package logstorage

import (
	"strconv"
	"sync"
	"time"

	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/encoding"
	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
)

type blockSearchWork struct {
	// p is the part where the block belongs to.
	p *part

	// so contains search options for the block search
	so *searchOptions

	// bh is the header of the block to search.
	bh blockHeader
}

func newBlockSearchWork(p *part, so *searchOptions, bh *blockHeader) *blockSearchWork {
	var bsw blockSearchWork
	bsw.p = p
	bsw.so = so
	bsw.bh.copyFrom(bh)
	return &bsw
}

func getBlockSearch() *blockSearch {
	v := blockSearchPool.Get()
	if v == nil {
		return &blockSearch{}
	}
	return v.(*blockSearch)
}

func putBlockSearch(bs *blockSearch) {
	bs.reset()
	blockSearchPool.Put(bs)
}

var blockSearchPool sync.Pool

type blockSearch struct {
	// bsw is the actual work to perform on the given block pointed by bsw.ph
	bsw *blockSearchWork

	// br contains result for the search in the block after search() call
	br blockResult

	// timestampsCache contains cached timestamps for the given block.
	timestampsCache *encoding.Int64s

	// bloomFilterCache contains cached bloom filters for requested columns in the given block
	bloomFilterCache map[string]*bloomFilter

	// valuesCache contains cached values for requested columns in the given block
	valuesCache map[string]*stringBucket

	// sbu is used for unmarshaling local columns
	sbu stringsBlockUnmarshaler

	// csh is the columnsHeader associated with the given block
	csh columnsHeader
}

func (bs *blockSearch) reset() {
	bs.bsw = nil
	bs.br.reset()

	if bs.timestampsCache != nil {
		encoding.PutInt64s(bs.timestampsCache)
		bs.timestampsCache = nil
	}

	bloomFilterCache := bs.bloomFilterCache
	for k, bf := range bloomFilterCache {
		putBloomFilter(bf)
		delete(bloomFilterCache, k)
	}

	valuesCache := bs.valuesCache
	for k, values := range valuesCache {
		putStringBucket(values)
		delete(valuesCache, k)
	}

	bs.sbu.reset()
	bs.csh.reset()
}

func (bs *blockSearch) partPath() string {
	return bs.bsw.p.path
}

func (bs *blockSearch) search(bsw *blockSearchWork) {
	bs.reset()

	bs.bsw = bsw

	bs.csh.initFromBlockHeader(bsw.p, &bsw.bh)

	// search rows matching the given filter
	bm := getFilterBitmap(int(bsw.bh.rowsCount))
	bm.setBits()
	bs.bsw.so.filter.apply(bs, bm)

	bs.br.mustInit(bs, bm)
	if bm.isZero() {
		putFilterBitmap(bm)
		return
	}

	// fetch the requested columns to bs.br.
	for _, columnName := range bs.bsw.so.resultColumnNames {
		switch columnName {
		case "_stream":
			bs.br.addStreamColumn(bs)
		case "_time":
			bs.br.addTimeColumn(bs)
		default:
			v := bs.csh.getConstColumnValue(columnName)
			if v != "" {
				bs.br.addConstColumn(v)
				continue
			}
			ch := bs.csh.getColumnHeader(columnName)
			if ch == nil {
				bs.br.addConstColumn("")
			} else {
				bs.br.addColumn(bs, ch, bm)
			}
		}
	}
	putFilterBitmap(bm)
}

func (csh *columnsHeader) initFromBlockHeader(p *part, bh *blockHeader) {
	bb := longTermBufPool.Get()
	columnsHeaderSize := bh.columnsHeaderSize
	if columnsHeaderSize > maxColumnsHeaderSize {
		logger.Panicf("FATAL: %s: columns header size cannot exceed %d bytes; got %d bytes", p.path, maxColumnsHeaderSize, columnsHeaderSize)
	}
	bb.B = bytesutil.ResizeNoCopyMayOverallocate(bb.B, int(columnsHeaderSize))
	p.columnsHeaderFile.MustReadAt(bb.B, int64(bh.columnsHeaderOffset))

	if err := csh.unmarshal(bb.B); err != nil {
		logger.Panicf("FATAL: %s: cannot unmarshal columns header: %s", p.path, err)
	}
	longTermBufPool.Put(bb)
}

// getBloomFilterForColumn returns bloom filter for the given ch.
//
// The returned bloom filter belongs to bs, so it becomes invalid after bs reset.
func (bs *blockSearch) getBloomFilterForColumn(ch *columnHeader) *bloomFilter {
	bf := bs.bloomFilterCache[ch.name]
	if bf != nil {
		return bf
	}

	p := bs.bsw.p

	bloomFilterFile := p.fieldBloomFilterFile
	if ch.name == "" {
		bloomFilterFile = p.messageBloomFilterFile
	}

	bb := longTermBufPool.Get()
	bloomFilterSize := ch.bloomFilterSize
	if bloomFilterSize > maxBloomFilterBlockSize {
		logger.Panicf("FATAL: %s: bloom filter block size cannot exceed %d bytes; got %d bytes", bs.partPath(), maxBloomFilterBlockSize, bloomFilterSize)
	}
	bb.B = bytesutil.ResizeNoCopyMayOverallocate(bb.B, int(bloomFilterSize))
	bloomFilterFile.MustReadAt(bb.B, int64(ch.bloomFilterOffset))
	bf = getBloomFilter()
	if err := bf.unmarshal(bb.B); err != nil {
		logger.Panicf("FATAL: %s: cannot unmarshal bloom filter: %s", bs.partPath(), err)
	}
	longTermBufPool.Put(bb)

	if bs.bloomFilterCache == nil {
		bs.bloomFilterCache = make(map[string]*bloomFilter)
	}
	bs.bloomFilterCache[ch.name] = bf
	return bf
}

// getValuesForColumn returns block values for the given ch.
//
// The returned values belong to bs, so they become invalid after bs reset.
func (bs *blockSearch) getValuesForColumn(ch *columnHeader) []string {
	values := bs.valuesCache[ch.name]
	if values != nil {
		return values.a
	}

	p := bs.bsw.p

	valuesFile := p.fieldValuesFile
	if ch.name == "" {
		valuesFile = p.messageValuesFile
	}

	bb := longTermBufPool.Get()
	valuesSize := ch.valuesSize
	if valuesSize > maxValuesBlockSize {
		logger.Panicf("FATAL: %s: values block size cannot exceed %d bytes; got %d bytes", bs.partPath(), maxValuesBlockSize, valuesSize)
	}
	bb.B = bytesutil.ResizeNoCopyMayOverallocate(bb.B, int(valuesSize))
	valuesFile.MustReadAt(bb.B, int64(ch.valuesOffset))

	values = getStringBucket()
	var err error
	values.a, err = bs.sbu.unmarshal(values.a[:0], bb.B, bs.bsw.bh.rowsCount)
	longTermBufPool.Put(bb)
	if err != nil {
		logger.Panicf("FATAL: %s: cannot unmarshal column %q: %s", bs.partPath(), ch.name, err)
	}

	if bs.valuesCache == nil {
		bs.valuesCache = make(map[string]*stringBucket)
	}
	bs.valuesCache[ch.name] = values
	return values.a
}

// getTimestamps returns timestamps for the given bs.
//
// The returned timestamps belong to bs, so they become invalid after bs reset.
func (bs *blockSearch) getTimestamps() []int64 {
	timestamps := bs.timestampsCache
	if timestamps != nil {
		return timestamps.A
	}

	p := bs.bsw.p

	bb := longTermBufPool.Get()
	th := &bs.bsw.bh.timestampsHeader
	blockSize := th.blockSize
	if blockSize > maxTimestampsBlockSize {
		logger.Panicf("FATAL: %s: timestamps block size cannot exceed %d bytes; got %d bytes", bs.partPath(), maxTimestampsBlockSize, blockSize)
	}
	bb.B = bytesutil.ResizeNoCopyMayOverallocate(bb.B, int(blockSize))
	p.timestampsFile.MustReadAt(bb.B, int64(th.blockOffset))

	rowsCount := int(bs.bsw.bh.rowsCount)
	timestamps = encoding.GetInt64s(rowsCount)
	var err error
	timestamps.A, err = encoding.UnmarshalTimestamps(timestamps.A[:0], bb.B, th.marshalType, th.minTimestamp, rowsCount)
	longTermBufPool.Put(bb)
	if err != nil {
		logger.Panicf("FATAL: %s: cannot unmarshal timestamps: %s", bs.partPath(), err)
	}
	bs.timestampsCache = timestamps
	return timestamps.A
}

// mustReadBlockHeaders reads ih block headers from p, appends them to dst and returns the result.
func (ih *indexBlockHeader) mustReadBlockHeaders(dst []blockHeader, p *part) []blockHeader {
	bbCompressed := longTermBufPool.Get()
	indexBlockSize := ih.indexBlockSize
	if indexBlockSize > maxIndexBlockSize {
		logger.Panicf("FATAL: %s: index block size cannot exceed %d bytes; got %d bytes", p.indexFile.Path(), maxIndexBlockSize, indexBlockSize)
	}
	bbCompressed.B = bytesutil.ResizeNoCopyMayOverallocate(bbCompressed.B, int(indexBlockSize))
	p.indexFile.MustReadAt(bbCompressed.B, int64(ih.indexBlockOffset))

	bb := longTermBufPool.Get()
	var err error
	bb.B, err = encoding.DecompressZSTD(bb.B, bbCompressed.B)
	longTermBufPool.Put(bbCompressed)
	if err != nil {
		logger.Panicf("FATAL: %s: cannot decompress indexBlock read at offset %d with size %d: %s", p.indexFile.Path(), ih.indexBlockOffset, ih.indexBlockSize, err)
	}

	dst, err = unmarshalBlockHeaders(dst, bb.B)
	longTermBufPool.Put(bb)
	if err != nil {
		logger.Panicf("FATAL: %s: cannot unmarshal block headers read at offset %d with size %d: %s", p.indexFile.Path(), ih.indexBlockOffset, ih.indexBlockSize, err)
	}

	return dst
}

type blockResult struct {
	buf       []byte
	valuesBuf []string

	// streamID is streamID for the given blockResult
	streamID streamID

	// cs contain values for result columns
	cs []blockResultColumn

	// timestamps contain timestamps for the selected log entries
	timestamps []int64
}

func (br *blockResult) reset() {
	br.buf = br.buf[:0]

	vb := br.valuesBuf
	for i := range vb {
		vb[i] = ""
	}
	br.valuesBuf = vb[:0]

	br.streamID.reset()

	cs := br.cs
	for i := range cs {
		cs[i].reset()
	}
	br.cs = cs[:0]

	br.timestamps = br.timestamps[:0]
}

func (br *blockResult) RowsCount() int {
	return len(br.timestamps)
}

func (br *blockResult) mustInit(bs *blockSearch, bm *filterBitmap) {
	br.reset()

	br.streamID = bs.bsw.bh.streamID

	if !bm.isZero() {
		// Initialize timestamps, since they are used for determining the number of rows in br.RowsCount()
		srcTimestamps := bs.getTimestamps()
		dstTimestamps := br.timestamps[:0]
		bm.forEachSetBit(func(idx int) bool {
			ts := srcTimestamps[idx]
			dstTimestamps = append(dstTimestamps, ts)
			return true
		})
		br.timestamps = dstTimestamps
	}
}

func (br *blockResult) addColumn(bs *blockSearch, ch *columnHeader, bm *filterBitmap) {
	buf := br.buf
	valuesBuf := br.valuesBuf
	valuesBufLen := len(valuesBuf)
	var dictValues []string

	appendValue := func(v string) {
		bufLen := len(buf)
		buf = append(buf, v...)
		s := bytesutil.ToUnsafeString(buf[bufLen:])
		valuesBuf = append(valuesBuf, s)
	}

	switch ch.valueType {
	case valueTypeString:
		visitValues(bs, ch, bm, func(v string) bool {
			appendValue(v)
			return true
		})
	case valueTypeDict:
		dictValues = ch.valuesDict.values
		visitValues(bs, ch, bm, func(v string) bool {
			if len(v) != 1 {
				logger.Panicf("FATAL: %s: unexpected dict value size for column %q; got %d bytes; want 1 byte", bs.partPath(), ch.name, len(v))
			}
			dictIdx := v[0]
			if int(dictIdx) >= len(dictValues) {
				logger.Panicf("FATAL: %s: too big dict index for column %q: %d; should be smaller than %d", bs.partPath(), ch.name, dictIdx, len(dictValues))
			}
			appendValue(v)
			return true
		})
	case valueTypeUint8:
		visitValues(bs, ch, bm, func(v string) bool {
			if len(v) != 1 {
				logger.Panicf("FATAL: %s: unexpected size for uint8 column %q; got %d bytes; want 1 byte", bs.partPath(), ch.name, len(v))
			}
			appendValue(v)
			return true
		})
	case valueTypeUint16:
		visitValues(bs, ch, bm, func(v string) bool {
			if len(v) != 2 {
				logger.Panicf("FATAL: %s: unexpected size for uint16 column %q; got %d bytes; want 2 bytes", bs.partPath(), ch.name, len(v))
			}
			appendValue(v)
			return true
		})
	case valueTypeUint32:
		visitValues(bs, ch, bm, func(v string) bool {
			if len(v) != 4 {
				logger.Panicf("FATAL: %s: unexpected size for uint32 column %q; got %d bytes; want 4 bytes", bs.partPath(), ch.name, len(v))
			}
			appendValue(v)
			return true
		})
	case valueTypeUint64:
		visitValues(bs, ch, bm, func(v string) bool {
			if len(v) != 8 {
				logger.Panicf("FATAL: %s: unexpected size for uint64 column %q; got %d bytes; want 8 bytes", bs.partPath(), ch.name, len(v))
			}
			appendValue(v)
			return true
		})
	case valueTypeFloat64:
		visitValues(bs, ch, bm, func(v string) bool {
			if len(v) != 8 {
				logger.Panicf("FATAL: %s: unexpected size for float64 column %q; got %d bytes; want 8 bytes", bs.partPath(), ch.name, len(v))
			}
			appendValue(v)
			return true
		})
	case valueTypeIPv4:
		visitValues(bs, ch, bm, func(v string) bool {
			if len(v) != 4 {
				logger.Panicf("FATAL: %s: unexpected size for ipv4 column %q; got %d bytes; want 4 bytes", bs.partPath(), ch.name, len(v))
			}
			appendValue(v)
			return true
		})
	case valueTypeTimestampISO8601:
		visitValues(bs, ch, bm, func(v string) bool {
			if len(v) != 8 {
				logger.Panicf("FATAL: %s: unexpected size for timestmap column %q; got %d bytes; want 8 bytes", bs.partPath(), ch.name, len(v))
			}
			appendValue(v)
			return true
		})
	default:
		logger.Panicf("FATAL: %s: unknown valueType=%d for column %q", bs.partPath(), ch.valueType, ch.name)
	}

	encodedValues := valuesBuf[valuesBufLen:]

	valuesBufLen = len(valuesBuf)
	for _, v := range dictValues {
		appendValue(v)
	}
	dictValues = valuesBuf[valuesBufLen:]

	br.cs = append(br.cs, blockResultColumn{
		valueType:     ch.valueType,
		dictValues:    dictValues,
		encodedValues: encodedValues,
	})
	br.buf = buf
	br.valuesBuf = valuesBuf
}

func (br *blockResult) addTimeColumn(bs *blockSearch) {
	br.cs = append(br.cs, blockResultColumn{
		isTime: true,
	})
}

func (br *blockResult) addStreamColumn(bs *blockSearch) {
	bb := bbPool.Get()
	bb.B = bs.bsw.p.pt.appendStreamTagsByStreamID(bb.B[:0], &br.streamID)
	if len(bb.B) > 0 {
		st := GetStreamTags()
		mustUnmarshalStreamTags(st, bb.B)
		bb.B = st.marshalString(bb.B[:0])
		PutStreamTags(st)
	}
	s := bytesutil.ToUnsafeString(bb.B)
	br.addConstColumn(s)
	bbPool.Put(bb)
}

func (br *blockResult) addConstColumn(value string) {
	buf := br.buf
	bufLen := len(buf)
	buf = append(buf, value...)
	s := bytesutil.ToUnsafeString(buf[bufLen:])
	br.buf = buf

	valuesBuf := br.valuesBuf
	valuesBufLen := len(valuesBuf)
	valuesBuf = append(valuesBuf, s)
	br.valuesBuf = valuesBuf

	br.cs = append(br.cs, blockResultColumn{
		isConst:       true,
		valueType:     valueTypeUnknown,
		encodedValues: valuesBuf[valuesBufLen:],
	})
}

// getColumnValues returns values for the column with the given idx.
//
// The returned values are valid until br.reset() is called.
func (br *blockResult) getColumnValues(idx int) []string {
	c := &br.cs[idx]
	if c.values != nil {
		return c.values
	}

	buf := br.buf
	valuesBuf := br.valuesBuf
	valuesBufLen := len(valuesBuf)

	if c.isConst {
		v := c.encodedValues[0]
		for range br.timestamps {
			valuesBuf = append(valuesBuf, v)
		}
		c.values = valuesBuf[valuesBufLen:]
		br.valuesBuf = valuesBuf
		return c.values
	}
	if c.isTime {
		for _, timestamp := range br.timestamps {
			t := time.Unix(0, timestamp).UTC()
			bufLen := len(buf)
			buf = t.AppendFormat(buf, time.RFC3339Nano)
			s := bytesutil.ToUnsafeString(buf[bufLen:])
			valuesBuf = append(valuesBuf, s)
		}
		c.values = valuesBuf[valuesBufLen:]
		br.buf = buf
		br.valuesBuf = valuesBuf
		return c.values
	}

	appendValue := func(v string) {
		bufLen := len(buf)
		buf = append(buf, v...)
		s := bytesutil.ToUnsafeString(buf[bufLen:])
		valuesBuf = append(valuesBuf, s)
	}

	switch c.valueType {
	case valueTypeString:
		c.values = c.encodedValues
		return c.values
	case valueTypeDict:
		dictValues := c.dictValues
		for _, v := range c.encodedValues {
			dictIdx := v[0]
			appendValue(dictValues[dictIdx])
		}
	case valueTypeUint8:
		bb := bbPool.Get()
		for _, v := range c.encodedValues {
			n := uint64(v[0])
			bb.B = strconv.AppendUint(bb.B[:0], n, 10)
			appendValue(bytesutil.ToUnsafeString(bb.B))
		}
		bbPool.Put(bb)
	case valueTypeUint16:
		bb := bbPool.Get()
		for _, v := range c.encodedValues {
			b := bytesutil.ToUnsafeBytes(v)
			n := uint64(encoding.UnmarshalUint16(b))
			bb.B = strconv.AppendUint(bb.B[:0], n, 10)
			appendValue(bytesutil.ToUnsafeString(bb.B))
		}
		bbPool.Put(bb)
	case valueTypeUint32:
		bb := bbPool.Get()
		for _, v := range c.encodedValues {
			b := bytesutil.ToUnsafeBytes(v)
			n := uint64(encoding.UnmarshalUint32(b))
			bb.B = strconv.AppendUint(bb.B[:0], n, 10)
			appendValue(bytesutil.ToUnsafeString(bb.B))
		}
		bbPool.Put(bb)
	case valueTypeUint64:
		bb := bbPool.Get()
		for _, v := range c.encodedValues {
			b := bytesutil.ToUnsafeBytes(v)
			n := encoding.UnmarshalUint64(b)
			bb.B = strconv.AppendUint(bb.B[:0], n, 10)
			appendValue(bytesutil.ToUnsafeString(bb.B))
		}
		bbPool.Put(bb)
	case valueTypeFloat64:
		bb := bbPool.Get()
		for _, v := range c.encodedValues {
			bb.B = toFloat64String(bb.B[:0], v)
			appendValue(bytesutil.ToUnsafeString(bb.B))
		}
		bbPool.Put(bb)
	case valueTypeIPv4:
		bb := bbPool.Get()
		for _, v := range c.encodedValues {
			bb.B = toIPv4String(bb.B[:0], v)
			appendValue(bytesutil.ToUnsafeString(bb.B))
		}
		bbPool.Put(bb)
	case valueTypeTimestampISO8601:
		bb := bbPool.Get()
		for _, v := range c.encodedValues {
			bb.B = toTimestampISO8601String(bb.B[:0], v)
			appendValue(bytesutil.ToUnsafeString(bb.B))
		}
		bbPool.Put(bb)
	default:
		logger.Panicf("BUG: unknown valueType=%d", c.valueType)
	}

	c.values = valuesBuf[valuesBufLen:]
	br.buf = buf
	br.valuesBuf = valuesBuf

	return c.values
}

type blockResultColumn struct {
	// isConst is set to true if the column is const.
	//
	// The column value is stored in encodedValues[0]
	isConst bool

	// isTime is set to true if the column contains _time values.
	//
	// The column values are stored in blockResult.timestamps
	isTime bool

	// valueType is the type of non-cost value
	valueType valueType

	// dictValues contain dictionary values for valueTypeDict column
	dictValues []string

	// encodedValues contain encoded values for non-const column
	encodedValues []string

	// values contain decoded values after getColumnValues() call for the given column
	values []string
}

func (c *blockResultColumn) reset() {
	c.isConst = false
	c.isTime = false
	c.valueType = valueTypeUnknown
	c.dictValues = nil
	c.encodedValues = nil
	c.values = nil
}