the liveness channel, true
 * or false depending on whether the attempt succeeded.
 *
 * The gRPC server in turn monitors the state of the readiness probe and will
 * start issuing UNAVAILABLE response while the probe is not ready.
 *
 * startupRetryInterval -- interval between attempts to start
 * liveProbeInterval -- interval between liveness checks when in a live state
 * notLiveProbeInterval -- interval between liveness checks when in a notLive state
 *
 * liveProbeInterval and notLiveProbeInterval can be configured separately,
 * though the current default is that both are set to 60 seconds.
 */

func (core *Core) startKafkaManager(ctx context.Context, startupRetryInterval time.Duration, liveProbeInterval time.Duration, notLiveProbeInterval time.Duration) {
	logger.Infow("starting-kafka-manager-thread", log.Fields{"host": core.config.KafkaAdapterHost,
		"port": core.config.KafkaAdapterPort, "topic": core.config.CoreTopic})

	started := false
	for !started {
		// If we haven't started yet, then try to start
		logger.Infow("starting-kafka-proxy", log.Fields{})
		if err := core.kmp.Start(); err != nil {
			// We failed to start. Delay and then try again later.
			// Don't worry about liveness, as we can't be live until we've started.
			probe.UpdateStatusFromContext(ctx, "message-bus", probe.ServiceStatusNotReady)
			logger.Infow("error-starting-kafka-messaging-proxy", log.Fields{"error": err})
			time.Sleep(startupRetryInterval)
		} else {
			// We started. We only need to do this once.
			// Next we'll fall through and start checking liveness.
			logger.Infow("started-kafka-proxy", log.Fields{})

			// cannot do this until after the kmp is started
			if err := core.registerAdapterRequestHandlers(ctx, core.instanceID, core.deviceMgr, core.logicalDeviceMgr, core.adapterMgr, core.clusterDataProxy, core.localDataProxy); err != nil {
				logger.Fatal("Failure-registering-adapterRequestHandler")
			}

			started = true
		}
	}

	logger.Info("started-kafka-message-proxy")

	livenessChannel := core.kmp.EnableLivenessChannel(true)

	logger.Info("enabled-kafka-liveness-channel")

	timeout := liveProbeInterval
	for {
		timeoutTimer := time.NewTimer(timeout)
		select {
		case liveness := <-livenessChannel:
			logger.Infow("kafka-manager-thread-liveness-event", log.Fields{"liveness": liveness})
			// there was a state change in Kafka liveness
			if !liveness {
				probe.UpdateStatusFromContext(ctx, "message-bus", probe.ServiceStatusNotReady)

				if core.grpcServer != nil {
					logger.Info("kafka-manager-thread-set-server-notready")
				}

				// retry frequently while life is bad
				timeout = notLiveProbeInterval
			} else {
				probe.UpdateStatusFromContext(ctx, "message-bus", probe.ServiceStatusRunning)

				if core.grpcServer != nil {
					logger.Info("kafka-manager-thread-set-server-ready")
				}

				// retry infrequently while life is good
				timeout = liveProbeInterval
			}
			if !timeoutTimer.Stop() {
				<-timeoutTimer.C
			}
		case <-timeoutTimer.C:
			logger.Info("kafka-proxy-liveness-recheck")
			// send the liveness probe in a goroutine; we don't want to deadlock ourselves as
			// the liveness probe may wait (and block) writing to our channel.
			go func() {
				err := core.kmp.SendLiveness()
				if err != nil {
					// Catch possible error case if sending liveness after Sarama has been stopped.
					logger.Warnw("error-kafka-send-liveness", log.Fields{"error": err})
				}
			}()
		}
	}
}

// waitUntilKVStoreReachableOrMaxTries will wait until it can connect to a KV store or until maxtries has been reached
func (core *Core) waitUntilKVStoreReachableOrMaxTries(ctx context.Context, maxRetries int, retryInterval time.Duration) error {
	logger.Infow("verifying-KV-store-connectivity", log.Fields{"host": core.config.KVStoreHost,
		"port": core.config.KVStorePort, "retries": maxRetries, "retryInterval": retryInterval})
	count := 0
	for {
		if !core.kvClient.IsConnectionUp(ctx) {
			logger.Info("KV-store-unreachable")
			if maxRetries != -1 {
				if count >= maxRetries {
					return status.Error(codes.Unavailable, "kv store unreachable")
				}
			}
			count++
			//	Take a nap before retrying
			time.Sleep(retryInterval)
			logger.Infow("retry-KV-store-connectivity", log.Fields{"retryCount": count, "maxRetries": maxRetries, "retryInterval": retryInterval})

		} else {
			break
		}
	}
	logger.Info("KV-store-reachable")
	return nil
}

func (core *Core) registerAdapterRequestHandlers(ctx context.Context, coreInstanceID string, dMgr *DeviceManager,
	ldMgr *LogicalDeviceManager, aMgr *AdapterManager, cdProxy *model.Proxy, ldProxy *model.Proxy,
) error {
	requestProxy := NewAdapterRequestHandlerProxy(core, coreInstanceID, dMgr, ldMgr, aMgr, cdProxy, ldProxy,
		core.config.LongRunningRequestTimeout, core.config.DefaultRequestTimeout)

	// Register the broadcast topic to handle any core-bound broadcast requests
	if err := core.kmp.SubscribeWithRequestHandlerInterface(kafka.Topic{Name: core.config.CoreTopic}, requestProxy); err != nil {
		logger.Fatalw("Failed-registering-broadcast-handler", log.Fields{"topic": core.config.CoreTopic})
		return err
	}

	// Register the core-pair topic to handle core-bound requests destined to the core pair
	if err := core.kmp.SubscribeWithDefaultRequestHandler(kafka.Topic{Name: core.config.CorePairTopic}, kafka.OffsetNewest); err != nil {
		logger.Fatalw("Failed-registering-pair-handler", log.Fields{"topic": core.config.CorePairTopic})
		return err
	}

	logger.Info("request-handler-registered")
	return nil
}

func (core *Core) startDeviceManager(ctx context.Context) {
	logger.Info("DeviceManager-Starting...")
	core.deviceMgr.start(ctx, core.logicalDeviceMgr)
	logger.Info("DeviceManager-Started")
}

func (core *Core) startLogicalDeviceManager(ctx context.Context) {
	logger.Info("Logical-DeviceManager-Starting...")
	core.logicalDeviceMgr.start(ctx)
	logger.Info("Logical-DeviceManager-Started")
}

func (core *Core) startAdapterManager(ctx context.Context) {
	logger.Info("Adapter-Manager-Starting...")
	err := core.adapterMgr.start(ctx)
	if err != nil {
		logger.Fatalf("failed-to-start-adapter-manager: error %v ", err)
	}
	logger.Info("Adapter-Manager-Started")
}

/*
* Thread to monitor kvstore Liveness (connection status)
*
* This function constantly monitors Liveness State of kvstore as reported
* periodically by backend and updates the Status of kv-store service registered
* with rw_core probe.
*
* If no liveness event has been seen within a timeout, then the thread will
* perform a "liveness" check attempt, which will in turn trigger a liveness event on
* the liveness channel, true or false depending on whether the attempt succeeded.
*
* The gRPC server in turn monitors the state of the readiness probe and will
* start issuing UNAVAILABLE response while the probe is not ready.
 */
func (core *Core) monitorKvstoreLiveness(ctx context.Context) {
	logger.Info("start-monitoring-kvstore-liveness")

	// Instruct backend to create Liveness channel for transporting state updates
	livenessChannel := core.backend.EnableLivenessChannel()

	logger.Debug("enabled-kvstore-liveness-channel")

	// Default state for kvstore is alive for rw_core
	timeout := core.config.LiveProbeInterval
loop:
	for {
		timeoutTimer := time.NewTimer(timeout)
		select {

		case liveness := <-livenessChannel:
			logger.Debugw("received-liveness-change-notification", log.Fields{"liveness": liveness})

			if !liveness {
				probe.UpdateStatusFromContext(ctx, "kv-store", probe.ServiceStatusNotReady)

				if core.grpcServer != nil {
					logger.Info("kvstore-set-server-notready")
				}

				timeout = core.config.NotLiveProbeInterval

			} else {
				probe.UpdateStatusFromContext(ctx, "kv-store", probe.ServiceStatusRunning)

				if core.grpcServer != nil {
					logger.Info("kvstore-set-server-ready")
				}

				timeout = core.config.LiveProbeInterval
			}

			if !timeoutTimer.Stop() {
				<-timeoutTimer.C
			}

		case <-core.exitChannel:
			break loop

		case <-timeoutTimer.C:
			logger.Info("kvstore-perform-liveness-check-on-timeout")

			// Trigger Liveness check if no liveness update received within the timeout period.
			// The Liveness check will push Live state to same channel which this routine is
			// reading and processing. This, do it asynchronously to avoid blocking for
			// backend response and avoid any possibility of deadlock
			go core.backend.PerformLivenessCheck(ctx)
		}
	}
}