Feature request: Make forecasts relative to latest_update and add flexibility which hours are forecasted

[Kaboutersuper]

For home assistant, I would like to expand the forecasts, so that it is easier to interpret the forecast times. More precisely, I would like to have the forecasts relative to the latest_update, so for latest_update+1 hours, latest_update+2 hours, etc. For readibility, let's floor the latest_update to the hour. I would like to add more options for hours than what the advices give, i.e. we can have forecasts for hour=1,2,3,6,9,12,18 while the advices are only for 4:00, 10:00, 16:00 and 22:00

In code, this would imply something like changing the end of the function get_forecast_array to:

    dt = datetime.strptime(runtime, "%d-%m-%Y %H:%M")
    localdt = dt.astimezone(pytz.timezone("Europe/Amsterdam"))
    last_updated=self._last_updated.replace(second=0, microsecond=0, minute=0)
    local_last_updated=last_updated.astimezone(pytz.timezone("Europe/Amsterdam"))

    for offset in [1,2,3,6,9,12,18]:
        gf=self.get_forecast_at_offset(localdt, local_last_updated,offset, advice)
        forecast.append(gf)

and changing the function get_forecast_at_offset to:

def get_forecast_at_offset(
    self, runtime: datetime, last_updated: datetime, offset: int, advice: bool
) -> dict:
    """Get forecast at a certain offset."""
    offset_from_last_updated=int(offset+(last_updated-runtime).total_seconds()/3600)
    offset_advice=min(18,6*(offset_from_last_updated//6))
    if offset_from_last_updated>0:
        dt = {"offset":offset,"datetime": (runtime + timedelta(hours=offset_from_last_updated)).isoformat()}
        forecast = (
            {"advice": self.get_color(self.get_property("advies_" + str(offset_advice)))}
        )
        dt.update(forecast)

        return dt
    else:
        return False

An example output on 2025-02-11 14:31 could have the following raw advice:
model_runtime: 11-02-2025 10:00
advice_0: code_yellow
advice_6: code_orange
advice_12: code_red
advice_18: code_yellow

The forecast datapoints for offset=1,2,3,6,9,12 would be calculated as:
forecast_advice: [
{'offset': 1, 'datetime': '2025-02-11T15:00:00+01:00', 'advice': 'code_yellow'},
{'offset': 2, 'datetime': '2025-02-11T16:00:00+01:00', 'advice': 'code_orange'},
{'offset': 3, 'datetime': '2025-02-11T17:00:00+01:00', 'advice': 'code_orange'},
{'offset': 6, 'datetime': '2025-02-11T20:00:00+01:00', 'advice': 'code_orange'},
{'offset': 9, 'datetime': '2025-02-11T23:00:00+01:00', 'advice': 'code_red'},
{'offset': 12, 'datetime': '2025-02-12T02:00:00+01:00', 'advice': 'code_red'},
{'offset': 18, 'datetime': '2025-02-12T08:00:00+01:00', 'advice': 'code_yellow'}
]

With this information, it should be fairly easy to make attributes in the HomeAssistant sensor for forecast_1_hour_ahead,
forecast_2_hour_ahead, forecast_12_hour_ahead, etc by parsing the json.

[fwestenberg]

In my original PR for the latest update of Stookwijzer, there were attributes with forecast like Buienradar had. But this was not approved, as this should be in a service. At this point, also the Buienradar forecast is fetched by a service:

action: weather.get_forecasts
target:
  entity_id: weather.buienradar
data:
  type: daily

Response:

weather.buienradar:
  forecast:
    - datetime: "2025-02-11T00:00:00+01:00"
      condition: pouring
      wind_bearing: 135
      temperature: 4
      templow: 1
      wind_speed: 12.96
      precipitation: 12
....

So the forecast_advice result:

[{'datetime': '2025-02-11T16:00:00+01:00', 'advice': 'code_red'}, {'datetime': '2025-02-11T22:00:00+01:00', 'advice': 'code_red'}, {'datetime': '2025-02-12T04:00:00+01:00', 'advice': 'code_red'}, {'datetime': '2025-02-12T10:00:00+01:00', 'advice': 'code_red'}]

Can probably work with a HA service. But I don't have the time to fix this, so please create a PR in the Core repository.

[Kaboutersuper]

It is understandable that the preference is to convert it into a service. Someone just made a request to introduce the forecast into the Core repository: home-assistant/core#138292

Regardless of home assistant, would the feature request have added value, (ie. turn the current forecast for 4AM, 10AM, 4PM and 10PM into a forecast for the next 1,2,3,6,9,18 hours)?