# Source code for abydos.distance._hassanat

# Copyright 2019-2020 by Christopher C. Little.
# This file is part of Abydos.
#
# Abydos is free software: you can redistribute it and/or modify
# 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._hassanat.

Hassanat distance
"""

from ._token_distance import _TokenDistance

__all__ = ['Hassanat']

[docs]class Hassanat(_TokenDistance):
r"""Hassanat distance.

For two multisets X and Y drawn from an alphabet S, Hassanat distance
:cite:Hassanat:2014 is

.. math::

dist_{Hassanat}(X, Y) = \sum_{i \in S} D(X_i, Y_i)

where

.. math::

D(X_i, Y_i) =
\left\{\begin{array}{ll}
1-\frac{1+min(X_i, Y_i)}{1+max(X_i, Y_i)}&,
min(X_i, Y_i) \geq 0
\\
\\
1-\frac{1+min(X_i, Y_i)+|min(X_i, Y_i)|}
{1+max(X_i, Y_i)+|min(X_i, Y_i)|}&,
min(X_i, Y_i) < 0
\end{array}\right.

"""

def __init__(self, tokenizer=None, **kwargs):
"""Initialize Hassanat 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.

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

[docs]    def dist_abs(self, src, tar):
"""Return the Hassanat 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
Hassanat distance

Examples
--------
>>> cmp = Hassanat()
>>> cmp.dist_abs('cat', 'hat')
2.0
>>> cmp.dist_abs('Niall', 'Neil')
3.5
>>> cmp.dist_abs('aluminum', 'Catalan')
7.166666666666667
>>> cmp.dist_abs('ATCG', 'TAGC')
5.0

"""
self._tokenize(src, tar)

distance = 0.0

for tok in self._total().keys():
x = self._src_tokens[tok]
y = self._tar_tokens[tok]

min_val = min(x, y)
if min_val >= 0:
distance += 1 - (1 + min_val) / (1 + max(x, y))
else:
distance += 1 - 1 / (1 + max(x, y) - min_val)

return distance

[docs]    def dist(self, src, tar):
"""Return the normalized Hassanat 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
Normalized Hassanat distance

Examples
--------
>>> cmp = Hassanat()
>>> cmp.dist('cat', 'hat')
0.3333333333333333
>>> cmp.dist('Niall', 'Neil')
0.3888888888888889
>>> cmp.dist('aluminum', 'Catalan')
0.4777777777777778
>>> cmp.dist('ATCG', 'TAGC')
0.5