Implement Home Assistant Discovery

The discovery logic is implemented and presents and interface that the modules need to implement in order to get their entities being exported to Home Assistant

pkg/controller/controller.go

@@ -6,13 +6,15 @@ import (
 	"github.com/gaetancollaud/digitalstrom-mqtt/pkg/config"
 	"github.com/gaetancollaud/digitalstrom-mqtt/pkg/controller/modules"
 	"github.com/gaetancollaud/digitalstrom-mqtt/pkg/digitalstrom"
+	"github.com/gaetancollaud/digitalstrom-mqtt/pkg/homeassistant"
 	"github.com/gaetancollaud/digitalstrom-mqtt/pkg/mqtt"
 	"github.com/rs/zerolog/log"
 )
 
 type Controller struct {
-	dsClient   digitalstrom.Client
-	mqttClient mqtt.Client
+	dsClient      digitalstrom.Client
+	mqttClient    mqtt.Client
+	hassDiscovery *homeassistant.HomeAssistantDiscovery
 
 	modules map[string]modules.Module
 }
@@ -33,10 +35,16 @@ func NewController(config *config.Config) *Controller {
 		SetTopicPrefix(config.Mqtt.TopicPrefix).
 		SetRetain(config.Mqtt.Retain)
 	mqttClient := mqtt.NewClient(mqttOptions)
+
+	hass := homeassistant.NewHomeAssistantDiscovery(
+		mqttClient,
+		&config.HomeAssistant)
+
 	controller := Controller{
-		dsClient:   dsClient,
-		mqttClient: mqttClient,
-		modules:    map[string]modules.Module{},
+		dsClient:      dsClient,
+		mqttClient:    mqttClient,
+		hassDiscovery: hass,
+		modules:       map[string]modules.Module{},
 	}
 
 	for name, builder := range modules.Modules {
@@ -63,6 +71,23 @@ func (c *Controller) Start() error {
 		}
 	}
 
+	// Retrieve from all the modules the discovery configs to be exported.
+	for name, module := range c.modules {
+		m, ok := module.(homeassistant.HomeAssistantDiscoveryInterface)
+		if !ok {
+			continue
+		}
+		configs, err := m.GetHomeAssistantEntities()
+		if err != nil {
+			return fmt.Errorf("error getting discovery configs from module '%s': %w", name, err)
+		}
+		c.hassDiscovery.AddConfigs(configs)
+	}
+	// Publishes Home Assistant Discovery messages.
+	if err := c.hassDiscovery.PublishDiscoveryMessages(); err != nil {
+		return err
+	}
+
 	return nil
 }
 

pkg/homeassistant/config.go

@@ -0,0 +1,126 @@
+package homeassistant
+
+// Interface to expose the endpoints to update any MQTT config needed by the
+// Home Assistant discovery package.
+type MqttConfig interface {
+	// Returns a pointer to the device object for any modification required.
+	GetDevice() *Device
+	// Adds a new entry on the list of Availability topics.
+	AddAvailability(Availability) MqttConfig
+	// Get name of the entity.
+	GetName() string
+	// Set name for the entity.
+	SetName(string) MqttConfig
+}
+
+// Structure that encapsulates the information for the device exposed in
+// Home Assistant.
+type Device struct {
+	ConfigurationUrl string   `json:"configuration_url"`
+	Identifiers      []string `json:"identifiers"`
+	Manufacturer     string   `json:"manufacturer"`
+	Model            string   `json:"model"`
+	Name             string   `json:"name"`
+}
+
+// Structure that encapsulates the information to retrieve availability of
+// devices and entities.
+type Availability struct {
+	Topic               string `json:"topic"`
+	PayloadAvailable    string `json:"payload_available,omitempty"`
+	PayloadNotAvailable string `json:"payload_not_available,omitempty"`
+}
+
+// Base config for all MQTT discovery configs.
+type BaseConfig struct {
+	Device           Device         `json:"device"`
+	Name             string         `json:"name"`
+	UniqueId         string         `json:"unique_id"`
+	Retain           bool           `json:"retain"`
+	Availability     []Availability `json:"availability"`
+	AvailabilityMode string         `json:"availability_mode"`
+	QoS              int            `json:"qos"`
+}
+
+// Returns a pointer to the device object.
+func (c *BaseConfig) GetDevice() *Device {
+	return &c.Device
+}
+
+// Adds a new entry on the list of Availability topics.
+func (c *BaseConfig) AddAvailability(availability Availability) MqttConfig {
+	c.Availability = append(c.Availability, availability)
+	return c
+}
+
+// Get the name of the entity in the configuration.
+func (c *BaseConfig) GetName() string {
+	return c.Name
+}
+
+// Set the name for the entity in the configuration.
+func (c *BaseConfig) SetName(name string) MqttConfig {
+	c.Name = name
+	return c
+}
+
+// Light configuration:
+// https://www.home-assistant.io/integrations/light.mqtt/
+type LightMqttConfig struct {
+	BaseConfig
+	CommandTopic           string `json:"command_topic,omitempty"`
+	StateTopic             string `json:"state_topic,omitempty"`
+	PayloadOn              string `json:"payload_on,omitempty"`
+	PayloadOff             string `json:"payload_off,omitempty"`
+	OnCommandType          string `json:"on_command_type,omitempty"`
+	BrightnessScale        int    `json:"brigthness_scale,omitempty"`
+	BrightnessStateTopic   string `json:"brightness_state_topic,omitempty"`
+	BrightnessCommandTopic string `json:"brightness_command_topic,omitempty"`
+}
+
+// Cover configuration:
+// https://www.home-assistant.io/integrations/cover.mqtt/
+type CoverConfig struct {
+	BaseConfig
+	StateTopic       string `json:"state_topic,omitempty"`
+	StateClosed      string `json:"state_closed,omitempty"`
+	StateOpen        string `json:"state_open,omitempty"`
+	CommandTopic     string `json:"command_topic,omitempty"`
+	PayloadClose     string `json:"payload_close,omitempty"`
+	PayloadOpen      string `json:"payload_open,omitempty"`
+	PayloadStop      string `json:"payload_stop,omitempty"`
+	PositionTopic    string `json:"position_topic,omitempty"`
+	SetPositionTopic string `json:"set_position_topic,omitempty"`
+	PositionTemplate string `json:"position_template,omitempty"`
+}
+
+// Sensor configuration:
+// https://www.home-assistant.io/integrations/sensor.mqtt/
+type SensorConfig struct {
+	BaseConfig
+	StateTopic        string `json:"state_topic,omitempty"`
+	UnitOfMeasurement string `json:"unit_of_measurement,omitempty"`
+	DeviceClass       string `json:"device_class,omitempty"`
+	Icon              string `json:"icon,omitempty"`
+}
+
+// Scene configuration:
+// https://www.home-assistant.io/integrations/scene.mqtt/
+type SceneConfig struct {
+	BaseConfig
+	CommandTopic     string `json:"command_topic,omitempty"`
+	PayloadOn        string `json:"payload_on,omitempty"`
+	Icon             string `json:"icon,omitempty"`
+	EnabledByDefault bool   `json:"enabled_by_default,omitempty"`
+}
+
+// Device Trigger configuration:
+// https://www.home-assistant.io/integrations/device_trigger.mqtt/
+type DeviceTriggerConfig struct {
+	BaseConfig
+	AutomationType string `json:"automation_type"`
+	Payload        string `json:"payload,omitempty"`
+	Topic          string `json:"topic"`
+	Type           string `json:"type"`
+	Subtype        string `json:"subtype"`
+}

pkg/homeassistant/discovery.go

@@ -0,0 +1,97 @@
+package homeassistant
+
+import (
+	"encoding/json"
+	"fmt"
+	"path"
+
+	"github.com/gaetancollaud/digitalstrom-mqtt/pkg/config"
+	"github.com/gaetancollaud/digitalstrom-mqtt/pkg/mqtt"
+	"github.com/gaetancollaud/digitalstrom-mqtt/pkg/utils"
+)
+
+type Domain string
+
+const (
+	Sensor           Domain = "sensor"
+	Light            Domain = "light"
+	DeviceAutomation Domain = "device_automation"
+	Cover            Domain = "cover"
+)
+
+type DiscoveryConfig struct {
+	Domain   Domain
+	DeviceId string
+	ObjectId string
+	Config   MqttConfig
+}
+
+type HomeAssistantDiscoveryInterface interface {
+	// Returns the list of Home Assitant MQTT entities that each module would
+	// be exporting for discovery.
+	// This will be run after the method Start is called and therefore it can
+	// assume that the logic there will be run.
+	GetHomeAssistantEntities() ([]DiscoveryConfig, error)
+}
+
+type HomeAssistantDiscovery struct {
+	mqttClient mqtt.Client
+	config     *config.ConfigHomeAssistant
+
+	discoveryConfigs []DiscoveryConfig
+}
+
+func NewHomeAssistantDiscovery(mqttClient mqtt.Client, config *config.ConfigHomeAssistant) *HomeAssistantDiscovery {
+	return &HomeAssistantDiscovery{
+		mqttClient:       mqttClient,
+		config:           config,
+		discoveryConfigs: []DiscoveryConfig{},
+	}
+}
+
+func (hass *HomeAssistantDiscovery) AddConfigs(configs []DiscoveryConfig) {
+	systemAvailability := Availability{
+		Topic:               hass.mqttClient.ServerStatusTopic(),
+		PayloadAvailable:    mqtt.Online,
+		PayloadNotAvailable: mqtt.Offline,
+	}
+	for _, config := range configs {
+		entityName := config.Config.GetName()
+		config.Config.
+			SetName(
+				utils.RemoveRegexp(
+					entityName,
+					hass.config.RemoveRegexpFromName)).
+			AddAvailability(systemAvailability)
+		// Update the config with some generic attributes for all
+		// configurations.
+		device := config.Config.GetDevice()
+		device.Manufacturer = "DigitalStrom"
+		device.ConfigurationUrl = "https://" + hass.config.DigitalStromHost
+
+		hass.discoveryConfigs = append(hass.discoveryConfigs, config)
+	}
+}
+
+func (hass *HomeAssistantDiscovery) PublishDiscoveryMessages() error {
+	if !hass.config.DiscoveryEnabled {
+		return nil
+	}
+
+	for _, config := range hass.discoveryConfigs {
+		topic := path.Join(
+			hass.config.DiscoveryTopicPrefix,
+			string(config.Domain),
+			config.DeviceId,
+			config.ObjectId,
+			"config")
+		json, err := json.Marshal(config.Config)
+		if err != nil {
+			return fmt.Errorf("error serializing dicovery config to JSON: %w", err)
+		}
+		if err := hass.mqttClient.Publish(topic, json); err != nil {
+			return fmt.Errorf("error publishing discovery message to MQTT: %w", err)
+		}
+	}
+	return nil
+}

pkg/mqtt/client.go

@@ -30,8 +30,11 @@ type Client interface {
 
 	// Publishes a message under the prefix topic of DigitalStrom.
 	Publish(topic string, message interface{}) error
-
+	// Subscribe to a topic and calls the given handler when a message is
+	// received.
 	Subscribe(topic string, messageHandler mqtt.MessageHandler) error
+	// Returns the topic used to publish the server status.
+	ServerStatusTopic() string
 }
 
 type client struct {
@@ -101,6 +104,10 @@ func (c *client) publishServerStatus(message string) error {
 	return c.Publish(serverStatus, message)
 }
 
+func (c *client) ServerStatusTopic() string {
+	return path.Join(c.options.TopicPrefix, serverStatus)
+}
+
 func normalizeForTopicName(item string) string {
 	output := ""
 	for i := 0; i < len(item); i++ {