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# Apache License, Version 2.0 (the "License"); you may not use this file except in
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#
#     http://www.apache.org/licenses/LICENSE-2.0
#
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"""Module contains an interface for operator builder classes."""

from typing import Optional


class Operator(object):
    """Interface for building operators that can execute in parallel across partitions."""

    def __init__(self):
        raise ValueError(
            "Please use {}.register instead of the constructor".format(
                type(self).__name__
            )
        )

    @classmethod
    def call(cls, func, **call_kwds):
        """
        Build operator that applies source function across the entire dataset.

        Parameters
        ----------
        func : callable
            Source function.
        **call_kwds : kwargs
            Kwargs that will be used for building.

        Returns
        -------
        callable
        """
        raise NotImplementedError("Please implement in child class")

    @classmethod
    # FIXME: `register` is an alias for `call` method. One of them should be removed.
    def register(cls, func, **kwargs):
        """
        Build operator that applies source function across the entire dataset.

        Parameters
        ----------
        func : callable
            Source function.
        **kwargs : kwargs
            Kwargs that will be passed to the builder function.

        Returns
        -------
        callable
        """
        return cls.call(func, **kwargs)

    @classmethod
    def validate_axis(cls, axis: Optional[int]) -> int:
        """
        Ensure that axis to apply function on has valid value.

        Parameters
        ----------
        axis : int, optional
            0 or None means apply on index, 1 means apply on columns.

        Returns
        -------
        int
            Integer representation of given axis.
        """
        return 0 if axis is None else axis