# Copyright 2019-2020 by Christopher C. Little.
# This file is part of Abydos.
#
# Abydos is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Abydos is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Abydos. If not, see <http://www.gnu.org/licenses/>.

"""abydos.distance._whittaker.

Whittaker distance
"""

from typing import Any, Optional

from ._token_distance import _TokenDistance
from ..tokenizer import _Tokenizer

__all__ = ['Whittaker']


class Whittaker(_TokenDistance):
    r"""Whittaker distance.

    For two multisets X and Y drawn from an alphabet S, Whittaker distance
    :cite:`Whittaker:1952` is

        .. math::

            sim_{Whittaker}(X, Y) = 1 -
            \frac{1}{2}\sum_{i \in S} \Bigg| \frac{|X_i|}{|X|} -
            \frac{|Y_i|}{|Y|} \Bigg|

    .. versionadded:: 0.4.0
    """

    def __init__(
        self, tokenizer: Optional[_Tokenizer] = None, **kwargs: Any
    ) -> None:
        """Initialize Whittaker instance.

        Parameters
        ----------
        tokenizer : _Tokenizer
            A tokenizer instance from the :py:mod:`abydos.tokenizer` package
        **kwargs
            Arbitrary keyword arguments

        Other Parameters
        ----------------
        qval : int
            The length of each q-gram. Using this parameter and tokenizer=None
            will cause the instance to use the QGram tokenizer with this
            q value.


        .. versionadded:: 0.4.0

        """
        super(Whittaker, self).__init__(tokenizer=tokenizer, **kwargs)

    def sim(self, src: str, tar: str) -> float:
        """Return the Whittaker distance of two strings.

        Parameters
        ----------
        src : str
            Source string (or QGrams/Counter objects) for comparison
        tar : str
            Target string (or QGrams/Counter objects) for comparison

        Returns
        -------
        float
            Whittaker distance

        Examples
        --------
        >>> cmp = Whittaker()
        >>> cmp.sim('cat', 'hat')
        0.5
        >>> cmp.sim('Niall', 'Neil')
        0.33333333333333
        >>> cmp.sim('aluminum', 'Catalan')
        0.11111111111111
        >>> cmp.sim('ATCG', 'TAGC')
        0.0


        .. versionadded:: 0.4.0

        """
        self._tokenize(src, tar)

        alphabet = self._total().keys()

        src_card = self._src_card()
        tar_card = self._tar_card()

        return float(
            round(
                1
                - 0.5
                * sum(
                    abs(
                        (self._src_tokens[tok] / src_card if src_card else 0.0)
                        - (
                            self._tar_tokens[tok] / tar_card
                            if tar_card
                            else 0.0
                        )
                    )
                    for tok in alphabet
                ),
                14,
            )
        )


if __name__ == '__main__':
    import doctest

    doctest.testmod()
