package sync

import (
	"context"
	"fmt"
	"time"

	libp2pcore "github.com/libp2p/go-libp2p-core"
	"github.com/libp2p/go-libp2p-core/helpers"
	"github.com/libp2p/go-libp2p-core/mux"
	"github.com/libp2p/go-libp2p-core/peer"
	"github.com/prysmaticlabs/prysm/beacon-chain/p2p"
	"github.com/prysmaticlabs/prysm/beacon-chain/p2p/types"
	"github.com/sirupsen/logrus"
)

var backOffTime = map[types.SSZUint64]time.Duration{
	// Do not dial peers which are from a different/unverifiable
	// network.
	types.GoodbyeCodeWrongNetwork:          24 * time.Hour,
	types.GoodbyeCodeUnableToVerifyNetwork: 24 * time.Hour,
	// If local peer is banned, we back off for
	// 2 hours to let the remote peer score us
	// back up again.
	types.GoodbyeCodeBadScore:       2 * time.Hour,
	types.GoodbyeCodeBanned:         2 * time.Hour,
	types.GoodbyeCodeClientShutdown: 1 * time.Hour,
	// Wait 5 minutes before dialing a peer who is
	// 'full'
	types.GoodbyeCodeTooManyPeers: 5 * time.Minute,
	types.GoodbyeCodeGenericError: 2 * time.Minute,
}

// goodbyeRPCHandler reads the incoming goodbye rpc message from the peer.
func (s *Service) goodbyeRPCHandler(_ context.Context, msg interface{}, stream libp2pcore.Stream) error {
	defer func() {
		if err := stream.Close(); err != nil {
			log.WithError(err).Error("Failed to close stream")
		}
	}()
	SetRPCStreamDeadlines(stream)

	m, ok := msg.(*types.SSZUint64)
	if !ok {
		return fmt.Errorf("wrong message type for goodbye, got %T, wanted *uint64", msg)
	}
	if err := s.rateLimiter.validateRequest(stream, 1); err != nil {
		return err
	}
	s.rateLimiter.add(stream, 1)
	log := log.WithField("Reason", goodbyeMessage(*m))
	log.WithField("peer", stream.Conn().RemotePeer()).Debug("Peer has sent a goodbye message")
	s.p2p.Peers().SetNextValidTime(stream.Conn().RemotePeer(), goodByeBackoff(*m))
	// closes all streams with the peer
	return s.p2p.Disconnect(stream.Conn().RemotePeer())
}

// disconnectBadPeer checks whether peer is considered bad by some scorer, and tries to disconnect
// the peer, if that is the case. Additionally, disconnection reason is obtained from scorer.
func (s *Service) disconnectBadPeer(ctx context.Context, id peer.ID) {
	if !s.p2p.Peers().IsBad(id) {
		return
	}
	goodbyeCode := types.ErrToGoodbyeCode(s.p2p.Peers().Scorers().ValidationError(id))
	if err := s.sendGoodByeAndDisconnect(ctx, goodbyeCode, id); err != nil {
		log.Debugf("Error when disconnecting with bad peer: %v", err)
	}
}

// A custom goodbye method that is used by our connection handler, in the
// event we receive bad peers.
func (s *Service) sendGoodbye(ctx context.Context, id peer.ID) error {
	return s.sendGoodByeAndDisconnect(ctx, types.GoodbyeCodeGenericError, id)
}

func (s *Service) sendGoodByeAndDisconnect(ctx context.Context, code types.RPCGoodbyeCode, id peer.ID) error {
	if err := s.sendGoodByeMessage(ctx, code, id); err != nil {
		log.WithFields(logrus.Fields{
			"error": err,
			"peer":  id,
		}).Debug("Could not send goodbye message to peer")
	}
	return s.p2p.Disconnect(id)
}

func (s *Service) sendGoodByeMessage(ctx context.Context, code types.RPCGoodbyeCode, id peer.ID) error {
	ctx, cancel := context.WithTimeout(ctx, respTimeout)
	defer cancel()

	stream, err := s.p2p.Send(ctx, &code, p2p.RPCGoodByeTopic, id)
	if err != nil {
		return err
	}
	defer func() {
		if err := helpers.FullClose(stream); err != nil && err.Error() != mux.ErrReset.Error() {
			log.WithError(err).Debugf("Failed to reset stream with protocol %s", stream.Protocol())
		}
	}()
	log := log.WithField("Reason", goodbyeMessage(code))
	log.WithField("peer", stream.Conn().RemotePeer()).Debug("Sending Goodbye message to peer")
	return nil
}

func goodbyeMessage(num types.RPCGoodbyeCode) string {
	reason, ok := types.GoodbyeCodeMessages[num]
	if ok {
		return reason
	}
	return fmt.Sprintf("unknown goodbye value of %d received", num)
}

// determines which backoff time to use depending on the
// goodbye code provided.
func goodByeBackoff(num types.RPCGoodbyeCode) time.Time {
	duration, ok := backOffTime[num]
	if !ok {
		return time.Time{}
	}
	return time.Now().Add(duration)
}