Modernize invertergui: MQTT write support, HA integration, UI updates

plugins/mqttclient/mqtt.go

@@ -2,9 +2,14 @@ package mqttclient
 
 import (
 	"encoding/json"
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+	"sync"
 	"time"
 
-	"github.com/diebietse/invertergui/mk2driver"
+	"invertergui/mk2driver"
 	mqtt "github.com/eclipse/paho.mqtt.golang"
 	"github.com/sirupsen/logrus"
 )
@@ -13,42 +18,758 @@ var log = logrus.WithField("ctx", "inverter-gui-mqtt")
 
 const keepAlive = 5 * time.Second
 
-// Config sets MQTT client configuration
-type Config struct {
-	Broker   string
-	ClientID string
-	Topic    string
-	Username string
-	Password string
+const (
+	commandKindSetting = "setting"
+	commandKindRAMVar  = "ram_var"
+	commandKindPanel   = "panel_state"
+	commandKindStandby = "standby"
+
+	writeStatusOK    = "ok"
+	writeStatusError = "error"
+)
+
+type HomeAssistantConfig struct {
+	Enabled         bool
+	DiscoveryPrefix string
+	NodeID          string
+	DeviceName      string
 }
 
-// New creates an MQTT client that starts publishing MK2 data as it is received.
-func New(mk2 mk2driver.Mk2, config Config) error {
+// Config sets MQTT client configuration
+type Config struct {
+	Broker        string
+	ClientID      string
+	Topic         string
+	CommandTopic  string
+	StatusTopic   string
+	HomeAssistant HomeAssistantConfig
+	Username      string
+	Password      string
+}
+
+type writeCommand struct {
+	RequestID     string
+	Kind          string
+	ID            uint16
+	Value         int16
+	HasSwitch     bool
+	SwitchState   mk2driver.PanelSwitchState
+	SwitchName    string
+	CurrentLimitA *float64
+	Standby       *bool
+}
+
+type writeCommandPayload struct {
+	RequestID     string          `json:"request_id"`
+	Kind          string          `json:"kind"`
+	Type          string          `json:"type"`
+	ID            *uint16         `json:"id"`
+	Value         json.RawMessage `json:"value"`
+	Switch        string          `json:"switch"`
+	SwitchState   string          `json:"switch_state"`
+	CurrentLimitA *float64        `json:"current_limit"`
+	Standby       *bool           `json:"standby"`
+}
+
+type writeStatus struct {
+	RequestID     string    `json:"request_id,omitempty"`
+	Status        string    `json:"status"`
+	Kind          string    `json:"kind,omitempty"`
+	ID            uint16    `json:"id"`
+	Value         int16     `json:"value"`
+	Switch        string    `json:"switch,omitempty"`
+	CurrentLimitA *float64  `json:"current_limit,omitempty"`
+	Standby       *bool     `json:"standby,omitempty"`
+	Error         string    `json:"error,omitempty"`
+	Timestamp     time.Time `json:"timestamp"`
+}
+
+type haDiscoveryDefinition struct {
+	Component string
+	ObjectID  string
+	Config    map[string]any
+}
+
+type panelStateCache struct {
+	mu          sync.Mutex
+	hasSwitch   bool
+	switchName  string
+	switchState mk2driver.PanelSwitchState
+}
+
+// New creates an MQTT client that publishes MK2 updates and optionally handles setting write commands.
+func New(mk2 mk2driver.Mk2, writer mk2driver.SettingsWriter, config Config) error {
 	c := mqtt.NewClient(getOpts(config))
 	if token := c.Connect(); token.Wait() && token.Error() != nil {
 		return token.Error()
 	}
+	cache := &panelStateCache{}
+
+	if config.HomeAssistant.Enabled {
+		if err := publishHAAvailability(c, config, "online"); err != nil {
+			return fmt.Errorf("could not publish Home Assistant availability: %w", err)
+		}
+		if err := publishHADiscovery(c, config); err != nil {
+			return fmt.Errorf("could not publish Home Assistant discovery payloads: %w", err)
+		}
+		if writer != nil {
+			if err := subscribeHAPanelModeState(c, config, cache); err != nil {
+				log.Warnf("Could not subscribe to Home Assistant panel mode state topic: %v", err)
+			}
+		}
+	}
+
+	if config.CommandTopic != "" {
+		if writer == nil {
+			log.Warnf("MQTT command topic %q configured, but no settings writer is available", config.CommandTopic)
+		} else {
+			t := c.Subscribe(config.CommandTopic, 1, commandHandler(c, writer, config, cache))
+			t.Wait()
+			if t.Error() != nil {
+				return fmt.Errorf("could not subscribe to MQTT command topic %q: %w", config.CommandTopic, t.Error())
+			}
+			log.Infof("Subscribed to MQTT command topic: %s", config.CommandTopic)
+		}
+	}
 
 	go func() {
 		for e := range mk2.C() {
-			if e.Valid {
-				data, err := json.Marshal(e)
-				if err != nil {
-					log.Errorf("Could not parse data source: %v", err)
-					continue
-				}
-
-				t := c.Publish(config.Topic, 0, false, data)
-				t.Wait()
-				if t.Error() != nil {
-					log.Errorf("Could not publish data: %v", t.Error())
-				}
+			if e == nil || !e.Valid {
+				continue
+			}
+			if err := publishJSON(c, config.Topic, e, 0, false); err != nil {
+				log.Errorf("Could not publish update to MQTT topic %q: %v", config.Topic, err)
 			}
 		}
 	}()
+
 	return nil
 }
 
+func subscribeHAPanelModeState(client mqtt.Client, config Config, cache *panelStateCache) error {
+	if cache == nil {
+		return nil
+	}
+
+	stateTopic := haPanelSwitchStateTopic(config)
+	t := client.Subscribe(stateTopic, 1, func(_ mqtt.Client, msg mqtt.Message) {
+		switchState, switchName, err := normalizePanelSwitch(string(msg.Payload()))
+		if err != nil {
+			return
+		}
+		cache.remember(writeCommand{
+			Kind:        commandKindPanel,
+			HasSwitch:   true,
+			SwitchState: switchState,
+			SwitchName:  switchName,
+		})
+	})
+	t.Wait()
+	return t.Error()
+}
+
+func commandHandler(client mqtt.Client, writer mk2driver.SettingsWriter, config Config, cache *panelStateCache) mqtt.MessageHandler {
+	if cache == nil {
+		cache = &panelStateCache{}
+	}
+
+	return func(_ mqtt.Client, msg mqtt.Message) {
+		cmd, err := decodeWriteCommand(msg.Payload())
+		if err != nil {
+			log.Errorf("Invalid MQTT write command payload from topic %q: %v", msg.Topic(), err)
+			publishWriteStatus(client, config.StatusTopic, writeStatus{
+				Status:    writeStatusError,
+				Error:     err.Error(),
+				Timestamp: time.Now().UTC(),
+			})
+			return
+		}
+
+		execCmd := cmd
+		status := writeStatus{
+			RequestID: cmd.RequestID,
+			Status:    writeStatusOK,
+			Kind:      cmd.Kind,
+			Timestamp: time.Now().UTC(),
+		}
+		switch cmd.Kind {
+		case commandKindPanel:
+			execCmd, err = cache.resolvePanelCommand(cmd)
+			if err != nil {
+				status.Status = writeStatusError
+				status.Error = err.Error()
+				log.Errorf("Invalid MQTT write command %s: %v", formatWriteCommandLog(cmd), err)
+				publishWriteStatus(client, config.StatusTopic, status)
+				return
+			}
+			status.Switch = execCmd.SwitchName
+			status.CurrentLimitA = execCmd.CurrentLimitA
+		case commandKindStandby:
+			status.Standby = copyBoolPtr(execCmd.Standby)
+		default:
+			status.ID = cmd.ID
+			status.Value = cmd.Value
+		}
+
+		if err := executeWriteCommand(writer, execCmd); err != nil {
+			status.Status = writeStatusError
+			status.Error = err.Error()
+			log.Errorf("Failed MQTT write command %s: %v", formatWriteCommandLog(execCmd), err)
+		} else {
+			log.Infof("Applied MQTT write command %s", formatWriteCommandLog(execCmd))
+			cache.remember(execCmd)
+			if config.HomeAssistant.Enabled {
+				if err := publishHAControlState(client, config, execCmd); err != nil {
+					log.Errorf("Could not publish Home Assistant control state update: %v", err)
+				}
+			}
+		}
+
+		publishWriteStatus(client, config.StatusTopic, status)
+	}
+}
+
+func (c *panelStateCache) resolvePanelCommand(cmd writeCommand) (writeCommand, error) {
+	if cmd.Kind != commandKindPanel {
+		return cmd, nil
+	}
+
+	if cmd.HasSwitch {
+		return cmd, nil
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if !c.hasSwitch {
+		return writeCommand{}, errors.New("panel_state command missing switch and no prior mode is known; set mode once first")
+	}
+
+	cmd.HasSwitch = true
+	cmd.SwitchName = c.switchName
+	cmd.SwitchState = c.switchState
+	return cmd, nil
+}
+
+func (c *panelStateCache) remember(cmd writeCommand) {
+	if cmd.Kind != commandKindPanel || !cmd.HasSwitch {
+		return
+	}
+
+	c.mu.Lock()
+	c.hasSwitch = true
+	c.switchName = cmd.SwitchName
+	c.switchState = cmd.SwitchState
+	c.mu.Unlock()
+}
+
+func decodeWriteCommand(payload []byte) (writeCommand, error) {
+	msg := writeCommandPayload{}
+	if err := json.Unmarshal(payload, &msg); err != nil {
+		return writeCommand{}, fmt.Errorf("invalid JSON payload: %w", err)
+	}
+
+	kind := msg.Kind
+	if kind == "" {
+		kind = msg.Type
+	}
+	normalizedKind, err := normalizeWriteKind(kind)
+	if err != nil {
+		return writeCommand{}, err
+	}
+
+	if normalizedKind == commandKindPanel {
+		switchName := msg.Switch
+		if switchName == "" {
+			switchName = msg.SwitchState
+		}
+
+		hasSwitch := false
+		switchState := mk2driver.PanelSwitchState(0)
+		normalizedSwitchName := ""
+		if switchName != "" {
+			var err error
+			switchState, normalizedSwitchName, err = normalizePanelSwitch(switchName)
+			if err != nil {
+				return writeCommand{}, err
+			}
+			hasSwitch = true
+		}
+		if msg.CurrentLimitA != nil && *msg.CurrentLimitA < 0 {
+			return writeCommand{}, fmt.Errorf("current_limit must be >= 0, got %.3f", *msg.CurrentLimitA)
+		}
+		if !hasSwitch && msg.CurrentLimitA == nil {
+			return writeCommand{}, errors.New(`missing required field "switch" (or "switch_state"), or "current_limit"`)
+		}
+
+		return writeCommand{
+			RequestID:     msg.RequestID,
+			Kind:          normalizedKind,
+			HasSwitch:     hasSwitch,
+			SwitchState:   switchState,
+			SwitchName:    normalizedSwitchName,
+			CurrentLimitA: msg.CurrentLimitA,
+		}, nil
+	}
+
+	if normalizedKind == commandKindStandby {
+		standby, err := decodeStandbyValue(msg)
+		if err != nil {
+			return writeCommand{}, err
+		}
+
+		return writeCommand{
+			RequestID: msg.RequestID,
+			Kind:      normalizedKind,
+			Standby:   &standby,
+		}, nil
+	}
+
+	if msg.ID == nil {
+		return writeCommand{}, errors.New(`missing required field "id"`)
+	}
+	value, err := decodeInt16Value(msg.Value)
+	if err != nil {
+		return writeCommand{}, err
+	}
+
+	return writeCommand{
+		RequestID: msg.RequestID,
+		Kind:      normalizedKind,
+		ID:        *msg.ID,
+		Value:     value,
+	}, nil
+}
+
+func normalizeWriteKind(raw string) (string, error) {
+	switch strings.ToLower(strings.TrimSpace(raw)) {
+	case "setting", "settings":
+		return commandKindSetting, nil
+	case "ram", "ramvar", "ram_var", "ram-variable", "ramvariable":
+		return commandKindRAMVar, nil
+	case "panel", "panel_state", "switch", "remote_panel":
+		return commandKindPanel, nil
+	case "standby", "panel_standby", "remote_panel_standby":
+		return commandKindStandby, nil
+	default:
+		return "", fmt.Errorf("unsupported write command kind %q", raw)
+	}
+}
+
+func normalizePanelSwitch(raw string) (mk2driver.PanelSwitchState, string, error) {
+	switch strings.ToLower(strings.TrimSpace(raw)) {
+	case "1", "charger_only", "charger-only", "charger":
+		return mk2driver.PanelSwitchChargerOnly, "charger_only", nil
+	case "2", "inverter_only", "inverter-only", "inverter":
+		return mk2driver.PanelSwitchInverterOnly, "inverter_only", nil
+	case "3", "on":
+		return mk2driver.PanelSwitchOn, "on", nil
+	case "4", "off":
+		return mk2driver.PanelSwitchOff, "off", nil
+	default:
+		return 0, "", fmt.Errorf("unsupported panel switch %q", raw)
+	}
+}
+
+func executeWriteCommand(writer mk2driver.SettingsWriter, cmd writeCommand) error {
+	if writer == nil {
+		return errors.New("settings writer is not available")
+	}
+	switch cmd.Kind {
+	case commandKindPanel:
+		if !cmd.HasSwitch {
+			return errors.New("panel_state command requires a switch state")
+		}
+		return writer.SetPanelState(cmd.SwitchState, cmd.CurrentLimitA)
+	case commandKindStandby:
+		if cmd.Standby == nil {
+			return errors.New("standby command missing standby value")
+		}
+		return writer.SetStandby(*cmd.Standby)
+	case commandKindRAMVar:
+		return writer.WriteRAMVar(cmd.ID, cmd.Value)
+	case commandKindSetting:
+		return writer.WriteSetting(cmd.ID, cmd.Value)
+	default:
+		return fmt.Errorf("unsupported write command kind %q", cmd.Kind)
+	}
+}
+
+func formatWriteCommandLog(cmd writeCommand) string {
+	switch cmd.Kind {
+	case commandKindPanel:
+		switchName := cmd.SwitchName
+		if switchName == "" {
+			switchName = "<cached>"
+		}
+		if cmd.CurrentLimitA == nil {
+			return fmt.Sprintf("kind=%s switch=%s", cmd.Kind, switchName)
+		}
+		return fmt.Sprintf("kind=%s switch=%s current_limit=%.3f", cmd.Kind, switchName, *cmd.CurrentLimitA)
+	case commandKindStandby:
+		if cmd.Standby == nil {
+			return fmt.Sprintf("kind=%s standby=<unset>", cmd.Kind)
+		}
+		return fmt.Sprintf("kind=%s standby=%t", cmd.Kind, *cmd.Standby)
+	default:
+		return fmt.Sprintf("kind=%s id=%d value=%d", cmd.Kind, cmd.ID, cmd.Value)
+	}
+}
+
+func decodeInt16Value(raw json.RawMessage) (int16, error) {
+	if len(raw) == 0 {
+		return 0, errors.New(`missing required field "value"`)
+	}
+
+	var value int16
+	if err := json.Unmarshal(raw, &value); err != nil {
+		return 0, fmt.Errorf(`field "value" must be a signed integer: %w`, err)
+	}
+	return value, nil
+}
+
+func decodeStandbyValue(msg writeCommandPayload) (bool, error) {
+	if msg.Standby != nil {
+		return *msg.Standby, nil
+	}
+	if len(msg.Value) == 0 {
+		return false, errors.New(`missing required field "standby" (or boolean "value")`)
+	}
+
+	var boolValue bool
+	if err := json.Unmarshal(msg.Value, &boolValue); err == nil {
+		return boolValue, nil
+	}
+
+	var stringValue string
+	if err := json.Unmarshal(msg.Value, &stringValue); err == nil {
+		switch strings.ToLower(strings.TrimSpace(stringValue)) {
+		case "1", "true", "on", "enable", "enabled":
+			return true, nil
+		case "0", "false", "off", "disable", "disabled":
+			return false, nil
+		}
+	}
+
+	var intValue int
+	if err := json.Unmarshal(msg.Value, &intValue); err == nil {
+		switch intValue {
+		case 1:
+			return true, nil
+		case 0:
+			return false, nil
+		}
+	}
+
+	return false, errors.New(`field "standby" must be true/false`)
+}
+
+func publishWriteStatus(client mqtt.Client, topic string, status writeStatus) {
+	if topic == "" {
+		return
+	}
+	if err := publishJSON(client, topic, status, 1, false); err != nil {
+		log.Errorf("Could not publish command status to MQTT topic %q: %v", topic, err)
+	}
+}
+
+func publishHADiscovery(client mqtt.Client, config Config) error {
+	definitions := buildHADiscoveryDefinitions(config)
+	prefix := haDiscoveryPrefix(config)
+	nodeID := haNodeID(config)
+
+	for _, def := range definitions {
+		topic := fmt.Sprintf("%s/%s/%s/%s/config", prefix, def.Component, nodeID, def.ObjectID)
+		if err := publishJSON(client, topic, def.Config, 1, true); err != nil {
+			return fmt.Errorf("could not publish discovery for %s/%s: %w", def.Component, def.ObjectID, err)
+		}
+	}
+
+	return nil
+}
+
+func buildHADiscoveryDefinitions(config Config) []haDiscoveryDefinition {
+	if !config.HomeAssistant.Enabled {
+		return nil
+	}
+
+	nodeID := haNodeID(config)
+	device := map[string]any{
+		"identifiers":  []string{fmt.Sprintf("invertergui_%s", nodeID)},
+		"name":         haDeviceName(config),
+		"manufacturer": "Victron Energy",
+		"model":        "MultiPlus",
+		"sw_version":   "invertergui",
+	}
+	availabilityTopic := haAvailabilityTopic(config)
+	stateTopic := config.Topic
+
+	sensors := []haDiscoveryDefinition{
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "battery_voltage", "Battery Voltage", "{{ value_json.BatVoltage }}", "V", "voltage", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "battery_current", "Battery Current", "{{ value_json.BatCurrent }}", "A", "current", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "battery_charge", "Battery Charge", "{{ ((value_json.ChargeState | float(0)) * 100) | round(1) }}", "%", "battery", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "input_voltage", "Input Voltage", "{{ value_json.InVoltage }}", "V", "voltage", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "input_current", "Input Current", "{{ value_json.InCurrent }}", "A", "current", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "input_frequency", "Input Frequency", "{{ value_json.InFrequency }}", "Hz", "frequency", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "output_voltage", "Output Voltage", "{{ value_json.OutVoltage }}", "V", "voltage", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "output_current", "Output Current", "{{ value_json.OutCurrent }}", "A", "current", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "output_frequency", "Output Frequency", "{{ value_json.OutFrequency }}", "Hz", "frequency", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "input_power", "Input Power", "{{ ((value_json.InVoltage | float(0)) * (value_json.InCurrent | float(0))) | round(1) }}", "VA", "", "measurement"),
+		buildHASensor(device, availabilityTopic, stateTopic, nodeID, "output_power", "Output Power", "{{ ((value_json.OutVoltage | float(0)) * (value_json.OutCurrent | float(0))) | round(1) }}", "VA", "", "measurement"),
+		{
+			Component: "binary_sensor",
+			ObjectID:  "data_valid",
+			Config: map[string]any{
+				"name":               "Data Valid",
+				"unique_id":          fmt.Sprintf("%s_data_valid", nodeID),
+				"state_topic":        stateTopic,
+				"value_template":     "{{ value_json.Valid }}",
+				"payload_on":         "true",
+				"payload_off":        "false",
+				"availability_topic": availabilityTopic,
+				"device":             device,
+				"entity_category":    "diagnostic",
+			},
+		},
+	}
+
+	if config.CommandTopic != "" {
+		sensors = append(sensors,
+			haDiscoveryDefinition{
+				Component: "select",
+				ObjectID:  "remote_panel_mode",
+				Config: map[string]any{
+					"name":               "Remote Panel Mode",
+					"unique_id":          fmt.Sprintf("%s_remote_panel_mode", nodeID),
+					"state_topic":        haPanelSwitchStateTopic(config),
+					"command_topic":      config.CommandTopic,
+					"command_template":   "{\"kind\":\"panel_state\",\"switch\":\"{{ value }}\"}",
+					"options":            []string{"charger_only", "inverter_only", "on", "off"},
+					"availability_topic": availabilityTopic,
+					"device":             device,
+					"icon":               "mdi:transmission-tower-export",
+				},
+			},
+			haDiscoveryDefinition{
+				Component: "number",
+				ObjectID:  "remote_panel_current_limit",
+				Config: map[string]any{
+					"name":                "Remote Panel Current Limit",
+					"unique_id":           fmt.Sprintf("%s_remote_panel_current_limit", nodeID),
+					"state_topic":         haCurrentLimitStateTopic(config),
+					"command_topic":       config.CommandTopic,
+					"command_template":    "{\"kind\":\"panel_state\",\"current_limit\":{{ value | float(0) }}}",
+					"unit_of_measurement": "A",
+					"device_class":        "current",
+					"mode":                "box",
+					"min":                 0,
+					"max":                 100,
+					"step":                0.1,
+					"availability_topic":  availabilityTopic,
+					"device":              device,
+					"icon":                "mdi:current-ac",
+				},
+			},
+			haDiscoveryDefinition{
+				Component: "switch",
+				ObjectID:  "remote_panel_standby",
+				Config: map[string]any{
+					"name":               "Remote Panel Standby",
+					"unique_id":          fmt.Sprintf("%s_remote_panel_standby", nodeID),
+					"state_topic":        haStandbyStateTopic(config),
+					"command_topic":      config.CommandTopic,
+					"payload_on":         "{\"kind\":\"standby\",\"standby\":true}",
+					"payload_off":        "{\"kind\":\"standby\",\"standby\":false}",
+					"state_on":           "ON",
+					"state_off":          "OFF",
+					"availability_topic": availabilityTopic,
+					"device":             device,
+					"icon":               "mdi:power-sleep",
+				},
+			},
+		)
+	}
+
+	return sensors
+}
+
+func buildHASensor(device map[string]any, availabilityTopic, stateTopic, nodeID, objectID, name, valueTemplate, unit, deviceClass, stateClass string) haDiscoveryDefinition {
+	config := map[string]any{
+		"name":               name,
+		"unique_id":          fmt.Sprintf("%s_%s", nodeID, objectID),
+		"state_topic":        stateTopic,
+		"value_template":     valueTemplate,
+		"availability_topic": availabilityTopic,
+		"device":             device,
+	}
+	if unit != "" {
+		config["unit_of_measurement"] = unit
+	}
+	if deviceClass != "" {
+		config["device_class"] = deviceClass
+	}
+	if stateClass != "" {
+		config["state_class"] = stateClass
+	}
+
+	return haDiscoveryDefinition{
+		Component: "sensor",
+		ObjectID:  objectID,
+		Config:    config,
+	}
+}
+
+func publishHAAvailability(client mqtt.Client, config Config, status string) error {
+	return publishString(client, haAvailabilityTopic(config), status, 1, true)
+}
+
+func publishHAControlState(client mqtt.Client, config Config, cmd writeCommand) error {
+	switch cmd.Kind {
+	case commandKindPanel:
+		if err := publishString(client, haPanelSwitchStateTopic(config), cmd.SwitchName, 1, true); err != nil {
+			return err
+		}
+		if cmd.CurrentLimitA != nil {
+			limit := strconv.FormatFloat(*cmd.CurrentLimitA, 'f', 1, 64)
+			if err := publishString(client, haCurrentLimitStateTopic(config), limit, 1, true); err != nil {
+				return err
+			}
+		}
+	case commandKindStandby:
+		if cmd.Standby == nil {
+			return nil
+		}
+		state := "OFF"
+		if *cmd.Standby {
+			state = "ON"
+		}
+		if err := publishString(client, haStandbyStateTopic(config), state, 1, true); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func publishJSON(client mqtt.Client, topic string, payload any, qos byte, retained bool) error {
+	if topic == "" {
+		return errors.New("topic is empty")
+	}
+
+	data, err := json.Marshal(payload)
+	if err != nil {
+		return fmt.Errorf("could not marshal payload: %w", err)
+	}
+
+	t := client.Publish(topic, qos, retained, data)
+	t.Wait()
+	if t.Error() != nil {
+		return t.Error()
+	}
+
+	return nil
+}
+
+func publishString(client mqtt.Client, topic, payload string, qos byte, retained bool) error {
+	if topic == "" {
+		return errors.New("topic is empty")
+	}
+
+	t := client.Publish(topic, qos, retained, payload)
+	t.Wait()
+	if t.Error() != nil {
+		return t.Error()
+	}
+	return nil
+}
+
+func mqttTopicRoot(topic string) string {
+	t := strings.Trim(strings.TrimSpace(topic), "/")
+	if t == "" {
+		return "invertergui"
+	}
+	if strings.HasSuffix(t, "/updates") {
+		root := strings.TrimSuffix(t, "/updates")
+		if root != "" {
+			return root
+		}
+	}
+	return t
+}
+
+func haAvailabilityTopic(config Config) string {
+	return fmt.Sprintf("%s/homeassistant/availability", mqttTopicRoot(config.Topic))
+}
+
+func haPanelSwitchStateTopic(config Config) string {
+	return fmt.Sprintf("%s/homeassistant/remote_panel_mode/state", mqttTopicRoot(config.Topic))
+}
+
+func haCurrentLimitStateTopic(config Config) string {
+	return fmt.Sprintf("%s/homeassistant/remote_panel_current_limit/state", mqttTopicRoot(config.Topic))
+}
+
+func haStandbyStateTopic(config Config) string {
+	return fmt.Sprintf("%s/homeassistant/remote_panel_standby/state", mqttTopicRoot(config.Topic))
+}
+
+func haDiscoveryPrefix(config Config) string {
+	prefix := strings.Trim(strings.TrimSpace(config.HomeAssistant.DiscoveryPrefix), "/")
+	if prefix == "" {
+		return "homeassistant"
+	}
+	return prefix
+}
+
+func haNodeID(config Config) string {
+	nodeID := normalizeID(config.HomeAssistant.NodeID)
+	if nodeID == "" {
+		nodeID = normalizeID(config.ClientID)
+	}
+	if nodeID == "" {
+		return "invertergui"
+	}
+	return nodeID
+}
+
+func haDeviceName(config Config) string {
+	name := strings.TrimSpace(config.HomeAssistant.DeviceName)
+	if name == "" {
+		return "Victron Inverter"
+	}
+	return name
+}
+
+func normalizeID(in string) string {
+	trimmed := strings.TrimSpace(strings.ToLower(in))
+	if trimmed == "" {
+		return ""
+	}
+	var b strings.Builder
+	lastUnderscore := false
+	for _, r := range trimmed {
+		valid := (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == '-' || r == '_'
+		if valid {
+			b.WriteRune(r)
+			lastUnderscore = false
+			continue
+		}
+		if !lastUnderscore {
+			b.WriteRune('_')
+			lastUnderscore = true
+		}
+	}
+
+	return strings.Trim(b.String(), "_")
+}
+
+func copyBoolPtr(in *bool) *bool {
+	if in == nil {
+		return nil
+	}
+	value := *in
+	return &value
+}
+
 func getOpts(config Config) *mqtt.ClientOptions {
 	opts := mqtt.NewClientOptions()
 	opts.AddBroker(config.Broker)
@@ -60,6 +781,9 @@ func getOpts(config Config) *mqtt.ClientOptions {
 	if config.Password != "" {
 		opts.SetPassword(config.Password)
 	}
+	if config.HomeAssistant.Enabled {
+		opts.SetWill(haAvailabilityTopic(config), "offline", 1, true)
+	}
 	opts.SetKeepAlive(keepAlive)
 
 	opts.SetOnConnectHandler(func(mqtt.Client) {
@@ -67,7 +791,6 @@ func getOpts(config Config) *mqtt.ClientOptions {
 	})
 	opts.SetConnectionLostHandler(func(_ mqtt.Client, err error) {
 		log.Errorf("Client connection to broker lost: %v", err)
-
 	})
 	return opts
 }