package txlog

import (
	"bytes"
	"errors"
	"fmt"
	"hash/crc32"
	"os"
	"path/filepath"
	"sync"

	octopus "gordenko.dev/dima/diploma"
	"gordenko.dev/dima/diploma/bin"
	"gordenko.dev/dima/diploma/proto"
)

const (
	lsnSize          = 4
	packetPrefixSize = 12 // 4 lsn + 4 packet length + 4 crc32

	lengthIdx   = 0
	checksumIdx = 4
	lsnIdx      = 8

	filePerm = 0770

	dumpSnapshotAfterNBytes = 1024 * 1024 * 1024 // 1 GB
)

const (
	CodeAddedMetric                 byte = 1
	CodeDeletedMetric               byte = 2
	CodeAppendedMeasure             byte = 4
	CodeAppendedMeasures            byte = 5
	CodeAppendedMeasureWithOverflow byte = 6
	CodeDeletedMeasures             byte = 7
)

func JoinChangesFileName(dir string, logNumber int) string {
	return filepath.Join(dir, fmt.Sprintf("%d.changes", logNumber))
}

type Changes struct {
	Records       []any
	LogNumber     int
	ForceSnapshot bool
	ExitWaitGroup *sync.WaitGroup
	WaitCh        chan struct{}
}

type Writer struct {
	mutex               sync.Mutex
	logNumber           int
	dir                 string
	file                *os.File
	buf                 *bytes.Buffer
	redoFilesToDelete   []string
	workerReqs          []any
	waitCh              chan struct{}
	appendToWorkerQueue func(any)
	lsn                 uint32
	written             int64
	isExited            bool
	exitCh              chan struct{}
	waitGroup           *sync.WaitGroup
	signalCh            chan struct{}
}

type WriterOptions struct {
	Dir                 string
	LogNumber           int // номер журнала
	AppendToWorkerQueue func(any)
	ExitCh              chan struct{}
	WaitGroup           *sync.WaitGroup
}

func NewWriter(opt WriterOptions) (*Writer, error) {
	if opt.Dir == "" {
		return nil, errors.New("Dir option is required")
	}
	if opt.AppendToWorkerQueue == nil {
		return nil, errors.New("AppendToWorkerQueue option is required")
	}
	if opt.ExitCh == nil {
		return nil, errors.New("ExitCh option is required")
	}
	if opt.WaitGroup == nil {
		return nil, errors.New("WaitGroup option is required")
	}

	s := &Writer{
		dir:                 opt.Dir,
		buf:                 bytes.NewBuffer(nil),
		appendToWorkerQueue: opt.AppendToWorkerQueue,
		logNumber:           opt.LogNumber,
		exitCh:              opt.ExitCh,
		waitGroup:           opt.WaitGroup,
		signalCh:            make(chan struct{}, 1),
	}

	var err error

	if opt.LogNumber > 0 {
		s.file, err = os.OpenFile(
			JoinChangesFileName(opt.Dir, s.logNumber),
			os.O_APPEND|os.O_WRONLY,
			filePerm,
		)
		if err != nil {
			return nil, err
		}
	} else {
		s.logNumber = 1
		s.file, err = os.OpenFile(
			JoinChangesFileName(opt.Dir, s.logNumber),
			os.O_CREATE|os.O_WRONLY,
			filePerm,
		)
		if err != nil {
			return nil, err
		}
	}

	s.reset()
	return s, nil
}

func (s *Writer) Run() {
	for {
		select {
		case <-s.signalCh:
			if err := s.flush(); err != nil {
				octopus.Abort(octopus.FailedWriteToTxLog, err)
			}

		case <-s.exitCh:
			s.exit()
			return
		}
	}
}

func (s *Writer) reset() {
	s.buf.Reset()
	s.buf.Write([]byte{
		0, 0, 0, 0, // packet length
		0, 0, 0, 0, // crc32
		0, 0, 0, 0, // lsn

	})
	s.redoFilesToDelete = nil
	s.workerReqs = nil
	s.waitCh = make(chan struct{})
}

func (s *Writer) flush() error {
	s.mutex.Lock()

	workerReqs := s.workerReqs
	waitCh := s.waitCh
	isExited := s.isExited

	var exitWaitGroup *sync.WaitGroup
	if s.isExited {
		exitWaitGroup = s.waitGroup
	}

	if s.buf.Len() > packetPrefixSize {
		redoFilesToDelete := s.redoFilesToDelete
		s.lsn++
		lsn := s.lsn
		packet := make([]byte, s.buf.Len())
		copy(packet, s.buf.Bytes())
		s.reset()

		s.written += int64(len(packet)) + 12
		s.mutex.Unlock()

		bin.PutUint32(packet[lengthIdx:], uint32(len(packet)-packetPrefixSize))
		bin.PutUint32(packet[lsnIdx:], lsn)
		bin.PutUint32(packet[checksumIdx:], crc32.ChecksumIEEE(packet[8:]))

		n, err := s.file.Write(packet)
		if err != nil {
			return fmt.Errorf("TxLog write: %s", err)
		}

		if n != len(packet) {
			return fmt.Errorf("TxLog written %d != packet size %d", n, len(packet))
		}

		if err := s.file.Sync(); err != nil {
			return fmt.Errorf("TxLog sync: %s", err)
		}

		for _, fileName := range redoFilesToDelete {
			err = os.Remove(fileName)
			if err != nil {
				octopus.Abort(octopus.RemoveREDOFileFailed, err)
			}
		}
	} else {
		s.waitCh = make(chan struct{})
		s.mutex.Unlock()
	}

	var forceSnapshot bool

	if s.written > dumpSnapshotAfterNBytes {
		forceSnapshot = true
	}

	if isExited && s.written > 0 {
		forceSnapshot = true
	}

	if forceSnapshot {
		if err := s.file.Close(); err != nil {
			return fmt.Errorf("close changes file: %s", err)
		}
		s.logNumber++
		var err error
		s.file, err = os.OpenFile(
			JoinChangesFileName(s.dir, s.logNumber),
			os.O_CREATE|os.O_WRONLY,
			filePerm,
		)
		if err != nil {
			return fmt.Errorf("create new changes file: %s", err)
		}

		s.written = 0
	}

	s.appendToWorkerQueue(Changes{
		Records:       workerReqs,
		ForceSnapshot: forceSnapshot,
		LogNumber:     s.logNumber,
		WaitCh:        waitCh,
		ExitWaitGroup: exitWaitGroup,
	})
	return nil
}

func (s *Writer) exit() {
	s.mutex.Lock()
	s.isExited = true
	s.mutex.Unlock()

	if err := s.flush(); err != nil {
		octopus.Abort(octopus.FailedWriteToTxLog, err)
	}
}

// API

type AddedMetric struct {
	MetricID   uint32
	MetricType octopus.MetricType
	FracDigits int
}

func (s *Writer) WriteAddedMetric(req AddedMetric) chan struct{} {
	arr := []byte{
		CodeAddedMetric,
		0, 0, 0, 0, //
		byte(req.MetricType),
		byte(req.FracDigits),
	}
	bin.PutUint32(arr[1:], req.MetricID)
	// пишу в буфер
	s.mutex.Lock()
	s.buf.Write(arr)
	s.workerReqs = append(s.workerReqs, req)
	s.mutex.Unlock()

	s.sendSignal()
	return s.waitCh
}

type DeletedMetric struct {
	MetricID       uint32
	FreeDataPages  []uint32
	FreeIndexPages []uint32
}

func (s *Writer) WriteDeletedMetric(req DeletedMetric) chan struct{} {
	arr := []byte{
		CodeDeletedMetric,
		0, 0, 0, 0, // metricID
	}
	bin.PutUint32(arr[1:], req.MetricID)

	// пишу в буфер
	s.mutex.Lock()
	defer s.mutex.Unlock()

	s.buf.Write(arr)
	s.packFreeDataAndIndexPages(req.FreeDataPages, req.FreeIndexPages)
	s.workerReqs = append(s.workerReqs, req)

	s.sendSignal()
	return s.waitCh
}

type AppendedMeasure struct {
	MetricID  uint32
	Timestamp uint32
	Value     float64
}

func (s *Writer) WriteAppendMeasure(req AppendedMeasure) chan struct{} {
	arr := []byte{
		CodeAppendedMeasure,
		0, 0, 0, 0, // metricID
		0, 0, 0, 0, // timestamp
		0, 0, 0, 0, 0, 0, 0, 0, // value
	}
	bin.PutUint32(arr[1:], req.MetricID)
	bin.PutUint32(arr[5:], req.Timestamp)
	bin.PutFloat64(arr[9:], req.Value)
	//
	s.mutex.Lock()
	s.buf.Write(arr)
	s.workerReqs = append(s.workerReqs, req)
	s.mutex.Unlock()

	s.sendSignal()
	return s.waitCh
}

type AppendedMeasures struct {
	MetricID uint32
	Measures []proto.Measure
}

type AppendedMeasuresExtended struct {
	Record   AppendedMeasures
	HoldLock bool
}

func (s *Writer) WriteAppendMeasures(req AppendedMeasures, holdLock bool) chan struct{} {
	arr := []byte{
		CodeAppendedMeasures,
		0, 0, 0, 0, // metricID
		0, 0, // qty
	}
	bin.PutUint32(arr[1:], req.MetricID)
	bin.PutUint16(arr[5:], uint16(len(req.Measures)))
	//
	s.mutex.Lock()
	s.buf.Write(arr)
	for _, measure := range req.Measures {
		bin.WriteUint32(s.buf, measure.Timestamp)
		bin.WriteFloat64(s.buf, measure.Value)
	}
	s.workerReqs = append(s.workerReqs, AppendedMeasuresExtended{
		Record:   req,
		HoldLock: holdLock,
	})
	s.mutex.Unlock()

	s.sendSignal()
	return s.waitCh
}

type AppendedMeasureWithOverflow struct {
	MetricID         uint32
	Timestamp        uint32
	Value            float64
	IsDataPageReused bool
	DataPageNo       uint32
	IsRootChanged    bool
	RootPageNo       uint32
	ReusedIndexPages []uint32
}

type AppendedMeasureWithOverflowExtended struct {
	Record   AppendedMeasureWithOverflow
	HoldLock bool
}

/*
Формат:
1b   code
4b   metricID
4b   timestamp
8b   value
1b   isReusedDataPage
4b   dataPageNo
1b   isRootChanged
[4b] newRootPageNo
1b   reusedIndexPages length
[N * 4b] reusedIndexPages
*/
func (s *Writer) WriteAppendedMeasureWithOverflow(req AppendedMeasureWithOverflow, redoFileName string, holdLock bool) chan struct{} {
	size := 24 + len(req.ReusedIndexPages)*4
	if req.IsRootChanged {
		size += 4
	}

	tmp := make([]byte, size)

	tmp[0] = CodeAppendedMeasureWithOverflow
	bin.PutUint32(tmp[1:], req.MetricID)
	bin.PutUint32(tmp[5:], req.Timestamp)
	bin.PutFloat64(tmp[9:], req.Value)
	if req.IsDataPageReused {
		tmp[17] = 1
	}
	bin.PutUint32(tmp[18:], req.DataPageNo)

	pos := 22
	if req.IsRootChanged {
		tmp[pos] = 1
		bin.PutUint32(tmp[pos+1:], req.RootPageNo)
		pos += 5
	} else {
		tmp[pos] = 0
		pos += 1
	}

	tmp[pos] = byte(len(req.ReusedIndexPages))
	pos += 1
	for _, indexPageNo := range req.ReusedIndexPages {
		bin.PutUint32(tmp[pos:], indexPageNo)
		pos += 4
	}

	s.mutex.Lock()
	s.buf.Write(tmp)
	s.workerReqs = append(s.workerReqs, AppendedMeasureWithOverflowExtended{
		Record:   req,
		HoldLock: holdLock,
	})
	s.redoFilesToDelete = append(s.redoFilesToDelete, redoFileName)
	s.mutex.Unlock()

	s.sendSignal()
	return s.waitCh
}

type DeletedMeasures struct {
	MetricID       uint32
	FreeDataPages  []uint32
	FreeIndexPages []uint32
}

/*
Формат:
1b   code
4b   metricID
1b   freeDataPages length
[N * 4b] freeDataPages
1b   freeIndexPages length
[N * 4b] freeIndexPages
*/
func (s *Writer) WriteDeletedMeasures(op DeletedMeasures) chan struct{} {
	tmp := []byte{
		CodeDeletedMeasures,
		0, 0, 0, 0,
	}
	bin.PutUint32(tmp[1:], op.MetricID)

	// записываю часть фиксированного размера
	s.mutex.Lock()
	s.buf.Write(tmp)
	s.packFreeDataAndIndexPages(op.FreeDataPages, op.FreeIndexPages)
	s.workerReqs = append(s.workerReqs, op)
	s.mutex.Unlock()

	s.sendSignal()
	return s.waitCh
}

type DeletedMeasuresSince struct {
	MetricID       uint32
	LastPageNo     uint32
	IsRootChanged  bool
	RootPageNo     uint32
	FreeDataPages  []uint32
	FreeIndexPages []uint32
	TimestampsBuf  []byte
	ValuesBuf      []byte
}

func (s *Writer) sendSignal() {
	select {
	case s.signalCh <- struct{}{}:
	default:
	}
}

// helper

func (s *Writer) packFreeDataAndIndexPages(freeDataPages, freeIndexPages []uint32) {
	// записываю data pages
	bin.WriteVarUint64(s.buf, uint64(len(freeDataPages)))
	for _, dataPageNo := range freeDataPages {
		bin.WriteUint32(s.buf, dataPageNo)
	}
	// записываю index pages
	bin.WriteVarUint64(s.buf, uint64(len(freeIndexPages)))
	for _, indexPageNo := range freeIndexPages {
		bin.WriteUint32(s.buf, indexPageNo)
	}
}