package event

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

	provider "github.com/cs3org/go-cs3apis/cs3/storage/provider/v1beta1"
	"github.com/qsfera/server/pkg/log"
	"github.com/qsfera/server/services/search/pkg/metrics"
	"github.com/qsfera/server/services/search/pkg/search"
	"github.com/opencloud-eu/reva/v2/pkg/events"
	"github.com/opencloud-eu/reva/v2/pkg/events/raw"
	"github.com/opencloud-eu/reva/v2/pkg/storagespace"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/trace"
)

var tracer trace.Tracer

func init() {
	tracer = otel.Tracer("github.com/qsfera/server/services/search/pkg/service/event")
}

// Service defines the service handlers.
type Service struct {
	ctx                 context.Context
	log                 log.Logger
	tp                  trace.TracerProvider
	m                   *metrics.Metrics
	index               search.Searcher
	events              []events.Unmarshaller
	stream              raw.Stream
	indexSpaceDebouncer *SpaceDebouncer
	numConsumers        int
	stopCh              chan struct{}
	stopped             *atomic.Bool
}

// New returns a service implementation for Service.
func New(ctx context.Context, stream raw.Stream, logger log.Logger, tp trace.TracerProvider, m *metrics.Metrics, index search.Searcher, debounceDuration int, numConsumers int, asyncUploads bool) (Service, error) {
	svc := Service{
		ctx:     ctx,
		log:     logger,
		tp:      tp,
		m:       m,
		index:   index,
		stream:  stream,
		stopCh:  make(chan struct{}, 1),
		stopped: new(atomic.Bool),
		events: []events.Unmarshaller{
			events.ItemTrashed{},
			events.ItemPurged{},
			events.ItemRestored{},
			events.ItemMoved{},
			events.TrashbinPurged{},
			events.ContainerCreated{},
			events.FileTouched{},
			events.FileVersionRestored{},
			events.TagsAdded{},
			events.TagsRemoved{},
			events.SpaceRenamed{},
			events.LabelAdded{},
			events.LabelRemoved{},
		},
		numConsumers: numConsumers,
	}

	if asyncUploads {
		svc.events = append(svc.events, events.UploadReady{})
	} else {
		svc.events = append(svc.events, events.FileUploaded{})
	}

	svc.indexSpaceDebouncer = NewSpaceDebouncer(time.Duration(debounceDuration)*time.Millisecond, 30*time.Second, func(id *provider.StorageSpaceId) {
		if err := svc.index.IndexSpace(id, false); err != nil {
			svc.log.Error().Err(err).Interface("spaceID", id).Msg("error while indexing a space")
		}
	}, svc.log)

	return svc, nil
}

// Run to fulfil Runner interface
func (s Service) Run() error {
	ch, err := s.stream.Consume("search-pull", s.events...)
	if err != nil {
		return err
	}

	if s.m != nil {
		monitorMetrics(s.ctx, s.stream, "search-pull", s.m, s.log)
	}

	var wg sync.WaitGroup
	ctx, cancel := context.WithCancel(s.ctx)
	defer cancel()

	s.log.Debug().Int("worker.count", s.numConsumers).
		Str("messaging.consumer.group.name", "search-pull").
		Str("messaging.system", "nats").
		Str("messaging.operation.name", "receive").
		Msg("starting event processing workers")

	// start workers
	for i := 0; i < s.numConsumers; i++ {
		wg.Add(1)
		go func(workerID int) {
			defer wg.Done()
			for {
				select {
				case <-ctx.Done():
					return
				case e, ok := <-ch:
					if !ok {
						return
					}
					if err := s.processEvent(e); err != nil {
						s.log.Error().Err(err).
							Int("worker", workerID).
							Interface("event", e).
							Msg("failed to process event")
					}
				}
			}
		}(i)
	}

	// wait for stop signal
	<-s.stopCh
	cancel() // signal workers to stop
	wg.Wait()

	return nil
}

// Close will make the service to stop processing, so the `Run`
// method can finish.
// TODO: Underlying services can't be stopped. This means that some goroutines
// will get stuck trying to push events through a channel nobody is reading
// from, so resources won't be freed and there will be memory leaks. For now,
// if the service is stopped, you should close the app soon after.
func (s Service) Close() {
	if s.stopped.CompareAndSwap(false, true) {
		close(s.stopCh)
	}
}

func getSpaceID(ref *provider.Reference) *provider.StorageSpaceId {
	return &provider.StorageSpaceId{
		OpaqueId: storagespace.FormatResourceID(
			&provider.ResourceId{
				StorageId: ref.GetResourceId().GetStorageId(),
				SpaceId:   ref.GetResourceId().GetSpaceId(),
			},
		),
	}
}

func (s Service) processEvent(e raw.Event) error {
	ctx := e.GetTraceContext(s.ctx)
	_, span := tracer.Start(ctx, "processEvent")
	defer span.End()

	e.InProgress() // let nats know that we are processing this event
	s.log.Debug().Interface("event", e).Msg("updating index")

	switch ev := e.Event.Event.(type) {
	case events.ItemTrashed:
		s.index.TrashItem(ev.ID)
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.Ref), e.Ack)
	case events.ItemPurged:
		s.index.PurgeItem(ev.Ref)
		e.Ack()
	case events.TrashbinPurged:
		s.index.PurgeDeleted(getSpaceID(ev.Ref))
		e.Ack()
	case events.ItemMoved:
		s.index.MoveItem(ev.Ref)
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.Ref), e.Ack)
	case events.ItemRestored:
		s.index.RestoreItem(ev.Ref)
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.Ref), e.Ack)
	case events.ContainerCreated:
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.Ref), e.Ack)
	case events.FileTouched:
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.Ref), e.Ack)
	case events.FileVersionRestored:
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.Ref), e.Ack)
	case events.TagsAdded:
		s.index.UpsertItem(ev.Ref)
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.Ref), e.Ack)
	case events.TagsRemoved:
		s.index.UpsertItem(ev.Ref)
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.Ref), e.Ack)
	case events.FileUploaded:
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.Ref), e.Ack)
	case events.UploadReady:
		s.indexSpaceDebouncer.Debounce(getSpaceID(ev.FileRef), e.Ack)
	case events.SpaceRenamed:
		s.indexSpaceDebouncer.Debounce(ev.ID, e.Ack)
	case events.LabelAdded:
		s.index.UpsertItem(ev.Ref)
	case events.LabelRemoved:
		s.index.UpsertItem(ev.Ref)
	}
	return nil
}

func monitorMetrics(ctx context.Context, stream raw.Stream, name string, m *metrics.Metrics, logger log.Logger) {
	consumer, err := stream.JetStream().Consumer(ctx, name)
	if err != nil {
		logger.Error().Err(err).Msg("failed to get consumer")
	}
	ticker := time.NewTicker(5 * time.Second)
	go func() {
		defer ticker.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case <-ticker.C:
				info, err := consumer.Info(ctx)
				if err != nil {
					logger.Error().Err(err).Msg("failed to get consumer")
					continue
				}

				m.EventsOutstandingAcks.Set(float64(info.NumAckPending))
				m.EventsUnprocessed.Set(float64(info.NumPending))
				m.EventsRedelivered.Set(float64(info.NumRedelivered))
				logger.Trace().Msg("updated search event metrics")
			}
		}
	}()
}