erigon-pulse/txpool/pool.go

/*
   Copyright 2021 Erigon contributors

   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 txpool

import (
	"container/heap"
	"context"
	"fmt"
	"math"
	"sync"
	"time"

	"github.com/google/btree"
	lru "github.com/hashicorp/golang-lru"
	"github.com/holiman/uint256"
	"go.uber.org/atomic"
)

// Pool is interface for the transaction pool
// This interface exists for the convinience of testing, and not yet because
// there are multiple implementations
type Pool interface {
	// IdHashKnown check whether transaction with given Id hash is known to the pool
	IdHashKnown(hash []byte) bool
	GetRlp(hash []byte) []byte
	Add(newTxs TxSlots) error
	OnNewBlock(stateChanges map[string]senderInfo, unwindTxs, minedTxs TxSlots, protocolBaseFee, blockBaseFee, blockHeight uint64) error

	AddNewGoodPeer(peerID PeerID)
}

// SubPoolMarker ordered bitset responsible to sort transactions by sub-pools. Bits meaning:
// 1. Minimum fee requirement. Set to 1 if feeCap of the transaction is no less than in-protocol parameter of minimal base fee. Set to 0 if feeCap is less than minimum base fee, which means this transaction will never be included into this particular chain.
// 2. Absence of nonce gaps. Set to 1 for transactions whose nonce is N, state nonce for the sender is M, and there are transactions for all nonces between M and N from the same sender. Set to 0 is the transaction's nonce is divided from the state nonce by one or more nonce gaps.
// 3. Sufficient balance for gas. Set to 1 if the balance of sender's account in the state is B, nonce of the sender in the state is M, nonce of the transaction is N, and the sum of feeCap x gasLimit + transferred_value of all transactions from this sender with nonces N+1 ... M is no more than B. Set to 0 otherwise. In other words, this bit is set if there is currently a guarantee that the transaction and all its required prior transactions will be able to pay for gas.
// 4. Dynamic fee requirement. Set to 1 if feeCap of the transaction is no less than baseFee of the currently pending block. Set to 0 otherwise.
// 5. Local transaction. Set to 1 if transaction is local.
type SubPoolMarker uint8

const (
	EnoughFeeCapProtocol = 0b10000
	NoNonceGaps          = 0b01000
	EnoughBalance        = 0b00100
	EnoughFeeCapBlock    = 0b00010
	IsLocal              = 0b00001
)

// metaTx holds transaction and some metadata
type metaTx struct {
	subPool        SubPoolMarker
	effectiveTip   uint64 // max(minTip, minFeeCap - baseFee)
	Tx             *TxSlot
	bestIndex      int
	worstIndex     int
	currentSubPool SubPoolType
}

func newMetaTx(slot *TxSlot, isLocal bool) *metaTx {
	mt := &metaTx{Tx: slot, worstIndex: -1, bestIndex: -1}
	if isLocal {
		mt.subPool = IsLocal
	}
	return mt
}

type SubPoolType uint8

const PendingSubPool SubPoolType = 1
const BaseFeeSubPool SubPoolType = 2
const QueuedSubPool SubPoolType = 3

const PendingSubPoolLimit = 1024
const BaseFeeSubPoolLimit = 1024
const QueuedSubPoolLimit = 1024

type nonce2Tx struct{ *btree.BTree }

type senderInfo struct {
	balance    uint256.Int
	nonce      uint64
	txNonce2Tx *nonce2Tx // sorted map of nonce => *metaTx
}

//nolint
func newSenderInfo(nonce uint64, balance uint256.Int) *senderInfo {
	return &senderInfo{nonce: nonce, balance: balance, txNonce2Tx: &nonce2Tx{btree.New(32)}}
}

type nonce2TxItem struct{ *metaTx }

func (i *nonce2TxItem) Less(than btree.Item) bool {
	return i.metaTx.Tx.nonce < than.(*nonce2TxItem).metaTx.Tx.nonce
}

// TxPool - holds all pool-related data structures and lock-based tiny methods
// most of logic implemented by pure tests-friendly functions
type TxPool struct {
	lock *sync.RWMutex

	blockHeight     atomic.Uint64
	protocolBaseFee atomic.Uint64
	blockBaseFee    atomic.Uint64

	senderIDs                map[string]uint64
	senderInfo               map[uint64]*senderInfo
	byHash                   map[string]*metaTx // tx_hash => tx
	pending, baseFee, queued *SubPool

	// track isLocal flag of already mined transactions. used at unwind.
	localsHistory *lru.Cache

	// fields for transaction propagation
	recentlyConnectedPeers *recentlyConnectedPeers
	newTxs                 chan Hashes
	//lastTxPropagationTimestamp time.Time
}

func New(newTxs chan Hashes) *TxPool {
	localsHistory, _ := lru.New(1024)
	return &TxPool{
		lock:                   &sync.RWMutex{},
		senderInfo:             map[uint64]*senderInfo{},
		byHash:                 map[string]*metaTx{},
		localsHistory:          localsHistory,
		recentlyConnectedPeers: &recentlyConnectedPeers{},
		pending:                NewSubPool(),
		baseFee:                NewSubPool(),
		queued:                 NewSubPool(),
		newTxs:                 newTxs,
	}
}

func (p *TxPool) GetRlp(hash []byte) []byte {
	p.lock.RLock()
	defer p.lock.RUnlock()

	txn, ok := p.byHash[string(hash)]
	if !ok {
		return nil
	}
	return txn.Tx.rlp
}
func (p *TxPool) AppendLocalHashes(buf []byte) {
	p.lock.RLock()
	defer p.lock.RUnlock()
	i := 0
	for hash, txn := range p.byHash {
		if txn.subPool&IsLocal == 0 {
			continue
		}
		copy(buf[i*32:(i+1)*32], hash)
		i++
	}
}
func (p *TxPool) AppendRemoteHashes(buf []byte) {
	p.lock.RLock()
	defer p.lock.RUnlock()

	i := 0
	for hash, txn := range p.byHash {
		if txn.subPool&IsLocal != 0 {
			continue
		}
		copy(buf[i*32:(i+1)*32], hash)
		i++
	}
}
func (p *TxPool) AppendAllHashes(buf []byte) {
	p.AppendLocalHashes(buf)
	p.AppendRemoteHashes(buf[len(buf):])
}
func (p *TxPool) IdHashKnown(hash []byte) bool {
	p.lock.RLock()
	defer p.lock.RUnlock()

	_, ok := p.byHash[string(hash)]
	return ok
}
func (p *TxPool) IdHashIsLocal(hash []byte) bool {
	p.lock.RLock()
	defer p.lock.RUnlock()

	txn, ok := p.byHash[string(hash)]
	if !ok {
		return false
	}
	return txn.subPool&IsLocal != 0
}
func (p *TxPool) OnNewPeer(peerID PeerID) { p.recentlyConnectedPeers.AddPeer(peerID) }

func (p *TxPool) Add(newTxs TxSlots) error {
	p.lock.Lock()
	defer p.lock.Unlock()
	if err := newTxs.Valid(); err != nil {
		return err
	}

	protocolBaseFee, blockBaseFee := p.protocolBaseFee.Load(), p.blockBaseFee.Load()
	if protocolBaseFee == 0 || blockBaseFee == 0 {
		return fmt.Errorf("non-zero base fee")
	}

	setTxSenderID(p.senderIDs, p.senderInfo, newTxs)
	if err := onNewTxs(p.senderInfo, newTxs, protocolBaseFee, blockBaseFee, p.pending, p.baseFee, p.queued, p.byHash, p.localsHistory); err != nil {
		return err
	}

	notifyNewTxs := make(Hashes, 0, 32*len(newTxs.txs))
	for i := range newTxs.txs {
		_, ok := p.byHash[string(newTxs.txs[i].idHash[:])]
		if !ok {
			continue
		}
		notifyNewTxs = append(notifyNewTxs, newTxs.txs[i].idHash[:]...)
	}
	if len(notifyNewTxs) > 0 {
		select {
		case p.newTxs <- notifyNewTxs:
		default:
		}
	}

	return nil
}
func onNewTxs(senderInfo map[uint64]*senderInfo, newTxs TxSlots, protocolBaseFee, blockBaseFee uint64, pending, baseFee, queued *SubPool, byHash map[string]*metaTx, localsHistory *lru.Cache) error {
	for i := range newTxs.txs {
		if newTxs.txs[i].senderID == 0 {
			return fmt.Errorf("senderID can't be zero")
		}
	}

	unsafeAddToPool(senderInfo, newTxs, queued, QueuedSubPool, func(i *metaTx) {
		if _, ok := localsHistory.Get(i.Tx.idHash); ok {
			//TODO: also check if sender is in list of local-senders
			i.subPool |= IsLocal
		}
		byHash[string(i.Tx.idHash[:])] = i
		replaced := senderInfo[i.Tx.senderID].txNonce2Tx.ReplaceOrInsert(&nonce2TxItem{i})
		if replaced != nil {
			replacedMT := replaced.(*nonce2TxItem).metaTx
			delete(byHash, string(replacedMT.Tx.idHash[:]))
			switch replacedMT.currentSubPool {
			case PendingSubPool:
				pending.UnsafeRemove(replacedMT)
			case BaseFeeSubPool:
				baseFee.UnsafeRemove(replacedMT)
			case QueuedSubPool:
				queued.UnsafeRemove(replacedMT)
			default:
				//already removed
			}
		}
	})

	for i := range senderInfo {
		// TODO: aggregate changed senders before call this func
		onSenderChange(senderInfo[i], protocolBaseFee, blockBaseFee)
	}

	pending.EnforceInvariants()
	baseFee.EnforceInvariants()
	queued.EnforceInvariants()

	promote(pending, baseFee, queued, func(i *metaTx) {
		delete(byHash, string(i.Tx.idHash[:]))
		senderInfo[i.Tx.senderID].txNonce2Tx.Delete(&nonce2TxItem{i})
		if i.subPool&IsLocal != 0 {
			//TODO: only add to history if sender is not in list of local-senders
			localsHistory.Add(i.Tx.idHash, struct{}{})
		}
	})

	return nil
}
func (p *TxPool) OnNewBlock(stateChanges map[string]senderInfo, unwindTxs, minedTxs TxSlots, protocolBaseFee, blockBaseFee, blockHeight uint64) error {
	p.lock.Lock()
	defer p.lock.Unlock()
	if err := unwindTxs.Valid(); err != nil {
		return err
	}
	if err := minedTxs.Valid(); err != nil {
		return err
	}

	p.blockHeight.Store(blockHeight)
	p.protocolBaseFee.Store(protocolBaseFee)
	p.blockBaseFee.Store(blockBaseFee)

	setTxSenderID(p.senderIDs, p.senderInfo, unwindTxs)
	setTxSenderID(p.senderIDs, p.senderInfo, minedTxs)
	for addr, id := range p.senderIDs { // merge state changes
		if v, ok := stateChanges[addr]; ok {
			p.senderInfo[id] = &v
		}
	}
	if err := onNewBlock(p.senderInfo, unwindTxs, minedTxs.txs, protocolBaseFee, blockBaseFee, p.pending, p.baseFee, p.queued, p.byHash, p.localsHistory); err != nil {
		return err
	}

	notifyNewTxs := make(Hashes, 0, 32*len(unwindTxs.txs))
	for i := range unwindTxs.txs {
		_, ok := p.byHash[string(unwindTxs.txs[i].idHash[:])]
		if !ok {
			continue
		}
		notifyNewTxs = append(notifyNewTxs, unwindTxs.txs[i].idHash[:]...)
	}
	if len(notifyNewTxs) > 0 {
		select {
		case p.newTxs <- notifyNewTxs:
		default:
		}
	}

	return nil
}
func setTxSenderID(senderIDs map[string]uint64, senderInfo map[uint64]*senderInfo, txs TxSlots) {
	for i := range txs.txs {
		addr := string(txs.senders.At(i))

		id, ok := senderIDs[addr]
		if !ok {
			for i := range senderInfo { //TODO: create field for it?
				if id < i {
					id = i
				}
			}
			id++
			senderIDs[addr] = id
		}
		txs.txs[i].senderID = id
	}
}

func onNewBlock(senderInfo map[uint64]*senderInfo, unwindTxs TxSlots, minedTxs []*TxSlot, protocolBaseFee, blockBaseFee uint64, pending, baseFee, queued *SubPool, byHash map[string]*metaTx, localsHistory *lru.Cache) error {
	for i := range unwindTxs.txs {
		if unwindTxs.txs[i].senderID == 0 {
			return fmt.Errorf("onNewBlock.unwindTxs: senderID can't be zero")
		}
	}
	for i := range minedTxs {
		if minedTxs[i].senderID == 0 {
			return fmt.Errorf("onNewBlock.minedTxs: senderID can't be zero")
		}
	}

	removeMined(senderInfo, minedTxs, pending, baseFee, queued, func(i *metaTx) {
		delete(byHash, string(i.Tx.idHash[:]))
		senderInfo[i.Tx.senderID].txNonce2Tx.Delete(&nonce2TxItem{i})
		if i.subPool&IsLocal != 0 {
			//TODO: only add to history if sender is not in list of local-senders
			localsHistory.Add(i.Tx.idHash, struct{}{})
		}
	})

	// This can be thought of a reverse operation from the one described before.
	// When a block that was deemed "the best" of its height, is no longer deemed "the best", the
	// transactions contained in it, are now viable for inclusion in other blocks, and therefore should
	// be returned into the transaction pool.
	// An interesting note here is that if the block contained any transactions local to the node,
	// by being first removed from the pool (from the "local" part of it), and then re-injected,
	// they effective lose their priority over the "remote" transactions. In order to prevent that,
	// somehow the fact that certain transactions were local, needs to be remembered for some
	// time (up to some "immutability threshold").
	unsafeAddToPool(senderInfo, unwindTxs, pending, PendingSubPool, func(i *metaTx) {
		//fmt.Printf("add: %d,%d\n", i.Tx.senderID, i.Tx.nonce)
		if _, ok := localsHistory.Get(i.Tx.idHash); ok {
			//TODO: also check if sender is in list of local-senders
			i.subPool |= IsLocal
		}
		byHash[string(i.Tx.idHash[:])] = i
		replaced := senderInfo[i.Tx.senderID].txNonce2Tx.ReplaceOrInsert(&nonce2TxItem{i})
		if replaced != nil {
			replacedMT := replaced.(*nonce2TxItem).metaTx
			delete(byHash, string(replacedMT.Tx.idHash[:]))
			switch replacedMT.currentSubPool {
			case PendingSubPool:
				pending.UnsafeRemove(replacedMT)
			case BaseFeeSubPool:
				baseFee.UnsafeRemove(replacedMT)
			case QueuedSubPool:
				queued.UnsafeRemove(replacedMT)
			default:
				//already removed
			}
		}
	})

	for i := range senderInfo {
		// TODO: aggregate changed senders before call this func
		onSenderChange(senderInfo[i], protocolBaseFee, blockBaseFee)
	}

	pending.EnforceInvariants()
	baseFee.EnforceInvariants()
	queued.EnforceInvariants()

	promote(pending, baseFee, queued, func(i *metaTx) {
		//fmt.Printf("del1 nonce: %d, %d,%d\n", i.Tx.senderID, senderInfo[i.Tx.senderID].nonce, i.Tx.nonce)
		//fmt.Printf("del2 balance: %d,%d,%d\n", i.Tx.value.Uint64(), i.Tx.tip, senderInfo[i.Tx.senderID].balance.Uint64())
		delete(byHash, string(i.Tx.idHash[:]))
		senderInfo[i.Tx.senderID].txNonce2Tx.Delete(&nonce2TxItem{i})
		if i.subPool&IsLocal != 0 {
			//TODO: only add to history if sender is not in list of local-senders
			localsHistory.Add(i.Tx.idHash, struct{}{})
		}
	})

	return nil
}

// removeMined - apply new highest block (or batch of blocks)
//
// 1. New best block arrives, which potentially changes the balance and the nonce of some senders.
// We use senderIds data structure to find relevant senderId values, and then use senders data structure to
// modify state_balance and state_nonce, potentially remove some elements (if transaction with some nonce is
// included into a block), and finally, walk over the transaction records and update SubPool fields depending on
// the actual presence of nonce gaps and what the balance is.
func removeMined(senderInfo map[uint64]*senderInfo, minedTxs []*TxSlot, pending, baseFee, queued *SubPool, discard func(tx *metaTx)) {
	for _, tx := range minedTxs {
		sender, ok := senderInfo[tx.senderID]
		if !ok {
			panic("not implemented yet")
		}
		// delete mined transactions from everywhere
		sender.txNonce2Tx.Ascend(func(i btree.Item) bool {
			it := i.(*nonce2TxItem)
			if it.metaTx.Tx.nonce > sender.nonce {
				return false
			}
			// TODO: save local transactions to cache with TTL, in case of re-org - to restore isLocal flag of re-injected transactions

			// del from nonce2tx mapping
			sender.txNonce2Tx.Delete(i)
			// del from sub-pool
			switch it.metaTx.currentSubPool {
			case PendingSubPool:
				pending.UnsafeRemove(it.metaTx)
				discard(it.metaTx)
			case BaseFeeSubPool:
				baseFee.UnsafeRemove(it.metaTx)
				discard(it.metaTx)
			case QueuedSubPool:
				queued.UnsafeRemove(it.metaTx)
				discard(it.metaTx)
			default:
				//already removed
			}
			return true
		})
	}
}

// unwind
func unsafeAddToPool(senderInfo map[uint64]*senderInfo, unwindTxs TxSlots, to *SubPool, subPoolType SubPoolType, beforeAdd func(tx *metaTx)) {
	for i, tx := range unwindTxs.txs {
		sender, ok := senderInfo[tx.senderID]
		if !ok {
			panic("not implemented yet")
		}

		mt := newMetaTx(tx, unwindTxs.isLocal[i])
		// Insert to pending pool, if pool doesn't have tx with same Nonce and bigger Tip
		if found := sender.txNonce2Tx.Get(&nonce2TxItem{mt}); found != nil {
			if tx.tip <= found.(*nonce2TxItem).metaTx.Tx.tip {
				continue
			}
		}
		beforeAdd(mt)
		to.UnsafeAdd(mt, subPoolType)
	}
}

func onSenderChange(sender *senderInfo, protocolBaseFee, blockBaseFee uint64) {
	prevNonce := sender.nonce
	cumulativeRequiredBalance := uint256.NewInt(0)
	minFeeCap := uint64(math.MaxUint64)
	minTip := uint64(math.MaxUint64)
	sender.txNonce2Tx.Ascend(func(i btree.Item) bool {
		it := i.(*nonce2TxItem)

		// Sender has enough balance for: gasLimit x feeCap + transferred_value
		needBalance := uint256.NewInt(it.metaTx.Tx.gas)
		needBalance.Mul(needBalance, uint256.NewInt(it.metaTx.Tx.feeCap))
		needBalance.Add(needBalance, &it.metaTx.Tx.value)
		minFeeCap = min(minFeeCap, it.metaTx.Tx.feeCap)
		minTip = min(minTip, it.metaTx.Tx.tip)
		if blockBaseFee >= minFeeCap {
			it.metaTx.effectiveTip = minTip
		} else {
			it.metaTx.effectiveTip = minFeeCap - blockBaseFee
		}
		// 1. Minimum fee requirement. Set to 1 if feeCap of the transaction is no less than in-protocol
		// parameter of minimal base fee. Set to 0 if feeCap is less than minimum base fee, which means
		// this transaction will never be included into this particular chain.
		it.metaTx.subPool &^= EnoughFeeCapProtocol
		if it.metaTx.Tx.feeCap >= protocolBaseFee {
			//fmt.Printf("alex1: %d,%d,%d,%d\n", it.metaTx.NeedBalance.Uint64(), it.metaTx.Tx.gas, it.metaTx.Tx.feeCap, it.metaTx.Tx.value.Uint64())
			//fmt.Printf("alex2: %d,%t\n", sender.balance.Uint64(), it.metaTx.SenderHasEnoughBalance)
			it.metaTx.subPool |= EnoughFeeCapProtocol
		}

		// 2. Absence of nonce gaps. Set to 1 for transactions whose nonce is N, state nonce for
		// the sender is M, and there are transactions for all nonces between M and N from the same
		// sender. Set to 0 is the transaction's nonce is divided from the state nonce by one or more nonce gaps.
		it.metaTx.subPool &^= NoNonceGaps
		if uint64(prevNonce)+1 == it.metaTx.Tx.nonce {
			it.metaTx.subPool |= NoNonceGaps
			prevNonce = it.Tx.nonce
		}

		// 3. Sufficient balance for gas. Set to 1 if the balance of sender's account in the
		// state is B, nonce of the sender in the state is M, nonce of the transaction is N, and the
		// sum of feeCap x gasLimit + transferred_value of all transactions from this sender with
		// nonces N+1 ... M is no more than B. Set to 0 otherwise. In other words, this bit is
		// set if there is currently a guarantee that the transaction and all its required prior
		// transactions will be able to pay for gas.
		cumulativeRequiredBalance = cumulativeRequiredBalance.Add(cumulativeRequiredBalance, needBalance) // already deleted all transactions with nonce <= sender.nonce
		it.metaTx.subPool &^= EnoughBalance
		if sender.balance.Gt(cumulativeRequiredBalance) || sender.balance.Eq(cumulativeRequiredBalance) {
			it.metaTx.subPool |= EnoughBalance
		}

		// 4. Dynamic fee requirement. Set to 1 if feeCap of the transaction is no less than
		// baseFee of the currently pending block. Set to 0 otherwise.
		it.metaTx.subPool &^= EnoughFeeCapBlock
		if it.metaTx.Tx.feeCap >= blockBaseFee {
			it.metaTx.subPool |= EnoughFeeCapBlock
		}

		// 5. Local transaction. Set to 1 if transaction is local.
		// can't change

		return true
	})
}

func promote(pending, baseFee, queued *SubPool, discard func(tx *metaTx)) {
	//1. If top element in the worst green queue has subPool != 0b1111 (binary), it needs to be removed from the green pool.
	//   If subPool < 0b1000 (not satisfying minimum fee), discard.
	//   If subPool == 0b1110, demote to the yellow pool, otherwise demote to the red pool.
	for worst := pending.Worst(); pending.Len() > 0; worst = pending.Worst() {
		if worst.subPool >= 0b11110 {
			break
		}
		if worst.subPool >= 0b11100 {
			baseFee.Add(pending.PopWorst(), BaseFeeSubPool)
			continue
		}
		if worst.subPool >= 0b10000 {
			queued.Add(pending.PopWorst(), QueuedSubPool)
			continue
		}
		discard(pending.PopWorst())
	}

	//2. If top element in the worst green queue has subPool == 0b1111, but there is not enough room in the pool, discard.
	for worst := pending.Worst(); pending.Len() > PendingSubPoolLimit; worst = pending.Worst() {
		if worst.subPool >= 0b11111 { // TODO: here must 'subPool == 0b1111' or 'subPool <= 0b1111' ?
			break
		}
		pending.PopWorst()
	}

	//3. If the top element in the best yellow queue has subPool == 0b1111, promote to the green pool.
	for best := baseFee.Best(); baseFee.Len() > 0; best = baseFee.Best() {
		if best.subPool < 0b11110 {
			break
		}
		pending.Add(baseFee.PopBest(), PendingSubPool)
	}

	//4. If the top element in the worst yellow queue has subPool != 0x1110, it needs to be removed from the yellow pool.
	//   If subPool < 0b1000 (not satisfying minimum fee), discard. Otherwise, demote to the red pool.
	for worst := baseFee.Worst(); baseFee.Len() > 0; worst = baseFee.Worst() {
		if worst.subPool >= 0b11100 {
			break
		}
		if worst.subPool >= 0b10000 {
			queued.Add(baseFee.PopWorst(), QueuedSubPool)
			continue
		}
		discard(baseFee.PopWorst())
	}

	//5. If the top element in the worst yellow queue has subPool == 0x1110, but there is not enough room in the pool, discard.
	for worst := baseFee.Worst(); baseFee.Len() > BaseFeeSubPoolLimit; worst = baseFee.Worst() {
		if worst.subPool >= 0b11110 {
			break
		}
		discard(baseFee.PopWorst())
	}

	//6. If the top element in the best red queue has subPool == 0x1110, promote to the yellow pool. If subPool == 0x1111, promote to the green pool.
	for best := queued.Best(); queued.Len() > 0; best = queued.Best() {
		if best.subPool < 0b11100 {
			break
		}
		if best.subPool < 0b11110 {
			baseFee.Add(queued.PopBest(), BaseFeeSubPool)
			continue
		}

		pending.Add(queued.PopBest(), PendingSubPool)
	}

	//7. If the top element in the worst red queue has subPool < 0b1000 (not satisfying minimum fee), discard.
	for worst := queued.Worst(); queued.Len() > 0; worst = queued.Worst() {
		if worst.subPool >= 0b10000 {
			break
		}

		discard(queued.PopWorst())
	}

	//8. If the top element in the worst red queue has subPool >= 0b100, but there is not enough room in the pool, discard.
	for _ = queued.Worst(); queued.Len() > QueuedSubPoolLimit; _ = queued.Worst() {
		discard(queued.PopWorst())
	}
}

type SubPool struct {
	best  *BestQueue
	worst *WorstQueue
}

func NewSubPool() *SubPool {
	return &SubPool{best: &BestQueue{}, worst: &WorstQueue{}}
}

func (p *SubPool) EnforceInvariants() {
	heap.Init(p.worst)
	heap.Init(p.best)
}
func (p *SubPool) Best() *metaTx {
	if len(*p.best) == 0 {
		return nil
	}
	return (*p.best)[0]
}
func (p *SubPool) Worst() *metaTx {
	if len(*p.worst) == 0 {
		return nil
	}
	return (*p.worst)[0]
}
func (p *SubPool) PopBest() *metaTx {
	i := heap.Pop(p.best).(*metaTx)
	heap.Remove(p.worst, i.worstIndex)
	return i
}
func (p *SubPool) PopWorst() *metaTx {
	i := heap.Pop(p.worst).(*metaTx)
	heap.Remove(p.best, i.bestIndex)
	return i
}
func (p *SubPool) Len() int { return p.best.Len() }
func (p *SubPool) Add(i *metaTx, subPoolType SubPoolType) {
	i.currentSubPool = subPoolType
	heap.Push(p.best, i)
	heap.Push(p.worst, i)
}

// UnsafeRemove - does break Heap invariants, but it has O(1) instead of O(log(n)) complexity.
// Must manually call heap.Init after such changes.
// Make sense to batch unsafe changes
func (p *SubPool) UnsafeRemove(i *metaTx) {
	if p.Len() == 0 {
		return
	}
	if p.Len() == 1 && i.bestIndex == 0 {
		p.worst.Pop()
		p.best.Pop()
		return
	}
	// manually call funcs instead of heap.Pop
	p.worst.Swap(i.worstIndex, p.worst.Len()-1)
	p.worst.Pop()
	p.best.Swap(i.bestIndex, p.best.Len()-1)
	p.best.Pop()
}
func (p *SubPool) UnsafeAdd(i *metaTx, subPoolType SubPoolType) {
	i.currentSubPool = subPoolType
	p.worst.Push(i)
	p.best.Push(i)
}
func (p *SubPool) DebugPrint() {
	for i, it := range *p.best {
		fmt.Printf("best: %d, %d, %d\n", i, it.subPool, it.bestIndex)
	}
	for i, it := range *p.worst {
		fmt.Printf("worst: %d, %d, %d\n", i, it.subPool, it.worstIndex)
	}
}

type BestQueue []*metaTx

func (mt *metaTx) Less(than *metaTx) bool {
	if mt.subPool != than.subPool {
		return mt.subPool < than.subPool
	}

	if mt.effectiveTip != than.effectiveTip {
		return mt.effectiveTip < than.effectiveTip
	}

	if mt.Tx.nonce != than.Tx.nonce {
		return mt.Tx.nonce < than.Tx.nonce
	}
	return false
}

func (p BestQueue) Len() int           { return len(p) }
func (p BestQueue) Less(i, j int) bool { return !p[i].Less(p[j]) } // We want Pop to give us the highest, not lowest, priority so we use !less here.
func (p BestQueue) Swap(i, j int) {
	p[i], p[j] = p[j], p[i]
	p[i].bestIndex = i
	p[j].bestIndex = j
}
func (p *BestQueue) Push(x interface{}) {
	n := len(*p)
	item := x.(*metaTx)
	item.bestIndex = n
	*p = append(*p, item)
}

func (p *BestQueue) Pop() interface{} {
	old := *p
	n := len(old)
	item := old[n-1]
	old[n-1] = nil          // avoid memory leak
	item.bestIndex = -1     // for safety
	item.currentSubPool = 0 // for safety
	*p = old[0 : n-1]
	return item
}

type WorstQueue []*metaTx

func (p WorstQueue) Len() int           { return len(p) }
func (p WorstQueue) Less(i, j int) bool { return p[i].Less(p[j]) }
func (p WorstQueue) Swap(i, j int) {
	p[i], p[j] = p[j], p[i]
	p[i].worstIndex = i
	p[j].worstIndex = j
}
func (p *WorstQueue) Push(x interface{}) {
	n := len(*p)
	item := x.(*metaTx)
	item.worstIndex = n
	*p = append(*p, x.(*metaTx))
}
func (p *WorstQueue) Pop() interface{} {
	old := *p
	n := len(old)
	item := old[n-1]
	old[n-1] = nil          // avoid memory leak
	item.worstIndex = -1    // for safety
	item.currentSubPool = 0 // for safety
	*p = old[0 : n-1]
	return item
}

// BroadcastLoop - does:
// send pending byHash to p2p:
//      - new byHash
//      - all pooled byHash to recently connected peers
//      - all local pooled byHash to random peers periodically
// promote/demote transactions
// reorgs
func BroadcastLoop(ctx context.Context, p *TxPool, newTxs chan Hashes, send *Send, timings Timings) {
	propagateAllNewTxsEvery := time.NewTicker(timings.propagateAllNewTxsEvery)
	defer propagateAllNewTxsEvery.Stop()

	syncToNewPeersEvery := time.NewTicker(timings.syncToNewPeersEvery)
	defer syncToNewPeersEvery.Stop()

	broadcastLocalTransactionsEvery := time.NewTicker(timings.broadcastLocalTransactionsEvery)
	defer broadcastLocalTransactionsEvery.Stop()

	localTxHashes := make([]byte, 0, 128)
	remoteTxHashes := make([]byte, 0, 128)

	for {
		select {
		case <-ctx.Done():
			return
		case h := <-newTxs:
			// first broadcast all local txs to all peers, then non-local to random sqrt(peersAmount) peers
			localTxHashes = localTxHashes[:0]
			remoteTxHashes = remoteTxHashes[:0]

			for i := 0; i < h.Len(); i++ {
				if p.IdHashIsLocal(h.At(i)) {
					localTxHashes = append(localTxHashes, h.At(i)...)
				} else {
					remoteTxHashes = append(localTxHashes, h.At(i)...)
				}
			}

			send.BroadcastLocalPooledTxs(localTxHashes)
			send.BroadcastRemotePooledTxs(remoteTxHashes)
		case <-syncToNewPeersEvery.C: // new peer
			newPeers := p.recentlyConnectedPeers.GetAndClean()
			if len(newPeers) == 0 {
				continue
			}
			p.AppendAllHashes(remoteTxHashes[:0])
			send.PropagatePooledTxsToPeersList(newPeers, remoteTxHashes)
		}
	}
}

// recentlyConnectedPeers does buffer IDs of recently connected good peers
// then sync of pooled Transaction can happen to all of then at once
// DoS protection and performance saving
// it doesn't track if peer disconnected, it's fine
type recentlyConnectedPeers struct {
	lock  sync.RWMutex
	peers []PeerID
}

func (l *recentlyConnectedPeers) AddPeer(p PeerID) {
	l.lock.Lock()
	defer l.lock.Unlock()
	l.peers = append(l.peers, p)
}

func (l *recentlyConnectedPeers) GetAndClean() []PeerID {
	l.lock.Lock()
	defer l.lock.Unlock()
	peers := l.peers
	l.peers = nil
	return peers
}

func min(a, b uint64) uint64 {
	if a <= b {
		return a
	}
	return b
}