package services

import (
	lucifer3 "git.aiterp.net/lucifer3/server"
	"git.aiterp.net/lucifer3/server/commands"
	"git.aiterp.net/lucifer3/server/device"
	"git.aiterp.net/lucifer3/server/events"
	"git.aiterp.net/lucifer3/server/internal/gentools"
	"github.com/google/uuid"
	"sync"
	"sync/atomic"
	"time"
)

func NewEffectEnforcer(resolver device.Resolver, sceneMap device.SceneMap) lucifer3.ActiveService {
	s := &effectEnforcer{
		resolver: resolver,
		sceneMap: sceneMap,
		list:     make([]*effectEnforcerRun, 0, 16),
		index:    make(map[string]*effectEnforcerRun, 8),
	}

	return s
}

type effectEnforcer struct {
	mu       sync.Mutex
	resolver device.Resolver
	sceneMap device.SceneMap

	started uint32

	list  []*effectEnforcerRun
	index map[string]*effectEnforcerRun
}

func (s *effectEnforcer) Active() bool {
	return true
}

func (s *effectEnforcer) HandleEvent(_ *lucifer3.EventBus, event lucifer3.Event) {
	switch event := event.(type) {
	case events.DeviceReady:
		// If the device is managed by the effect enforcer, cause the effect to be
		// re-ran.
		s.mu.Lock()
		if run, ok := s.index[event.ID]; ok {
			run.due = time.Now()
		}
		s.mu.Unlock()
	}
}

func (s *effectEnforcer) HandleCommand(bus *lucifer3.EventBus, command lucifer3.Command) {
	switch command := command.(type) {
	case commands.Assign:
		pointers := s.resolver.Resolve(command.Match)
		allowedIDs := make([]string, 0, len(pointers))
		for _, ptr := range pointers {
			if s.sceneMap.SceneID(ptr.ID) == nil {
				allowedIDs = append(allowedIDs, ptr.ID)
			}
		}
		if len(pointers) == 0 {
			if command.ID != nil {
				bus.RunEvent(events.AssignmentRemoved{ID: *command.ID})
			} else {
				bus.RunEvent(events.Log{
					Level:   "info",
					Code:    "assignment_matched_none",
					Message: "Assignment to \"" + command.Match + "\" matched no devices.",
				})
			}

			return
		}

		id := uuid.New()
		if command.ID != nil {
			id = *command.ID
		}

		bus.RunEvent(events.AssignmentCreated{
			ID:     id,
			Match:  command.Match,
			Effect: command.Effect,
		})

		s.mu.Lock()
		// Create a new run
		newRun := &effectEnforcerRun{
			id:     id,
			due:    time.Now(),
			ids:    allowedIDs,
			effect: command.Effect,
		}
		s.list = append(s.list, newRun)

		// Switch over the indices.
		for _, id := range allowedIDs {
			if oldRun := s.index[id]; oldRun != nil {
				oldRun.remove(id)
			}
			s.index[id] = newRun
		}
		s.mu.Unlock()

		if atomic.CompareAndSwapUint32(&s.started, 0, 1) {
			go s.runLoop(bus)
		}

		for _, deviceID := range allowedIDs {
			bus.RunEvent(events.DeviceAssigned{
				DeviceID:     deviceID,
				AssignmentID: gentools.Ptr(id),
			})
		}
	}
}

func (s *effectEnforcer) runLoop(bus *lucifer3.EventBus) {
	deleteList := make([]int, 0, 8)
	batch := make(commands.SetStateBatch, 64)
	deleteIDs := make([]uuid.UUID, 0)

	for now := range time.NewTicker(time.Millisecond * 50).C {
		deleteIDs = deleteIDs[:0]

		s.mu.Lock()
		for i, run := range s.list {
			if run.dead {
				deleteIDs = append(deleteIDs, run.id)
				deleteList = append(deleteList, i-len(deleteList))
				continue
			}
			if run.due.IsZero() || now.Before(run.due) {
				continue
			}

			for j, id := range run.ids {
				if id == "" {
					continue
				}

				state := run.effect.State(j, len(run.ids), run.round)
				batch[id] = state
			}

			if freq := run.effect.Frequency(); freq > 0 {
				if freq < 100*time.Millisecond {
					run.due = now
				} else {
					run.due = run.due.Add(freq)
				}

				run.round += 1
			} else {
				run.due = time.Time{}
			}
		}

		if len(deleteList) > 0 {
			for _, i := range deleteList {
				s.list = append(s.list[:i], s.list[i+1:]...)
			}

			deleteList = deleteList[:0]
		}
		s.mu.Unlock()

		for _, id := range deleteIDs {
			bus.RunEvent(events.AssignmentRemoved{ID: id})
		}

		if len(batch) > 0 {
			bus.RunCommand(batch)
			batch = make(commands.SetStateBatch, 64)
		}
	}
}

type effectEnforcerRun struct {
	id     uuid.UUID
	due    time.Time
	ids    []string
	effect lucifer3.Effect
	dead   bool
	round  int
}

// remove takes out an id from the effect, and returns whether the effect is empty.
func (r *effectEnforcerRun) remove(id string) {
	anyLeft := false
	for i, id2 := range r.ids {
		if id2 == id {
			r.ids[i] = ""
		} else if id2 != "" {
			anyLeft = true
		}
	}

	if !anyLeft {
		r.dead = true
	}

	return
}