RFC: Event platform

[puddly]

This is a stub PR that explores implementing the Home Assistant Core "event" platform for ZHA. This platform is a little different from the others in that it does not expose state but rather expects events to be triggered at runtime via core_entity.trigger_event(event_type).

The functionality exposed by this platform has always been a pain point for ZHA (since we rely on device automation triggers at the moment) and I think brings up the first difficulty with quirks v2. Below is a sample implementation that fits within the constraints of quirks v2:

class DevelcoButtonEventTypes(StrEnum):
    PRESSED = "pressed"
    RELEASED = "released"


def setup_triggers(device: Device, trigger_event: Callable[[str], None]) -> None:
    """Map device events to event entity triggers."""

    class Listener:
        def attribute_updated(
            self, attribute_id: int, value: Any, timestamp: datetime
        ) -> None:
            if attribute_id != BinaryInput.present_value:
                return

            if value:
                trigger_event(DevelcoButtonEventTypes.PRESSED)
            else:
                trigger_event(DevelcoButtonEventTypes.RELEASED)

    device.endpoints[1].binary_input.add_listener(Listener())


# Quirk defined here
(
    QuirkBuilder("develco", "button")
    .event(
        unique_id_suffix="button",
        translation_key="button",
        fallback_name="Button",
        event_types=DevelcoButtonEventTypes,
        setup_triggers=setup_triggers,
    )
    .add_to_registry()
)

An alternative implementation that relies on quirks directly creating ZHA entities is something that I somewhat prefer:

from zha.platforms.event import EventEntity

class DevelcoButtonEntity(EventEntity):
    _attr_event_types = DevelcoButtonEventTypes
    _attr_translation_key = "button"
    _unique_id_suffix = "button"
    _fallback_name = "Button"

    def on_add(self):
        self.device.endpoints[1].binary_input.add_listener(self)  # TODO: make this better in zigpy...
        self._on_remove_callbacks.append(lambda: self.device.remove_listener(self))

    def attribute_updated(
        self, attribute_id: int, value: Any, timestamp: datetime
    ) -> None:
        if attribute_id != BinaryInput.present_value:
            return

        if value:
            self.trigger_event(DevelcoButtonEventTypes.PRESSED)
        else:
            self.trigger_event(DevelcoButtonEventTypes.RELEASED)

(
    QuirkBuilder("develco", "button")
    .prevent_default_entity_creation(...)
    .register_entity(DevelcoButtonEntity)
    .add_to_registry()
)

[codecov]

Codecov Report

Attention: Patch coverage is 5.55556% with 34 lines in your changes missing coverage. Please review.

Project coverage is 96.37%. Comparing base (5ed0dbf) to head (9e513e2).

Files with missing lines	Patch %	Lines
zha/application/platforms/event/__init__.py	0.00%	29 Missing ⚠️
zha/application/platforms/event/const.py	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #419      +/-   ##
==========================================
- Coverage   96.70%   96.37%   -0.34%     
==========================================
  Files          61       63       +2     
  Lines        9874     9910      +36     
==========================================
+ Hits         9549     9551       +2     
- Misses        325      359      +34     

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