package notify

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

const bulkDedicatedLaneMicroBatchWait = 50 * time.Microsecond

type bulkDedicatedLaneBatchRequest struct {
	Ctx      context.Context
	DataID   uint64
	Items    []bulkDedicatedSendRequest
	Deadline time.Time
	wait     bool
	resultCh chan error
	state    bulkDedicatedRequestState
	aborted  atomic.Bool
}

var bulkDedicatedLaneBatchRequestPool sync.Pool

type bulkDedicatedLaneSender struct {
	conn   net.Conn
	encode func([]bulkDedicatedOutboundBatch) ([]byte, func(), error)
	fail   func(error)

	reqCh    chan *bulkDedicatedLaneBatchRequest
	stopCh   chan struct{}
	doneCh   chan struct{}
	stopOnce sync.Once
	flushMu  sync.Mutex
	queued   atomic.Int64

	errMu sync.Mutex
	err   error
}

func newBulkDedicatedLaneSender(conn net.Conn, encode func([]bulkDedicatedOutboundBatch) ([]byte, func(), error), fail func(error)) *bulkDedicatedLaneSender {
	sender := &bulkDedicatedLaneSender{
		conn:   conn,
		encode: encode,
		fail:   fail,
		reqCh:  make(chan *bulkDedicatedLaneBatchRequest, bulkDedicatedSendQueueSize),
		stopCh: make(chan struct{}),
		doneCh: make(chan struct{}),
	}
	go sender.run()
	return sender
}

func getBulkDedicatedLaneBatchRequest() *bulkDedicatedLaneBatchRequest {
	if pooled, ok := bulkDedicatedLaneBatchRequestPool.Get().(*bulkDedicatedLaneBatchRequest); ok && pooled != nil {
		pooled.reset()
		return pooled
	}
	req := &bulkDedicatedLaneBatchRequest{
		resultCh: make(chan error, 1),
	}
	req.reset()
	return req
}

func (r *bulkDedicatedLaneBatchRequest) reset() {
	if r == nil {
		return
	}
	r.Ctx = nil
	r.DataID = 0
	r.Deadline = time.Time{}
	r.wait = false
	r.Items = r.Items[:0]
	r.state.value.Store(bulkDedicatedRequestQueued)
	r.aborted.Store(false)
	if r.resultCh != nil {
		select {
		case <-r.resultCh:
		default:
		}
	}
}

func (r *bulkDedicatedLaneBatchRequest) prepare(ctx context.Context, dataID uint64, items []bulkDedicatedSendRequest, wait bool) {
	if r == nil {
		return
	}
	r.reset()
	r.Ctx = ctx
	r.DataID = dataID
	r.wait = wait
	if deadline, ok := ctx.Deadline(); ok {
		r.Deadline = deadline
	}
	if cap(r.Items) < len(items) {
		r.Items = make([]bulkDedicatedSendRequest, len(items))
	} else {
		r.Items = r.Items[:len(items)]
	}
	copy(r.Items, items)
}

func (r *bulkDedicatedLaneBatchRequest) recycle() {
	if r == nil {
		return
	}
	r.reset()
	bulkDedicatedLaneBatchRequestPool.Put(r)
}

func (s *bulkDedicatedLaneSender) submitData(ctx context.Context, dataID uint64, seq uint64, payload []byte) error {
	if s == nil {
		return errTransportDetached
	}
	items := []bulkDedicatedSendRequest{{
		Type:    bulkFastPayloadTypeData,
		Seq:     seq,
		Payload: append([]byte(nil), payload...),
	}}
	return s.submitBatch(ctx, dataID, items, false)
}

func (s *bulkDedicatedLaneSender) submitWrite(ctx context.Context, dataID uint64, startSeq uint64, payload []byte, chunkSize int) (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 itemBuf [bulkDedicatedBatchMaxItems]bulkDedicatedSendRequest
		items := itemBuf[:0]
		batchBytes := bulkDedicatedBatchHeaderLen
		start := written
		for written < len(payload) && len(items) < bulkDedicatedBatchMaxItems {
			end := written + chunkSize
			if end > len(payload) {
				end = len(payload)
			}
			itemLen := bulkDedicatedSendRequestLenFromPayloadLen(end - written)
			if len(items) > 0 && batchBytes+itemLen > bulkDedicatedBatchMaxPlainBytes {
				break
			}
			items = append(items, bulkDedicatedSendRequest{
				Type:    bulkFastPayloadTypeData,
				Seq:     seq,
				Payload: payload[written:end],
			})
			batchBytes += itemLen
			seq++
			written = end
		}
		if len(items) == 0 {
			end := written + chunkSize
			if end > len(payload) {
				end = len(payload)
			}
			items = append(items, bulkDedicatedSendRequest{
				Type:    bulkFastPayloadTypeData,
				Seq:     seq,
				Payload: payload[written:end],
			})
			seq++
			written = end
		}
		if err := s.submitWriteBatch(ctx, dataID, items); err != nil {
			return start, err
		}
		start = written
	}
	return written, nil
}

func (s *bulkDedicatedLaneSender) submitWriteBatch(ctx context.Context, dataID uint64, items []bulkDedicatedSendRequest) error {
	if s == nil {
		return errTransportDetached
	}
	if len(items) == 0 {
		return nil
	}
	if submitted, err := s.tryDirectSubmitBatch(ctx, dataID, items); submitted {
		return err
	}
	queuedItems := copyBulkDedicatedSendRequests(items)
	return s.submitBatch(ctx, dataID, queuedItems, true)
}

func (s *bulkDedicatedLaneSender) submitControl(ctx context.Context, dataID uint64, frameType uint8, flags uint8, seq uint64, payload []byte) error {
	if s == nil {
		return errTransportDetached
	}
	items := []bulkDedicatedSendRequest{{
		Type:  frameType,
		Flags: flags,
		Seq:   seq,
	}}
	if len(payload) > 0 {
		items[0].Payload = append([]byte(nil), payload...)
	}
	return s.submitBatch(ctx, dataID, items, true)
}

func (s *bulkDedicatedLaneSender) submitBatch(ctx context.Context, dataID uint64, items []bulkDedicatedSendRequest, wait bool) error {
	if s == nil {
		return errTransportDetached
	}
	if ctx == nil {
		ctx = context.Background()
	}
	if err := s.errSnapshot(); err != nil {
		return err
	}
	req := getBulkDedicatedLaneBatchRequest()
	req.prepare(ctx, dataID, items, wait)
	s.queued.Add(1)
	select {
	case <-ctx.Done():
		s.queued.Add(-1)
		req.recycle()
		return normalizeStreamDeadlineError(ctx.Err())
	case <-s.stopCh:
		s.queued.Add(-1)
		req.recycle()
		return s.stoppedErr()
	case s.reqCh <- req:
		if !wait {
			return nil
		}
		return s.waitAck(req)
	}
}

func (s *bulkDedicatedLaneSender) tryDirectSubmitBatch(ctx context.Context, dataID uint64, items []bulkDedicatedSendRequest) (bool, error) {
	if s == nil {
		return true, errTransportDetached
	}
	if ctx == nil {
		ctx = context.Background()
	}
	if len(items) == 0 {
		return true, nil
	}
	if err := s.errSnapshot(); err != nil {
		return true, err
	}
	select {
	case <-ctx.Done():
		return true, normalizeStreamDeadlineError(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
	}
	select {
	case <-ctx.Done():
		return true, normalizeStreamDeadlineError(ctx.Err())
	case <-s.stopCh:
		return true, s.stoppedErr()
	default:
	}
	deadline, _ := ctx.Deadline()
	if err := s.flush([]bulkDedicatedOutboundBatch{{
		DataID: dataID,
		Items:  items,
	}}, deadline); err != nil {
		err = normalizeDedicatedBulkSendError(err)
		s.setErr(err)
		s.failPending(err)
		if s.fail != nil {
			go s.fail(err)
		}
		return true, err
	}
	return true, nil
}

func (s *bulkDedicatedLaneSender) waitAck(req *bulkDedicatedLaneBatchRequest) error {
	if s == nil {
		return errTransportDetached
	}
	if req == nil {
		return errTransportDetached
	}
	ctx := req.Ctx
	if ctx == nil {
		ctx = context.Background()
	}
	select {
	case err := <-req.resultCh:
		req.recycle()
		return normalizeDedicatedBulkSendError(err)
	case <-ctx.Done():
		if req.tryCancel() {
			req.aborted.Store(true)
			return normalizeStreamDeadlineError(ctx.Err())
		}
		err := <-req.resultCh
		req.recycle()
		return normalizeDedicatedBulkSendError(err)
	}
}

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

func (s *bulkDedicatedLaneSender) run() {
	defer close(s.doneCh)
	var carry *bulkDedicatedLaneBatchRequest
	for {
		req, ok := s.nextRequest(carry)
		carry = nil
		if !ok {
			return
		}
		if !req.tryStart() {
			s.finishRequest(req, req.canceledErr())
			continue
		}
		if err := req.contextErr(); err != nil {
			s.finishRequest(req, err)
			continue
		}
		batchReqs := []*bulkDedicatedLaneBatchRequest{req}
		batches := []bulkDedicatedOutboundBatch{{
			DataID: req.DataID,
			Items:  req.Items,
		}}
		batchBytes := bulkDedicatedBatchesPlainLen(batches)
		deadline := req.Deadline
		s.flushMu.Lock()
		err := s.errSnapshot()
		if err == nil {
			carry, err = s.collectBatchRequests(&batchReqs, &batches, &batchBytes, &deadline)
			if err == nil {
				err = s.flush(batches, deadline)
			}
		}
		s.flushMu.Unlock()
		if err != nil {
			err = normalizeDedicatedBulkSendError(err)
			s.setErr(err)
			s.finishBatchRequests(batchReqs, err)
			if carry != nil {
				s.finishRequest(carry, err)
				carry = nil
			}
			s.failPending(err)
			if s.fail != nil {
				go s.fail(err)
			}
			return
		}
		s.finishBatchRequests(batchReqs, nil)
	}
}

func appendBulkDedicatedLaneBatch(batches *[]bulkDedicatedOutboundBatch, req *bulkDedicatedLaneBatchRequest) {
	if req == nil {
		return
	}
	if len(*batches) > 0 && (*batches)[len(*batches)-1].DataID == req.DataID {
		last := &(*batches)[len(*batches)-1]
		last.Items = append(last.Items, req.Items...)
		return
	}
	*batches = append(*batches, bulkDedicatedOutboundBatch{
		DataID: req.DataID,
		Items:  req.Items,
	})
}

func bulkDedicatedLaneBatchItemCount(batches []bulkDedicatedOutboundBatch) int {
	total := 0
	for _, batch := range batches {
		total += len(batch.Items)
	}
	return total
}

func bulkDedicatedLaneNextBatchBytes(batches []bulkDedicatedOutboundBatch, req *bulkDedicatedLaneBatchRequest, currentBytes int) int {
	reqBytes := bulkDedicatedSendRequestsLen(req.Items)
	if len(batches) == 0 {
		return bulkDedicatedBatchHeaderLen + reqBytes
	}
	last := batches[len(batches)-1]
	if last.DataID == req.DataID {
		return currentBytes + reqBytes
	}
	if len(batches) == 1 {
		return bulkDedicatedSuperBatchHeaderLen +
			bulkDedicatedSuperBatchGroupHeaderLen + bulkDedicatedSendRequestsLen(batches[0].Items) +
			bulkDedicatedSuperBatchGroupHeaderLen + reqBytes
	}
	return currentBytes + bulkDedicatedSuperBatchGroupHeaderLen + reqBytes
}

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

func (r *bulkDedicatedLaneBatchRequest) tryStart() bool {
	if r == nil {
		return false
	}
	return r.state.value.CompareAndSwap(bulkDedicatedRequestQueued, bulkDedicatedRequestStarted)
}

func (r *bulkDedicatedLaneBatchRequest) tryCancel() bool {
	if r == nil {
		return false
	}
	return r.state.value.CompareAndSwap(bulkDedicatedRequestQueued, bulkDedicatedRequestCanceled)
}

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

func (s *bulkDedicatedLaneSender) nextRequest(carry *bulkDedicatedLaneBatchRequest) (*bulkDedicatedLaneBatchRequest, bool) {
	if carry != nil {
		select {
		case <-s.stopCh:
			err := s.stoppedErr()
			s.finishRequest(carry, err)
			s.failPending(err)
			return nil, false
		default:
			return carry, true
		}
	}
	select {
	case <-s.stopCh:
		s.failPending(s.stoppedErr())
		return nil, false
	case req := <-s.reqCh:
		return req, true
	}
}

func (s *bulkDedicatedLaneSender) collectBatchRequests(batchReqs *[]*bulkDedicatedLaneBatchRequest, batches *[]bulkDedicatedOutboundBatch, batchBytes *int, deadline *time.Time) (*bulkDedicatedLaneBatchRequest, error) {
	if s == nil || bulkDedicatedLaneBatchItemCount(*batches) >= bulkDedicatedBatchMaxItems || *batchBytes >= bulkDedicatedBatchMaxPlainBytes {
		return nil, nil
	}
	wait := bulkDedicatedLaneMicroBatchWait
	var (
		timer   *time.Timer
		timerCh <-chan time.Time
		waited  bool
	)
	if wait > 0 {
		timer = time.NewTimer(wait)
		timerCh = timer.C
		defer timer.Stop()
	}
	for {
		if bulkDedicatedLaneBatchItemCount(*batches) >= bulkDedicatedBatchMaxItems || *batchBytes >= bulkDedicatedBatchMaxPlainBytes {
			return nil, nil
		}
		var (
			req *bulkDedicatedLaneBatchRequest
			ok  bool
		)
		select {
		case <-s.stopCh:
			return nil, s.stoppedErr()
		case req = <-s.reqCh:
			ok = true
		default:
		}
		if !ok {
			if waited || timerCh == nil {
				return nil, nil
			}
			waited = true
			select {
			case <-s.stopCh:
				return nil, s.stoppedErr()
			case req = <-s.reqCh:
			case <-timerCh:
				return nil, nil
			}
		}
		if err := req.contextErr(); err != nil {
			if req.tryCancel() {
				s.finishRequest(req, err)
				continue
			}
			s.finishRequest(req, req.canceledErr())
			continue
		}
		nextItems := bulkDedicatedLaneBatchItemCount(*batches) + len(req.Items)
		if nextItems > bulkDedicatedBatchMaxItems {
			return req, nil
		}
		nextBytes := bulkDedicatedLaneNextBatchBytes(*batches, req, *batchBytes)
		if nextBytes > bulkDedicatedBatchMaxPlainBytes {
			return req, nil
		}
		if !req.tryStart() {
			s.finishRequest(req, req.canceledErr())
			continue
		}
		if err := req.contextErr(); err != nil {
			s.finishRequest(req, err)
			continue
		}
		*batchReqs = append(*batchReqs, req)
		appendBulkDedicatedLaneBatch(batches, req)
		*batchBytes = nextBytes
		*deadline = earlierDeadline(*deadline, req.Deadline)
	}
}

func earlierDeadline(current time.Time, next time.Time) time.Time {
	if current.IsZero() {
		return next
	}
	if next.IsZero() || current.Before(next) {
		return current
	}
	return next
}

func (s *bulkDedicatedLaneSender) flush(batches []bulkDedicatedOutboundBatch, deadline time.Time) error {
	if s == nil || s.conn == nil {
		return errTransportDetached
	}
	payload, release, err := s.encode(batches)
	if err != nil {
		return err
	}
	if release != nil {
		defer release()
	}
	return writeBulkDedicatedRecordWithDeadline(s.conn, payload, deadline)
}

func (s *bulkDedicatedLaneSender) finishRequest(req *bulkDedicatedLaneBatchRequest, err error) {
	if s != nil {
		s.queued.Add(-1)
	}
	if req == nil {
		return
	}
	if req.wait && req.resultCh != nil {
		if req.aborted.Load() {
			req.recycle()
			return
		}
		req.resultCh <- err
		return
	}
	req.recycle()
}

func (s *bulkDedicatedLaneSender) finishBatchRequests(reqs []*bulkDedicatedLaneBatchRequest, err error) {
	for _, req := range reqs {
		s.finishRequest(req, err)
	}
}

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

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

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

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