// Copyright 2018 The dexon-consensus Authors
// This file is part of the dexon-consensus library.
//
// The dexon-consensus library is free software: you can redistribute it
// and/or modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// The dexon-consensus library is distributed in the hope that it will be
// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
// General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the dexon-consensus library. If not, see
// <http://www.gnu.org/licenses/>.

// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package dex

import (
	"encoding/hex"
	"errors"
	"fmt"
	"sync"
	"time"

	mapset "github.com/deckarep/golang-set"
	coreCommon "github.com/dexon-foundation/dexon-consensus/common"
	coreTypes "github.com/dexon-foundation/dexon-consensus/core/types"
	dkgTypes "github.com/dexon-foundation/dexon-consensus/core/types/dkg"

	"github.com/dexon-foundation/dexon/common"
	"github.com/dexon-foundation/dexon/core/types"
	"github.com/dexon-foundation/dexon/crypto"
	"github.com/dexon-foundation/dexon/log"
	"github.com/dexon-foundation/dexon/p2p"
	"github.com/dexon-foundation/dexon/p2p/enode"
	"github.com/dexon-foundation/dexon/p2p/enr"
	"github.com/dexon-foundation/dexon/rlp"
)

var (
	errClosed            = errors.New("peer set is closed")
	errAlreadyRegistered = errors.New("peer is already registered")
	errNotRegistered     = errors.New("peer is not registered")
)

const (
	maxKnownTxs     = 32768 // Maximum transactions hashes to keep in the known list (prevent DOS)
	maxKnownRecords = 32768 // Maximum records hashes to keep in the known list (prevent DOS)
	maxKnownBlocks  = 1024  // Maximum block hashes to keep in the known list (prevent DOS)

	/*
		maxKnownLatticeBLocks       = 2048
		maxKnownVotes               = 2048
		maxKnownAgreements          = 10240
		maxKnownRandomnesses        = 10240
		maxKnownDKGPrivateShare     = 1024 // this related to DKG Size
		maxKnownDKGPartialSignature = 1024 // this related to DKG Size
	*/

	// maxQueuedTxs is the maximum number of transaction lists to queue up before
	// dropping broadcasts. This is a sensitive number as a transaction list might
	// contain a single transaction, or thousands.
	maxQueuedTxs = 1024

	maxQueuedRecords = 512

	// maxQueuedProps is the maximum number of block propagations to queue up before
	// dropping broadcasts. There's not much point in queueing stale blocks, so a few
	// that might cover uncles should be enough.
	maxQueuedProps = 4

	// maxQueuedAnns is the maximum number of block announcements to queue up before
	// dropping broadcasts. Similarly to block propagations, there's no point to queue
	// above some healthy uncle limit, so use that.
	maxQueuedAnns = 4

	maxQueuedLatticeBlocks        = 16
	maxQueuedVotes                = 128
	maxQueuedAgreements           = 16
	maxQueuedRandomnesses         = 16
	maxQueuedDKGPrivateShare      = 16
	maxQueuedDKGParitialSignature = 16
	maxQueuedPullBlocks           = 128
	maxQueuedPullVotes            = 128
	maxQueuedPullRandomness       = 128

	handshakeTimeout = 5 * time.Second

	groupConnNum     = 3
	groupConnTimeout = 3 * time.Minute
)

// PeerInfo represents a short summary of the Ethereum sub-protocol metadata known
// about a connected peer.
type PeerInfo struct {
	Version int    `json:"version"` // Ethereum protocol version negotiated
	Number  uint64 `json:"number"`  // Number the peer's blockchain
	Head    string `json:"head"`    // SHA3 hash of the peer's best owned block
}

type setType uint32

const (
	dkgset = iota
	notaryset
)

type peerLabel struct {
	set     setType
	chainID uint32
	round   uint64
}

func (p peerLabel) String() string {
	var t string
	switch p.set {
	case dkgset:
		t = fmt.Sprintf("DKGSet round: %d", p.round)
	case notaryset:
		t = fmt.Sprintf("NotarySet round: %d chain: %d", p.round, p.chainID)
	}
	return t
}

type peer struct {
	id string

	*p2p.Peer
	rw p2p.MsgReadWriter

	version int // Protocol version negotiated

	head   common.Hash
	number uint64
	lock   sync.RWMutex

	knownTxs                   mapset.Set // Set of transaction hashes known to be known by this peer
	knownRecords               mapset.Set // Set of node record known to be known by this peer
	knownBlocks                mapset.Set // Set of block hashes known to be known by this peer
	knownLatticeBlocks         mapset.Set
	knownVotes                 mapset.Set
	knownAgreements            mapset.Set
	knownRandomnesses          mapset.Set
	knownDKGPrivateShares      mapset.Set
	knownDKGPartialSignatures  mapset.Set
	queuedTxs                  chan []*types.Transaction // Queue of transactions to broadcast to the peer
	queuedRecords              chan []*enr.Record        // Queue of node records to broadcast to the peer
	queuedProps                chan *types.Block         // Queue of blocks to broadcast to the peer
	queuedAnns                 chan *types.Block         // Queue of blocks to announce to the peer
	queuedLatticeBlocks        chan *coreTypes.Block
	queuedVotes                chan *coreTypes.Vote
	queuedAgreements           chan *coreTypes.AgreementResult
	queuedRandomnesses         chan *coreTypes.BlockRandomnessResult
	queuedDKGPrivateShares     chan *dkgTypes.PrivateShare
	queuedDKGPartialSignatures chan *dkgTypes.PartialSignature
	queuedPullBlocks           chan coreCommon.Hashes
	queuedPullVotes            chan coreTypes.Position
	queuedPullRandomness       chan coreCommon.Hashes
	term                       chan struct{} // Termination channel to stop the broadcaster
}

func newPeer(version int, p *p2p.Peer, rw p2p.MsgReadWriter) *peer {
	return &peer{
		Peer:                       p,
		rw:                         rw,
		version:                    version,
		id:                         p.ID().String(),
		knownTxs:                   mapset.NewSet(),
		knownRecords:               mapset.NewSet(),
		knownBlocks:                mapset.NewSet(),
		knownLatticeBlocks:         mapset.NewSet(),
		knownVotes:                 mapset.NewSet(),
		knownAgreements:            mapset.NewSet(),
		knownRandomnesses:          mapset.NewSet(),
		knownDKGPrivateShares:      mapset.NewSet(),
		knownDKGPartialSignatures:  mapset.NewSet(),
		queuedTxs:                  make(chan []*types.Transaction, maxQueuedTxs),
		queuedRecords:              make(chan []*enr.Record, maxQueuedRecords),
		queuedProps:                make(chan *types.Block, maxQueuedProps),
		queuedAnns:                 make(chan *types.Block, maxQueuedAnns),
		queuedLatticeBlocks:        make(chan *coreTypes.Block, maxQueuedLatticeBlocks),
		queuedVotes:                make(chan *coreTypes.Vote, maxQueuedVotes),
		queuedAgreements:           make(chan *coreTypes.AgreementResult, maxQueuedAgreements),
		queuedRandomnesses:         make(chan *coreTypes.BlockRandomnessResult, maxQueuedRandomnesses),
		queuedDKGPrivateShares:     make(chan *dkgTypes.PrivateShare, maxQueuedDKGPrivateShare),
		queuedDKGPartialSignatures: make(chan *dkgTypes.PartialSignature, maxQueuedDKGParitialSignature),
		queuedPullBlocks:           make(chan coreCommon.Hashes, maxQueuedPullBlocks),
		queuedPullVotes:            make(chan coreTypes.Position, maxQueuedPullVotes),
		queuedPullRandomness:       make(chan coreCommon.Hashes, maxQueuedPullRandomness),
		term:                       make(chan struct{}),
	}
}

// broadcast is a write loop that multiplexes block propagations, announcements,
// transaction and notary node records broadcasts into the remote peer.
// The goal is to have an async writer that does not lock up node internals.
func (p *peer) broadcast() {
	for {
		select {
		case records := <-p.queuedRecords:
			if err := p.SendNodeRecords(records); err != nil {
				return
			}
			p.Log().Trace("Broadcast node records", "count", len(records))

		case block := <-p.queuedProps:
			if err := p.SendNewBlock(block); err != nil {
				return
			}
			p.Log().Trace("Propagated block", "number", block.Number(), "hash", block.Hash())

		case block := <-p.queuedAnns:
			if err := p.SendNewBlockHashes([]common.Hash{block.Hash()}, []uint64{block.NumberU64()}); err != nil {
				return
			}
			p.Log().Trace("Announced block", "number", block.Number(), "hash", block.Hash())
		case block := <-p.queuedLatticeBlocks:
			if err := p.SendLatticeBlock(block); err != nil {
				return
			}
			p.Log().Trace("Broadcast lattice block")
		case vote := <-p.queuedVotes:
			if err := p.SendVote(vote); err != nil {
				return
			}
			p.Log().Trace("Broadcast vote", "vote", vote.String(), "hash", rlpHash(vote))
		case agreement := <-p.queuedAgreements:
			if err := p.SendAgreement(agreement); err != nil {
				return
			}
			p.Log().Trace("Broadcast agreement")
		case randomness := <-p.queuedRandomnesses:
			if err := p.SendRandomness(randomness); err != nil {
				return
			}
			p.Log().Trace("Broadcast randomness")
		case privateShare := <-p.queuedDKGPrivateShares:
			if err := p.SendDKGPrivateShare(privateShare); err != nil {
				return
			}
			p.Log().Trace("Broadcast DKG private share")
		case psig := <-p.queuedDKGPartialSignatures:
			if err := p.SendDKGPartialSignature(psig); err != nil {
				return
			}
			p.Log().Trace("Broadcast DKG partial signature")
		case hashes := <-p.queuedPullBlocks:
			if err := p.SendPullBlocks(hashes); err != nil {
				return
			}
			p.Log().Trace("Pulling Blocks", "hashes", hashes)
		case pos := <-p.queuedPullVotes:
			if err := p.SendPullVotes(pos); err != nil {
				return
			}
			p.Log().Trace("Pulling Votes", "position", pos)
		case hashes := <-p.queuedPullRandomness:
			if err := p.SendPullRandomness(hashes); err != nil {
				return
			}
			p.Log().Trace("Pulling Randomness", "hashes", hashes)
		case <-p.term:
			return
		case <-time.After(100 * time.Millisecond):
		}
		select {
		case txs := <-p.queuedTxs:
			if err := p.SendTransactions(txs); err != nil {
				return
			}
			p.Log().Trace("Broadcast transactions", "count", len(txs))
		default:
		}
	}
}

// close signals the broadcast goroutine to terminate.
func (p *peer) close() {
	close(p.term)
}

// Info gathers and returns a collection of metadata known about a peer.
func (p *peer) Info() *PeerInfo {
	hash, number := p.Head()

	return &PeerInfo{
		Version: p.version,
		Number:  number,
		Head:    hash.Hex(),
	}
}

// Head retrieves a copy of the current head hash and number of the
// peer.
func (p *peer) Head() (hash common.Hash, number uint64) {
	p.lock.RLock()
	defer p.lock.RUnlock()

	copy(hash[:], p.head[:])
	return hash, p.number
}

// SetHead updates the head hash and number of the peer.
func (p *peer) SetHead(hash common.Hash, number uint64) {
	p.lock.Lock()
	defer p.lock.Unlock()

	copy(p.head[:], hash[:])
	p.number = number
}

// MarkBlock marks a block as known for the peer, ensuring that the block will
// never be propagated to this particular peer.
func (p *peer) MarkBlock(hash common.Hash) {
	// If we reached the memory allowance, drop a previously known block hash
	for p.knownBlocks.Cardinality() >= maxKnownBlocks {
		p.knownBlocks.Pop()
	}
	p.knownBlocks.Add(hash)
}

// MarkTransaction marks a transaction as known for the peer, ensuring that it
// will never be propagated to this particular peer.
func (p *peer) MarkTransaction(hash common.Hash) {
	// If we reached the memory allowance, drop a previously known transaction hash
	for p.knownTxs.Cardinality() >= maxKnownTxs {
		p.knownTxs.Pop()
	}
	p.knownTxs.Add(hash)
}

func (p *peer) MarkNodeRecord(hash common.Hash) {
	for p.knownRecords.Cardinality() >= maxKnownRecords {
		p.knownRecords.Pop()
	}
	p.knownRecords.Add(hash)
}

// SendTransactions sends transactions to the peer and includes the hashes
// in its transaction hash set for future reference.
func (p *peer) SendTransactions(txs types.Transactions) error {
	for _, tx := range txs {
		p.knownTxs.Add(tx.Hash())
	}
	return p2p.Send(p.rw, TxMsg, txs)
}

// AsyncSendTransactions queues list of transactions propagation to a remote
// peer. If the peer's broadcast queue is full, the event is silently dropped.
func (p *peer) AsyncSendTransactions(txs []*types.Transaction) {
	select {
	case p.queuedTxs <- txs:
		for _, tx := range txs {
			p.knownTxs.Add(tx.Hash())
		}
	default:
		p.Log().Debug("Dropping transaction propagation", "count", len(txs))
	}
}

// SendNodeRecords sends the records to the peer and includes the hashes
// in its records hash set for future reference.
func (p *peer) SendNodeRecords(records []*enr.Record) error {
	for _, record := range records {
		p.knownRecords.Add(rlpHash(record))
	}
	return p2p.Send(p.rw, RecordMsg, records)
}

// AsyncSendNodeRecord queues list of notary node records propagation to a
// remote peer. If the peer's broadcast queue is full, the event is silently
// dropped.
func (p *peer) AsyncSendNodeRecords(records []*enr.Record) {
	select {
	case p.queuedRecords <- records:
		for _, record := range records {
			p.knownRecords.Add(rlpHash(record))
		}
	default:
		p.Log().Debug("Dropping node record propagation", "count", len(records))
	}
}

// SendNewBlockHashes announces the availability of a number of blocks through
// a hash notification.
func (p *peer) SendNewBlockHashes(hashes []common.Hash, numbers []uint64) error {
	for _, hash := range hashes {
		p.knownBlocks.Add(hash)
	}
	request := make(newBlockHashesData, len(hashes))
	for i := 0; i < len(hashes); i++ {
		request[i].Hash = hashes[i]
		request[i].Number = numbers[i]
	}
	return p2p.Send(p.rw, NewBlockHashesMsg, request)
}

// AsyncSendNewBlockHash queues the availability of a block for propagation to a
// remote peer. If the peer's broadcast queue is full, the event is silently
// dropped.
func (p *peer) AsyncSendNewBlockHash(block *types.Block) {
	select {
	case p.queuedAnns <- block:
		p.knownBlocks.Add(block.Hash())
	default:
		p.Log().Debug("Dropping block announcement", "number", block.NumberU64(), "hash", block.Hash())
	}
}

// SendNewBlock propagates an entire block to a remote peer.
func (p *peer) SendNewBlock(block *types.Block) error {
	p.knownBlocks.Add(block.Hash())
	return p2p.Send(p.rw, NewBlockMsg, block)
}

// AsyncSendNewBlock queues an entire block for propagation to a remote peer. If
// the peer's broadcast queue is full, the event is silently dropped.
func (p *peer) AsyncSendNewBlock(block *types.Block) {
	select {
	case p.queuedProps <- block:
		p.knownBlocks.Add(block.Hash())
	default:
		p.Log().Debug("Dropping block propagation", "number", block.NumberU64(), "hash", block.Hash())
	}
}

func (p *peer) SendLatticeBlock(block *coreTypes.Block) error {
	p.knownLatticeBlocks.Add(rlpHash(block))
	return p2p.Send(p.rw, LatticeBlockMsg, block)
}

func (p *peer) AsyncSendLatticeBlock(block *coreTypes.Block) {
	select {
	case p.queuedLatticeBlocks <- block:
		p.knownLatticeBlocks.Add(rlpHash(block))
	default:
		p.Log().Debug("Dropping lattice block propagation")
	}
}

func (p *peer) SendVote(vote *coreTypes.Vote) error {
	p.knownVotes.Add(rlpHash(vote))
	return p2p.Send(p.rw, VoteMsg, vote)
}

func (p *peer) AsyncSendVote(vote *coreTypes.Vote) {
	select {
	case p.queuedVotes <- vote:
		p.knownVotes.Add(rlpHash(vote))
	default:
		p.Log().Debug("Dropping vote propagation")
	}
}

func (p *peer) SendAgreement(agreement *coreTypes.AgreementResult) error {
	p.knownAgreements.Add(rlpHash(agreement))
	return p2p.Send(p.rw, AgreementMsg, agreement)
}

func (p *peer) AsyncSendAgreement(agreement *coreTypes.AgreementResult) {
	select {
	case p.queuedAgreements <- agreement:
		p.knownAgreements.Add(rlpHash(agreement))
	default:
		p.Log().Debug("Dropping agreement result")
	}
}

func (p *peer) SendRandomness(randomness *coreTypes.BlockRandomnessResult) error {
	p.knownRandomnesses.Add(rlpHash(randomness))
	return p2p.Send(p.rw, RandomnessMsg, randomness)
}

func (p *peer) AsyncSendRandomness(randomness *coreTypes.BlockRandomnessResult) {
	select {
	case p.queuedRandomnesses <- randomness:
		p.knownRandomnesses.Add(rlpHash(randomness))
	default:
		p.Log().Debug("Dropping randomness result")
	}
}

func (p *peer) SendDKGPrivateShare(privateShare *dkgTypes.PrivateShare) error {
	p.knownDKGPrivateShares.Add(rlpHash(privateShare))
	return p2p.Send(p.rw, DKGPrivateShareMsg, privateShare)
}

func (p *peer) AsyncSendDKGPrivateShare(privateShare *dkgTypes.PrivateShare) {
	select {
	case p.queuedDKGPrivateShares <- privateShare:
		p.knownDKGPrivateShares.Add(rlpHash(privateShare))
	default:
		p.Log().Debug("Dropping DKG private share")
	}
}

func (p *peer) SendDKGPartialSignature(psig *dkgTypes.PartialSignature) error {
	p.knownDKGPartialSignatures.Add(rlpHash(psig))
	return p2p.Send(p.rw, DKGPartialSignatureMsg, psig)
}

func (p *peer) AsyncSendDKGPartialSignature(psig *dkgTypes.PartialSignature) {
	select {
	case p.queuedDKGPartialSignatures <- psig:
		p.knownDKGPartialSignatures.Add(rlpHash(psig))
	default:
		p.Log().Debug("Dropping DKG partial signature")
	}
}

func (p *peer) SendPullBlocks(hashes coreCommon.Hashes) error {
	return p2p.Send(p.rw, PullBlocksMsg, hashes)
}

func (p *peer) AsyncSendPullBlocks(hashes coreCommon.Hashes) {
	select {
	case p.queuedPullBlocks <- hashes:
	default:
		p.Log().Debug("Dropping Pull Blocks")
	}
}

func (p *peer) SendPullVotes(pos coreTypes.Position) error {
	return p2p.Send(p.rw, PullVotesMsg, pos)
}

func (p *peer) AsyncSendPullVotes(pos coreTypes.Position) {
	select {
	case p.queuedPullVotes <- pos:
	default:
		p.Log().Debug("Dropping Pull Votes")
	}
}

func (p *peer) SendPullRandomness(hashes coreCommon.Hashes) error {
	return p2p.Send(p.rw, PullRandomnessMsg, hashes)
}

func (p *peer) AsyncSendPullRandomness(hashes coreCommon.Hashes) {
	select {
	case p.queuedPullRandomness <- hashes:
	default:
		p.Log().Debug("Dropping Pull Randomness")
	}
}

// SendBlockHeaders sends a batch of block headers to the remote peer.
func (p *peer) SendBlockHeaders(headers []*types.HeaderWithGovState) error {
	return p2p.Send(p.rw, BlockHeadersMsg, headers)
}

// SendBlockBodies sends a batch of block contents to the remote peer.
func (p *peer) SendBlockBodies(bodies []*blockBody) error {
	return p2p.Send(p.rw, BlockBodiesMsg, blockBodiesData(bodies))
}

// SendBlockBodiesRLP sends a batch of block contents to the remote peer from
// an already RLP encoded format.
func (p *peer) SendBlockBodiesRLP(bodies []rlp.RawValue) error {
	return p2p.Send(p.rw, BlockBodiesMsg, bodies)
}

// SendNodeDataRLP sends a batch of arbitrary internal data, corresponding to the
// hashes requested.
func (p *peer) SendNodeData(data [][]byte) error {
	return p2p.Send(p.rw, NodeDataMsg, data)
}

// SendReceiptsRLP sends a batch of transaction receipts, corresponding to the
// ones requested from an already RLP encoded format.
func (p *peer) SendReceiptsRLP(receipts []rlp.RawValue) error {
	return p2p.Send(p.rw, ReceiptsMsg, receipts)
}

func (p *peer) SendGovState(govState *types.GovState) error {
	return p2p.Send(p.rw, GovStateMsg, govState)
}

// RequestOneHeader is a wrapper around the header query functions to fetch a
// single header. It is used solely by the fetcher.
func (p *peer) RequestOneHeader(hash common.Hash) error {
	p.Log().Debug("Fetching single header", "hash", hash)
	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: hash}, Amount: uint64(1), Skip: uint64(0), Reverse: false, WithGov: false})
}

// RequestHeadersByHash fetches a batch of blocks' headers corresponding to the
// specified header query, based on the hash of an origin block.
func (p *peer) RequestHeadersByHash(origin common.Hash, amount int, skip int, reverse, withGov bool) error {
	p.Log().Debug("Fetching batch of headers", "count", amount, "fromhash", origin, "skip", skip, "reverse", reverse, "withgov", withGov)
	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse, WithGov: withGov})
}

// RequestHeadersByNumber fetches a batch of blocks' headers corresponding to the
// specified header query, based on the number of an origin block.
func (p *peer) RequestHeadersByNumber(origin uint64, amount int, skip int, reverse, withGov bool) error {
	p.Log().Debug("Fetching batch of headers", "count", amount, "fromnum", origin, "skip", skip, "reverse", reverse, "withgov", withGov)
	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Number: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse, WithGov: withGov})
}

func (p *peer) RequestGovStateByHash(hash common.Hash) error {
	p.Log().Debug("Fetching one gov state", "hash", hash)
	return p2p.Send(p.rw, GetGovStateMsg, hash)
}

// RequestBodies fetches a batch of blocks' bodies corresponding to the hashes
// specified.
func (p *peer) RequestBodies(hashes []common.Hash) error {
	p.Log().Debug("Fetching batch of block bodies", "count", len(hashes))
	return p2p.Send(p.rw, GetBlockBodiesMsg, hashes)
}

// RequestNodeData fetches a batch of arbitrary data from a node's known state
// data, corresponding to the specified hashes.
func (p *peer) RequestNodeData(hashes []common.Hash) error {
	p.Log().Debug("Fetching batch of state data", "count", len(hashes))
	return p2p.Send(p.rw, GetNodeDataMsg, hashes)
}

// RequestReceipts fetches a batch of transaction receipts from a remote node.
func (p *peer) RequestReceipts(hashes []common.Hash) error {
	p.Log().Debug("Fetching batch of receipts", "count", len(hashes))
	return p2p.Send(p.rw, GetReceiptsMsg, hashes)
}

// Handshake executes the eth protocol handshake, negotiating version number,
// network IDs, difficulties, head and genesis blocks.
func (p *peer) Handshake(network uint64, dMoment uint64, number uint64, head common.Hash, genesis common.Hash) error {
	// Send out own handshake in a new thread
	errc := make(chan error, 2)
	var status statusData // safe to read after two values have been received from errc

	go func() {
		errc <- p2p.Send(p.rw, StatusMsg, &statusData{
			ProtocolVersion: uint32(p.version),
			NetworkId:       network,
			DMoment:         dMoment,
			Number:          number,
			CurrentBlock:    head,
			GenesisBlock:    genesis,
		})
	}()
	go func() {
		errc <- p.readStatus(network, dMoment, &status, genesis)
	}()
	timeout := time.NewTimer(handshakeTimeout)
	defer timeout.Stop()
	for i := 0; i < 2; i++ {
		select {
		case err := <-errc:
			if err != nil {
				return err
			}
		case <-timeout.C:
			return p2p.DiscReadTimeout
		}
	}
	p.number, p.head = status.Number, status.CurrentBlock
	return nil
}

func (p *peer) readStatus(network uint64, dMoment uint64, status *statusData, genesis common.Hash) (err error) {
	msg, err := p.rw.ReadMsg()
	if err != nil {
		return err
	}
	if msg.Code != StatusMsg {
		return errResp(ErrNoStatusMsg, "first msg has code %x (!= %x)", msg.Code, StatusMsg)
	}
	if msg.Size > ProtocolMaxMsgSize {
		return errResp(ErrMsgTooLarge, "%v > %v", msg.Size, ProtocolMaxMsgSize)
	}
	// Decode the handshake and make sure everything matches
	if err := msg.Decode(&status); err != nil {
		return errResp(ErrDecode, "msg %v: %v", msg, err)
	}
	if status.GenesisBlock != genesis {
		return errResp(ErrGenesisBlockMismatch, "%x (!= %x)", status.GenesisBlock[:8], genesis[:8])
	}
	if status.NetworkId != network {
		return errResp(ErrNetworkIdMismatch, "%d (!= %d)", status.NetworkId, network)
	}
	if status.DMoment != dMoment {
		return errResp(ErrDMomentMismatch, "%d (!= %d)", status.DMoment, dMoment)
	}
	if int(status.ProtocolVersion) != p.version {
		return errResp(ErrProtocolVersionMismatch, "%d (!= %d)", status.ProtocolVersion, p.version)
	}
	return nil
}

// String implements fmt.Stringer.
func (p *peer) String() string {
	return fmt.Sprintf("Peer %s [%s]", p.id,
		fmt.Sprintf("dex/%2d", p.version),
	)
}

// peerSet represents the collection of active peers currently participating in
// the Ethereum sub-protocol.
type peerSet struct {
	peers  map[string]*peer
	lock   sync.RWMutex
	closed bool
	tab    *nodeTable
	selfPK string

	srvr p2pServer
	gov  governance

	label2Nodes    map[peerLabel]map[string]*enode.Node
	directConn     map[peerLabel]struct{}
	groupConnPeers map[peerLabel]map[string]time.Time
	allDirectPeers map[string]map[peerLabel]struct{}
}

// newPeerSet creates a new peer set to track the active participants.
func newPeerSet(gov governance, srvr p2pServer, tab *nodeTable) *peerSet {
	return &peerSet{
		peers:          make(map[string]*peer),
		gov:            gov,
		srvr:           srvr,
		tab:            tab,
		selfPK:         hex.EncodeToString(crypto.FromECDSAPub(&srvr.GetPrivateKey().PublicKey)),
		label2Nodes:    make(map[peerLabel]map[string]*enode.Node),
		directConn:     make(map[peerLabel]struct{}),
		groupConnPeers: make(map[peerLabel]map[string]time.Time),
		allDirectPeers: make(map[string]map[peerLabel]struct{}),
	}
}

// Register injects a new peer into the working set, or returns an error if the
// peer is already known. If a new peer it registered, its broadcast loop is also
// started.
func (ps *peerSet) Register(p *peer) error {
	ps.lock.Lock()
	defer ps.lock.Unlock()

	if ps.closed {
		return errClosed
	}
	if _, ok := ps.peers[p.id]; ok {
		return errAlreadyRegistered
	}
	ps.peers[p.id] = p
	go p.broadcast()

	return nil
}

// Unregister removes a remote peer from the active set, disabling any further
// actions to/from that particular entity.
func (ps *peerSet) Unregister(id string) error {
	ps.lock.Lock()
	defer ps.lock.Unlock()

	p, ok := ps.peers[id]
	if !ok {
		return errNotRegistered
	}
	delete(ps.peers, id)
	p.close()

	return nil
}

// Peer retrieves the registered peer with the given id.
func (ps *peerSet) Peer(id string) *peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()

	return ps.peers[id]
}

// Len returns if the current number of peers in the set.
func (ps *peerSet) Len() int {
	ps.lock.RLock()
	defer ps.lock.RUnlock()

	return len(ps.peers)
}

// Peers retrieves all of the peers.
func (ps *peerSet) Peers() []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()

	list := make([]*peer, 0, len(ps.peers))
	for _, p := range ps.peers {
		list = append(list, p)
	}
	return list
}

// PeersWithoutBlock retrieves a list of peers that do not have a given block in
// their set of known hashes.
func (ps *peerSet) PeersWithoutBlock(hash common.Hash) []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()

	list := make([]*peer, 0, len(ps.peers))
	for _, p := range ps.peers {
		if !p.knownBlocks.Contains(hash) {
			list = append(list, p)
		}
	}
	return list
}

// PeersWithoutTx retrieves a list of peers that do not have a given transaction
// in their set of known hashes.
func (ps *peerSet) PeersWithoutTx(hash common.Hash) []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()

	list := make([]*peer, 0, len(ps.peers))
	for _, p := range ps.peers {
		if !p.knownTxs.Contains(hash) {
			list = append(list, p)
		}
	}
	return list
}

func (ps *peerSet) PeersWithLabel(label peerLabel) []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()
	list := make([]*peer, 0, len(ps.label2Nodes[label]))
	for id := range ps.label2Nodes[label] {
		if p, ok := ps.peers[id]; ok {
			list = append(list, p)
		}
	}
	return list
}

func (ps *peerSet) PeersWithoutVote(hash common.Hash, label peerLabel) []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()

	list := make([]*peer, 0, len(ps.label2Nodes[label]))
	for id := range ps.label2Nodes[label] {
		if p, ok := ps.peers[id]; ok {
			if !p.knownVotes.Contains(hash) {
				list = append(list, p)
			}
		}
	}
	return list
}

// PeersWithoutNodeRecord retrieves a list of peers that do not have a
// given record in their set of known hashes.
func (ps *peerSet) PeersWithoutNodeRecord(hash common.Hash) []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()
	list := make([]*peer, 0, len(ps.peers))
	for _, p := range ps.peers {
		if !p.knownRecords.Contains(hash) {
			list = append(list, p)
		}
	}
	return list
}

func (ps *peerSet) PeersWithoutLatticeBlock(hash common.Hash) []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()
	list := make([]*peer, 0, len(ps.peers))
	for _, p := range ps.peers {
		if !p.knownLatticeBlocks.Contains(hash) {
			list = append(list, p)
		}
	}
	return list
}

func (ps *peerSet) PeersWithoutAgreement(hash common.Hash) []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()
	list := make([]*peer, 0, len(ps.peers))
	for _, p := range ps.peers {
		if !p.knownAgreements.Contains(hash) {
			list = append(list, p)
		}
	}
	return list
}

func (ps *peerSet) PeersWithoutRandomness(hash common.Hash) []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()
	list := make([]*peer, 0, len(ps.peers))
	for _, p := range ps.peers {
		if !p.knownRandomnesses.Contains(hash) {
			list = append(list, p)
		}
	}
	return list
}

func (ps *peerSet) PeersWithoutDKGPartialSignature(hash common.Hash) []*peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()
	list := make([]*peer, 0, len(ps.peers))
	for _, p := range ps.peers {
		if !p.knownDKGPartialSignatures.Contains(hash) {
			list = append(list, p)
		}
	}
	return list
}

// BestPeer retrieves the known peer with the currently highest total difficulty.
func (ps *peerSet) BestPeer() *peer {
	ps.lock.RLock()
	defer ps.lock.RUnlock()

	var (
		bestPeer   *peer
		bestNumber uint64
	)
	for _, p := range ps.peers {
		if _, number := p.Head(); bestPeer == nil || number > bestNumber {
			bestPeer, bestNumber = p, number
		}
	}
	return bestPeer
}

// Close disconnects all peers.
// No new peers can be registered after Close has returned.
func (ps *peerSet) Close() {
	ps.lock.Lock()
	defer ps.lock.Unlock()

	for _, p := range ps.peers {
		p.Disconnect(p2p.DiscQuitting)
	}
	ps.closed = true
}

func (ps *peerSet) BuildConnection(round uint64) {
	ps.lock.Lock()
	defer ps.lock.Unlock()

	dkgLabel := peerLabel{set: dkgset, round: round}
	if _, ok := ps.label2Nodes[dkgLabel]; !ok {
		dkgPKs, err := ps.gov.DKGSet(round)
		if err != nil {
			log.Error("get DKG set fail", "round", round, "err", err)
		}

		nodes := ps.pksToNodes(dkgPKs)
		ps.label2Nodes[dkgLabel] = nodes

		if _, exists := nodes[ps.srvr.Self().ID().String()]; exists {
			ps.buildDirectConn(dkgLabel)
		} else {
			ps.buildGroupConn(dkgLabel)
		}
	}

	for chainID := uint32(0); chainID < ps.gov.GetNumChains(round); chainID++ {
		notaryLabel := peerLabel{set: notaryset, chainID: chainID, round: round}
		if _, ok := ps.label2Nodes[notaryLabel]; !ok {
			notaryPKs, err := ps.gov.NotarySet(round, chainID)
			if err != nil {
				log.Error("get notary set fail",
					"round", round, "chainID", chainID, "err", err)
				continue
			}

			nodes := ps.pksToNodes(notaryPKs)
			ps.label2Nodes[notaryLabel] = nodes

			if _, exists := nodes[ps.srvr.Self().ID().String()]; exists {
				ps.buildDirectConn(notaryLabel)
			} else {
				ps.buildGroupConn(notaryLabel)
			}
		}
	}
}

func (ps *peerSet) ForgetConnection(round uint64) {
	ps.lock.Lock()
	defer ps.lock.Unlock()

	for label := range ps.directConn {
		if label.round <= round {
			ps.forgetDirectConn(label)
		}
	}

	for label := range ps.groupConnPeers {
		if label.round <= round {
			ps.forgetGroupConn(label)
		}
	}

	for label := range ps.label2Nodes {
		if label.round <= round {
			delete(ps.label2Nodes, label)
		}
	}
}

func (ps *peerSet) EnsureGroupConn() {
	ps.lock.Lock()
	defer ps.lock.Unlock()

	now := time.Now()
	for label, peers := range ps.groupConnPeers {
		// Remove timeout group conn peer.
		for id, addtime := range peers {
			if ps.peers[id] == nil && time.Since(addtime) > groupConnTimeout {
				ps.removeDirectPeer(id, label)
				delete(ps.groupConnPeers[label], id)
			}
		}

		// Add new group conn peer.
		for id := range ps.label2Nodes[label] {
			if len(ps.groupConnPeers[label]) >= groupConnNum {
				break
			}
			ps.groupConnPeers[label][id] = now
			ps.addDirectPeer(id, label)
		}
	}
}

func (ps *peerSet) Refresh() {
	ps.lock.Lock()
	defer ps.lock.Unlock()
	for id := range ps.allDirectPeers {
		if ps.peers[id] == nil {
			if node := ps.tab.GetNode(enode.HexID(id)); node != nil {
				ps.srvr.AddDirectPeer(node)
			}
		}
	}
}

func (ps *peerSet) buildDirectConn(label peerLabel) {
	ps.directConn[label] = struct{}{}
	for id := range ps.label2Nodes[label] {
		ps.addDirectPeer(id, label)
	}
}

func (ps *peerSet) forgetDirectConn(label peerLabel) {
	for id := range ps.label2Nodes[label] {
		ps.removeDirectPeer(id, label)
	}
	delete(ps.directConn, label)
}

func (ps *peerSet) buildGroupConn(label peerLabel) {
	peers := make(map[string]time.Time)
	now := time.Now()
	for id := range ps.label2Nodes[label] {
		peers[id] = now
		ps.addDirectPeer(id, label)
		if len(peers) >= groupConnNum {
			break
		}
	}
	ps.groupConnPeers[label] = peers
}

func (ps *peerSet) forgetGroupConn(label peerLabel) {
	for id := range ps.groupConnPeers[label] {
		ps.removeDirectPeer(id, label)
	}
	delete(ps.groupConnPeers, label)
}

func (ps *peerSet) addDirectPeer(id string, label peerLabel) {
	if len(ps.allDirectPeers[id]) > 0 {
		ps.allDirectPeers[id][label] = struct{}{}
		return
	}
	ps.allDirectPeers[id] = map[peerLabel]struct{}{label: {}}

	node := ps.tab.GetNode(enode.HexID(id))
	if node == nil {
		node = ps.label2Nodes[label][id]
	}
	ps.srvr.AddDirectPeer(node)
}

func (ps *peerSet) removeDirectPeer(id string, label peerLabel) {
	if len(ps.allDirectPeers[id]) == 0 {
		return
	}

	delete(ps.allDirectPeers[id], label)
	if len(ps.allDirectPeers[id]) == 0 {
		ps.srvr.RemoveDirectPeer(ps.label2Nodes[label][id])
		delete(ps.allDirectPeers, id)
	}
}

func (ps *peerSet) pksToNodes(pks map[string]struct{}) map[string]*enode.Node {
	nodes := map[string]*enode.Node{}
	for pk := range pks {
		n := ps.newEmptyNode(pk)
		if n.ID() == ps.srvr.Self().ID() {
			n = ps.srvr.Self()
		}
		nodes[n.ID().String()] = n
	}
	return nodes
}

func (ps *peerSet) newEmptyNode(pk string) *enode.Node {
	b, err := hex.DecodeString(pk)
	if err != nil {
		panic(err)
	}

	pubkey, err := crypto.UnmarshalPubkey(b)
	if err != nil {
		panic(err)
	}
	return enode.NewV4(pubkey, nil, 0, 0)
}

func (ps *peerSet) Status() {
	ps.lock.Lock()
	defer ps.lock.Unlock()
	for label := range ps.directConn {
		l := label.String()
		for id := range ps.label2Nodes[label] {
			_, ok := ps.peers[id]
			log.Debug("direct conn", "label", l, "id", id, "connected", ok)
		}
	}

	for label, peers := range ps.groupConnPeers {
		l := label.String()
		for id := range peers {
			_, ok := ps.peers[id]
			log.Debug("group conn", "label", l, "id", id, "connected", ok)
		}
	}

	connected := 0
	for id := range ps.allDirectPeers {
		if _, ok := ps.peers[id]; ok {
			connected++
		}
	}
	log.Debug("all direct peers",
		"connected", connected, "all", len(ps.allDirectPeers))
}