Add Mill config flow (#35136)

* Mill config, wip

* add tests

* fix merge

* update tests

* unique id

* Mill strings

* mill config flow

* mill config flow

* test import

* test import

* req

* ccoverage

* Apply suggestions from code review

Co-authored-by: J. Nick Koston <nick@koston.org>

* style

* Apply suggestions from code review

Co-authored-by: Paulus Schoutsen <balloob@gmail.com>

* update strings

* add test

Co-authored-by: J. Nick Koston <nick@koston.org>
Co-authored-by: Paulus Schoutsen <balloob@gmail.com>

homeassistant/components/mill/config_flow.py

@@ -0,0 +1,55 @@
+"""Adds config flow for Mill integration."""
+import logging
+
+from mill import Mill
+import voluptuous as vol
+
+from homeassistant import config_entries
+from homeassistant.const import CONF_PASSWORD, CONF_USERNAME
+from homeassistant.helpers.aiohttp_client import async_get_clientsession
+
+from .const import DOMAIN  # pylint:disable=unused-import
+
+_LOGGER = logging.getLogger(__name__)
+
+DATA_SCHEMA = vol.Schema(
+    {vol.Required(CONF_USERNAME): str, vol.Required(CONF_PASSWORD): str}
+)
+
+
+class MillConfigFlow(config_entries.ConfigFlow, domain=DOMAIN):
+    """Handle a config flow for Mill integration."""
+
+    VERSION = 1
+    CONNECTION_CLASS = config_entries.CONN_CLASS_CLOUD_POLL
+
+    async def async_step_user(self, user_input=None):
+        """Handle the initial step."""
+        if user_input is None:
+            return self.async_show_form(
+                step_id="user", data_schema=DATA_SCHEMA, errors={},
+            )
+
+        username = user_input[CONF_USERNAME].replace(" ", "")
+        password = user_input[CONF_PASSWORD].replace(" ", "")
+
+        mill_data_connection = Mill(
+            username, password, websession=async_get_clientsession(self.hass),
+        )
+
+        errors = {}
+
+        if not await mill_data_connection.connect():
+            errors["connection_error"] = "connection_error"
+            return self.async_show_form(
+                step_id="user", data_schema=DATA_SCHEMA, errors=errors,
+            )
+
+        unique_id = username
+
+        await self.async_set_unique_id(unique_id)
+        self._abort_if_unique_id_configured()
+
+        return self.async_create_entry(
+            title=unique_id, data={CONF_USERNAME: username, CONF_PASSWORD: password},
+        )