package docker

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

	"github.com/puzpuzpuz/xsync/v3"
	"github.com/rs/zerolog/log"
	"github.com/samber/lo"
	"golang.org/x/sync/semaphore"
)

type ContainerStore struct {
	containers              *xsync.MapOf[string, *Container]
	subscribers             *xsync.MapOf[context.Context, chan<- ContainerEvent]
	newContainerSubscribers *xsync.MapOf[context.Context, chan<- Container]
	client                  Client
	statsCollector          *StatsCollector
	wg                      sync.WaitGroup
	connected               atomic.Bool
	events                  chan ContainerEvent
	ctx                     context.Context
	filter                  ContainerFilter
}

func NewContainerStore(ctx context.Context, client Client, filter ContainerFilter) *ContainerStore {
	s := &ContainerStore{
		containers:              xsync.NewMapOf[string, *Container](),
		client:                  client,
		subscribers:             xsync.NewMapOf[context.Context, chan<- ContainerEvent](),
		newContainerSubscribers: xsync.NewMapOf[context.Context, chan<- Container](),
		statsCollector:          NewStatsCollector(client, filter),
		wg:                      sync.WaitGroup{},
		events:                  make(chan ContainerEvent),
		ctx:                     ctx,
		filter:                  filter,
	}

	s.wg.Add(1)

	go s.init()

	return s
}

var (
	ErrContainerNotFound = errors.New("container not found")
	maxFetchParallelism  = int64(30)
)

func (s *ContainerStore) checkConnectivity() error {
	if s.connected.CompareAndSwap(false, true) {
		go func() {
			log.Debug().Str("host", s.client.Host().Name).Msg("docker store subscribing docker events")
			err := s.client.ContainerEvents(s.ctx, s.events)
			if !errors.Is(err, context.Canceled) {
				log.Error().Err(err).Str("host", s.client.Host().Name).Msg("docker store unexpectedly disconnected from docker events")
			}
			s.connected.Store(false)
		}()

		ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second) // 3s is enough to fetch all containers
		defer cancel()
		if containers, err := s.client.ListContainers(ctx, s.filter); err != nil {
			return err
		} else {
			s.containers.Clear()

			for _, c := range containers {
				s.containers.Store(c.ID, &c)
			}

			running := lo.Filter(containers, func(item Container, index int) bool {
				return item.State != "exited"
			})

			sem := semaphore.NewWeighted(maxFetchParallelism)

			for i, c := range running {
				if err := sem.Acquire(s.ctx, 1); err != nil {
					log.Error().Err(err).Msg("failed to acquire semaphore")
					break
				}
				go func(c Container, i int) {
					defer sem.Release(1)
					ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second) // 2s is hardcoded timeout for fetching container
					defer cancel()
					if container, err := s.client.FindContainer(ctx, c.ID); err == nil {
						s.containers.Store(c.ID, &container)
					}
				}(c, i)
			}

			if err := sem.Acquire(s.ctx, maxFetchParallelism); err != nil {
				log.Error().Err(err).Msg("failed to acquire semaphore")
			}

			log.Debug().Int("containers", len(containers)).Msg("finished initializing container store")
		}
	}

	return nil
}

func (s *ContainerStore) ListContainers(filter ContainerFilter) ([]Container, error) {
	s.wg.Wait()

	if err := s.checkConnectivity(); err != nil {
		return nil, err
	}

	validContainers, err := s.client.ListContainers(s.ctx, filter)
	if err != nil {
		return nil, err
	}

	validIDMap := lo.KeyBy(validContainers, func(item Container) string {
		return item.ID
	})

	containers := make([]Container, 0)
	s.containers.Range(func(_ string, c *Container) bool {
		if _, ok := validIDMap[c.ID]; ok {
			containers = append(containers, *c)
		}
		return true
	})

	return containers, nil
}

func (s *ContainerStore) FindContainer(id string) (Container, error) {
	s.wg.Wait()
	container, ok := s.containers.Load(id)

	if ok {
		return *container, nil
	} else {
		log.Warn().Str("id", id).Msg("container not found")
		return Container{}, ErrContainerNotFound
	}
}

func (s *ContainerStore) Client() Client {
	return s.client
}

func (s *ContainerStore) SubscribeEvents(ctx context.Context, events chan<- ContainerEvent) {
	go func() {
		if s.statsCollector.Start(s.ctx) {
			s.containers.Range(func(_ string, c *Container) bool {
				c.Stats.Clear()
				return true
			})
		}
	}()

	s.subscribers.Store(ctx, events)
	go func() {
		<-ctx.Done()
		s.subscribers.Delete(ctx)
		s.statsCollector.Stop()
	}()
}

func (s *ContainerStore) SubscribeStats(ctx context.Context, stats chan<- ContainerStat) {
	s.statsCollector.Subscribe(ctx, stats)
}

func (s *ContainerStore) SubscribeNewContainers(ctx context.Context, containers chan<- Container) {
	s.newContainerSubscribers.Store(ctx, containers)
	go func() {
		<-ctx.Done()
		s.newContainerSubscribers.Delete(ctx)
	}()
}

func (s *ContainerStore) init() {
	stats := make(chan ContainerStat)
	s.statsCollector.Subscribe(s.ctx, stats)

	s.checkConnectivity()

	s.wg.Done()

	for {
		select {
		case event := <-s.events:
			log.Trace().Str("event", event.Name).Str("id", event.ActorID).Msg("received container event")
			switch event.Name {
			case "start":
				ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)

				if container, err := s.client.FindContainer(ctx, event.ActorID); err == nil {
					list, _ := s.client.ListContainers(ctx, s.filter)

					// make sure the container is in the list of containers when using filter
					valid := lo.ContainsBy(list, func(item Container) bool {
						return item.ID == container.ID
					})

					if valid {
						log.Debug().Str("id", container.ID).Msg("container started")
						s.containers.Store(container.ID, &container)
						s.newContainerSubscribers.Range(func(c context.Context, containers chan<- Container) bool {
							select {
							case containers <- container:
							case <-c.Done():
							}
							return true
						})
					}
				}
				cancel()
			case "destroy":
				log.Debug().Str("id", event.ActorID).Msg("container destroyed")
				s.containers.Delete(event.ActorID)

			case "die":
				s.containers.Compute(event.ActorID, func(c *Container, loaded bool) (*Container, bool) {
					if loaded {
						log.Debug().Str("id", c.ID).Msg("container died")
						c.State = "exited"
						return c, false
					} else {
						return c, true
					}
				})
			case "health_status: healthy", "health_status: unhealthy":
				healthy := "unhealthy"
				if event.Name == "health_status: healthy" {
					healthy = "healthy"
				}

				s.containers.Compute(event.ActorID, func(c *Container, loaded bool) (*Container, bool) {
					if loaded {
						log.Debug().Str("id", c.ID).Str("health", healthy).Msg("container health status changed")
						c.Health = healthy
						return c, false
					} else {
						return c, true
					}
				})

			case "rename":
				s.containers.Compute(event.ActorID, func(c *Container, loaded bool) (*Container, bool) {
					if loaded {
						log.Debug().Str("id", event.ActorID).Str("name", event.ActorAttributes["name"]).Msg("container renamed")
						c.Name = event.ActorAttributes["name"]
						return c, false
					} else {
						return c, true
					}
				})
			}
			s.subscribers.Range(func(c context.Context, events chan<- ContainerEvent) bool {
				select {
				case events <- event:
				case <-c.Done():
					s.subscribers.Delete(c)
				}
				return true
			})

		case stat := <-stats:
			if container, ok := s.containers.Load(stat.ID); ok {
				stat.ID = ""
				container.Stats.Push(stat)
			}
		case <-s.ctx.Done():
			return
		}
	}
}