from ..externals import six
from collections import defaultdict

# The :mod:`sklearn.pipeline` module implements utilities to build a composite
# estimator, as a chain of transforms and estimators.
# Author: Edouard Duchesnay
#         Gael Varoquaux
#         Virgile Fritsch
#         Alexandre Gramfort
#         Lars Buitinck
# Licence: BSD


def _name_estimators(estimators):
    """Generate names for estimators."""

    names = [type(estimator).__name__.lower() for estimator in estimators]
    namecount = defaultdict(int)
    for _, name in zip(estimators, names):
        namecount[name] += 1

    for k, v in list(six.iteritems(namecount)):
        if v == 1:
            del namecount[k]

    for i in reversed(range(len(estimators))):
        name = names[i]
        if name in namecount:
            names[i] += "-%d" % namecount[name]
            namecount[name] -= 1

    return list(zip(names, estimators))