package notify

import (
	"context"
	"net"
	"sync"
	"sync/atomic"
	"time"
)

const (
	bulkBatchMaxPayloads     = 64
	bulkBatchMaxPayloadBytes = bulkFastBatchMaxPlainBytes
	bulkBatchMaxFlushDelay   = 50 * time.Microsecond
)

const (
	bulkBatchRequestQueued int32 = iota
	bulkBatchRequestStarted
	bulkBatchRequestCanceled
)

type bulkBatchRequestState struct {
	value atomic.Int32
}

type bulkBatchCodec struct {
	encodeSingle func(bulkFastFrame) ([]byte, func(), error)
	encodeBatch  func([]bulkFastFrame) ([]byte, func(), error)
}

type bulkBatchRequest struct {
	ctx             context.Context
	frames          []bulkFastFrame
	fastPathVersion uint8
	payloadOwned    bool
	deadline        time.Time
	done            chan error
	state           *bulkBatchRequestState
	release         func()
}

type bulkBatchEncodedPayload struct {
	payload []byte
	release func()
}

func (p *bulkBatchEncodedPayload) done() {
	if p == nil || p.release == nil {
		return
	}
	p.release()
	p.release = nil
}

type bulkBatchSender struct {
	binding              *transportBinding
	codec                bulkBatchCodec
	writeTimeoutProvider func() time.Duration
	reqCh                chan bulkBatchRequest
	stopCh               chan struct{}
	doneCh               chan struct{}

	stopOnce sync.Once
	flushMu  sync.Mutex
	queued   atomic.Int64
	errMu    sync.Mutex
	err      error
}

func newBulkBatchSender(binding *transportBinding, codec bulkBatchCodec, writeTimeoutProvider func() time.Duration) *bulkBatchSender {
	sender := &bulkBatchSender{
		binding:              binding,
		codec:                codec,
		writeTimeoutProvider: writeTimeoutProvider,
		reqCh:                make(chan bulkBatchRequest, bulkBatchMaxPayloads*4),
		stopCh:               make(chan struct{}),
		doneCh:               make(chan struct{}),
	}
	go sender.run()
	return sender
}

func (s *bulkBatchSender) submitData(ctx context.Context, dataID uint64, seq uint64, fastPathVersion uint8, payload []byte) error {
	return s.submitFramesOwned(ctx, []bulkFastFrame{{
		Type:    bulkFastPayloadTypeData,
		DataID:  dataID,
		Seq:     seq,
		Payload: payload,
	}}, fastPathVersion, false)
}

func (s *bulkBatchSender) submitControl(ctx context.Context, frameType uint8, flags uint8, dataID uint64, seq uint64, fastPathVersion uint8, payload []byte) error {
	return s.submitFramesOwned(ctx, []bulkFastFrame{{
		Type:    frameType,
		Flags:   flags,
		DataID:  dataID,
		Seq:     seq,
		Payload: payload,
	}}, fastPathVersion, false)
}

func (s *bulkBatchSender) submitWrite(ctx context.Context, dataID uint64, startSeq uint64, fastPathVersion uint8, payload []byte, chunkSize int, payloadOwned bool) (int, error) {
	if s == nil {
		return 0, errTransportDetached
	}
	if len(payload) == 0 {
		return 0, nil
	}
	if chunkSize <= 0 {
		chunkSize = defaultBulkChunkSize
	}
	written := 0
	seq := startSeq
	for written < len(payload) {
		var batch [bulkFastBatchMaxItems]bulkFastFrame
		frames := batch[:0]
		batchBytes := bulkFastBatchHeaderLen
		start := written
		for written < len(payload) && len(frames) < bulkFastBatchMaxItems {
			end := written + chunkSize
			if end > len(payload) {
				end = len(payload)
			}
			frame := bulkFastFrame{
				Type:    bulkFastPayloadTypeData,
				DataID:  dataID,
				Seq:     seq,
				Payload: payload[written:end],
			}
			frameLen := bulkFastBatchFrameLen(frame)
			if len(frames) > 0 && batchBytes+frameLen > bulkFastBatchMaxPlainBytes {
				break
			}
			frames = append(frames, frame)
			batchBytes += frameLen
			seq++
			written = end
		}
		if len(frames) == 0 {
			end := written + chunkSize
			if end > len(payload) {
				end = len(payload)
			}
			frames = append(frames, bulkFastFrame{
				Type:    bulkFastPayloadTypeData,
				DataID:  dataID,
				Seq:     seq,
				Payload: payload[written:end],
			})
			seq++
			written = end
		}
		if err := s.submitFramesOwned(ctx, frames, fastPathVersion, payloadOwned); err != nil {
			return start, err
		}
	}
	return written, nil
}

func (s *bulkBatchSender) submitFrames(ctx context.Context, frames []bulkFastFrame, fastPathVersion uint8) error {
	return s.submitFramesOwned(ctx, frames, fastPathVersion, false)
}

func (s *bulkBatchSender) submitFramesOwned(ctx context.Context, frames []bulkFastFrame, fastPathVersion uint8, payloadOwned bool) error {
	if s == nil {
		return errTransportDetached
	}
	if ctx == nil {
		ctx = context.Background()
	}
	if len(frames) == 0 {
		return nil
	}
	req := bulkBatchRequest{
		ctx:             ctx,
		frames:          frames,
		fastPathVersion: normalizeBulkFastPathVersion(fastPathVersion),
		payloadOwned:    payloadOwned,
		done:            make(chan error, 1),
		state:           &bulkBatchRequestState{},
	}
	if deadline, ok := ctx.Deadline(); ok {
		req.deadline = deadline
	}
	if err := s.errSnapshot(); err != nil {
		return err
	}
	if s.shouldDirectSubmit(req) {
		if submitted, err := s.tryDirectSubmit(req); submitted {
			return err
		}
	}
	req = cloneQueuedBulkBatchRequest(req)
	s.queued.Add(1)
	select {
	case <-ctx.Done():
		s.queued.Add(-1)
		if req.release != nil {
			req.release()
		}
		return normalizeStreamDeadlineError(ctx.Err())
	case <-s.stopCh:
		s.queued.Add(-1)
		if req.release != nil {
			req.release()
		}
		return s.stoppedErr()
	case s.reqCh <- req:
	}
	select {
	case err := <-req.done:
		return err
	case <-ctx.Done():
		if req.tryCancel() {
			return normalizeStreamDeadlineError(ctx.Err())
		}
		return <-req.done
	}
}

func (s *bulkBatchSender) shouldDirectSubmit(req bulkBatchRequest) bool {
	if len(req.frames) == 0 {
		return false
	}
	return !bulkBatchRequestSupportsSharedSuperBatch(req)
}

func (s *bulkBatchSender) tryDirectSubmit(req bulkBatchRequest) (bool, error) {
	if s == nil {
		return true, errTransportDetached
	}
	if err := s.errSnapshot(); err != nil {
		return true, err
	}
	select {
	case <-req.ctx.Done():
		return true, normalizeStreamDeadlineError(req.ctx.Err())
	case <-s.stopCh:
		return true, s.stoppedErr()
	default:
	}
	if s.queued.Load() != 0 {
		return false, nil
	}
	if !s.flushMu.TryLock() {
		return false, nil
	}
	defer s.flushMu.Unlock()
	if s.queued.Load() != 0 {
		return false, nil
	}
	if err := s.errSnapshot(); err != nil {
		return true, err
	}
	if !req.tryStart() {
		return true, req.canceledErr()
	}
	if err := req.contextErr(); err != nil {
		return true, err
	}
	err := s.flush([]bulkBatchRequest{req})
	if err != nil {
		s.setErr(err)
		s.failPending(err)
		return true, err
	}
	return true, nil
}

func (s *bulkBatchSender) run() {
	defer close(s.doneCh)
	for {
		req, ok := s.nextRequest()
		if !ok {
			return
		}
		batch := []bulkBatchRequest{req}
		batchBytes := bulkBatchRequestApproxBytes(req)
		timer := (*time.Timer)(nil)
		timerCh := (<-chan time.Time)(nil)
		if bulkBatchShouldWaitForMore(batch, batchBytes) {
			timer = time.NewTimer(bulkBatchMaxFlushDelay)
			timerCh = timer.C
		}
	drain:
		for len(batch) < bulkBatchMaxPayloads && batchBytes < bulkBatchMaxPayloadBytes {
			if timerCh == nil {
				select {
				case <-s.stopCh:
					s.failPending(s.stoppedErr())
					return
				case next := <-s.reqCh:
					batch = append(batch, next)
					batchBytes += bulkBatchRequestApproxBytes(next)
				default:
					break drain
				}
				continue
			}
			select {
			case <-s.stopCh:
				if timer != nil {
					timer.Stop()
				}
				s.failPending(s.stoppedErr())
				return
			case next := <-s.reqCh:
				batch = append(batch, next)
				batchBytes += bulkBatchRequestApproxBytes(next)
			case <-timerCh:
				timerCh = nil
				break drain
			}
		}
		if timer != nil {
			if !timer.Stop() && timerCh != nil {
				select {
				case <-timer.C:
				default:
				}
			}
		}
		s.flushMu.Lock()
		err := s.errSnapshot()
		active := make([]bulkBatchRequest, 0, len(batch))
		for _, item := range batch {
			if !item.tryStart() {
				s.finishRequest(item, item.canceledErr())
				continue
			}
			if itemErr := item.contextErr(); itemErr != nil {
				s.finishRequest(item, itemErr)
				continue
			}
			active = append(active, item)
		}
		if len(active) == 0 {
			s.flushMu.Unlock()
			continue
		}
		if err == nil {
			err = s.flush(active)
		}
		s.flushMu.Unlock()
		if err != nil {
			s.setErr(err)
			for _, item := range active {
				s.finishRequest(item, err)
			}
			s.failPending(err)
			return
		}
		for _, item := range active {
			s.finishRequest(item, nil)
		}
	}
}

func (s *bulkBatchSender) nextRequest() (bulkBatchRequest, bool) {
	select {
	case <-s.stopCh:
		s.failPending(s.stoppedErr())
		return bulkBatchRequest{}, false
	case req := <-s.reqCh:
		return req, true
	}
}

func (r bulkBatchRequest) contextErr() error {
	if r.ctx == nil {
		return nil
	}
	select {
	case <-r.ctx.Done():
		return normalizeStreamDeadlineError(r.ctx.Err())
	default:
		return nil
	}
}

func (r bulkBatchRequest) tryStart() bool {
	if r.state == nil {
		return true
	}
	return r.state.value.CompareAndSwap(bulkBatchRequestQueued, bulkBatchRequestStarted)
}

func (r bulkBatchRequest) tryCancel() bool {
	if r.state == nil {
		return false
	}
	return r.state.value.CompareAndSwap(bulkBatchRequestQueued, bulkBatchRequestCanceled)
}

func (r bulkBatchRequest) canceledErr() error {
	if err := r.contextErr(); err != nil {
		return err
	}
	return context.Canceled
}

func (s *bulkBatchSender) flush(requests []bulkBatchRequest) error {
	if s == nil || s.binding == nil {
		return errTransportDetached
	}
	queue := s.binding.queueSnapshot()
	if queue == nil {
		return errTransportFrameQueueUnavailable
	}
	payloads, err := s.encodeRequests(requests)
	if err != nil {
		return err
	}
	defer func() {
		for index := range payloads {
			payloads[index].done()
		}
	}()
	writeTimeout := s.transportWriteTimeout()
	frames := make([][]byte, 0, len(payloads))
	payloadBytes := 0
	for _, payload := range payloads {
		frames = append(frames, payload.payload)
		payloadBytes += len(payload.payload)
	}
	started := time.Now()
	err = s.binding.withConnWriteLockDeadline(writeDeadlineFromTimeout(writeTimeout), func(conn net.Conn) error {
		return writeFramedPayloadBatchUnlocked(conn, queue, frames)
	})
	s.binding.observeBulkAdaptivePayloadWrite(payloadBytes, time.Since(started), writeTimeout, err)
	return err
}

func (s *bulkBatchSender) encodeRequests(requests []bulkBatchRequest) ([]bulkBatchEncodedPayload, error) {
	if len(requests) == 0 {
		return nil, nil
	}
	payloads := make([]bulkBatchEncodedPayload, 0, len(requests))
	batch := make([]bulkFastFrame, 0, minInt(len(requests), bulkFastBatchMaxItems))
	mixedBatchLimit := s.sharedMixedPayloadLimit()
	batchRequestIndex := -1
	batchDataID := uint64(0)
	batchMixed := false
	flushBatch := func() error {
		if len(batch) == 0 {
			return nil
		}
		payload, release, err := s.encodeBatch(batch)
		if err != nil {
			return err
		}
		payloads = append(payloads, bulkBatchEncodedPayload{payload: payload, release: release})
		batch = batch[:0]
		batchRequestIndex = -1
		batchDataID = 0
		batchMixed = false
		return nil
	}
	batchBytes := bulkFastBatchHeaderLen
	for reqIndex, req := range requests {
		for _, frame := range req.frames {
			if !bulkFastPathSupportsSharedBatch(req.fastPathVersion) {
				if err := flushBatch(); err != nil {
					return nil, err
				}
				batchBytes = bulkFastBatchHeaderLen
				payload, release, err := s.encodeSingle(frame)
				if err != nil {
					return nil, err
				}
				payloads = append(payloads, bulkBatchEncodedPayload{payload: payload, release: release})
				continue
			}
			frameLen := bulkFastBatchFrameLen(frame)
			if frameLen+bulkFastBatchHeaderLen > bulkFastBatchMaxPlainBytes {
				if err := flushBatch(); err != nil {
					return nil, err
				}
				batchBytes = bulkFastBatchHeaderLen
				payload, release, err := s.encodeSingle(frame)
				if err != nil {
					return nil, err
				}
				payloads = append(payloads, bulkBatchEncodedPayload{payload: payload, release: release})
				continue
			}
			nextMixed := batchMixed
			if len(batch) > 0 && (batchRequestIndex != reqIndex || (batchDataID != 0 && batchDataID != frame.DataID)) {
				nextMixed = true
			}
			batchLimit := bulkFastBatchMaxPlainBytes
			if nextMixed && mixedBatchLimit > 0 && mixedBatchLimit < batchLimit {
				batchLimit = mixedBatchLimit
			}
			if len(batch) > 0 && (len(batch) >= bulkFastBatchMaxItems || batchBytes+frameLen > batchLimit) {
				if err := flushBatch(); err != nil {
					return nil, err
				}
				batchBytes = bulkFastBatchHeaderLen
				nextMixed = false
			}
			if len(batch) == 0 {
				batchRequestIndex = reqIndex
				batchDataID = frame.DataID
				batchMixed = false
			} else if batchRequestIndex != reqIndex || (batchDataID != 0 && batchDataID != frame.DataID) {
				batchMixed = true
			}
			batch = append(batch, frame)
			batchBytes += frameLen
		}
	}
	if err := flushBatch(); err != nil {
		return nil, err
	}
	return payloads, nil
}

func bulkBatchRequestApproxBytes(req bulkBatchRequest) int {
	total := 0
	for _, frame := range req.frames {
		total += bulkFastBatchFrameLen(frame)
	}
	return total
}

func bulkBatchRequestSupportsSharedSuperBatch(req bulkBatchRequest) bool {
	if len(req.frames) == 0 || !bulkFastPathSupportsSharedBatch(req.fastPathVersion) {
		return false
	}
	for _, frame := range req.frames {
		switch frame.Type {
		case bulkFastPayloadTypeData:
		default:
			return false
		}
	}
	return true
}

func bulkBatchShouldWaitForMore(batch []bulkBatchRequest, batchBytes int) bool {
	if bulkBatchMaxFlushDelay <= 0 || len(batch) == 0 {
		return false
	}
	if len(batch) >= bulkBatchMaxPayloads || batchBytes >= bulkBatchMaxPayloadBytes {
		return false
	}
	for _, req := range batch {
		if !bulkBatchRequestSupportsSharedSuperBatch(req) {
			return false
		}
	}
	return true
}

func cloneQueuedBulkBatchRequest(req bulkBatchRequest) bulkBatchRequest {
	if len(req.frames) == 0 || req.payloadOwned {
		return req
	}
	clonedFrames := make([]bulkFastFrame, len(req.frames))
	totalPayload := 0
	for _, frame := range req.frames {
		totalPayload += len(frame.Payload)
	}
	var payloadBuf []byte
	if totalPayload > 0 {
		payloadBuf = getBulkAsyncWritePayload(totalPayload)
		req.release = func() {
			putBulkAsyncWritePayload(payloadBuf)
		}
	}
	offset := 0
	for index, frame := range req.frames {
		clonedFrames[index] = frame
		if len(frame.Payload) == 0 {
			clonedFrames[index].Payload = nil
			continue
		}
		next := offset + len(frame.Payload)
		clonedFrames[index].Payload = payloadBuf[offset:next]
		copy(clonedFrames[index].Payload, frame.Payload)
		offset = next
	}
	req.frames = clonedFrames
	return req
}

func (s *bulkBatchSender) encodeSingle(frame bulkFastFrame) ([]byte, func(), error) {
	if s == nil || s.codec.encodeSingle == nil {
		return nil, nil, errTransportDetached
	}
	return s.codec.encodeSingle(frame)
}

func (s *bulkBatchSender) encodeBatch(frames []bulkFastFrame) ([]byte, func(), error) {
	if len(frames) == 1 || s.codec.encodeBatch == nil {
		return s.encodeSingle(frames[0])
	}
	return s.codec.encodeBatch(frames)
}

func (s *bulkBatchSender) stop() {
	if s == nil {
		return
	}
	s.stopOnce.Do(func() {
		s.setErr(errTransportDetached)
		close(s.stopCh)
	})
	<-s.doneCh
}

func (s *bulkBatchSender) failPending(err error) {
	for {
		select {
		case item := <-s.reqCh:
			s.finishRequest(item, err)
		default:
			return
		}
	}
}

func (s *bulkBatchSender) finishRequest(req bulkBatchRequest, err error) {
	if s != nil {
		s.queued.Add(-1)
	}
	if req.release != nil {
		req.release()
	}
	req.done <- err
}

func (s *bulkBatchSender) setErr(err error) {
	if s == nil || err == nil {
		return
	}
	s.errMu.Lock()
	if s.err == nil {
		s.err = err
	}
	s.errMu.Unlock()
}

func (s *bulkBatchSender) errSnapshot() error {
	if s == nil {
		return errTransportDetached
	}
	s.errMu.Lock()
	defer s.errMu.Unlock()
	return s.err
}

func (s *bulkBatchSender) stoppedErr() error {
	if err := s.errSnapshot(); err != nil {
		return err
	}
	return errTransportDetached
}

func (s *bulkBatchSender) transportWriteDeadline() time.Time {
	if s == nil || s.writeTimeoutProvider == nil {
		return time.Time{}
	}
	return writeDeadlineFromTimeout(s.writeTimeoutProvider())
}

func (s *bulkBatchSender) transportWriteTimeout() time.Duration {
	if s == nil || s.writeTimeoutProvider == nil {
		return 0
	}
	return s.writeTimeoutProvider()
}

func (s *bulkBatchSender) sharedMixedPayloadLimit() int {
	if s == nil || s.binding == nil {
		return bulkAdaptiveSoftPayloadFallbackBytes
	}
	return s.binding.bulkAdaptiveSoftPayloadBytesSnapshot()
}

func minInt(a int, b int) int {
	if a < b {
		return a
	}
	return b
}