// Package node defines the services that a beacon chain node would perform.
package node

import (
	"context"
	"fmt"
	"os"
	"os/signal"
	"sync"
	"syscall"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethclient"
	gethRPC "github.com/ethereum/go-ethereum/rpc"
	"github.com/prysmaticlabs/prysm/beacon-chain/blockchain"
	"github.com/prysmaticlabs/prysm/beacon-chain/powchain"
	"github.com/prysmaticlabs/prysm/beacon-chain/rpc"
	"github.com/prysmaticlabs/prysm/beacon-chain/simulator"
	rbcsync "github.com/prysmaticlabs/prysm/beacon-chain/sync"
	initialsync "github.com/prysmaticlabs/prysm/beacon-chain/sync/initial-sync"
	"github.com/prysmaticlabs/prysm/beacon-chain/utils"
	"github.com/prysmaticlabs/prysm/shared"
	"github.com/prysmaticlabs/prysm/shared/cmd"
	"github.com/prysmaticlabs/prysm/shared/database"
	"github.com/prysmaticlabs/prysm/shared/debug"
	"github.com/prysmaticlabs/prysm/shared/p2p"
	"github.com/sirupsen/logrus"
	"github.com/urfave/cli"
)

var log = logrus.WithField("prefix", "node")
var beaconChainDBName = "beaconchaindata"

// BeaconNode defines a struct that handles the services running a random beacon chain
// full PoS node. It handles the lifecycle of the entire system and registers
// services to a service registry.
type BeaconNode struct {
	ctx      *cli.Context
	services *shared.ServiceRegistry
	lock     sync.RWMutex
	stop     chan struct{} // Channel to wait for termination notifications.
	db       *database.DB
}

// NewBeaconNode creates a new node instance, sets up configuration options, and registers
// every required service to the node.
func NewBeaconNode(ctx *cli.Context) (*BeaconNode, error) {
	registry := shared.NewServiceRegistry()

	beacon := &BeaconNode{
		ctx:      ctx,
		services: registry,
		stop:     make(chan struct{}),
	}

	if err := beacon.startDB(ctx); err != nil {
		return nil, err
	}

	if err := beacon.registerP2P(); err != nil {
		return nil, err
	}

	if err := beacon.registerPOWChainService(ctx); err != nil {
		return nil, err
	}

	if err := beacon.registerBlockchainService(ctx); err != nil {
		return nil, err
	}

	if err := beacon.registerSyncService(); err != nil {
		return nil, err
	}

	if err := beacon.registerInitialSyncService(); err != nil {
		return nil, err
	}

	if err := beacon.registerSimulatorService(ctx); err != nil {
		return nil, err
	}

	if err := beacon.registerRPCService(ctx); err != nil {
		return nil, err
	}

	return beacon, nil
}

// Start the BeaconNode and kicks off every registered service.
func (b *BeaconNode) Start() {
	b.lock.Lock()

	log.Info("Starting beacon node")

	b.services.StartAll()

	stop := b.stop
	b.lock.Unlock()

	go func() {
		sigc := make(chan os.Signal, 1)
		signal.Notify(sigc, syscall.SIGINT, syscall.SIGTERM)
		defer signal.Stop(sigc)
		<-sigc
		log.Info("Got interrupt, shutting down...")
		go b.Close()
		for i := 10; i > 0; i-- {
			<-sigc
			if i > 1 {
				log.Info("Already shutting down, interrupt more to panic", "times", i-1)
			}
		}
		debug.Exit() // Ensure trace and CPU profile data are flushed.
		panic("Panic closing the beacon node")
	}()

	// Wait for stop channel to be closed.
	<-stop
}

// Close handles graceful shutdown of the system.
func (b *BeaconNode) Close() {
	b.lock.Lock()
	defer b.lock.Unlock()

	log.Info("Stopping beacon node")
	b.services.StopAll()
	b.db.Close()
	close(b.stop)
}

func (b *BeaconNode) startDB(ctx *cli.Context) error {
	path := ctx.GlobalString(cmd.DataDirFlag.Name)
	config := &database.DBConfig{DataDir: path, Name: beaconChainDBName, InMemory: false}
	db, err := database.NewDB(config)
	if err != nil {
		return err
	}

	b.db = db
	return nil
}

func (b *BeaconNode) registerP2P() error {
	beaconp2p, err := p2p.NewServer()
	if err != nil {
		return fmt.Errorf("could not register p2p service: %v", err)
	}
	return b.services.RegisterService(beaconp2p)
}

func (b *BeaconNode) registerBlockchainService(ctx *cli.Context) error {
	var web3Service *powchain.Web3Service
	if ctx.GlobalBool(utils.ValidatorFlag.Name) {
		if err := b.services.FetchService(&web3Service); err != nil {
			return err
		}
	}

	beaconChain, err := blockchain.NewBeaconChain(b.db.DB())
	if err != nil {
		return fmt.Errorf("could not register blockchain service: %v", err)
	}

	blockchainService, err := blockchain.NewChainService(context.TODO(), &blockchain.Config{
		BeaconDB:         b.db.DB(),
		Web3Service:      web3Service,
		Chain:            beaconChain,
		BeaconBlockBuf:   10,
		IncomingBlockBuf: 100, // Big buffer to accommodate other feed subscribers.
	})
	if err != nil {
		return fmt.Errorf("could not register blockchain service: %v", err)
	}
	return b.services.RegisterService(blockchainService)
}

func (b *BeaconNode) registerPOWChainService(ctx *cli.Context) error {
	if !ctx.GlobalBool(utils.ValidatorFlag.Name) {
		return nil
	}

	rpcClient, err := gethRPC.Dial(b.ctx.GlobalString(utils.Web3ProviderFlag.Name))
	if err != nil {
		log.Fatalf("Access to PoW chain is required for validator. Unable to connect to Geth node: %v", err)
	}
	powClient := ethclient.NewClient(rpcClient)

	web3Service, err := powchain.NewWeb3Service(context.TODO(), &powchain.Web3ServiceConfig{
		Endpoint: b.ctx.GlobalString(utils.Web3ProviderFlag.Name),
		Pubkey:   b.ctx.GlobalString(utils.PubKeyFlag.Name),
		VrcAddr:  common.HexToAddress(b.ctx.GlobalString(utils.VrcContractFlag.Name)),
	}, powClient, powClient, powClient)
	if err != nil {
		return fmt.Errorf("could not register proof-of-work chain web3Service: %v", err)
	}
	return b.services.RegisterService(web3Service)
}

func (b *BeaconNode) registerSyncService() error {
	var chainService *blockchain.ChainService
	if err := b.services.FetchService(&chainService); err != nil {
		return err
	}

	var p2pService *p2p.Server
	if err := b.services.FetchService(&p2pService); err != nil {
		return err
	}

	syncService := rbcsync.NewSyncService(context.Background(), rbcsync.DefaultConfig(), p2pService, chainService)
	return b.services.RegisterService(syncService)
}

func (b *BeaconNode) registerInitialSyncService() error {
	var p2pService *p2p.Server
	if err := b.services.FetchService(&p2pService); err != nil {
		return err
	}

	var chainService *blockchain.ChainService
	if err := b.services.FetchService(&chainService); err != nil {
		return err
	}

	var syncService *rbcsync.Service
	if err := b.services.FetchService(&syncService); err != nil {
		return err
	}

	initialSyncService := initialsync.NewInitialSyncService(context.Background(), initialsync.DefaultConfig(), p2pService, chainService, syncService)
	return b.services.RegisterService(initialSyncService)
}

func (b *BeaconNode) registerSimulatorService(ctx *cli.Context) error {
	if !ctx.GlobalBool(utils.SimulatorFlag.Name) {
		return nil
	}
	var p2pService *p2p.Server
	if err := b.services.FetchService(&p2pService); err != nil {
		return err
	}

	var web3Service *powchain.Web3Service
	var isValidator = ctx.GlobalBool(utils.ValidatorFlag.Name)
	if isValidator {
		if err := b.services.FetchService(&web3Service); err != nil {
			return err
		}
	}

	var chainService *blockchain.ChainService
	if err := b.services.FetchService(&chainService); err != nil {
		return err
	}

	defaultConf := simulator.DefaultConfig()
	cfg := &simulator.Config{
		Delay:           defaultConf.Delay,
		BlockRequestBuf: defaultConf.BlockRequestBuf,
		BeaconDB:        b.db.DB(),
		P2P:             p2pService,
		Web3Service:     web3Service,
		ChainService:    chainService,
		Validator:       isValidator,
	}
	simulatorService := simulator.NewSimulator(context.TODO(), cfg)
	return b.services.RegisterService(simulatorService)
}

func (b *BeaconNode) registerRPCService(ctx *cli.Context) error {
	var chainService *blockchain.ChainService
	if err := b.services.FetchService(&chainService); err != nil {
		return err
	}

	port := ctx.GlobalString(utils.RPCPort.Name)
	cert := ctx.GlobalString(utils.CertFlag.Name)
	key := ctx.GlobalString(utils.KeyFlag.Name)
	rpcService := rpc.NewRPCService(context.TODO(), &rpc.Config{
		Port:            port,
		CertFlag:        cert,
		KeyFlag:         key,
		SubscriptionBuf: 100,
	}, chainService)

	return b.services.RegisterService(rpcService)
}