Feature View Protocol

@runtime_checkable
class FeatureViewSourceProtocol(Protocol):  # pragma: nocover
    """
    The contract needed to expose the [AmoraModel](amora-model) definition as a [Feature View](feature-view.md)

    To expose an `AmoraModel` as a Feature View, one must decorate it with
    `amora.feature_store.decorators.feature_view` and implement the
    `FeatureViewProcotol` class methods.

    !!! hint
        An example can be found at `examples.amora_project.models.step_count_by_source.py`

    """

    @classmethod
    def feature_view_entities(cls) -> List[Column]:
        """
        Returns a list of the model columns that should be used as an [entity](feature-view.md#entities). E.g:

        An `AmoraModel` with a single `customer_id` entity:

        ```python
        @classmethod
        def feature_view_entities(cls) -> List[Column]:
            return [cls.customer_id]
        ```

        An `AmoraModel` with multiple entities, `customer_id` and `company_id`:

        ```python
        @classmethod
        def feature_view_entities(cls) -> List[Column]:
            return [cls.customer_id, cls.company_id]
        ```

        A model with no entities:

        ```python
        @classmethod
        def feature_view_entities(cls) -> List[Column]:
            return []
        ```
        """
        ...

    @classmethod
    def feature_view_features(cls) -> List[Column]:
        """
        Returns a list of the model columns that should be used as [features](feature-view.md#features). E.g:

        Features of a customer entity could be _the number of transactions
        they have made on a month_ as `count_transactions_last_30d` and _the sum
        of the transactions amounts they have made on a month_
        as `sum_transactions_last_30d`:

        ```python
        @classmethod
        def feature_view_features(cls) -> List[Column]:
            return [cls.count_transactions_last_30d, cls.sum_transactions_last_30d]
        ```
        """
        ...

    @classmethod
    def feature_view_event_timestamp(cls) -> Column:
        """
        Event timestamp column used for point-in-time joins of feature values. E.g:

        ```python
        @classmethod
        def feature_view_event_timestamp(cls) -> Column:
            return cls.event_timestamp
        ```

        At your Amora Model, the column should be defined as such:

        ```python
        from sqlalchemy import TIMESTAMP, Column

        from amora.models import AmoraModel, Field


        @feature_view
        class FeatureViewModel(AmoraModel):
            ...
            event_timestamp: datetime = Field(TIMESTAMP)
        ```

        """
        ...