Nest config flow (#14921)

* Move nest to dir based component

* Add config flow for Nest

* Load Nest platforms via config entry

* Add tests for Nest config flow

* Import existing access tokens as config entries

* Lint

* Update coverage

* Update translation

* Fix tests

* Address strings

* Use python-nest token resolution

* Lint

* Do not do I/O inside constructor

* Lint

* Update test requirements

homeassistant/components/nest/local_auth.py

@@ -0,0 +1,45 @@
+"""Local Nest authentication."""
+import asyncio
+from functools import partial
+
+from homeassistant.core import callback
+from . import config_flow
+from .const import DOMAIN
+
+
+@callback
+def initialize(hass, client_id, client_secret):
+    """Initialize a local auth provider."""
+    config_flow.register_flow_implementation(
+        hass, DOMAIN, 'local', partial(generate_auth_url, client_id),
+        partial(resolve_auth_code, hass, client_id, client_secret)
+    )
+
+
+async def generate_auth_url(client_id, flow_id):
+    """Generate an authorize url."""
+    from nest.nest import AUTHORIZE_URL
+    return AUTHORIZE_URL.format(client_id, flow_id)
+
+
+async def resolve_auth_code(hass, client_id, client_secret, code):
+    """Resolve an authorization code."""
+    from nest.nest import NestAuth, AuthorizationError
+
+    result = asyncio.Future()
+    auth = NestAuth(
+        client_id=client_id,
+        client_secret=client_secret,
+        auth_callback=result.set_result,
+    )
+    auth.pin = code
+
+    try:
+        await hass.async_add_job(auth.login)
+        return await result
+    except AuthorizationError as err:
+        if err.response.status_code == 401:
+            raise config_flow.CodeInvalid()
+        else:
+            raise config_flow.NestAuthError('Unknown error: {} ({})'.format(
+                err, err.response.status_code))