/*
   Copyright 2022 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 state

import (
	"bytes"
	"container/heap"
	"context"
	"encoding/binary"
	"fmt"
	"io/fs"
	"math"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/RoaringBitmap/roaring/roaring64"
	"github.com/c2h5oh/datasize"
	"github.com/google/btree"
	"github.com/ledgerwatch/log/v3"
	"golang.org/x/exp/slices"
	"golang.org/x/sync/semaphore"

	"github.com/ledgerwatch/erigon-lib/common/cmp"
	"github.com/ledgerwatch/erigon-lib/common/dir"
	"github.com/ledgerwatch/erigon-lib/compress"
	"github.com/ledgerwatch/erigon-lib/etl"
	"github.com/ledgerwatch/erigon-lib/kv"
	"github.com/ledgerwatch/erigon-lib/kv/bitmapdb"
	"github.com/ledgerwatch/erigon-lib/recsplit"
	"github.com/ledgerwatch/erigon-lib/recsplit/eliasfano32"
)

type InvertedIndex struct {
	tx              kv.RwTx
	files           *btree.BTreeG[*filesItem]
	indexKeysTable  string // txnNum_u64 -> key (k+auto_increment)
	indexTable      string // k -> txnNum_u64 , Needs to be table with DupSort
	dir             string // Directory where static files are created
	tmpdir          string // Directory where static files are created
	filenameBase    string
	aggregationStep uint64
	txNum           uint64
	workers         int
	txNumBytes      [8]byte

	wal     *invertedIndexWAL
	walLock sync.RWMutex
}

func NewInvertedIndex(
	dir, tmpdir string,
	aggregationStep uint64,
	filenameBase string,
	indexKeysTable string,
	indexTable string,
) (*InvertedIndex, error) {
	ii := InvertedIndex{
		dir:             dir,
		tmpdir:          tmpdir,
		files:           btree.NewG[*filesItem](32, filesItemLess),
		aggregationStep: aggregationStep,
		filenameBase:    filenameBase,
		indexKeysTable:  indexKeysTable,
		indexTable:      indexTable,
		workers:         1,
	}
	files, err := os.ReadDir(dir)
	if err != nil {
		return nil, fmt.Errorf("NewInvertedIndex: %s, %w", filenameBase, err)
	}
	ii.scanStateFiles(files)
	if err = ii.openFiles(); err != nil {
		return nil, fmt.Errorf("NewInvertedIndex: %s, %w", filenameBase, err)
	}
	return &ii, nil
}

func (ii *InvertedIndex) scanStateFiles(files []fs.DirEntry) {
	re := regexp.MustCompile("^" + ii.filenameBase + ".([0-9]+)-([0-9]+).ef$")
	var err error
	var uselessFiles []string
	for _, f := range files {
		if !f.Type().IsRegular() {
			continue
		}

		name := f.Name()
		subs := re.FindStringSubmatch(name)
		if len(subs) != 3 {
			if len(subs) != 0 {
				log.Warn("File ignored by inverted index scan, more than 3 submatches", "name", name, "submatches", len(subs))
			}
			continue
		}
		var startStep, endStep uint64
		if startStep, err = strconv.ParseUint(subs[1], 10, 64); err != nil {
			log.Warn("File ignored by inverted index scan, parsing startTxNum", "error", err, "name", name)
			continue
		}
		if endStep, err = strconv.ParseUint(subs[2], 10, 64); err != nil {
			log.Warn("File ignored by inverted index scan, parsing endTxNum", "error", err, "name", name)
			continue
		}
		if startStep > endStep {
			log.Warn("File ignored by inverted index scan, startTxNum > endTxNum", "name", name)
			continue
		}

		startTxNum, endTxNum := startStep*ii.aggregationStep, endStep*ii.aggregationStep
		var item = &filesItem{startTxNum: startTxNum, endTxNum: endTxNum}
		{
			var subSet, superSet *filesItem
			ii.files.DescendLessOrEqual(item, func(it *filesItem) bool {
				if it.isSubsetOf(item) {
					subSet = it
				} else if item.isSubsetOf(it) {
					superSet = it
				}
				return true
			})
			if subSet != nil {
				ii.files.Delete(subSet)
				uselessFiles = append(uselessFiles,
					fmt.Sprintf("%s.%d-%d.ef", ii.filenameBase, subSet.startTxNum/ii.aggregationStep, subSet.endTxNum/ii.aggregationStep),
					fmt.Sprintf("%s.%d-%d.efi", ii.filenameBase, subSet.startTxNum/ii.aggregationStep, subSet.endTxNum/ii.aggregationStep),
				)
			}
			if superSet != nil {
				uselessFiles = append(uselessFiles,
					fmt.Sprintf("%s.%d-%d.ef", ii.filenameBase, startStep, endStep),
					fmt.Sprintf("%s.%d-%d.efi", ii.filenameBase, startStep, endStep),
				)
				continue
			}
		}
		{
			var subSet, superSet *filesItem
			ii.files.AscendGreaterOrEqual(item, func(it *filesItem) bool {
				if it.isSubsetOf(item) {
					subSet = it
				} else if item.isSubsetOf(it) {
					superSet = it
				}
				return false
			})
			if subSet != nil {
				ii.files.Delete(subSet)
				uselessFiles = append(uselessFiles,
					fmt.Sprintf("%s.%d-%d.ef", ii.filenameBase, subSet.startTxNum/ii.aggregationStep, subSet.endTxNum/ii.aggregationStep),
					fmt.Sprintf("%s.%d-%d.efi", ii.filenameBase, subSet.startTxNum/ii.aggregationStep, subSet.endTxNum/ii.aggregationStep),
				)
			}
			if superSet != nil {
				uselessFiles = append(uselessFiles,
					fmt.Sprintf("%s.%d-%d.ef", ii.filenameBase, startStep, endStep),
					fmt.Sprintf("%s.%d-%d.efi", ii.filenameBase, startStep, endStep),
				)
				continue
			}
		}
		ii.files.ReplaceOrInsert(item)
	}
	if len(uselessFiles) > 0 {
		log.Info("[snapshots] history can delete", "files", strings.Join(uselessFiles, ","))
	}
}

func (ii *InvertedIndex) missedIdxFiles() (l []*filesItem) {
	ii.files.Ascend(func(item *filesItem) bool { // don't run slow logic while iterating on btree
		fromStep, toStep := item.startTxNum/ii.aggregationStep, item.endTxNum/ii.aggregationStep
		if !dir.FileExist(filepath.Join(ii.dir, fmt.Sprintf("%s.%d-%d.efi", ii.filenameBase, fromStep, toStep))) {
			l = append(l, item)
		}
		return true
	})
	return l
}

// BuildMissedIndices - produce .efi/.vi/.kvi from .ef/.v/.kv
func (ii *InvertedIndex) BuildMissedIndices(ctx context.Context, sem *semaphore.Weighted) (err error) {
	missedFiles := ii.missedIdxFiles()
	errs := make(chan error, len(missedFiles))
	wg := sync.WaitGroup{}
	for _, item := range missedFiles {
		if err := sem.Acquire(ctx, 1); err != nil {
			errs <- err
			break
		}
		wg.Add(1)
		go func(item *filesItem) {
			defer sem.Release(1)
			defer wg.Done()
			fromStep, toStep := item.startTxNum/ii.aggregationStep, item.endTxNum/ii.aggregationStep
			fName := fmt.Sprintf("%s.%d-%d.efi", ii.filenameBase, fromStep, toStep)
			idxPath := filepath.Join(ii.dir, fName)
			log.Info("[snapshots] build idx", "file", fName)
			_, err := buildIndex(ctx, item.decompressor, idxPath, ii.tmpdir, item.decompressor.Count()/2, false)
			if err != nil {
				errs <- err
			}
		}(item)
	}
	go func() {
		wg.Wait()
		close(errs)
	}()
	var lastError error
	for err := range errs {
		if err != nil {
			lastError = err
		}
	}
	if lastError != nil {
		return lastError
	}
	return ii.openFiles()
}

func (ii *InvertedIndex) openFiles() error {
	var err error
	var totalKeys uint64
	var invalidFileItems []*filesItem
	ii.files.Ascend(func(item *filesItem) bool {
		if item.decompressor != nil {
			item.decompressor.Close()
		}
		fromStep, toStep := item.startTxNum/ii.aggregationStep, item.endTxNum/ii.aggregationStep
		datPath := filepath.Join(ii.dir, fmt.Sprintf("%s.%d-%d.ef", ii.filenameBase, fromStep, toStep))
		if !dir.FileExist(datPath) {
			invalidFileItems = append(invalidFileItems, item)
		}
		if item.decompressor, err = compress.NewDecompressor(datPath); err != nil {
			log.Debug("InvertedIndex.openFiles: %w, %s", err, datPath)
			return false
		}

		if item.index == nil {
			idxPath := filepath.Join(ii.dir, fmt.Sprintf("%s.%d-%d.efi", ii.filenameBase, fromStep, toStep))
			if dir.FileExist(idxPath) {
				if item.index, err = recsplit.OpenIndex(idxPath); err != nil {
					log.Debug("InvertedIndex.openFiles: %w, %s", err, idxPath)
					return false
				}
				totalKeys += item.index.KeyCount()
			}
		}
		return true
	})
	for _, item := range invalidFileItems {
		ii.files.Delete(item)
	}
	if err != nil {
		return err
	}
	return nil
}

func (ii *InvertedIndex) closeFiles() {
	ii.files.Ascend(func(item *filesItem) bool {
		if item.decompressor != nil {
			item.decompressor.Close()
		}
		if item.index != nil {
			item.index.Close()
		}
		return true
	})
}

func (ii *InvertedIndex) Close() {
	ii.closeFiles()
}

func (ii *InvertedIndex) Files() (res []string) {
	ii.files.Ascend(func(item *filesItem) bool {
		if item.decompressor != nil {
			_, fName := filepath.Split(item.decompressor.FilePath())
			res = append(res, filepath.Join("history", fName))
		}
		return true
	})
	return res
}

func (ii *InvertedIndex) SetTx(tx kv.RwTx) {
	ii.tx = tx
}

func (ii *InvertedIndex) SetTxNum(txNum uint64) {
	ii.txNum = txNum
	binary.BigEndian.PutUint64(ii.txNumBytes[:], ii.txNum)
}

func (ii *InvertedIndex) add(key, indexKey []byte) (err error) {
	ii.walLock.RLock()
	err = ii.wal.add(key, indexKey)
	ii.walLock.RUnlock()
	return err
}

func (ii *InvertedIndex) Add(key []byte) error {
	return ii.add(key, key)
}

func (ii *InvertedIndex) DiscardHistory(tmpdir string) {
	ii.walLock.Lock()
	defer ii.walLock.Unlock()
	ii.wal = ii.newWriter(tmpdir, false, true)
}
func (ii *InvertedIndex) StartWrites(tmpdir string) {
	ii.walLock.Lock()
	defer ii.walLock.Unlock()
	ii.wal = ii.newWriter(tmpdir, true, false)
}
func (ii *InvertedIndex) FinishWrites() {
	ii.walLock.Lock()
	defer ii.walLock.Unlock()
	ii.wal.close()
	ii.wal = nil
}

func (ii *InvertedIndex) Rotate() *invertedIndexWAL {
	ii.walLock.Lock()
	defer ii.walLock.Unlock()
	wal := ii.wal
	if wal != nil {
		ii.wal = ii.newWriter(ii.wal.tmpdir, ii.wal.buffered, ii.wal.discard)
	}
	return wal
}

type invertedIndexWAL struct {
	ii        *InvertedIndex
	index     *etl.Collector
	indexKeys *etl.Collector
	tmpdir    string
	buffered  bool
	discard   bool
}

// loadFunc - is analog of etl.Identity, but it signaling to etl - use .Put instead of .AppendDup - to allow duplicates
// maybe in future we will improve etl, to sort dupSort values in the way that allow use .AppendDup
func loadFunc(k, v []byte, table etl.CurrentTableReader, next etl.LoadNextFunc) error {
	return next(k, k, v)
}

func (ii *invertedIndexWAL) Flush(tx kv.RwTx) error {
	if ii.discard {
		return nil
	}
	if err := ii.index.Load(tx, ii.ii.indexTable, loadFunc, etl.TransformArgs{}); err != nil {
		return err
	}
	if err := ii.indexKeys.Load(tx, ii.ii.indexKeysTable, loadFunc, etl.TransformArgs{}); err != nil {
		return err
	}
	ii.close()
	return nil
}

func (ii *invertedIndexWAL) close() {
	if ii == nil {
		return
	}
	if ii.index != nil {
		ii.index.Close()
	}
	if ii.indexKeys != nil {
		ii.indexKeys.Close()
	}
}

var WALCollectorRam = etl.BufferOptimalSize / 16

func init() {
	v, _ := os.LookupEnv("ERIGON_WAL_COLLETOR_RAM")
	if v != "" {
		var err error
		WALCollectorRam, err = datasize.ParseString(v)
		if err != nil {
			panic(err)
		}
	}
}

func (ii *InvertedIndex) newWriter(tmpdir string, buffered, discard bool) *invertedIndexWAL {
	w := &invertedIndexWAL{ii: ii,
		buffered: buffered,
		discard:  discard,
		tmpdir:   tmpdir,
	}
	if buffered {
		// 3 history + 4 indices = 10 etl collectors, 10*256Mb/16 = 256mb - for all indices buffers
		// etl collector doesn't fsync: means if have enough ram, all files produced by all collectors will be in ram
		w.index = etl.NewCollector(ii.indexTable, tmpdir, etl.NewSortableBuffer(WALCollectorRam))
		w.indexKeys = etl.NewCollector(ii.indexKeysTable, tmpdir, etl.NewSortableBuffer(WALCollectorRam))
		w.index.LogLvl(log.LvlTrace)
		w.indexKeys.LogLvl(log.LvlTrace)
	}
	return w
}

func (ii *invertedIndexWAL) add(key, indexKey []byte) error {
	if ii.discard {
		return nil
	}

	if ii.buffered {
		if err := ii.indexKeys.Collect(ii.ii.txNumBytes[:], key); err != nil {
			return err
		}

		if err := ii.index.Collect(indexKey, ii.ii.txNumBytes[:]); err != nil {
			return err
		}
	} else {
		if err := ii.ii.tx.Put(ii.ii.indexKeysTable, ii.ii.txNumBytes[:], key); err != nil {
			return err
		}
		if err := ii.ii.tx.Put(ii.ii.indexTable, indexKey, ii.ii.txNumBytes[:]); err != nil {
			return err
		}
	}
	return nil
}

func (ii *InvertedIndex) MakeContext() *InvertedIndexContext {
	var ic = InvertedIndexContext{ii: ii}
	ic.files = btree.NewG[ctxItem](32, ctxItemLess)
	ii.files.Ascend(func(item *filesItem) bool {
		if item.index == nil {
			return false
		}

		ic.files.ReplaceOrInsert(ctxItem{
			startTxNum: item.startTxNum,
			endTxNum:   item.endTxNum,
			getter:     item.decompressor.MakeGetter(),
			reader:     recsplit.NewIndexReader(item.index),
		})
		return true
	})
	return &ic
}

// InvertedIterator allows iteration over range of tx numbers
// Iteration is not implmented via callback function, because there is often
// a requirement for interators to be composable (for example, to implement AND and OR for indices)
// InvertedIterator must be closed after use to prevent leaking of resources like cursor
type InvertedIterator struct {
	roTx           kv.Tx
	cursor         kv.CursorDupSort
	efIt           *eliasfano32.EliasFanoIter
	indexTable     string
	key            []byte
	stack          []ctxItem
	startTxNum     uint64
	endTxNum       uint64
	next           uint64
	hasNextInFiles bool
	hasNextInDb    bool
}

func (it *InvertedIterator) Close() {
	if it.cursor != nil {
		it.cursor.Close()
	}
}

func (it *InvertedIterator) advanceInFiles() {
	for {
		for it.efIt == nil {
			if len(it.stack) == 0 {
				it.hasNextInFiles = false
				return
			}
			item := it.stack[len(it.stack)-1]
			it.stack = it.stack[:len(it.stack)-1]
			offset := item.reader.Lookup(it.key)
			g := item.getter
			g.Reset(offset)
			if k, _ := g.NextUncompressed(); bytes.Equal(k, it.key) {
				eliasVal, _ := g.NextUncompressed()
				ef, _ := eliasfano32.ReadEliasFano(eliasVal)
				it.efIt = ef.Iterator()
			}
		}
		for it.efIt.HasNext() {
			n := it.efIt.Next()
			if n >= it.endTxNum {
				it.hasNextInFiles = false
				return
			}
			if n >= it.startTxNum {
				it.hasNextInFiles = true
				it.next = n
				return
			}
		}
		it.efIt = nil // Exhausted this iterator
	}
}

func (it *InvertedIterator) advanceInDb() {
	var v []byte
	var err error
	if it.cursor == nil {
		if it.cursor, err = it.roTx.CursorDupSort(it.indexTable); err != nil {
			// TODO pass error properly around
			panic(err)
		}
		var k []byte
		if k, v, err = it.cursor.Seek(it.key); err != nil {
			// TODO pass error properly around
			panic(err)
		}
		if !bytes.Equal(k, it.key) {
			it.cursor.Close()
			it.hasNextInDb = false
			return
		}
	} else {
		_, v, err = it.cursor.NextDup()
		if err != nil {
			// TODO pass error properly around
			panic(err)
		}
	}
	for ; err == nil && v != nil; _, v, err = it.cursor.NextDup() {
		n := binary.BigEndian.Uint64(v)
		if n >= it.endTxNum {
			it.cursor.Close()
			it.hasNextInDb = false
			return
		}
		if n >= it.startTxNum {
			it.hasNextInDb = true
			it.next = n
			return
		}
	}
	if err != nil {
		// TODO pass error properly around
		panic(err)
	}
	it.cursor.Close()
	it.hasNextInDb = false
}

func (it *InvertedIterator) advance() {
	if it.hasNextInFiles {
		it.advanceInFiles()
	}
	if it.hasNextInDb && !it.hasNextInFiles {
		it.advanceInDb()
	}
}

func (it *InvertedIterator) HasNext() bool {
	return it.hasNextInFiles || it.hasNextInDb
}

func (it *InvertedIterator) Next() uint64 {
	n := it.next
	it.advance()
	return n
}

type InvertedIndexContext struct {
	ii    *InvertedIndex
	files *btree.BTreeG[ctxItem]
}

// IterateRange is to be used in public API, therefore it relies on read-only transaction
// so that iteration can be done even when the inverted index is being updated.
// [startTxNum; endNumTx)
func (ic *InvertedIndexContext) IterateRange(key []byte, startTxNum, endTxNum uint64, roTx kv.Tx) InvertedIterator {
	it := InvertedIterator{
		key:        key,
		startTxNum: startTxNum,
		endTxNum:   endTxNum,
		indexTable: ic.ii.indexTable,
		roTx:       roTx,
	}
	var search ctxItem
	it.hasNextInDb = true
	search.startTxNum = 0
	search.endTxNum = startTxNum
	ic.files.DescendGreaterThan(search, func(item ctxItem) bool {
		if item.startTxNum < endTxNum {
			it.stack = append(it.stack, item)
			it.hasNextInFiles = true
		}
		if item.endTxNum >= endTxNum {
			it.hasNextInDb = false
		}
		return true
	})
	it.advance()
	return it
}

type InvertedIterator1 struct {
	roTx           kv.Tx
	cursor         kv.CursorDupSort
	indexTable     string
	key            []byte
	h              ReconHeap
	nextKey        []byte
	nextFileKey    []byte
	nextDbKey      []byte
	endTxNum       uint64
	startTxNum     uint64
	startTxKey     [8]byte
	hasNextInDb    bool
	hasNextInFiles bool
}

func (it *InvertedIterator1) Close() {
	if it.cursor != nil {
		it.cursor.Close()
	}
}

func (it *InvertedIterator1) advanceInFiles() {
	for it.h.Len() > 0 {
		top := heap.Pop(&it.h).(*ReconItem)
		key := top.key
		val, _ := top.g.NextUncompressed()
		if top.g.HasNext() {
			top.key, _ = top.g.NextUncompressed()
			heap.Push(&it.h, top)
		}
		if !bytes.Equal(key, it.key) {
			ef, _ := eliasfano32.ReadEliasFano(val)
			min := ef.Get(0)
			max := ef.Max()
			if min < it.endTxNum && max >= it.startTxNum { // Intersection of [min; max) and [it.startTxNum; it.endTxNum)
				it.key = key
				it.nextFileKey = key
				return
			}
		}
	}
	it.hasNextInFiles = false
}

func (it *InvertedIterator1) advanceInDb() {
	var k, v []byte
	var err error
	if it.cursor == nil {
		if it.cursor, err = it.roTx.CursorDupSort(it.indexTable); err != nil {
			// TODO pass error properly around
			panic(err)
		}
		if k, _, err = it.cursor.First(); err != nil {
			// TODO pass error properly around
			panic(err)
		}
	} else {
		if k, _, err = it.cursor.NextNoDup(); err != nil {
			panic(err)
		}
	}
	for k != nil {
		if v, err = it.cursor.SeekBothRange(k, it.startTxKey[:]); err != nil {
			panic(err)
		}
		if v != nil {
			txNum := binary.BigEndian.Uint64(v)
			if txNum < it.endTxNum {
				it.nextDbKey = append(it.nextDbKey[:0], k...)
				return
			}
		}
		if k, _, err = it.cursor.NextNoDup(); err != nil {
			panic(err)
		}
	}
	it.cursor.Close()
	it.cursor = nil
	it.hasNextInDb = false
}

func (it *InvertedIterator1) advance() {
	if it.hasNextInFiles {
		if it.hasNextInDb {
			c := bytes.Compare(it.nextFileKey, it.nextDbKey)
			if c < 0 {
				it.nextKey = append(it.nextKey[:0], it.nextFileKey...)
				it.advanceInFiles()
			} else if c > 0 {
				it.nextKey = append(it.nextKey[:0], it.nextDbKey...)
				it.advanceInDb()
			} else {
				it.nextKey = append(it.nextKey[:0], it.nextFileKey...)
				it.advanceInDb()
				it.advanceInFiles()
			}
		} else {
			it.nextKey = append(it.nextKey[:0], it.nextFileKey...)
			it.advanceInFiles()
		}
	} else if it.hasNextInDb {
		it.nextKey = append(it.nextKey[:0], it.nextDbKey...)
		it.advanceInDb()
	} else {
		it.nextKey = nil
	}
}

func (it *InvertedIterator1) HasNext() bool {
	return it.hasNextInFiles || it.hasNextInDb || it.nextKey != nil
}

func (it *InvertedIterator1) Next(keyBuf []byte) []byte {
	result := append(keyBuf, it.nextKey...)
	it.advance()
	return result
}

func (ic *InvertedIndexContext) IterateChangedKeys(startTxNum, endTxNum uint64, roTx kv.Tx) InvertedIterator1 {
	var ii1 InvertedIterator1
	ii1.hasNextInDb = true
	ii1.roTx = roTx
	ii1.indexTable = ic.ii.indexTable
	ic.files.AscendGreaterOrEqual(ctxItem{endTxNum: startTxNum}, func(item ctxItem) bool {
		if item.endTxNum >= endTxNum {
			ii1.hasNextInDb = false
		}
		if item.endTxNum <= startTxNum {
			return true
		}
		if item.startTxNum >= endTxNum {
			return false
		}
		g := item.getter
		if g.HasNext() {
			key, _ := g.NextUncompressed()
			heap.Push(&ii1.h, &ReconItem{startTxNum: item.startTxNum, endTxNum: item.endTxNum, g: g, txNum: ^item.endTxNum, key: key})
			ii1.hasNextInFiles = true
		}
		return true
	})
	binary.BigEndian.PutUint64(ii1.startTxKey[:], startTxNum)
	ii1.startTxNum = startTxNum
	ii1.endTxNum = endTxNum
	ii1.advanceInDb()
	ii1.advanceInFiles()
	ii1.advance()
	return ii1
}

func (ii *InvertedIndex) collate(ctx context.Context, txFrom, txTo uint64, roTx kv.Tx, logEvery *time.Ticker) (map[string]*roaring64.Bitmap, error) {
	keysCursor, err := roTx.CursorDupSort(ii.indexKeysTable)
	if err != nil {
		return nil, fmt.Errorf("create %s keys cursor: %w", ii.filenameBase, err)
	}
	defer keysCursor.Close()
	indexBitmaps := map[string]*roaring64.Bitmap{}
	var txKey [8]byte
	binary.BigEndian.PutUint64(txKey[:], txFrom)
	var k, v []byte
	for k, v, err = keysCursor.Seek(txKey[:]); err == nil && k != nil; k, v, err = keysCursor.Next() {
		txNum := binary.BigEndian.Uint64(k)
		if txNum >= txTo {
			break
		}
		var bitmap *roaring64.Bitmap
		var ok bool
		if bitmap, ok = indexBitmaps[string(v)]; !ok {
			bitmap = bitmapdb.NewBitmap64()
			indexBitmaps[string(v)] = bitmap
		}
		bitmap.Add(txNum)

		select {
		case <-logEvery.C:
			log.Info("[snapshots] collate history", "name", ii.filenameBase, "range", fmt.Sprintf("%.2f-%.2f", float64(txNum)/float64(ii.aggregationStep), float64(txTo)/float64(ii.aggregationStep)))
			bitmap.RunOptimize()
		case <-ctx.Done():
			err := ctx.Err()
			log.Warn("index collate cancelled", "err", err)
			return nil, err
		default:
		}
	}
	if err != nil {
		return nil, fmt.Errorf("iterate over %s keys cursor: %w", ii.filenameBase, err)
	}
	return indexBitmaps, nil
}

type InvertedFiles struct {
	decomp *compress.Decompressor
	index  *recsplit.Index
}

func (sf InvertedFiles) Close() {
	if sf.decomp != nil {
		sf.decomp.Close()
	}
	if sf.index != nil {
		sf.index.Close()
	}
}

func (ii *InvertedIndex) buildFiles(ctx context.Context, step uint64, bitmaps map[string]*roaring64.Bitmap) (InvertedFiles, error) {
	var decomp *compress.Decompressor
	var index *recsplit.Index
	var comp *compress.Compressor
	var err error
	closeComp := true
	defer func() {
		if closeComp {
			if comp != nil {
				comp.Close()
			}
			if decomp != nil {
				decomp.Close()
			}
			if index != nil {
				index.Close()
			}
		}
	}()
	txNumFrom := step * ii.aggregationStep
	txNumTo := (step + 1) * ii.aggregationStep
	datPath := filepath.Join(ii.dir, fmt.Sprintf("%s.%d-%d.ef", ii.filenameBase, txNumFrom/ii.aggregationStep, txNumTo/ii.aggregationStep))
	comp, err = compress.NewCompressor(ctx, "ef", datPath, ii.tmpdir, compress.MinPatternScore, ii.workers, log.LvlTrace)
	if err != nil {
		return InvertedFiles{}, fmt.Errorf("create %s compressor: %w", ii.filenameBase, err)
	}
	var buf []byte
	keys := make([]string, 0, len(bitmaps))
	for key := range bitmaps {
		keys = append(keys, key)
	}
	slices.Sort(keys)
	for _, key := range keys {
		if err = comp.AddUncompressedWord([]byte(key)); err != nil {
			return InvertedFiles{}, fmt.Errorf("add %s key [%x]: %w", ii.filenameBase, key, err)
		}
		bitmap := bitmaps[key]
		ef := eliasfano32.NewEliasFano(bitmap.GetCardinality(), bitmap.Maximum())
		it := bitmap.Iterator()
		for it.HasNext() {
			ef.AddOffset(it.Next())
		}
		ef.Build()
		buf = ef.AppendBytes(buf[:0])
		if err = comp.AddUncompressedWord(buf); err != nil {
			return InvertedFiles{}, fmt.Errorf("add %s val: %w", ii.filenameBase, err)
		}
	}
	if err = comp.Compress(); err != nil {
		return InvertedFiles{}, fmt.Errorf("compress %s: %w", ii.filenameBase, err)
	}
	comp.Close()
	comp = nil
	if decomp, err = compress.NewDecompressor(datPath); err != nil {
		return InvertedFiles{}, fmt.Errorf("open %s decompressor: %w", ii.filenameBase, err)
	}
	idxPath := filepath.Join(ii.dir, fmt.Sprintf("%s.%d-%d.efi", ii.filenameBase, txNumFrom/ii.aggregationStep, txNumTo/ii.aggregationStep))
	if index, err = buildIndex(ctx, decomp, idxPath, ii.tmpdir, len(keys), false /* values */); err != nil {
		return InvertedFiles{}, fmt.Errorf("build %s efi: %w", ii.filenameBase, err)
	}
	closeComp = false
	return InvertedFiles{decomp: decomp, index: index}, nil
}

func (ii *InvertedIndex) integrateFiles(sf InvertedFiles, txNumFrom, txNumTo uint64) {
	ii.files.ReplaceOrInsert(&filesItem{
		startTxNum:   txNumFrom,
		endTxNum:     txNumTo,
		decompressor: sf.decomp,
		index:        sf.index,
	})
}

func (ii *InvertedIndex) warmup(txFrom, limit uint64, tx kv.Tx) error {
	keysCursor, err := tx.CursorDupSort(ii.indexKeysTable)
	if err != nil {
		return fmt.Errorf("create %s keys cursor: %w", ii.filenameBase, err)
	}
	defer keysCursor.Close()
	var txKey [8]byte
	binary.BigEndian.PutUint64(txKey[:], txFrom)
	var k, v []byte
	idxC, err := tx.CursorDupSort(ii.indexTable)
	if err != nil {
		return err
	}
	defer idxC.Close()
	k, v, err = keysCursor.Seek(txKey[:])
	if err != nil {
		return err
	}
	if k == nil {
		return nil
	}
	txFrom = binary.BigEndian.Uint64(k)
	txTo := txFrom + ii.aggregationStep
	if limit != math.MaxUint64 && limit != 0 {
		txTo = txFrom + limit
	}
	for ; err == nil && k != nil; k, v, err = keysCursor.Next() {
		txNum := binary.BigEndian.Uint64(k)
		if txNum >= txTo {
			break
		}
		_, _ = idxC.SeekBothRange(v, k)
	}
	if err != nil {
		return fmt.Errorf("iterate over %s keys: %w", ii.filenameBase, err)
	}
	return nil
}

// [txFrom; txTo)
func (ii *InvertedIndex) prune(ctx context.Context, txFrom, txTo, limit uint64, logEvery *time.Ticker) error {
	select {
	case <-ctx.Done():
		return nil
	default:
	}

	keysCursor, err := ii.tx.RwCursorDupSort(ii.indexKeysTable)
	if err != nil {
		return fmt.Errorf("create %s keys cursor: %w", ii.filenameBase, err)
	}
	defer keysCursor.Close()
	var txKey [8]byte
	binary.BigEndian.PutUint64(txKey[:], txFrom)
	k, v, err := keysCursor.Seek(txKey[:])
	if err != nil {
		return err
	}
	if k == nil {
		return nil
	}
	txFrom = binary.BigEndian.Uint64(k)
	if limit != math.MaxUint64 && limit != 0 {
		txTo = cmp.Min(txTo, txFrom+limit)
	}
	if txFrom >= txTo {
		return nil
	}

	idxC, err := ii.tx.RwCursorDupSort(ii.indexTable)
	if err != nil {
		return err
	}
	defer idxC.Close()
	for ; err == nil && k != nil; k, v, err = keysCursor.Next() {
		txNum := binary.BigEndian.Uint64(k)
		if txNum >= txTo {
			break
		}
		if err = idxC.DeleteExact(v, k); err != nil {
			return err
		}
		// This DeleteCurrent needs to the last in the loop iteration, because it invalidates k and v
		if err = keysCursor.DeleteCurrent(); err != nil {
			return err
		}
		select {
		case <-logEvery.C:
			log.Info("[snapshots] prune history", "name", ii.filenameBase, "range", fmt.Sprintf("%.2f-%.2f", float64(txNum)/float64(ii.aggregationStep), float64(txTo)/float64(ii.aggregationStep)))
		default:
		}
	}
	if err != nil {
		return fmt.Errorf("iterate over %s keys: %w", ii.filenameBase, err)
	}
	return nil
}

func (ii *InvertedIndex) DisableReadAhead() {
	ii.files.Ascend(func(item *filesItem) bool {
		item.decompressor.DisableReadAhead()
		if item.index != nil {
			item.index.DisableReadAhead()
		}
		return true
	})
}

func (ii *InvertedIndex) EnableReadAhead() *InvertedIndex {
	ii.files.Ascend(func(item *filesItem) bool {
		item.decompressor.EnableReadAhead()
		if item.index != nil {
			item.index.EnableReadAhead()
		}
		return true
	})
	return ii
}
func (ii *InvertedIndex) EnableMadvWillNeed() *InvertedIndex {
	ii.files.Ascend(func(item *filesItem) bool {
		item.decompressor.EnableWillNeed()
		if item.index != nil {
			item.index.EnableWillNeed()
		}
		return true
	})
	return ii
}
func (ii *InvertedIndex) EnableMadvNormalReadAhead() *InvertedIndex {
	ii.files.Ascend(func(item *filesItem) bool {
		item.decompressor.EnableMadvNormal()
		if item.index != nil {
			item.index.EnableMadvNormal()
		}
		return true
	})
	return ii
}

func (ii *InvertedIndex) collectFilesStat() (filesCount, filesSize, idxSize uint64) {
	if ii.files == nil {
		return 0, 0, 0
	}
	ii.files.Ascend(func(item *filesItem) bool {
		if item.index == nil {
			return false
		}
		filesSize += uint64(item.decompressor.Size())
		idxSize += uint64(item.index.Size())
		filesCount += 2

		return true
	})
	return filesCount, filesSize, idxSize
}