"""
Feature agglomeration. Base classes and functions for performing feature
agglomeration.
"""
# Author: V. Michel, A. Gramfort
# License: BSD 3 clause

import numpy as np

from ..base import TransformerMixin
from ..utils import array2d


###############################################################################
# Mixin class for feature agglomeration.

class AgglomerationTransform(TransformerMixin):
    """
    A class for feature agglomeration via the transform interface
    """

    def transform(self, X, pooling_func=np.mean):
        """
        Transform a new matrix using the built clustering

        Parameters
        ---------
        X : array-like, shape = [n_samples, n_features]
            A M by N array of M observations in N dimensions or a length
            M array of M one-dimensional observations.

        pooling_func : a function that takes an array of shape = [M, N] and
                       return an array of value of size M.
                       Defaut is np.mean
        """
        X = array2d(X)
        nX = []
        if len(self.labels_) != X.shape[1]:
            raise ValueError("X has a different number of features than "
                             "during fitting.")

        for l in np.unique(self.labels_):
            nX.append(pooling_func(X[:, self.labels_ == l], axis=1))
        return np.array(nX).T

    def inverse_transform(self, Xred):
        """
        Inverse the transformation.
        Return a vector of size nb_features with the values of Xred assigned
        to each group of features

        Parameters
        ----------
        Xred : array of size k
            The values to be assigned to each cluster of samples

        Returns
        -------
        X : array of size nb_samples
            A vector of size nb_samples with the values of Xred assigned to
            each of the cluster of samples.
        """
        if np.size((Xred.shape)) == 1:
            X = np.zeros([self.labels_.shape[0]])
        else:
            X = np.zeros([Xred.shape[0], self.labels_.shape[0]])
        unil = np.unique(self.labels_)
        for i in range(len(unil)):
            if np.size((Xred.shape)) == 1:
                X[self.labels_ == unil[i]] = Xred[i]
            else:
                X[:, self.labels_ == unil[i]] = array2d(Xred[:, i]).T
        return X
