Add forecasts to MetOffice integration (#50876)

* MetOfficeData now retrieves both 3-hourly and daily data (full forecast data, as well as "now" snapshot) on each update

* Bump datapoint API up to latest version

* Create 2 sets of sensors - one of each set for 3-hourly and for daily data (same ones initially enabled, for now)

* Create two entities (one each for 3-hourly and daily data) and also add in the forecast data for each dataset

* Testing changes to accommodate now having two sets of everything for 3-hourly and daily update data

* Removed unused import (reported by flake8)

* As per conversation with @MatthewFlamm leave the 3-hourly entity's unique_id unchanged (although the display name is changed)

* Make some improvements based on reviews

Make some improvements and fix up the formatting/linting failures.

* Make some improvements based on reviews

Make some improvements and fix up the formatting/linting failures.

* Added more test coverage

* import asyncio

* Try to fix test

* Rewrote everything using CoordinatorEntity

* Fixed config flow

* Fixed lint errors

Co-authored-by: MrHarcombe <ian.harcombe@gmail.com>
Co-authored-by: Henco Appel <hencoappel+github@gmail.com>

homeassistant/components/metoffice/helpers.py

@@ -0,0 +1,44 @@
+"""Helpers used for Met Office integration."""
+
+import logging
+
+import datapoint
+
+from homeassistant.helpers.update_coordinator import UpdateFailed
+from homeassistant.util import utcnow
+
+from .data import MetOfficeData
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def fetch_site(connection: datapoint.Manager, latitude, longitude):
+    """Fetch site information from Datapoint API."""
+    try:
+        return connection.get_nearest_forecast_site(
+            latitude=latitude, longitude=longitude
+        )
+    except datapoint.exceptions.APIException as err:
+        _LOGGER.error("Received error from Met Office Datapoint: %s", err)
+        return None
+
+
+def fetch_data(connection: datapoint.Manager, site, mode) -> MetOfficeData:
+    """Fetch weather and forecast from Datapoint API."""
+    try:
+        forecast = connection.get_forecast_for_site(site.id, mode)
+    except (ValueError, datapoint.exceptions.APIException) as err:
+        _LOGGER.error("Check Met Office connection: %s", err.args)
+        raise UpdateFailed from err
+    else:
+        time_now = utcnow()
+        return MetOfficeData(
+            forecast.now(),
+            [
+                timestep
+                for day in forecast.days
+                for timestep in day.timesteps
+                if timestep.date > time_now
+            ],
+            site,
+        )