Proactive Alexa ChangeReport messages (#18114)

* Alexa: implement auth and proactive ChangeReport messages

* refactor after rebase from dev to use the new AlexaDirective and Response classes

* move to aiohttp; cleanup

* better function name

* move endpoint to config

* allow passing token function

* remove uneeded state get

* use iterable directly

Co-Authored-By: abmantis <abmantis@users.noreply.github.com>

* missing delete from previous commit

* checks for when user has no auth config

* update cloud component

* PR suggestions

* string lint

* Revert "string lint"

This reverts commit a05a1f134c9ebc7a6e67c093009744f142256365.

* linters are now happier

* more happy linters

* use internal date parser; improve json response handling

* remove unused import

* use await instead of async_add_job

* protect access token update method

* add test_report_state

* line too long

* add docstring

* Update test_smart_home.py

* test accept grant api

* init prefs if None

* add tests for auth and token requests

* replace global with hass.data

* doc lint

homeassistant/components/alexa/auth.py

@@ -0,0 +1,154 @@
+"""Support for Alexa skill auth."""
+
+import asyncio
+import json
+import logging
+from datetime import timedelta
+import aiohttp
+import async_timeout
+
+from homeassistant.core import callback
+from homeassistant.helpers import aiohttp_client
+from homeassistant.util import dt
+from .const import DEFAULT_TIMEOUT
+
+_LOGGER = logging.getLogger(__name__)
+
+LWA_TOKEN_URI = "https://api.amazon.com/auth/o2/token"
+LWA_HEADERS = {
+    "Content-Type": "application/x-www-form-urlencoded;charset=UTF-8"
+}
+
+PREEMPTIVE_REFRESH_TTL_IN_SECONDS = 300
+STORAGE_KEY = 'alexa_auth'
+STORAGE_VERSION = 1
+STORAGE_EXPIRE_TIME = "expire_time"
+STORAGE_ACCESS_TOKEN = "access_token"
+STORAGE_REFRESH_TOKEN = "refresh_token"
+
+
+class Auth:
+    """Handle authentication to send events to Alexa."""
+
+    def __init__(self, hass, client_id, client_secret):
+        """Initialize the Auth class."""
+        self.hass = hass
+
+        self.client_id = client_id
+        self.client_secret = client_secret
+
+        self._prefs = None
+        self._store = hass.helpers.storage.Store(STORAGE_VERSION, STORAGE_KEY)
+
+        self._get_token_lock = asyncio.Lock(loop=hass.loop)
+
+    async def async_do_auth(self, accept_grant_code):
+        """Do authentication with an AcceptGrant code."""
+        # access token not retrieved yet for the first time, so this should
+        # be an access token request
+
+        lwa_params = {
+            "grant_type": "authorization_code",
+            "code": accept_grant_code,
+            "client_id": self.client_id,
+            "client_secret": self.client_secret
+        }
+        _LOGGER.debug("Calling LWA to get the access token (first time), "
+                      "with: %s", json.dumps(lwa_params))
+
+        return await self._async_request_new_token(lwa_params)
+
+    async def async_get_access_token(self):
+        """Perform access token or token refresh request."""
+        async with self._get_token_lock:
+            if self._prefs is None:
+                await self.async_load_preferences()
+
+            if self.is_token_valid():
+                _LOGGER.debug("Token still valid, using it.")
+                return self._prefs[STORAGE_ACCESS_TOKEN]
+
+            if self._prefs[STORAGE_REFRESH_TOKEN] is None:
+                _LOGGER.debug("Token invalid and no refresh token available.")
+                return None
+
+            lwa_params = {
+                "grant_type": "refresh_token",
+                "refresh_token": self._prefs[STORAGE_REFRESH_TOKEN],
+                "client_id": self.client_id,
+                "client_secret": self.client_secret
+            }
+
+            _LOGGER.debug("Calling LWA to refresh the access token.")
+            return await self._async_request_new_token(lwa_params)
+
+    @callback
+    def is_token_valid(self):
+        """Check if a token is already loaded and if it is still valid."""
+        if not self._prefs[STORAGE_ACCESS_TOKEN]:
+            return False
+
+        expire_time = dt.parse_datetime(self._prefs[STORAGE_EXPIRE_TIME])
+        preemptive_expire_time = expire_time - timedelta(
+            seconds=PREEMPTIVE_REFRESH_TTL_IN_SECONDS)
+
+        return dt.utcnow() < preemptive_expire_time
+
+    async def _async_request_new_token(self, lwa_params):
+
+        try:
+            session = aiohttp_client.async_get_clientsession(self.hass)
+            with async_timeout.timeout(DEFAULT_TIMEOUT, loop=self.hass.loop):
+                response = await session.post(LWA_TOKEN_URI,
+                                              headers=LWA_HEADERS,
+                                              data=lwa_params,
+                                              allow_redirects=True)
+
+        except (asyncio.TimeoutError, aiohttp.ClientError):
+            _LOGGER.error("Timeout calling LWA to get auth token.")
+            return None
+
+        _LOGGER.debug("LWA response header: %s", response.headers)
+        _LOGGER.debug("LWA response status: %s", response.status)
+
+        if response.status != 200:
+            _LOGGER.error("Error calling LWA to get auth token.")
+            return None
+
+        response_json = await response.json()
+        _LOGGER.debug("LWA response body  : %s", response_json)
+
+        access_token = response_json["access_token"]
+        refresh_token = response_json["refresh_token"]
+        expires_in = response_json["expires_in"]
+        expire_time = dt.utcnow() + timedelta(seconds=expires_in)
+
+        await self._async_update_preferences(access_token, refresh_token,
+                                             expire_time.isoformat())
+
+        return access_token
+
+    async def async_load_preferences(self):
+        """Load preferences with stored tokens."""
+        self._prefs = await self._store.async_load()
+
+        if self._prefs is None:
+            self._prefs = {
+                STORAGE_ACCESS_TOKEN: None,
+                STORAGE_REFRESH_TOKEN: None,
+                STORAGE_EXPIRE_TIME: None
+            }
+
+    async def _async_update_preferences(self, access_token, refresh_token,
+                                        expire_time):
+        """Update user preferences."""
+        if self._prefs is None:
+            await self.async_load_preferences()
+
+        if access_token is not None:
+            self._prefs[STORAGE_ACCESS_TOKEN] = access_token
+        if refresh_token is not None:
+            self._prefs[STORAGE_REFRESH_TOKEN] = refresh_token
+        if expire_time is not None:
+            self._prefs[STORAGE_EXPIRE_TIME] = expire_time
+        await self._store.async_save(self._prefs)