package publisher

import (
	"context"
	"git.aiterp.net/lucifer/new-server/app/config"
	"git.aiterp.net/lucifer/new-server/models"
	"log"
	"sync"
	"time"
)

type Publisher struct {
	mu              sync.Mutex
	sceneData       map[int]*models.Scene
	scenes          []*Scene
	sceneAssignment map[int]*Scene
	started         map[int]bool
	pending         map[int][]models.Device
	waiting         map[int]chan struct{}
}

func (p *Publisher) SceneState(deviceID int) *models.DeviceState {
	p.mu.Lock()
	defer p.mu.Unlock()

	if s := p.sceneAssignment[deviceID]; s != nil {
		return s.LastState(deviceID)
	}

	return nil
}

func (p *Publisher) UpdateScene(data models.Scene) {
	p.mu.Lock()
	p.sceneData[data.ID] = &data

	for _, scene := range p.scenes {
		if scene.data.ID == data.ID {
			scene.UpdateScene(data)
		}
	}
	p.mu.Unlock()
}

func (p *Publisher) ReloadScenes(ctx context.Context) error {
	scenes, err := config.SceneRepository().FetchAll(ctx)
	if err != nil {
		return err
	}

	p.mu.Lock()
	for i, scene := range scenes {
		p.sceneData[scene.ID] = &scenes[i]
	}

	for _, scene := range p.scenes {
		scene.UpdateScene(*p.sceneData[scene.data.ID])
	}
	p.mu.Unlock()

	return nil
}

func (p *Publisher) ReloadDevices(ctx context.Context) error {
	devices, err := config.DeviceRepository().FetchByReference(ctx, models.RKAll, "")
	if err != nil {
		return err
	}

	p.Publish(devices...)

	return nil
}

func (p *Publisher) Publish(devices ...models.Device) {
	if len(devices) == 0 {
		return
	}

	p.mu.Lock()
	defer p.mu.Unlock()

	for _, device := range devices {
		if !p.started[device.BridgeID] {
			p.started[device.BridgeID] = true
			go p.runBridge(device.BridgeID)
		}

		p.reassignDevice(device)

		if p.sceneAssignment[device.ID] != nil {
			p.sceneAssignment[device.ID].UpsertDevice(device)
		} else {
			p.pending[device.BridgeID] = append(p.pending[device.BridgeID], device)
			if p.waiting[device.BridgeID] != nil {
				close(p.waiting[device.BridgeID])
				p.waiting[device.BridgeID] = nil
			}
		}
	}
}

func (p *Publisher) PublishChannel(ch <-chan []models.Device) {
	for list := range ch {
		p.Publish(list...)
	}
}

func (p *Publisher) Run() {
	ticker := time.NewTicker(time.Millisecond * 100)
	deleteList := make([]int, 0, 8)
	updatedList := make([]models.Device, 0, 16)
	reassignList := make([]models.Device, 0, 16)

	for range ticker.C {
		deleteList = deleteList[:0]
		updatedList = updatedList[:0]
		reassignList = reassignList[:0]

		p.mu.Lock()
		for i, scene := range p.scenes {
			if (!scene.endTime.IsZero() && time.Now().After(scene.endTime)) || scene.Empty() {
				deleteList = append(deleteList, i-len(deleteList))
				updatedList = append(updatedList, scene.AllDevices()...)
				reassignList = append(reassignList, scene.AllDevices()...)

				log.Printf("Removing scene instance for %s (%d)", scene.data.Name, scene.data.ID)

				for _, device := range scene.AllDevices() {
					p.sceneAssignment[device.ID] = nil
				}
				continue
			}

			if scene.Due() {
				updatedList = append(updatedList, scene.Run()...)
				updatedList = append(updatedList, scene.UnaffectedDevices()...)
			}
		}

		for _, i := range deleteList {
			p.scenes = append(p.scenes[:i], p.scenes[i+1:]...)
		}

		for _, device := range reassignList {
			p.reassignDevice(device)

			if p.sceneAssignment[device.ID] != nil {
				p.sceneAssignment[device.ID].UpsertDevice(device)
			}
		}

		for _, device := range updatedList {
			if !p.started[device.BridgeID] {
				p.started[device.BridgeID] = true
				go p.runBridge(device.BridgeID)
			}

			p.pending[device.BridgeID] = append(p.pending[device.BridgeID], device)
			if p.waiting[device.BridgeID] != nil {
				close(p.waiting[device.BridgeID])
				p.waiting[device.BridgeID] = nil
			}
		}
		p.mu.Unlock()
	}
}

// reassignDevice re-evaluates the device's scene assignment config. It will return whether the scene changed, which
// should trigger an update.
func (p *Publisher) reassignDevice(device models.Device) bool {
	var selectedAssignment *models.DeviceSceneAssignment
	for i, assignment := range device.SceneAssignments {
		duration := time.Duration(assignment.DurationMS) * time.Millisecond
		if duration <= 0 || time.Now().Before(assignment.StartTime.Add(duration)) {
			selectedAssignment = &device.SceneAssignments[i]
		}
	}

	if selectedAssignment == nil {
		if p.sceneAssignment[device.ID] != nil {
			p.sceneAssignment[device.ID].RemoveDevice(device)
			delete(p.sceneAssignment, device.ID)

			// Scene changed
			return true
		}

		// Stop here, no scene should be assigned.
		return false
	} else {
		if p.sceneData[selectedAssignment.SceneID] == nil {
			// Freeze until scene becomes available.
			return false
		}
	}

	if p.sceneAssignment[device.ID] != nil {
		scene := p.sceneAssignment[device.ID]
		if scene.data.ID == selectedAssignment.SceneID && scene.group == selectedAssignment.Group {
			// Current assignment is good.
			return false
		}

		p.sceneAssignment[device.ID].RemoveDevice(device)
		delete(p.sceneAssignment, device.ID)
	}

	for _, scene := range p.scenes {
		if scene.data.ID == selectedAssignment.SceneID && scene.group == selectedAssignment.Group {
			p.sceneAssignment[device.ID] = scene
			return true
		}
	}

	newScene := &Scene{
		data:       p.sceneData[selectedAssignment.SceneID],
		group:      selectedAssignment.Group,
		startTime:  selectedAssignment.StartTime,
		endTime:    selectedAssignment.StartTime.Add(time.Duration(selectedAssignment.DurationMS) * time.Millisecond),
		roleMap:    make(map[int]int, 16),
		roleList:   make(map[int][]models.Device, 16),
		lastStates: make(map[int]models.DeviceState, 16),
		due:        true,
	}
	p.sceneAssignment[device.ID] = newScene
	p.scenes = append(p.scenes, newScene)

	if selectedAssignment.DurationMS <= 0 {
		newScene.endTime = time.Time{}
	}

	return true
}

func (p *Publisher) runBridge(id int) {
	defer func() {
		p.mu.Lock()
		p.started[id] = false
		p.mu.Unlock()
	}()

	bridge, err := config.BridgeRepository().Find(context.Background(), id)
	if err != nil {
		log.Println("Failed to get bridge data:", err)
		return
	}

	driver, err := config.DriverProvider().Provide(bridge.Driver)
	if err != nil {
		log.Println("Failed to get bridge driver:", err)
		log.Println("Maybe Lucifer needs to be updated.")
		return
	}

	devices := make(map[int]models.Device)

	for {
		p.mu.Lock()
		if len(p.pending[id]) == 0 {
			if p.waiting[id] == nil {
				p.waiting[id] = make(chan struct{})
			}
			waitCh := p.waiting[id]
			p.mu.Unlock()
			<-waitCh
			p.mu.Lock()
		}

		updates := p.pending[id]
		p.pending[id] = p.pending[id][:0:0]
		p.mu.Unlock()

		// Only allow the latest update per device (this avoids slow bridges causing a backlog of cations).
		for key := range devices {
			delete(devices, key)
		}
		for _, update := range updates {
			devices[update.ID] = update
		}
		updates = updates[:0]
		for _, value := range devices {
			updates = append(updates, value)
		}

		err := driver.Publish(context.Background(), bridge, updates)
		if err != nil {
			log.Println("Failed to publish to driver:", err)

			p.mu.Lock()
			p.pending[id] = append(updates, p.pending[id]...)
			p.mu.Unlock()
			return
		}
	}
}

var publisher = Publisher{
	sceneData:       make(map[int]*models.Scene),
	scenes:          make([]*Scene, 0, 16),
	sceneAssignment: make(map[int]*Scene, 16),
	started:         make(map[int]bool),
	pending:         make(map[int][]models.Device),
	waiting:         make(map[int]chan struct{}),
}

func Global() *Publisher {
	return &publisher
}

func Initialize(ctx context.Context) error {
	err := publisher.ReloadScenes(ctx)
	if err != nil {
		return err
	}
	err = publisher.ReloadDevices(ctx)
	if err != nil {
		return err
	}

	go publisher.Run()
	time.Sleep(time.Millisecond * 50)
	go publisher.PublishChannel(config.PublishChannel)

	return nil
}