package main

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"

	mqtt "github.com/eclipse/paho.mqtt.golang"
	log "github.com/sirupsen/logrus"
)

// MQTT light state values exchanged with Home Assistant.
const (
	mqttStateOn  = "ON"
	mqttStateOff = "OFF"
	// mqttDefaultBrightness is used when a light is turned on without a level.
	mqttDefaultBrightness = 127

	// Availability payloads published on the source's availability topic and
	//  referenced by every discovery config so Home Assistant marks the entities
	//  unavailable when the bridge is offline.
	mqttAvailable    = "online"
	mqttNotAvailable = "offline"
)

// MQTTSource exposes a device's zones as one or more dimmable lights over MQTT,
// compatible with Home Assistant's JSON light schema. Each light drives its own
// configured set of zones; one broker connection is shared by all of them, along
// with an optional device-wide scene selector.
type MQTTSource struct {
	cfg     *SourceConfig
	dev     *Device
	binding *sourceBinding
	client  mqtt.Client

	lights []*mqttLight

	// availabilityTopic carries the bridge's online/offline state; it backs the
	//  Last Will and every entity's availability so Home Assistant marks them
	//  unavailable when the bridge dies.
	availabilityTopic string

	// Monitoring relay state. monitorBase/monitorPrefix root the topics raw "~"
	//  reports are published under; monitorFamilies filters which families to
	//  forward (nil forwards all).
	monitorBase     string
	monitorPrefix   string
	monitorFamilies map[string]bool

	// Scene selector state (device-wide), when enabled.
	sceneTopic string
	sceneSet   string

	mu        sync.Mutex
	scene     int
	sentScene int
}

// mqttLight is a single Home Assistant light backed by a fixed set of QSE zones.
// Brightness drives every zone in the set; the first zone is mirrored back as the
// aggregate state.
type mqttLight struct {
	src      *MQTTSource
	name     string
	topic    string
	topicSet string
	zones    []int

	mu             sync.Mutex
	state          string
	brightness     int
	sentState      string
	sentBrightness int
	published      bool
}

// newMQTTSource constructs an MQTT control source and its lights.
func newMQTTSource(cfg *SourceConfig, dev *Device, binding *sourceBinding) *MQTTSource {
	// Root the availability topic on the base topic when one is configured;
	//  otherwise (multi-light setups omit it) fall back to the source name.
	availBase := cfg.MQTT.Topic
	if availBase == "" {
		availBase = serviceName + "/" + mqttSlug(cfg.Name)
	}

	s := &MQTTSource{
		cfg:               cfg,
		dev:               dev,
		binding:           binding,
		availabilityTopic: availBase + "/availability",
		monitorBase:       availBase,
		monitorPrefix:     cfg.MQTT.MonitorPrefix,
		sceneTopic:        cfg.MQTT.Topic + "/scene",
		sceneSet:          cfg.MQTT.Topic + "/scene/set",
		scene:             -1, // Unknown until reported.
		sentScene:         -2,
	}
	// Build the family filter (uppercased); empty means forward everything.
	if len(cfg.MQTT.Monitor.Families) > 0 {
		s.monitorFamilies = make(map[string]bool, len(cfg.MQTT.Monitor.Families))
		for _, f := range cfg.MQTT.Monitor.Families {
			s.monitorFamilies[strings.ToUpper(f)] = true
		}
	}

	// Use the configured lights, or synthesize a single light over every zone when
	//  none are listed.
	lights := cfg.MQTT.Lights
	if len(lights) == 0 {
		zones := make([]int, dev.Zones())
		for i := range zones {
			zones[i] = i + 1
		}
		lights = []MQTTLightConfig{{Name: cfg.MQTT.DeviceName, Topic: cfg.MQTT.Topic, Zones: zones}}
	}
	for _, lc := range lights {
		name := lc.Name
		if name == "" {
			name = cfg.MQTT.DeviceName
		}
		s.lights = append(s.lights, &mqttLight{
			src:      s,
			name:     name,
			topic:    lc.Topic,
			topicSet: lc.Topic + "/set",
			zones:    append([]int(nil), lc.Zones...),
			state:    mqttStateOff,
		})
	}
	return s
}

// scenesEnabled reports whether this source exposes scene control.
func (s *MQTTSource) scenesEnabled() bool { return s.cfg.MQTT.Scenes > 0 }

// deviceSlug returns the Home Assistant device identifier shared by this source's
// lights, derived from the base topic and falling back to the source name when no
// base topic is configured.
func (s *MQTTSource) deviceSlug() string {
	if slug := mqttSlug(s.cfg.MQTT.Topic); slug != "" {
		return slug
	}
	return mqttSlug(s.cfg.Name)
}

// Name returns the source's configured name.
func (s *MQTTSource) Name() string { return s.cfg.Name }

// Start connects to the broker and wires the command and feedback paths.
func (s *MQTTSource) Start(ctx context.Context) error {
	// Mirror panel zone feedback into each light's aggregate state.
	s.dev.OnZoneFeedback(func(zone int, level byte) {
		for _, l := range s.lights {
			l.onZoneFeedback(zone, level)
		}
	})

	// Mirror the panel's active scene into the scene selector, when enabled.
	if s.scenesEnabled() {
		s.dev.NoteSceneControl()
		s.dev.OnSceneFeedback(func(scene int) {
			s.mu.Lock()
			s.scene = scene
			s.mu.Unlock()
			s.publishScene()
		})
	}

	// Relay the panel's raw monitoring out to MQTT topics, requesting the desired
	//  monitoring types from the panel first. Enabled when the source configures
	//  any monitoring types or a family filter.
	if len(s.cfg.MQTT.Monitor.Enable) > 0 || len(s.cfg.MQTT.Monitor.Families) > 0 {
		s.dev.NoteMonitoring(s.cfg.MQTT.Monitor.Enable...)
		s.dev.OnMonitor(s.publishMonitor)
	}

	clientID := s.cfg.MQTT.ClientID
	if clientID == "" {
		clientID = fmt.Sprintf("%s-%s-%d", serviceName, s.cfg.Name, os.Getpid())
	}

	opts := mqtt.NewClientOptions()
	opts.AddBroker(fmt.Sprintf("tcp://%s:%d", s.cfg.MQTT.Broker, s.cfg.MQTT.Port))
	opts.SetClientID(clientID)
	if s.cfg.MQTT.Username != "" {
		opts.SetUsername(s.cfg.MQTT.Username)
		opts.SetPassword(s.cfg.MQTT.Password)
	}
	opts.SetAutoReconnect(true)
	opts.SetConnectRetry(true)
	opts.SetConnectRetryInterval(5 * time.Second)
	// Register a retained Last Will so the broker marks the bridge offline if the
	//  connection drops; the matching birth message is published in onConnect.
	opts.SetWill(s.availabilityTopic, mqttNotAvailable, 1, true)
	opts.SetOnConnectHandler(s.onConnect)
	opts.SetConnectionLostHandler(func(_ mqtt.Client, err error) {
		log.Warnf("[%s] MQTT connection lost: %s", s.cfg.Name, err)
	})

	s.client = mqtt.NewClient(opts)
	// Connect in the background so a down broker doesn't block startup.
	go func() {
		token := s.client.Connect()
		token.Wait()
		if err := token.Error(); err != nil {
			log.Errorf("[%s] MQTT connect failed: %s", s.cfg.Name, err)
		}
	}()

	go func() {
		<-ctx.Done()
		s.Stop()
	}()
	return nil
}

// Stop disconnects from the broker.
func (s *MQTTSource) Stop() {
	if s.client != nil && s.client.IsConnected() {
		// Publish offline explicitly: a graceful disconnect doesn't trigger the
		//  Last Will, so without this the entities would stay "available".
		if token := s.client.Publish(s.availabilityTopic, 1, true, mqttNotAvailable); token.WaitTimeout(250*time.Millisecond) && token.Error() != nil {
			log.Warnf("[%s] MQTT availability publish failed on stop: %s", s.cfg.Name, token.Error())
		}
		s.client.Disconnect(250)
	}
}

// onConnect subscribes each light's command topic and publishes discovery and
// state, then wires up the scene selector when enabled.
func (s *MQTTSource) onConnect(c mqtt.Client) {
	log.Infof("[%s] Connected to MQTT broker", s.cfg.Name)

	// Announce the bridge online (retained) before discovery so entities appear
	//  available; the Last Will flips this to offline if the connection drops.
	if token := c.Publish(s.availabilityTopic, 1, true, mqttAvailable); token.Wait() && token.Error() != nil {
		log.Errorf("[%s] MQTT availability publish failed: %s", s.cfg.Name, token.Error())
	}

	for _, l := range s.lights {
		if token := c.Subscribe(l.topicSet, 0, l.onMessage); token.Wait() && token.Error() != nil {
			log.Errorf("[%s] MQTT subscribe failed for %s: %s", s.cfg.Name, l.topic, token.Error())
		}
		if s.cfg.MQTT.Discovery {
			l.publishDiscovery()
		}
		// Force the next publish to actually go out.
		l.mu.Lock()
		l.published = false
		l.mu.Unlock()
		l.publishState()
	}

	// Wire up the scene selector when enabled.
	if s.scenesEnabled() {
		if token := c.Subscribe(s.sceneSet, 0, s.onSceneMessage); token.Wait() && token.Error() != nil {
			log.Errorf("[%s] MQTT scene subscribe failed: %s", s.cfg.Name, token.Error())
		}
		if s.cfg.MQTT.Discovery {
			s.publishSceneDiscovery()
		}
		s.publishScene()
	}

	// Wire up the extended controls (shades, ramp buttons, locks, sequence).
	s.setupControls(c)
}

// onSceneMessage handles a scene-selection command (a plain scene number).
func (s *MQTTSource) onSceneMessage(_ mqtt.Client, msg mqtt.Message) {
	scene, err := strconv.Atoi(strings.TrimSpace(string(msg.Payload())))
	if err != nil || scene < 1 {
		log.Warnf("[%s] Bad MQTT scene payload: %q", s.cfg.Name, msg.Payload())
		return
	}
	log.Debugf("[%s] MQTT scene RX %d", s.cfg.Name, scene)
	if !s.dev.ApplyScene(s.binding, scene) {
		// Locked out by a higher-priority source; reflect the current scene back.
		s.publishScene()
	}
}

// publishScene publishes the active scene number when it has changed.
func (s *MQTTSource) publishScene() {
	if s.client == nil || !s.client.IsConnected() {
		return
	}
	s.mu.Lock()
	// Scene 0 is the panel's "unknown/none" report and isn't one of the select's
	//  options (1..N), so don't publish it as a state.
	if s.scene == s.sentScene || s.scene <= 0 {
		s.mu.Unlock()
		return
	}
	s.sentScene = s.scene
	payload := strconv.Itoa(s.scene)
	s.mu.Unlock()

	token := s.client.Publish(s.sceneTopic, 0, true, payload)
	if token.Wait() && token.Error() != nil {
		log.Warnf("[%s] MQTT scene publish failed: %s", s.cfg.Name, token.Error())
		return
	}
	log.Debugf("[%s] Published scene %s to %s", s.cfg.Name, payload, s.sceneTopic)
}

// publishMonitor forwards one monitoring message to an MQTT topic, after applying
// the family filter. The topic is <base>/<prefix>/<family>/<identifying fields>
// and the payload is the trailing field (Lutron reports put the value last), so
// every monitored message is relayed losslessly. These are raw state topics for
// automations; no Home Assistant discovery is published for them.
func (s *MQTTSource) publishMonitor(ev MonitorEvent) {
	if s.client == nil || !s.client.IsConnected() {
		return
	}
	if s.monitorFamilies != nil && !s.monitorFamilies[ev.Family] {
		return
	}
	segs := []string{s.monitorBase, s.monitorPrefix, strings.ToLower(ev.Family)}
	payload := ev.Raw
	if n := len(ev.Fields); n > 0 {
		segs = append(segs, ev.Fields[:n-1]...)
		payload = ev.Fields[n-1]
	}
	topic := strings.Join(segs, "/")

	token := s.client.Publish(topic, 0, true, payload)
	if token.Wait() && token.Error() != nil {
		log.Warnf("[%s] MQTT monitor publish failed for %s: %s", s.cfg.Name, topic, token.Error())
		return
	}
	log.Debugf("[%s] Published monitor %q to %s", s.cfg.Name, payload, topic)
}

// publishSceneDiscovery publishes a Home Assistant select entity for the scenes.
func (s *MQTTSource) publishSceneDiscovery() {
	slug := mqttSlug(s.cfg.MQTT.Topic) + "_scene"
	topic := fmt.Sprintf("%s/select/%s/config", s.cfg.MQTT.DiscoveryPrefix, slug)
	options := make([]string, s.cfg.MQTT.Scenes)
	for i := range options {
		options[i] = strconv.Itoa(i + 1)
	}
	deviceSlug := s.deviceSlug()
	payload, _ := json.Marshal(map[string]any{
		"name":                  s.cfg.MQTT.DeviceName + " Scene",
		"unique_id":             slug,
		"command_topic":         s.sceneSet,
		"state_topic":           s.sceneTopic,
		"options":               options,
		"availability_topic":    s.availabilityTopic,
		"payload_available":     mqttAvailable,
		"payload_not_available": mqttNotAvailable,
		"device": map[string]any{
			"identifiers":  []string{deviceSlug},
			"name":         s.cfg.MQTT.DeviceName,
			"manufacturer": "Lutron",
			"model":        "GRAFIK Eye QS",
		},
	})
	token := s.client.Publish(topic, 0, true, payload)
	if token.Wait() && token.Error() != nil {
		log.Errorf("[%s] MQTT scene discovery publish failed: %s", s.cfg.Name, token.Error())
		return
	}
	log.Infof("[%s] Published Home Assistant scene discovery to %s", s.cfg.Name, topic)
}

// setupControls subscribes the command topics and publishes discovery for the
// optional extended controls: shade covers, per-light raise/lower/stop buttons,
// zone/scene lock switches, and the sequence selector. Each is gated by its
// config toggle, mirroring how scenes are enabled.
func (s *MQTTSource) setupControls(c mqtt.Client) {
	base := s.cfg.MQTT.Topic

	// Shade columns as Home Assistant covers (open/close/stop).
	for col := 1; col <= s.cfg.MQTT.Shades; col++ {
		set := fmt.Sprintf("%s/shade/%d/set", base, col)
		if token := c.Subscribe(set, 0, s.shadeHandler(col)); token.Wait() && token.Error() != nil {
			log.Errorf("[%s] MQTT shade subscribe failed: %s", s.cfg.Name, token.Error())
		}
		if s.cfg.MQTT.Discovery {
			s.publishCoverDiscovery(col, set)
		}
	}

	// Raise/lower/stop buttons for each light's zones.
	if s.cfg.MQTT.ZoneRamp {
		for _, l := range s.lights {
			for _, action := range []string{"raise", "lower", "stop"} {
				set := fmt.Sprintf("%s/%s/set", l.topic, action)
				if token := c.Subscribe(set, 0, s.rampHandler(l, action)); token.Wait() && token.Error() != nil {
					log.Errorf("[%s] MQTT ramp subscribe failed: %s", s.cfg.Name, token.Error())
				}
				if s.cfg.MQTT.Discovery {
					s.publishButtonDiscovery(l, action, set)
				}
			}
		}
	}

	// Zone and scene lock switches.
	if s.cfg.MQTT.ZoneLock {
		set := base + "/zone_lock/set"
		if token := c.Subscribe(set, 0, s.lockHandler(false)); token.Wait() && token.Error() != nil {
			log.Errorf("[%s] MQTT zone-lock subscribe failed: %s", s.cfg.Name, token.Error())
		}
		if s.cfg.MQTT.Discovery {
			s.publishSwitchDiscovery("zone_lock", "Zone Lock", set)
		}
	}
	if s.cfg.MQTT.SceneLock {
		set := base + "/scene_lock/set"
		if token := c.Subscribe(set, 0, s.lockHandler(true)); token.Wait() && token.Error() != nil {
			log.Errorf("[%s] MQTT scene-lock subscribe failed: %s", s.cfg.Name, token.Error())
		}
		if s.cfg.MQTT.Discovery {
			s.publishSwitchDiscovery("scene_lock", "Scene Lock", set)
		}
	}

	// Sequence selector.
	if s.cfg.MQTT.Sequence {
		set := base + "/sequence/set"
		if token := c.Subscribe(set, 0, s.sequenceHandler); token.Wait() && token.Error() != nil {
			log.Errorf("[%s] MQTT sequence subscribe failed: %s", s.cfg.Name, token.Error())
		}
		if s.cfg.MQTT.Discovery {
			s.publishSequenceDiscovery(set)
		}
	}
}

// sequenceOptions are the Home Assistant select options for the sequence state,
// indexed by the Lutron sequence mode (0 off, 1 scenes 1-4, 2 scenes 5-16).
var sequenceOptions = []string{"Off", "Scenes 1-4", "Scenes 5-16"}

// shadeHandler drives a shade column from a Home Assistant cover command
// (OPEN/CLOSE/STOP, case-insensitive).
func (s *MQTTSource) shadeHandler(column int) mqtt.MessageHandler {
	return func(_ mqtt.Client, msg mqtt.Message) {
		action := strings.ToLower(strings.TrimSpace(string(msg.Payload())))
		log.Debugf("[%s] MQTT shade %d RX %s", s.cfg.Name, column, action)
		if !s.dev.ApplyShade(s.binding, column, action) {
			log.Warnf("[%s] Unknown shade action %q", s.cfg.Name, action)
		}
	}
}

// rampHandler starts or stops raising/lowering every zone of a light.
func (s *MQTTSource) rampHandler(l *mqttLight, action string) mqtt.MessageHandler {
	return func(_ mqtt.Client, _ mqtt.Message) {
		log.Debugf("[%s] MQTT %s %s", s.cfg.Name, l.topic, action)
		for _, z := range l.zones {
			switch action {
			case "raise":
				s.dev.RaiseZone(s.binding, z)
			case "lower":
				s.dev.LowerZone(s.binding, z)
			case "stop":
				s.dev.StopZone(s.binding, z)
			}
		}
	}
}

// lockHandler toggles the zone or scene lock from an ON/OFF switch command.
func (s *MQTTSource) lockHandler(scene bool) mqtt.MessageHandler {
	return func(_ mqtt.Client, msg mqtt.Message) {
		on := strings.EqualFold(strings.TrimSpace(string(msg.Payload())), mqttStateOn)
		if scene {
			s.dev.SetSceneLock(on)
		} else {
			s.dev.SetZoneLock(on)
		}
	}
}

// sequenceHandler sets the sequence state from a select command.
func (s *MQTTSource) sequenceHandler(_ mqtt.Client, msg mqtt.Message) {
	choice := strings.TrimSpace(string(msg.Payload()))
	for mode, opt := range sequenceOptions {
		if opt == choice {
			s.dev.SetSequence(mode)
			return
		}
	}
	log.Warnf("[%s] Unknown sequence option %q", s.cfg.Name, choice)
}

// haDevice returns the Home Assistant device block shared by this source's
// entities so they group under one device.
func (s *MQTTSource) haDevice() map[string]any {
	return map[string]any{
		"identifiers":  []string{s.deviceSlug()},
		"name":         s.cfg.MQTT.DeviceName,
		"manufacturer": "Lutron",
		"model":        "GRAFIK Eye QS",
	}
}

// publishConfig publishes a retained Home Assistant discovery config.
func (s *MQTTSource) publishConfig(topic string, payload []byte, kind string) {
	token := s.client.Publish(topic, 0, true, payload)
	if token.Wait() && token.Error() != nil {
		log.Errorf("[%s] MQTT %s discovery publish failed: %s", s.cfg.Name, kind, token.Error())
		return
	}
	log.Infof("[%s] Published Home Assistant %s discovery to %s", s.cfg.Name, kind, topic)
}

// publishCoverDiscovery publishes a Home Assistant cover for a shade column. The
// cover is optimistic since the panel reports no shade position.
func (s *MQTTSource) publishCoverDiscovery(column int, set string) {
	slug := fmt.Sprintf("%s_shade_%d", mqttSlug(s.cfg.MQTT.Topic), column)
	topic := fmt.Sprintf("%s/cover/%s/config", s.cfg.MQTT.DiscoveryPrefix, slug)
	payload, _ := json.Marshal(map[string]any{
		"name":                  fmt.Sprintf("%s Shade %d", s.cfg.MQTT.DeviceName, column),
		"unique_id":             slug,
		"command_topic":         set,
		"payload_open":          "open",
		"payload_close":         "close",
		"payload_stop":          "stop",
		"optimistic":            true,
		"availability_topic":    s.availabilityTopic,
		"payload_available":     mqttAvailable,
		"payload_not_available": mqttNotAvailable,
		"device":                s.haDevice(),
	})
	s.publishConfig(topic, payload, "cover")
}

// publishButtonDiscovery publishes a Home Assistant button for a light's
// raise/lower/stop action.
func (s *MQTTSource) publishButtonDiscovery(l *mqttLight, action, set string) {
	slug := fmt.Sprintf("%s_%s", mqttSlug(l.topic), action)
	topic := fmt.Sprintf("%s/button/%s/config", s.cfg.MQTT.DiscoveryPrefix, slug)
	label := strings.ToUpper(action[:1]) + action[1:]
	payload, _ := json.Marshal(map[string]any{
		"name":                  fmt.Sprintf("%s %s", l.name, label),
		"unique_id":             slug,
		"command_topic":         set,
		"availability_topic":    s.availabilityTopic,
		"payload_available":     mqttAvailable,
		"payload_not_available": mqttNotAvailable,
		"device":                s.haDevice(),
	})
	s.publishConfig(topic, payload, "button")
}

// publishSwitchDiscovery publishes a Home Assistant switch for a lock. The switch
// is optimistic since the panel reports no lock state.
func (s *MQTTSource) publishSwitchDiscovery(key, name, set string) {
	slug := fmt.Sprintf("%s_%s", mqttSlug(s.cfg.MQTT.Topic), key)
	topic := fmt.Sprintf("%s/switch/%s/config", s.cfg.MQTT.DiscoveryPrefix, slug)
	payload, _ := json.Marshal(map[string]any{
		"name":                  s.cfg.MQTT.DeviceName + " " + name,
		"unique_id":             slug,
		"command_topic":         set,
		"payload_on":            mqttStateOn,
		"payload_off":           mqttStateOff,
		"optimistic":            true,
		"availability_topic":    s.availabilityTopic,
		"payload_available":     mqttAvailable,
		"payload_not_available": mqttNotAvailable,
		"device":                s.haDevice(),
	})
	s.publishConfig(topic, payload, "switch")
}

// publishSequenceDiscovery publishes a Home Assistant select for the sequence
// state. It is optimistic since the panel reports no sequence state.
func (s *MQTTSource) publishSequenceDiscovery(set string) {
	slug := mqttSlug(s.cfg.MQTT.Topic) + "_sequence"
	topic := fmt.Sprintf("%s/select/%s/config", s.cfg.MQTT.DiscoveryPrefix, slug)
	payload, _ := json.Marshal(map[string]any{
		"name":                  s.cfg.MQTT.DeviceName + " Sequence",
		"unique_id":             slug,
		"command_topic":         set,
		"options":               sequenceOptions,
		"optimistic":            true,
		"availability_topic":    s.availabilityTopic,
		"payload_available":     mqttAvailable,
		"payload_not_available": mqttNotAvailable,
		"device":                s.haDevice(),
	})
	s.publishConfig(topic, payload, "select")
}

// onZoneFeedback mirrors the light's representative zone (the first in its set)
// into the aggregate light state.
func (l *mqttLight) onZoneFeedback(zone int, level byte) {
	if len(l.zones) == 0 || zone != l.zones[0] {
		return
	}
	l.mu.Lock()
	l.brightness = int(level)
	if level == 0 {
		l.state = mqttStateOff
	} else {
		l.state = mqttStateOn
	}
	l.mu.Unlock()
	l.publishState()
}

// onMessage handles a command on the light's set topic.
func (l *mqttLight) onMessage(_ mqtt.Client, msg mqtt.Message) {
	var cmd struct {
		State      string `json:"state"`
		Brightness *int   `json:"brightness"`
	}
	if err := json.Unmarshal(msg.Payload(), &cmd); err != nil {
		log.Warnf("[%s] Bad MQTT payload for %s: %s", l.src.cfg.Name, l.topic, err)
		return
	}
	log.Debugf("[%s] MQTT RX %s %s", l.src.cfg.Name, l.topic, msg.Payload())

	// Compute the requested target level.
	l.mu.Lock()
	if cmd.Brightness != nil {
		l.brightness = clampByte(*cmd.Brightness)
	}
	if cmd.State != "" && cmd.State != l.state {
		l.state = cmd.State
		// Turning on without a level defaults to roughly half brightness.
		if l.state == mqttStateOn && l.brightness == 0 {
			l.brightness = mqttDefaultBrightness
		}
	}
	target := 0
	if l.state == mqttStateOn {
		target = l.brightness
	}
	l.mu.Unlock()

	// Apply the level uniformly across this light's zones only.
	levels := make(map[int]byte, len(l.zones))
	for _, z := range l.zones {
		levels[z] = byte(target)
	}
	if !l.src.dev.ApplyZoneLevels(l.src.binding, levels) {
		// We can't take control — a higher-priority source (e.g. live DMX) is in
		//  control, or integration control is disabled. Mirror the device's real
		//  zone state back out instead of fighting it.
		targets := l.src.dev.ZoneTargets()
		l.mu.Lock()
		if len(l.zones) > 0 {
			if z := l.zones[0]; z >= 1 && z <= len(targets) {
				l.brightness = int(targets[z-1])
			}
		}
		if l.brightness == 0 {
			l.state = mqttStateOff
		} else {
			l.state = mqttStateOn
		}
		l.published = false
		l.mu.Unlock()
	}
	l.publishState()
}

// publishState publishes the light's aggregate state when it has changed.
func (l *mqttLight) publishState() {
	c := l.src.client
	if c == nil || !c.IsConnected() {
		return
	}
	l.mu.Lock()
	if l.published && l.state == l.sentState && l.brightness == l.sentBrightness {
		l.mu.Unlock()
		return
	}
	l.sentState = l.state
	l.sentBrightness = l.brightness
	l.published = true
	payload, _ := json.Marshal(map[string]any{
		"state":      l.state,
		"brightness": l.brightness,
	})
	l.mu.Unlock()

	token := c.Publish(l.topic, 0, true, payload)
	if token.Wait() && token.Error() != nil {
		log.Warnf("[%s] MQTT publish failed for %s: %s", l.src.cfg.Name, l.topic, token.Error())
		return
	}
	log.Debugf("[%s] Published %s to %s", l.src.cfg.Name, payload, l.topic)
}

// publishDiscovery publishes a Home Assistant MQTT discovery config (retained) so
// the light appears automatically. All of a source's lights are grouped under the
// same Home Assistant device.
func (l *mqttLight) publishDiscovery() {
	slug := mqttSlug(l.topic)
	topic := fmt.Sprintf("%s/light/%s/config", l.src.cfg.MQTT.DiscoveryPrefix, slug)
	deviceSlug := l.src.deviceSlug()
	payload, _ := json.Marshal(map[string]any{
		"schema":                "json",
		"name":                  l.name,
		"unique_id":             slug,
		"state_topic":           l.topic,
		"command_topic":         l.topicSet,
		"brightness":            true,
		"supported_color_modes": []string{"brightness"},
		"availability_topic":    l.src.availabilityTopic,
		"payload_available":     mqttAvailable,
		"payload_not_available": mqttNotAvailable,
		"device": map[string]any{
			"identifiers":  []string{deviceSlug},
			"name":         l.src.cfg.MQTT.DeviceName,
			"manufacturer": "Lutron",
			"model":        "GRAFIK Eye QS",
		},
	})
	token := l.src.client.Publish(topic, 0, true, payload)
	if token.Wait() && token.Error() != nil {
		log.Errorf("[%s] MQTT discovery publish failed for %s: %s", l.src.cfg.Name, l.topic, token.Error())
		return
	}
	log.Infof("[%s] Published Home Assistant discovery to %s", l.src.cfg.Name, topic)
}

// mqttSlug derives a stable identifier from the base topic for HA unique IDs.
func mqttSlug(topic string) string {
	var b strings.Builder
	for _, r := range topic {
		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') {
			b.WriteRune(r)
		} else {
			b.WriteRune('_')
		}
	}
	return strings.Trim(b.String(), "_")
}

// clampByte clamps an integer to the 0-255 DMX/brightness range.
func clampByte(v int) int {
	if v < 0 {
		return 0
	}
	if v > 255 {
		return 255
	}
	return v
}