package p2p

import (
	"context"
	"crypto/ecdsa"
	"strings"
	"time"

	"github.com/ethereum/go-ethereum/p2p/enode"
	ds "github.com/ipfs/go-datastore"
	dsync "github.com/ipfs/go-datastore/sync"
	"github.com/karlseguin/ccache"
	"github.com/libp2p/go-libp2p"
	"github.com/libp2p/go-libp2p-core/host"
	"github.com/libp2p/go-libp2p-core/network"
	"github.com/libp2p/go-libp2p-core/peer"
	"github.com/libp2p/go-libp2p-core/protocol"
	kaddht "github.com/libp2p/go-libp2p-kad-dht"
	dhtopts "github.com/libp2p/go-libp2p-kad-dht/opts"
	pubsub "github.com/libp2p/go-libp2p-pubsub"
	rhost "github.com/libp2p/go-libp2p/p2p/host/routed"
	ma "github.com/multiformats/go-multiaddr"
	"github.com/pkg/errors"
	"github.com/prysmaticlabs/prysm/beacon-chain/p2p/encoder"
	"github.com/prysmaticlabs/prysm/shared"
)

var _ = shared.Service(&Service{})

var pollingPeriod = 1 * time.Second
var ttl = 1 * time.Hour

const prysmProtocolPrefix = "/prysm/0.0.0"

// Service for managing peer to peer (p2p) networking.
type Service struct {
	ctx           context.Context
	cancel        context.CancelFunc
	started       bool
	cfg           *Config
	startupErr    error
	dv5Listener   Listener
	host          host.Host
	pubsub        *pubsub.PubSub
	exclusionList *ccache.Cache
	privKey       *ecdsa.PrivateKey
	dht           *kaddht.IpfsDHT
}

// NewService initializes a new p2p service compatible with shared.Service interface. No
// connections are made until the Start function is called during the service registry startup.
func NewService(cfg *Config) (*Service, error) {
	var err error
	ctx, cancel := context.WithCancel(context.Background())

	s := &Service{
		ctx:           ctx,
		cancel:        cancel,
		cfg:           cfg,
		exclusionList: ccache.New(ccache.Configure()),
	}

	dv5Nodes, kadDHTNodes := parseBootStrapAddrs(s.cfg.BootstrapNodeAddr)

	cfg.Discv5BootStrapAddr = dv5Nodes
	cfg.KademliaBootStrapAddr = kadDHTNodes

	ipAddr := ipAddr()
	s.privKey, err = privKey(s.cfg)
	if err != nil {
		log.WithError(err).Error("Failed to generate p2p private key")
		return nil, err
	}

	opts := buildOptions(s.cfg, ipAddr, s.privKey)
	h, err := libp2p.New(s.ctx, opts...)
	if err != nil {
		log.WithError(err).Error("Failed to create p2p host")
		return nil, err
	}

	if len(cfg.KademliaBootStrapAddr) != 0 && !cfg.NoDiscovery {
		dopts := []dhtopts.Option{
			dhtopts.Datastore(dsync.MutexWrap(ds.NewMapDatastore())),
			dhtopts.Protocols(
				protocol.ID(prysmProtocolPrefix + "/dht"),
			),
		}

		s.dht, err = kaddht.New(ctx, h, dopts...)
		if err != nil {
			return nil, err
		}
		// Wrap host with a routed host so that peers can be looked up in the
		// distributed hash table by their peer ID.
		h = rhost.Wrap(h, s.dht)
	}
	s.host = h

	// TODO(3147): Add gossip sub options
	// Gossipsub registration is done before we add in any new peers
	// due to libp2p's gossipsub implementation not taking into
	// account previously added peers when creating the gossipsub
	// object.
	psOpts := []pubsub.Option{
		pubsub.WithMessageSigning(false),
		pubsub.WithStrictSignatureVerification(false),
	}
	gs, err := pubsub.NewGossipSub(s.ctx, s.host, psOpts...)
	if err != nil {
		log.WithError(err).Error("Failed to start pubsub")
		return nil, err
	}
	s.pubsub = gs

	return s, nil
}

// Start the p2p service.
func (s *Service) Start() {
	if s.started {
		log.Error("Attempted to start p2p service when it was already started")
		return
	}

	var peersToWatch []string
	if s.cfg.RelayNodeAddr != "" {
		peersToWatch = append(peersToWatch, s.cfg.RelayNodeAddr)
		if err := dialRelayNode(s.ctx, s.host, s.cfg.RelayNodeAddr); err != nil {
			log.WithError(err).Errorf("Could not dial relay node")
		}
	}

	if len(s.cfg.Discv5BootStrapAddr) != 0 && !s.cfg.NoDiscovery {
		ipAddr := ipAddr()
		listener, err := startDiscoveryV5(ipAddr, s.privKey, s.cfg)
		if err != nil {
			log.WithError(err).Error("Failed to start discovery")
			s.startupErr = err
			return
		}
		err = s.addBootNodesToExclusionList()
		if err != nil {
			log.WithError(err).Error("Could not add bootnode to the exclusion list")
			s.startupErr = err
			return
		}
		s.dv5Listener = listener

		go s.listenForNewNodes()
	}

	if len(s.cfg.KademliaBootStrapAddr) != 0 && !s.cfg.NoDiscovery {
		for _, addr := range s.cfg.KademliaBootStrapAddr {
			peersToWatch = append(peersToWatch, addr)
			err := startDHTDiscovery(s.host, addr)
			if err != nil {
				log.WithError(err).Error("Could not connect to bootnode")
				s.startupErr = err
				return
			}
			if err := s.addKadDHTNodesToExclusionList(addr); err != nil {
				s.startupErr = err
				return
			}
		}
		bcfg := kaddht.DefaultBootstrapConfig
		bcfg.Period = time.Duration(30 * time.Second)
		if err := s.dht.BootstrapWithConfig(s.ctx, bcfg); err != nil {
			log.WithError(err).Error("Failed to bootstrap DHT")
		}
	}

	s.started = true

	if len(s.cfg.StaticPeers) > 0 {
		addrs, err := manyMultiAddrsFromString(s.cfg.StaticPeers)
		if err != nil {
			log.Errorf("Could not connect to static peer: %v", err)
		}
		s.connectWithAllPeers(addrs)
	}

	startPeerWatcher(s.ctx, s.host, peersToWatch...)
	registerMetrics(s)
	multiAddrs := s.host.Network().ListenAddresses()
	logIP4Addr(s.host.ID(), multiAddrs...)
}

// Stop the p2p service and terminate all peer connections.
func (s *Service) Stop() error {
	s.started = false
	if s.dv5Listener != nil {
		s.dv5Listener.Close()
	}
	return nil
}

// Status of the p2p service. Will return an error if the service is considered unhealthy to
// indicate that this node should not serve traffic until the issue has been resolved.
func (s *Service) Status() error {
	if !s.started {
		return errors.New("not running")
	}
	return nil
}

// Started returns true if the p2p service has successfully started.
func (s *Service) Started() bool {
	return s.started
}

// Encoding returns the configured networking encoding.
func (s *Service) Encoding() encoder.NetworkEncoding {
	encoding := s.cfg.Encoding
	switch encoding {
	case encoder.SSZ:
		return &encoder.SszNetworkEncoder{}
	case encoder.SSZSnappy:
		return &encoder.SszNetworkEncoder{UseSnappyCompression: true}
	default:
		panic("Invalid Network Encoding Flag Provided")
	}
}

// PubSub returns the p2p pubsub framework.
func (s *Service) PubSub() *pubsub.PubSub {
	return s.pubsub
}

// SetStreamHandler sets the protocol handler on the p2p host multiplexer.
// This method is a pass through to libp2pcore.Host.SetStreamHandler.
func (s *Service) SetStreamHandler(topic string, handler network.StreamHandler) {
	s.host.SetStreamHandler(protocol.ID(topic), handler)
}

// PeerID returns the Peer ID of the local peer.
func (s *Service) PeerID() peer.ID {
	return s.host.ID()
}

// Disconnect from a peer.
func (s *Service) Disconnect(pid peer.ID) error {
	return s.host.Network().ClosePeer(pid)
}

// listen for new nodes watches for new nodes in the network and adds them to the peerstore.
func (s *Service) listenForNewNodes() {
	ticker := time.NewTicker(pollingPeriod)
	bootNode, err := enode.Parse(enode.ValidSchemes, s.cfg.Discv5BootStrapAddr[0])
	if err != nil {
		log.Fatal(err)
	}
	for {
		select {
		case <-ticker.C:
			nodes := s.dv5Listener.Lookup(bootNode.ID())
			multiAddresses := convertToMultiAddr(nodes)
			s.connectWithAllPeers(multiAddresses)
		case <-s.ctx.Done():
			log.Debug("p2p context is closed, exiting routine")
			break
		}
	}
}

func (s *Service) connectWithAllPeers(multiAddrs []ma.Multiaddr) {
	addrInfos, err := peer.AddrInfosFromP2pAddrs(multiAddrs...)
	if err != nil {
		log.Errorf("Could not convert to peer address info's from multiaddresses: %v", err)
		return
	}
	for _, info := range addrInfos {
		if info.ID == s.host.ID() {
			continue
		}
		if s.exclusionList.Get(info.ID.String()) != nil {
			continue
		}
		if err := s.host.Connect(s.ctx, info); err != nil {
			log.Errorf("Could not connect with peer %s: %v", info.String(), err)
			s.exclusionList.Set(info.ID.String(), true, ttl)
		}
	}
}

func (s *Service) addBootNodesToExclusionList() error {
	for _, addr := range s.cfg.Discv5BootStrapAddr {
		bootNode, err := enode.Parse(enode.ValidSchemes, addr)
		if err != nil {
			return err
		}
		multAddr, err := convertToSingleMultiAddr(bootNode)
		if err != nil {
			return err
		}
		addrInfo, err := peer.AddrInfoFromP2pAddr(multAddr)
		if err != nil {
			return err
		}
		// bootnode is never dialled, so ttl is tentatively 1 year
		s.exclusionList.Set(addrInfo.ID.String(), true, 365*24*time.Hour)
	}

	return nil
}

func (s *Service) addKadDHTNodesToExclusionList(addr string) error {
	multiAddr, err := ma.NewMultiaddr(addr)
	if err != nil {
		return errors.Wrap(err, "could not get multiaddr")
	}
	addrInfo, err := peer.AddrInfoFromP2pAddr(multiAddr)
	if err != nil {
		return err
	}
	// bootnode is never dialled, so ttl is tentatively 1 year
	s.exclusionList.Set(addrInfo.ID.String(), true, 365*24*time.Hour)
	return nil
}

func logIP4Addr(id peer.ID, addrs ...ma.Multiaddr) {
	var correctAddr ma.Multiaddr
	for _, addr := range addrs {
		if strings.Contains(addr.String(), "/ip4/") {
			correctAddr = addr
			break
		}
	}
	if correctAddr != nil {
		log.WithField(
			"multiAddr",
			correctAddr.String()+"/p2p/"+id.String(),
		).Info("Node started p2p server")
	}
}