github.com/amazechain/amc@v0.1.3/internal/txspool/txs_list.go

// Copyright 2022 The AmazeChain Authors
// This file is part of the AmazeChain library.
//
// The AmazeChain 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 AmazeChain 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 AmazeChain library. If not, see <http://www.gnu.org/licenses/>.

package txspool

import (
	"container/heap"
	"github.com/amazechain/amc/common/transaction"
	"github.com/amazechain/amc/common/types"
	"github.com/holiman/uint256"
	"math"
	"sort"
	"sync"
	"sync/atomic"
	"time"
	"unsafe"
)

// addressByHeartbeat is an account address tagged with its last activity timestamp.
type addressByHeartbeat struct {
	address   types.Address
	heartbeat time.Time
}

type addressesByHeartbeat []addressByHeartbeat

func (a addressesByHeartbeat) Len() int           { return len(a) }
func (a addressesByHeartbeat) Less(i, j int) bool { return a[i].heartbeat.Before(a[j].heartbeat) }
func (a addressesByHeartbeat) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// accountSet is simply a set of addresses to check for existence, and a signer
// capable of deriving addresses from transactions.
type accountSet struct {
	accounts map[types.Address]struct{}
	cache    *[]types.Address
}

// newAccountSet creates a new address set with an associated signer for sender
// derivations.
func newAccountSet(addrs ...types.Address) *accountSet {
	as := &accountSet{
		accounts: make(map[types.Address]struct{}),
	}
	for _, addr := range addrs {
		as.add(addr)
	}
	return as
}

// contains checks if a given address is contained within the set.
func (as *accountSet) contains(addr types.Address) bool {
	_, exist := as.accounts[addr]
	return exist
}

func (as *accountSet) empty() bool {
	return len(as.accounts) == 0
}

// containsTx checks if the sender of a given tx is within the set. If the sender
// cannot be derived, this method returns false.
func (as *accountSet) containsTx(tx *transaction.Transaction) bool {
	return as.contains(*tx.From())
}

// add inserts a new address into the set to track.
func (as *accountSet) add(addr types.Address) {
	as.accounts[addr] = struct{}{}
	as.cache = nil
}

// addTx adds the sender of tx into the set.
func (as *accountSet) addTx(tx *transaction.Transaction) {
	as.add(*tx.From())
}

// flatten returns the list of addresses within this set, also caching it for later
// reuse. The returned slice should not be changed!
func (as *accountSet) flatten() []types.Address {
	if as.cache == nil {
		accounts := make([]types.Address, 0, len(as.accounts))
		for account := range as.accounts {
			accounts = append(accounts, account)
		}
		as.cache = &accounts
	}
	return *as.cache
}

// merge adds all addresses from the 'other' set into 'as'.
func (as *accountSet) merge(other *accountSet) {
	for addr := range other.accounts {
		as.accounts[addr] = struct{}{}
	}
	as.cache = nil
}

// txLookup is used internally by TxPool to track transactions while allowing
// lookup without mutex contention.
//
// Note, although this type is properly protected against concurrent access, it
// is **not** a type that should ever be mutated or even exposed outside of the
// transaction pool, since its internal state is tightly coupled with the pools
// internal mechanisms. The sole purpose of the type is to permit out-of-bound
// peeking into the pool in TxPool.Get without having to acquire the widely scoped
// TxPool.mu mutex.
//
// This lookup set combines the notion of "local transactions", which is useful
// to build upper-level structure.
type txLookup struct {
	slots   int
	lock    sync.RWMutex
	locals  map[types.Hash]*transaction.Transaction
	remotes map[types.Hash]*transaction.Transaction
}

// newTxLookup returns a new txLookup structure.
func newTxLookup() *txLookup {
	return &txLookup{
		locals:  make(map[types.Hash]*transaction.Transaction),
		remotes: make(map[types.Hash]*transaction.Transaction),
	}
}

// Range calls f on each key and value present in the map. The callback passed
// should return the indicator whether the iteration needs to be continued.
// Callers need to specify which set (or both) to be iterated.
func (t *txLookup) Range(f func(hash types.Hash, tx *transaction.Transaction, local bool) bool, local bool, remote bool) {
	t.lock.RLock()
	defer t.lock.RUnlock()

	if local {
		for key, value := range t.locals {
			if !f(key, value, true) {
				return
			}
		}
	}
	if remote {
		for key, value := range t.remotes {
			if !f(key, value, false) {
				return
			}
		}
	}
}

// Get returns a transaction if it exists in the lookup, or nil if not found.
func (t *txLookup) Get(hash types.Hash) *transaction.Transaction {
	t.lock.RLock()
	defer t.lock.RUnlock()

	if tx := t.locals[hash]; tx != nil {
		return tx
	}
	return t.remotes[hash]
}

// GetLocal returns a transaction if it exists in the lookup, or nil if not found.
func (t *txLookup) GetLocal(hash types.Hash) *transaction.Transaction {
	t.lock.RLock()
	defer t.lock.RUnlock()

	return t.locals[hash]
}

// GetRemote returns a transaction if it exists in the lookup, or nil if not found.
func (t *txLookup) GetRemote(hash types.Hash) *transaction.Transaction {
	t.lock.RLock()
	defer t.lock.RUnlock()

	return t.remotes[hash]
}

// Count returns the current number of transactions in the lookup.
func (t *txLookup) Count() int {
	t.lock.RLock()
	defer t.lock.RUnlock()

	return len(t.locals) + len(t.remotes)
}

// LocalCount returns the current number of local transactions in the lookup.
func (t *txLookup) LocalCount() int {
	t.lock.RLock()
	defer t.lock.RUnlock()

	return len(t.locals)
}

// RemoteCount returns the current number of remote transactions in the lookup.
func (t *txLookup) RemoteCount() int {
	t.lock.RLock()
	defer t.lock.RUnlock()

	return len(t.remotes)
}

// Slots returns the current number of slots used in the lookup.
func (t *txLookup) Slots() int {
	t.lock.RLock()
	defer t.lock.RUnlock()

	return t.slots
}

// Add adds a transaction to the lookup.
func (t *txLookup) Add(tx *transaction.Transaction, local bool) {
	t.lock.Lock()
	defer t.lock.Unlock()

	t.slots += numSlots(tx)
	//todo slotsGauge.Update(int64(t.slots))

	hash := tx.Hash()
	if local {
		t.locals[hash] = tx
	} else {
		t.remotes[hash] = tx
	}
}

// Remove removes a transaction from the lookup.
func (t *txLookup) Remove(hash types.Hash) {
	t.lock.Lock()
	defer t.lock.Unlock()

	tx, ok := t.locals[hash]
	if !ok {
		tx, ok = t.remotes[hash]
	}
	if !ok {
		//todo
		//log.Error("No transaction found to be deleted", "hash", hash)
		return
	}
	t.slots -= numSlots(tx)
	//todo slotsGauge.Update(int64(t.slots))

	delete(t.locals, hash)
	delete(t.remotes, hash)
}

// RemoteToLocals migrates the transactions belongs to the given locals to locals
// set. The assumption is held the locals set is thread-safe to be used.
func (t *txLookup) RemoteToLocals(locals *accountSet) int {
	t.lock.Lock()
	defer t.lock.Unlock()

	var migrated int
	for hash, tx := range t.remotes {
		if locals.containsTx(tx) {
			t.locals[hash] = tx
			delete(t.remotes, hash)
			migrated += 1
		}
	}
	return migrated
}

// RemotesBelowTip finds all remote transactions below the given tip threshold.
func (t *txLookup) RemotesBelowTip(threshold uint256.Int) []*transaction.Transaction {
	found := make([]*transaction.Transaction, 0, 128)
	t.Range(func(hash types.Hash, tx *transaction.Transaction, local bool) bool {
		if tx.GasPrice().Cmp(&threshold) < 0 {
			found = append(found, tx)
		}
		return true
	}, false, true) // Only iterate remotes
	return found
}

// numSlots calculates the number of slots needed for a single transaction.
func numSlots(tx *transaction.Transaction) int {
	//todo
	return int((int(unsafe.Sizeof(tx)) + txSlotSize - 1) / txSlotSize)
}

// TxByNonce implements the sort interface to allow sorting a list of transactions by their nonces.
type TxByNonce []*transaction.Transaction

func (s TxByNonce) Len() int           { return len(s) }
func (s TxByNonce) Less(i, j int) bool { return s[i].Nonce() < s[j].Nonce() }
func (s TxByNonce) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }

// nonceHeap is a heap.Interface implementation over 64bit unsigned integers for
// retrieving sorted transactions from the possibly gapped future queue.
type nonceHeap []uint64

func (h nonceHeap) Len() int           { return len(h) }
func (h nonceHeap) Less(i, j int) bool { return h[i] < h[j] }
func (h nonceHeap) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }

func (h *nonceHeap) Push(x interface{}) {
	*h = append(*h, x.(uint64))
}

func (h *nonceHeap) Pop() interface{} {
	old := *h
	n := len(old)
	x := old[n-1]
	*h = old[0 : n-1]
	return x
}

// txsSortedMap
type txsSortedMap struct {
	items map[uint64]*transaction.Transaction // hash map
	index *nonceHeap                          //
	cache []*transaction.Transaction          // Cache
}

// newTxSortedMap creates a new nonce-sorted transaction map.
func newTxSortedMap() *txsSortedMap {
	return &txsSortedMap{
		items: make(map[uint64]*transaction.Transaction),
		index: new(nonceHeap),
	}
}

// Get retrieves the current transactions associated with the given nonce.
func (m *txsSortedMap) Get(nonce uint64) *transaction.Transaction {
	return m.items[nonce]
}

// Put
func (m *txsSortedMap) Put(tx *transaction.Transaction) {
	nonce := tx.Nonce()
	if m.items[nonce] == nil {
		heap.Push(m.index, nonce)
	}
	m.items[nonce], m.cache = tx, nil
}

// Forward
func (m *txsSortedMap) Forward(threshold uint64) []*transaction.Transaction {
	var removed []*transaction.Transaction

	// Pop off heap items until the threshold is reached
	for m.index.Len() > 0 && (*m.index)[0] < threshold {
		nonce := heap.Pop(m.index).(uint64)
		removed = append(removed, m.items[nonce])
		delete(m.items, nonce)
	}
	// If we had a cached order, shift the front
	if m.cache != nil {
		m.cache = m.cache[len(removed):]
	}
	return removed
}

// Filter
func (m *txsSortedMap) Filter(filter func(*transaction.Transaction) bool) []*transaction.Transaction {
	removed := m.filter(filter)
	// If transactions were removed, the heap and cache are ruined
	if len(removed) > 0 {
		m.reheap()
	}
	return removed
}

func (m *txsSortedMap) reheap() {
	*m.index = make([]uint64, 0, len(m.items))
	for nonce := range m.items {
		*m.index = append(*m.index, nonce)
	}
	heap.Init(m.index)
	m.cache = nil
}

// filter is identical to Filter, but **does not** regenerate the heap. This method
// should only be used if followed immediately by a call to Filter or reheap()
func (m *txsSortedMap) filter(filter func(*transaction.Transaction) bool) []*transaction.Transaction {
	var removed []*transaction.Transaction

	// Collect all the transactions to filter out
	for nonce, tx := range m.items {
		if filter(tx) {
			removed = append(removed, tx)
			delete(m.items, nonce)
		}
	}
	if len(removed) > 0 {
		m.cache = nil
	}
	return removed
}

// Cap
func (m *txsSortedMap) Cap(threshold int) []*transaction.Transaction {
	// Short circuit if the number of items is under the limit
	if len(m.items) <= threshold {
		return nil
	}
	// Otherwise gather and drop the highest nonce'd transactions
	var drops []*transaction.Transaction

	sort.Sort(*m.index)
	for size := len(m.items); size > threshold; size-- {
		drops = append(drops, m.items[(*m.index)[size-1]])
		delete(m.items, (*m.index)[size-1])
	}
	*m.index = (*m.index)[:threshold]
	heap.Init(m.index)

	// If we had a cache, shift the back
	if m.cache != nil {
		m.cache = m.cache[:len(m.cache)-len(drops)]
	}
	return drops
}

// Remove
func (m *txsSortedMap) Remove(nonce uint64) bool {
	// Short circuit if no transaction is present
	_, ok := m.items[nonce]
	if !ok {
		return false
	}
	// Otherwise delete the transaction and fix the heap index
	for i := 0; i < m.index.Len(); i++ {
		if (*m.index)[i] == nonce {
			heap.Remove(m.index, i)
			break
		}
	}
	delete(m.items, nonce)
	m.cache = nil

	return true
}

// Ready retrieves a sequentially increasing list of transactions starting at the
// provided nonce that is ready for processing. The returned transactions will be
// removed from the list.
//
// Note, all transactions with nonces lower than start will also be returned to
// prevent getting into and invalid state. This is not something that should ever
// happen but better to be self correcting than failing!
func (m *txsSortedMap) Ready(start uint64) []*transaction.Transaction {
	// Short circuit if no transactions are available
	if m.index.Len() == 0 || (*m.index)[0] > start {
		return nil
	}
	// Otherwise start accumulating incremental transactions
	var ready []*transaction.Transaction
	for next := (*m.index)[0]; m.index.Len() > 0 && (*m.index)[0] == next; next++ {
		ready = append(ready, m.items[next])
		delete(m.items, next)
		heap.Pop(m.index)
	}
	m.cache = nil

	return ready
}

// Len returns the length of the transaction map.
func (m *txsSortedMap) Len() int {
	return len(m.items)
}

func (m *txsSortedMap) flatten() []*transaction.Transaction {
	// If the sorting was not cached yet, create and cache it
	if m.cache == nil {
		m.cache = make([]*transaction.Transaction, 0, len(m.items))
		for _, tx := range m.items {
			m.cache = append(m.cache, tx)
		}
		sort.Sort(TxByNonce(m.cache))
	}
	return m.cache
}

// Flatten creates a nonce-sorted slice of transactions based on the loosely
// sorted internal representation. The result of the sorting is cached in case
// it's requested again before any modifications are made to the contents.
func (m *txsSortedMap) Flatten() []*transaction.Transaction {
	// Copy the cache to prevent accidental modifications
	cache := m.flatten()
	txs := make([]*transaction.Transaction, len(cache))
	copy(txs, cache)
	return txs
}

// LastElement returns the last element of a flattened list, thus, the
// transaction with the highest nonce
func (m *txsSortedMap) LastElement() *transaction.Transaction {
	cache := m.flatten()
	return cache[len(cache)-1]
}

// txsList is a "list" of transactions belonging to an account, sorted by account
// nonce. The same type can be used both for storing contiguous transactions for
// the executable/pending queue; and for storing gapped transactions for the non-
// executable/future queue, with minor behavioral changes.
type txsList struct {
	strict  bool
	txs     *txsSortedMap
	costcap uint256.Int
	gascap  uint64
}

// newtxsList create a new transaction list for maintaining nonce-indexable fast,
// gapped, sortable transaction lists.
func newTxsList(strict bool) *txsList {
	return &txsList{
		strict:  strict,
		txs:     newTxSortedMap(),
		costcap: *uint256.NewInt(0),
	}
}

// Overlaps returns whether the transaction specified has the same nonce as one
// already contained within the list.
func (l *txsList) Overlaps(tx *transaction.Transaction) bool {
	return l.txs.Get(tx.Nonce()) != nil
}

// Add tries to insert a new transaction into the list, returning whether the
// transaction was accepted, and if yes, any previous transaction it replaced.
//
// If the new transaction is accepted into the list, the lists' cost and gas
// thresholds are also potentially updated.
func (l *txsList) Add(tx *transaction.Transaction, priceBump uint64) (bool, *transaction.Transaction) {
	// If there's an older better transaction, abort

	old := l.txs.Get(tx.Nonce())
	if old != nil {
		if old.GasFeeCapCmp(tx) >= 1 || old.GasTipCapCmp(tx) >= 1 {
			return false, nil
		}
		// thresholdFeeCap = oldFC  * (100 + priceBump) / 100
		a := uint256.NewInt(100 + priceBump)
		aFeeCap := new(uint256.Int).Mul(a, old.GasFeeCap())
		aTip := a.Mul(a, old.GasTipCap())

		// thresholdTip    = oldTip * (100 + priceBump) / 100
		b := uint256.NewInt(100)
		thresholdFeeCap := aFeeCap.Div(aFeeCap, b)
		thresholdTip := aTip.Div(aTip, b)

		// We have to ensure that both the new fee cap and tip are higher than the
		// old ones as well as checking the percentage threshold to ensure that
		// this is accurate for low (Wei-level) gas price replacements.
		if tx.GasFeeCapIntCmp(thresholdFeeCap) < 0 || tx.GasTipCapIntCmp(thresholdTip) < 0 {
			return false, nil
		}
	}
	// Otherwise overwrite the old transaction with the current one
	l.txs.Put(tx)

	cost := uint256.NewInt(0).Add(new(uint256.Int).Mul(tx.GasPrice(), uint256.NewInt(tx.Gas())), tx.Value())

	if l.costcap.Cmp(cost) < 0 {
		l.costcap = *cost
	}
	if gas := tx.Gas(); l.gascap < gas {
		l.gascap = gas
	}
	return true, old
}

// Forward removes all transactions from the list with a nonce lower than the
// provided threshold. Every removed transaction is returned for any post-removal
// maintenance.
func (l *txsList) Forward(threshold uint64) []*transaction.Transaction {
	return l.txs.Forward(threshold)
}

// Filter removes all transactions from the list with a cost or gas limit higher
// than the provided thresholds. Every removed transaction is returned for any
// post-removal maintenance. Strict-mode invalidated transactions are also
// returned.
//
// This method uses the cached costcap and gascap to quickly decide if there's even
// a point in calculating all the costs or if the balance covers all. If the threshold
// is lower than the costgas cap, the caps will be reset to a new high after removing
// the newly invalidated transactions.
func (l *txsList) Filter(costLimit uint256.Int, gasLimit uint64) ([]*transaction.Transaction, []*transaction.Transaction) {
	// If all transactions are below the threshold, short circuit
	if l.costcap.Cmp(&costLimit) <= 0 && l.gascap <= gasLimit {
		return nil, nil
	}
	l.costcap = costLimit // Lower the caps to the thresholds
	l.gascap = gasLimit

	// Filter out all the transactions above the account's funds
	removed := l.txs.Filter(func(tx *transaction.Transaction) bool {
		cost := uint256.NewInt(0).Add(tx.Value(), uint256.NewInt(0).Mul(tx.GasPrice(), uint256.NewInt(tx.Gas())))
		return tx.Gas() > gasLimit || cost.Cmp(&costLimit) > 0
	})

	if len(removed) == 0 {
		return nil, nil
	}
	var invalids []*transaction.Transaction
	// If the list was strict, filter anything above the lowest nonce
	if l.strict {
		lowest := uint64(math.MaxUint64)
		for _, tx := range removed {
			if nonce := tx.Nonce(); lowest > nonce {
				lowest = nonce
			}
		}
		invalids = l.txs.filter(func(tx *transaction.Transaction) bool { return tx.Nonce() > lowest })
	}
	l.txs.reheap()
	return removed, invalids
}

// Cap places a hard limit on the number of items, returning all transactions
// exceeding that limit.
func (l *txsList) Cap(threshold int) []*transaction.Transaction {
	return l.txs.Cap(threshold)
}

// Remove deletes a transaction from the maintained list, returning whether the
// transaction was found, and also returning any transaction invalidated due to
// the deletion (strict mode only).
func (l *txsList) Remove(tx *transaction.Transaction) (bool, []*transaction.Transaction) {
	// Remove the transaction from the set
	nonce := tx.Nonce()
	if removed := l.txs.Remove(nonce); !removed {
		return false, nil
	}
	// In strict mode, filter out non-executable transactions
	if l.strict {
		return true, l.txs.Filter(func(tx *transaction.Transaction) bool { return tx.Nonce() > nonce })
	}
	return true, nil
}

// Ready retrieves a sequentially increasing list of transactions starting at the
// provided nonce that is ready for processing. The returned transactions will be
// removed from the list.
//
// Note, all transactions with nonces lower than start will also be returned to
// prevent getting into and invalid state. This is not something that should ever
// happen but better to be self correcting than failing!
func (l *txsList) Ready(start uint64) []*transaction.Transaction {
	return l.txs.Ready(start)
}

// Len returns the length of the transaction list.
func (l *txsList) Len() int {
	return l.txs.Len()
}

// Empty returns whether the list of transactions is empty or not.
func (l *txsList) Empty() bool {
	return l.Len() == 0
}

// Flatten creates a nonce-sorted slice of transactions based on the loosely
// sorted internal representation. The result of the sorting is cached in case
// it's requested again before any modifications are made to the contents.
func (l *txsList) Flatten() []*transaction.Transaction {
	return l.txs.Flatten()
}

// LastElement returns the last element of a flattened list, thus, the
// transaction with the highest nonce
func (l *txsList) LastElement() *transaction.Transaction {
	return l.txs.LastElement()
}

// priceHeap is a heap.Interface implementation over transactions for retrieving
// price-sorted transactions to discard when the pool fills up. If baseFee is set
// then the heap is sorted based on the effective tip based on the given base fee.
// If baseFee is nil then the sorting is based on gasFeeCap.
type priceHeap struct {
	baseFee *uint256.Int // heap should always be re-sorted after baseFee is changed
	list    []*transaction.Transaction
}

func (h *priceHeap) Len() int      { return len(h.list) }
func (h *priceHeap) Swap(i, j int) { h.list[i], h.list[j] = h.list[j], h.list[i] }

func (h *priceHeap) Less(i, j int) bool {
	switch h.cmp(h.list[i], h.list[j]) {
	case -1:
		return true
	case 1:
		return false
	default:
		return h.list[i].Nonce() > h.list[j].Nonce()
	}
}

func (h *priceHeap) cmp(a, b *transaction.Transaction) int {
	if h.baseFee != nil {
		// Compare effective tips if baseFee is specified
		if c := a.EffectiveGasTipCmp(b, h.baseFee); c != 0 {
			return c
		}
	}
	// Compare fee caps if baseFee is not specified or effective tips are equal
	if c := a.GasPrice().Cmp(b.GasPrice()); c != 0 {
		return c
	}
	// Compare tips if effective tips and fee caps are equal
	return a.GasPrice().Cmp(b.GasPrice())
}

func (h *priceHeap) Push(x interface{}) {
	tx := x.(*transaction.Transaction)
	h.list = append(h.list, tx)
}

func (h *priceHeap) Pop() interface{} {
	old := h.list
	n := len(old)
	x := old[n-1]
	old[n-1] = nil
	h.list = old[0 : n-1]
	return x
}

// txPricedList is a price-sorted heap to allow operating on transactions pool
// contents in a price-incrementing way. It's built opon the all transactions
// in txpool but only interested in the remote part. It means only remote transactions
// will be considered for tracking, sorting, eviction, etc.
//
// Two heaps are used for sorting: the urgent heap (based on effective tip in the next
// block) and the floating heap (based on gasFeeCap). Always the bigger heap is chosen for
// eviction. Transactions evicted from the urgent heap are first demoted into the floating heap.
// In some cases (during a congestion, when blocks are full) the urgent heap can provide
// better candidates for inclusion while in other cases (at the top of the baseFee peak)
// the floating heap is better. When baseFee is decreasing they behave similarly.
type txPricedList struct {
	// Number of stale price points to (re-heap trigger).
	// This field is accessed atomically, and must be the first field
	// to ensure it has correct alignment for atomic.AddInt64.
	// See https://golang.org/pkg/sync/atomic/#pkg-note-BUG.
	stales int64

	all              *txLookup  // Pointer to the map of all transactions
	urgent, floating priceHeap  // Heaps of prices of all the stored **remote** transactions
	reheapMu         sync.Mutex // Mutex asserts that only one routine is reheaping the list
}

const (
	// urgentRatio : floatingRatio is the capacity ratio of the two queues
	urgentRatio   = 4
	floatingRatio = 1
)

// newTxPricedList creates a new price-sorted transaction heap.
func newTxPricedList(all *txLookup) *txPricedList {
	return &txPricedList{
		all: all,
	}
}

// Put inserts a new transaction into the heap.
func (l *txPricedList) Put(tx *transaction.Transaction, local bool) {
	if local {
		return
	}
	// Insert every new transaction to the urgent heap first; Discard will balance the heaps
	heap.Push(&l.urgent, tx)
}

// Removed notifies the prices transaction list that an old transaction dropped
// from the pool. The list will just keep a counter of stale objects and update
// the heap if a large enough ratio of transactions go stale.
func (l *txPricedList) Removed(count int) {
	// Bump the stale counter, but exit if still too low (< 25%)
	stales := atomic.AddInt64(&l.stales, int64(count))
	if int(stales) <= (len(l.urgent.list)+len(l.floating.list))/4 {
		return
	}
	// Seems we've reached a critical number of stale transactions, reheap
	l.Reheap()
}

// Underpriced checks whether a transaction is cheaper than (or as cheap as) the
// lowest priced (remote) transaction currently being tracked.
func (l *txPricedList) Underpriced(tx *transaction.Transaction) bool {
	// Note: with two queues, being underpriced is defined as being worse than the worst item
	// in all non-empty queues if there is any. If both queues are empty then nothing is underpriced.
	return (l.underpricedFor(&l.urgent, tx) || len(l.urgent.list) == 0) &&
		(l.underpricedFor(&l.floating, tx) || len(l.floating.list) == 0) &&
		(len(l.urgent.list) != 0 || len(l.floating.list) != 0)
}

// underpricedFor checks whether a transaction is cheaper than (or as cheap as) the
// lowest priced (remote) transaction in the given heap.
func (l *txPricedList) underpricedFor(h *priceHeap, tx *transaction.Transaction) bool {
	// Discard stale price points if found at the heap start
	for len(h.list) > 0 {
		hash := h.list[0].Hash()
		if l.all.GetRemote(hash) == nil { // Removed or migrated
			atomic.AddInt64(&l.stales, -1)
			heap.Pop(h)
			continue
		}
		break
	}
	// Check if the transaction is underpriced or not
	if len(h.list) == 0 {
		return false // There is no remote transaction at all.
	}
	// If the remote transaction is even cheaper than the
	// cheapest one tracked locally, reject it.
	return h.cmp(h.list[0], tx) >= 0
}

// Discard finds a number of most underpriced transactions, removes them from the
// priced list and returns them for further removal from the entire pool.
//
// Note local transaction won't be considered for eviction.
func (l *txPricedList) Discard(slots int, force bool) ([]*transaction.Transaction, bool) {
	drop := make([]*transaction.Transaction, 0, slots) // Remote underpriced transactions to drop
	for slots > 0 {
		if len(l.urgent.list)*floatingRatio > len(l.floating.list)*urgentRatio || floatingRatio == 0 {
			// Discard stale transactions if found during cleanup
			tx := heap.Pop(&l.urgent).(*transaction.Transaction)
			hash := tx.Hash()
			if l.all.GetRemote(hash) == nil { // Removed or migrated
				atomic.AddInt64(&l.stales, -1)
				continue
			}
			// Non stale transaction found, move to floating heap
			heap.Push(&l.floating, tx)
		} else {
			if len(l.floating.list) == 0 {
				// Stop if both heaps are empty
				break
			}
			// Discard stale transactions if found during cleanup
			tx := heap.Pop(&l.floating).(*transaction.Transaction)
			hash := tx.Hash()
			if l.all.GetRemote(hash) == nil { // Removed or migrated
				atomic.AddInt64(&l.stales, -1)
				continue
			}
			// Non stale transaction found, discard it
			drop = append(drop, tx)
			slots -= numSlots(tx)
		}
	}
	// If we still can't make enough room for the new transaction
	if slots > 0 && !force {
		for _, tx := range drop {
			heap.Push(&l.urgent, tx)
		}
		return nil, false
	}
	return drop, true
}

// Reheap forcibly rebuilds the heap based on the current remote transaction set.
func (l *txPricedList) Reheap() {
	l.reheapMu.Lock()
	defer l.reheapMu.Unlock()
	//start := time.Now()
	atomic.StoreInt64(&l.stales, 0)
	l.urgent.list = make([]*transaction.Transaction, 0, l.all.RemoteCount())
	l.all.Range(func(hash types.Hash, tx *transaction.Transaction, local bool) bool {
		l.urgent.list = append(l.urgent.list, tx)
		return true
	}, false, true) // Only iterate remotes
	heap.Init(&l.urgent)

	// balance out the two heaps by moving the worse half of transactions into the
	// floating heap
	// Note: Discard would also do this before the first eviction but Reheap can do
	// is more efficiently. Also, Underpriced would work suboptimally the first time
	// if the floating queue was empty.
	floatingCount := len(l.urgent.list) * floatingRatio / (urgentRatio + floatingRatio)
	l.floating.list = make([]*transaction.Transaction, floatingCount)
	for i := 0; i < floatingCount; i++ {
		l.floating.list[i] = heap.Pop(&l.urgent).(*transaction.Transaction)
	}
	heap.Init(&l.floating)

	//todo reheapTimer.Update(time.Since(start))
}

// SetBaseFee updates the base fee and triggers a re-heap. Note that Removed is not
// necessary to call right before SetBaseFee when processing a new block.
func (l *txPricedList) SetBaseFee(baseFee *uint256.Int) {
	l.urgent.baseFee = baseFee
	l.Reheap()
}