Add mqtt notify platform (#115653)

* Add mqtt notify platform

* Stale docstring

homeassistant/components/mqtt/notify.py

@@ -0,0 +1,95 @@
+"""Support for MQTT notify."""
+
+from __future__ import annotations
+
+import voluptuous as vol
+
+from homeassistant.components import notify
+from homeassistant.components.notify import NotifyEntity
+from homeassistant.config_entries import ConfigEntry
+from homeassistant.const import CONF_NAME
+from homeassistant.core import HomeAssistant
+import homeassistant.helpers.config_validation as cv
+from homeassistant.helpers.entity_platform import AddEntitiesCallback
+from homeassistant.helpers.typing import ConfigType
+
+from .config import DEFAULT_RETAIN, MQTT_BASE_SCHEMA
+from .const import (
+    CONF_COMMAND_TEMPLATE,
+    CONF_COMMAND_TOPIC,
+    CONF_ENCODING,
+    CONF_QOS,
+    CONF_RETAIN,
+)
+from .mixins import (
+    MQTT_ENTITY_COMMON_SCHEMA,
+    MqttEntity,
+    async_setup_entity_entry_helper,
+)
+from .models import MqttCommandTemplate
+from .util import valid_publish_topic
+
+DEFAULT_NAME = "MQTT notify"
+
+PLATFORM_SCHEMA_MODERN = MQTT_BASE_SCHEMA.extend(
+    {
+        vol.Optional(CONF_COMMAND_TEMPLATE): cv.template,
+        vol.Required(CONF_COMMAND_TOPIC): valid_publish_topic,
+        vol.Optional(CONF_NAME): vol.Any(cv.string, None),
+        vol.Optional(CONF_RETAIN, default=DEFAULT_RETAIN): cv.boolean,
+    }
+).extend(MQTT_ENTITY_COMMON_SCHEMA.schema)
+
+DISCOVERY_SCHEMA = PLATFORM_SCHEMA_MODERN.extend({}, extra=vol.REMOVE_EXTRA)
+
+
+async def async_setup_entry(
+    hass: HomeAssistant,
+    config_entry: ConfigEntry,
+    async_add_entities: AddEntitiesCallback,
+) -> None:
+    """Set up MQTT notify through YAML and through MQTT discovery."""
+    await async_setup_entity_entry_helper(
+        hass,
+        config_entry,
+        MqttNotify,
+        notify.DOMAIN,
+        async_add_entities,
+        DISCOVERY_SCHEMA,
+        PLATFORM_SCHEMA_MODERN,
+    )
+
+
+class MqttNotify(MqttEntity, NotifyEntity):
+    """Representation of a notification entity service that can send messages using MQTT."""
+
+    _default_name = DEFAULT_NAME
+    _entity_id_format = notify.ENTITY_ID_FORMAT
+
+    @staticmethod
+    def config_schema() -> vol.Schema:
+        """Return the config schema."""
+        return DISCOVERY_SCHEMA
+
+    def _setup_from_config(self, config: ConfigType) -> None:
+        """(Re)Setup the entity."""
+        self._command_template = MqttCommandTemplate(
+            config.get(CONF_COMMAND_TEMPLATE), entity=self
+        ).async_render
+
+    def _prepare_subscribe_topics(self) -> None:
+        """(Re)Subscribe to topics."""
+
+    async def _subscribe_topics(self) -> None:
+        """(Re)Subscribe to topics."""
+
+    async def async_send_message(self, message: str) -> None:
+        """Send a message."""
+        payload = self._command_template(message)
+        await self.async_publish(
+            self._config[CONF_COMMAND_TOPIC],
+            payload,
+            self._config[CONF_QOS],
+            self._config[CONF_RETAIN],
+            self._config[CONF_ENCODING],
+        )