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#  ┃ Copyright (c) 2017, the Perspective Authors.                              ┃
#  ┃ ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌ ┃
#  ┃ This file is part of the Perspective library, distributed under the terms ┃
#  ┃ of the [Apache License 2.0](https://www.apache.org/licenses/LICENSE-2.0). ┃
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class VirtualServerHandler:
    """
    An interface for implementing a Perspective `VirtualServer`. It operates
    thusly:

    -   A table is selected by name (validated via `get_hosted_tables`).

    -   The UI will ask the model to create a temporary table with the results
        of querying this table with a specific query `config`, a simple struct
        which reflects the UI configurable fields (see `get_features`).

    -   The UI will query slices of the temporary table as it needs them to
        render. This may be a rectangular slice, a whole column or the entire
        set, and it is returned from teh model via a custom push-only
        struct `PerspectiveColumn` for now, though in the future we will support
        e.g. Polars and other arrow-native formats directly.

    -   The UI will delete its own temporary tables via `view_delete` but it is
        ok for them to die intermittently, the UI will recover automatically.
    """

    def get_features(self):
        """
        [OPTIONAL] Toggle UI features through data model support. For example,
        setting `"group_by": False` would hide the "Group By" UI control, as
        well as prevent this field from appearing in `config` dicts later
        provided to `table_make_view`.

        This API defaults to just "columns", e.g. a simple flat datagrid in
        which you can just scroll, select and format columns.

        # Example

        ```python
        return {
            "group_by": True,
            "split_by": True,
            "sort": True,
            "expressions": True,
            "filter_ops": {
                "integer": ["==", "<"],
            },
            "aggregates": {
                "string": ["count"],
                "float": ["count", "sum"],
            },
        }
        ```
        """

        pass

    def get_hosted_tables(self) -> list[str]:
        """
        List of `Table` names available to query from.
        """

        pass

    def table_schema(self, table_name):
        """
        Get the _Perspective Schema_ for a `Table`, a mapping of column name to
        Perspective column types, a simplified set of six visually-relevant
        types mapped from DuckDB's much richer type system. Optionally,
        a model may also implement `view_schema` which describes temporary
        tables, but for DuckDB this method is identical.
        """

        pass

    def table_size(self, table_name):
        """
        Get a table's row count. Optionally, a model may also implement the
        `view_size` method to get the row count for temporary tables, but for
        DuckDB this method is identical.
        """

        pass

    def view_schema(self, view_name, config):
        return self.table_schema(view_name)

    def view_size(self, view_name):
        return self.table_size(view_name)

    def table_make_view(self, table_name, view_name, config):
        """
        Create a temporary table `view_name` from the results of querying
        `table_name` with a query configuration `config`.
        """

        pass

    def table_validate_expression(self, view_name, expression):
        """
        [OPTIONAL] Given a temporary table `view_name`, validate the type of
        a column expression string `expression`, or raise an error if the
        expression is invalid. This is enabeld by `"expressions"` via
        `get_features` and defaults to allow all expressions.
        """

        pass

    def view_delete(self, view_name):
        """
        Delete a temporary table. The UI will do this automatically, and it
        can recover.
        """

        pass

    def view_get_min_max(self, view_name, column_name, config):
        """
        [OPTIONAL] Get the min and max values of a column in a view.
        Returns a tuple of (min, max) as native Python values.
        """

        pass

    def view_get_data(self, view_name, config, viewport, data):
        """
        Serialize a rectangular slice `viewport` from temporary table
        `view_name`, into the `PerspectiveColumn` serialization API injected
        via `data`. The push-only `PerspectiveColumn` type can handle casting
        Python types as input, but once a type is pushed to a column name it
        must not be changed.
        """

        pass