# -*- coding: utf-8 -*-

"""This file is part of the TPOT library.

TPOT was primarily developed at the University of Pennsylvania by:

    - Randal S. Olson (rso@randalolson.com)

    - Weixuan Fu (weixuanf@upenn.edu)

    - Daniel Angell (dpa34@drexel.edu)

    - and many more generous open source contributors

TPOT is free software: you can redistribute it and/or modify

it under the terms of the GNU Lesser General Public License as

published by the Free Software Foundation, either version 3 of

the License, or (at your option) any later version.

TPOT 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public

License along with TPOT. If not, see <http://www.gnu.org/licenses/>.

"""

import numpy as np

from sklearn.metrics import make_scorer, SCORERS

def balanced_accuracy(y_true, y_pred):

    """Default scoring function: balanced accuracy.

    Balanced accuracy computes each class' accuracy on a per-class basis using a

    one-vs-rest encoding, then computes an unweighted average of the class accuracies.

    Parameters

    ----------

    y_true: numpy.ndarray {n_samples}

        True class labels

    y_pred: numpy.ndarray {n_samples}

        Predicted class labels by the estimator

    Returns

    -------

    fitness: float

        Returns a float value indicating the individual's balanced accuracy

        0.5 is as good as chance, and 1.0 is perfect predictive accuracy

    """

    all_classes = list(set(np.append(y_true, y_pred)))

    all_class_accuracies = []

    for this_class in all_classes:

        this_class_sensitivity = 0.

        this_class_specificity = 0.

        if sum(y_true == this_class) != 0:             

            this_class_sensitivity = \

                float(sum((y_pred == this_class) & (y_true == this_class))) /\

                float(sum((y_true == this_class)))

        if  sum(y_true != this_class) != 0:

            this_class_specificity = \

                float(sum((y_pred != this_class) & (y_true != this_class))) /\

                float(sum((y_true != this_class)))

            # print('class',this_class,'sensitivity:',this_class_sensitivity)

            # print('class',this_class,'specifity:',this_class_specificity)

        this_class_accuracy = (this_class_sensitivity + this_class_specificity) / 2.

        # print('class',this_class,'accuracy:',this_class_accuracy)

        all_class_accuracies.append(this_class_accuracy)

    return np.mean(all_class_accuracies)

# SCORERS['balanced_accuracy'] = make_scorer(balanced_accuracy)