"""Utilities for input validation"""
# Authors: Olivier Grisel
#          Gael Varoquaux
#          Andreas Mueller
#          Lars Buitinck
#          Alexandre Gramfort
#          Nicolas Tresegnie
# License: BSD 3 clause

import warnings
import numbers

import numpy as np
import scipy.sparse as sp

from ..externals import six
from inspect import getargspec


class DataConversionWarning(UserWarning):
    "A warning on implicit data conversions happening in the code"
    pass

warnings.simplefilter("always", DataConversionWarning)


class NonBLASDotWarning(UserWarning):
    "A warning on implicit dispatch to numpy.dot"
    pass


# Silenced by default to reduce verbosity. Turn on at runtime for
# performance profiling.
warnings.simplefilter('ignore', NonBLASDotWarning)


def _assert_all_finite(X):
    """Like assert_all_finite, but only for ndarray."""
    X = np.asanyarray(X)
    # First try an O(n) time, O(1) space solution for the common case that
    # everything is finite; fall back to O(n) space np.isfinite to prevent
    # false positives from overflow in sum method.
    if (X.dtype.char in np.typecodes['AllFloat'] and not np.isfinite(X.sum())
            and not np.isfinite(X).all()):
        raise ValueError("Input contains NaN, infinity"
                         " or a value too large for %r." % X.dtype)


def assert_all_finite(X):
    """Throw a ValueError if X contains NaN or infinity.

    Input MUST be an np.ndarray instance or a scipy.sparse matrix."""
    _assert_all_finite(X.data if sp.issparse(X) else X)


def as_float_array(X, copy=True, force_all_finite=True):
    """Converts an array-like to an array of floats

    The new dtype will be np.float32 or np.float64, depending on the original
    type. The function can create a copy or modify the argument depending
    on the argument copy.

    Parameters
    ----------
    X : {array-like, sparse matrix}

    copy : bool, optional
        If True, a copy of X will be created. If False, a copy may still be
        returned if X's dtype is not a floating point type.

    Returns
    -------
    XT : {array, sparse matrix}
        An array of type np.float
    """
    if isinstance(X, np.matrix) or (not isinstance(X, np.ndarray)
                                    and not sp.issparse(X)):
        return check_array(X, ['csr', 'csc', 'coo'], dtype=np.float64,
                           copy=copy, force_all_finite=force_all_finite,
                           ensure_2d=False)
    elif sp.issparse(X) and X.dtype in [np.float32, np.float64]:
        return X.copy() if copy else X
    elif X.dtype in [np.float32, np.float64]:  # is numpy array
        return X.copy('F' if X.flags['F_CONTIGUOUS'] else 'C') if copy else X
    else:
        return X.astype(np.float32 if X.dtype == np.int32 else np.float64)


def _num_samples(x):
    """Return number of samples in array-like x."""
    if not hasattr(x, '__len__') and not hasattr(x, 'shape'):
        if hasattr(x, '__array__'):
            x = np.asarray(x)
        else:
            raise TypeError("Expected sequence or array-like, got %r" % x)
    return x.shape[0] if hasattr(x, 'shape') else len(x)


def check_consistent_length(*arrays):
    """Check that all arrays have consistent first dimensions.

    Checks whether all objects in arrays have the same shape or length.

    Parameters
    ----------
    arrays : list or tuple of input objects.
        Objects that will be checked for consistent length.
    """

    uniques = np.unique([_num_samples(X) for X in arrays if X is not None])
    if len(uniques) > 1:
        raise ValueError("Found arrays with inconsistent numbers of samples: %s"
                         % str(uniques))


def indexable(*iterables):
    """Make arrays indexable for cross-validation.

    Checks consistent length, passes through None, and ensures that everything
    can be indexed by converting sparse matrices to csr and converting
    non-interable objects to arrays.

    Parameters
    ----------
    iterables : lists, dataframes, arrays, sparse matrices
        List of objects to ensure sliceability.
    """
    result = []
    for X in iterables:
        if sp.issparse(X):
            result.append(X.tocsr())
        elif hasattr(X, "__getitem__") or hasattr(X, "iloc"):
            result.append(X)
        elif X is None:
            result.append(X)
        else:
            result.append(np.array(X))
    check_consistent_length(*result)
    return result


def _ensure_sparse_format(spmatrix, accept_sparse, dtype, order, copy,
                          force_all_finite):
    """Convert a sparse matrix to a given format.

    Checks the sparse format of spmatrix and converts if necessary.

    Parameters
    ----------
    spmatrix : scipy sparse matrix
        Input to validate and convert.

    accept_sparse : string, list of string or None (default=None)
        String[s] representing allowed sparse matrix formats ('csc',
        'csr', 'coo', 'dok', 'bsr', 'lil', 'dia'). None means that sparse
        matrix input will raise an error.  If the input is sparse but not in
        the allowed format, it will be converted to the first listed format.

    dtype : string, type or None (default=none)
        Data type of result. If None, the dtype of the input is preserved.

    order : 'F', 'C' or None (default=None)
        Whether an array will be forced to be fortran or c-style.

    copy : boolean (default=False)
        Whether a forced copy will be triggered. If copy=False, a copy might
        be triggered by a conversion.

    force_all_finite : boolean (default=True)
        Whether to raise an error on np.inf and np.nan in X.

    Returns
    -------
    spmatrix_converted : scipy sparse matrix.
        Matrix that is ensured to have an allowed type.
    """
    if accept_sparse is None:
        raise TypeError('A sparse matrix was passed, but dense '
                        'data is required. Use X.toarray() to '
                        'convert to a dense numpy array.')
    sparse_type = spmatrix.format
    if dtype is None:
        dtype = spmatrix.dtype
    if sparse_type in accept_sparse:
        # correct type
        if dtype == spmatrix.dtype:
            # correct dtype
            if copy:
                spmatrix = spmatrix.copy()
        else:
            # convert dtype
            spmatrix = spmatrix.astype(dtype)
    else:
        # create new
        spmatrix = spmatrix.asformat(accept_sparse[0]).astype(dtype)
    if force_all_finite:
        if not hasattr(spmatrix, "data"):
            warnings.warn("Can't check %s sparse matrix for nan or inf."
                          % spmatrix.format)
        else:
            _assert_all_finite(spmatrix.data)
    if hasattr(spmatrix, "data"):
        spmatrix.data = np.array(spmatrix.data, copy=False, order=order)
    return spmatrix


def check_array(array, accept_sparse=None, dtype=None, order=None, copy=False,
                force_all_finite=True, ensure_2d=True, allow_nd=False):
    """Input validation on an array, list, sparse matrix or similar.

    By default, the input is converted to an at least 2nd numpy array.

    Parameters
    ----------
    array : object
        Input object to check / convert.

    accept_sparse : string, list of string or None (default=None)
        String[s] representing allowed sparse matrix formats, such as 'csc',
        'csr', etc.  None means that sparse matrix input will raise an error.
        If the input is sparse but not in the allowed format, it will be
        converted to the first listed format.

    dtype : string, type or None (default=none)
        Data type of result. If None, the dtype of the input is preserved.

    order : 'F', 'C' or None (default=None)
        Whether an array will be forced to be fortran or c-style.

    copy : boolean (default=False)
        Whether a forced copy will be triggered. If copy=False, a copy might
        be triggered by a conversion.

    force_all_finite : boolean (default=True)
        Whether to raise an error on np.inf and np.nan in X.

    ensure_2d : boolean (default=True)
        Whether to make X at least 2d.

    allow_nd : boolean (default=False)
        Whether to allow X.ndim > 2.

    Returns
    -------
    X_converted : object
        The converted and validated X.
    """
    if isinstance(accept_sparse, str):
        accept_sparse = [accept_sparse]

    if sp.issparse(array):
        array = _ensure_sparse_format(array, accept_sparse, dtype, order,
                                      copy, force_all_finite)
    else:
        if ensure_2d:
            array = np.atleast_2d(array)
        array = np.array(array, dtype=dtype, order=order, copy=copy)
        if not allow_nd and array.ndim >= 3:
            raise ValueError("Found array with dim %d. Expected <= 2" %
                             array.ndim)
        if force_all_finite:
            _assert_all_finite(array)

    return array


def check_X_y(X, y, accept_sparse=None, dtype=None, order=None, copy=False,
              force_all_finite=True, ensure_2d=True, allow_nd=False,
              multi_output=False):
    """Input validation for standard estimators.

    Checks X and y for consistent length, enforces X 2d and y 1d.
    Standard input checks are only applied to y. For multi-label y,
    set multi_ouput=True to allow 2d and sparse y.

    Parameters
    ----------
    X : nd-array, list or sparse matrix
        Input data.

    y : nd-array, list or sparse matrix
        Labels.

    accept_sparse : string, list of string or None (default=None)
        String[s] representing allowed sparse matrix formats, such as 'csc',
        'csr', etc.  None means that sparse matrix input will raise an error.
        If the input is sparse but not in the allowed format, it will be
        converted to the first listed format.

    dtype : string, type or None (default=none)
        Data type of result. If None, the dtype of the input is preserved.

    order : 'F', 'C' or None (default=None)
        Whether an array will be forced to be fortran or c-style.

    copy : boolean (default=False)
        Whether a forced copy will be triggered. If copy=False, a copy might
        be triggered by a conversion.

    force_all_finite : boolean (default=True)
        Whether to raise an error on np.inf and np.nan in X.

    ensure_2d : boolean (default=True)
        Whether to make X at least 2d.

    allow_nd : boolean (default=False)
        Whether to allow X.ndim > 2.

    multi_output : boolean (default=False)
        Whether to allow 2-d y (array or sparse matrix). If false, y will be
        validated as a vector.

    Returns
    -------
    X_converted : object
        The converted and validated X.
    """
    X = check_array(X, accept_sparse, dtype, order, copy, force_all_finite,
                    ensure_2d, allow_nd)
    if multi_output:
        y = check_array(y, 'csr', force_all_finite=True, ensure_2d=False)
    else:
        y = column_or_1d(y, warn=True)
        _assert_all_finite(y)

    check_consistent_length(X, y)

    return X, y


def column_or_1d(y, warn=False):
    """ Ravel column or 1d numpy array, else raises an error

    Parameters
    ----------
    y : array-like

    Returns
    -------
    y : array

    """
    shape = np.shape(y)
    if len(shape) == 1:
        return np.ravel(y)
    if len(shape) == 2 and shape[1] == 1:
        if warn:
            warnings.warn("A column-vector y was passed when a 1d array was"
                          " expected. Please change the shape of y to "
                          "(n_samples, ), for example using ravel().",
                          DataConversionWarning, stacklevel=2)
        return np.ravel(y)

    raise ValueError("bad input shape {0}".format(shape))


def warn_if_not_float(X, estimator='This algorithm'):
    """Warning utility function to check that data type is floating point.

    Returns True if a warning was raised (i.e. the input is not float) and
    False otherwise, for easier input validation.
    """
    if not isinstance(estimator, six.string_types):
        estimator = estimator.__class__.__name__
    if X.dtype.kind != 'f':
        warnings.warn("%s assumes floating point values as input, "
                      "got %s" % (estimator, X.dtype))
        return True
    return False


def check_random_state(seed):
    """Turn seed into a np.random.RandomState instance

    If seed is None, return the RandomState singleton used by np.random.
    If seed is an int, return a new RandomState instance seeded with seed.
    If seed is already a RandomState instance, return it.
    Otherwise raise ValueError.
    """
    if seed is None or seed is np.random:
        return np.random.mtrand._rand
    if isinstance(seed, (numbers.Integral, np.integer)):
        return np.random.RandomState(seed)
    if isinstance(seed, np.random.RandomState):
        return seed
    raise ValueError('%r cannot be used to seed a numpy.random.RandomState'
                     ' instance' % seed)

def has_fit_parameter(estimator, parameter):
    """ Checks whether the estimator's fit method supports the given parameter.

    Example
    -------
    >>> from sklearn.svm import SVC
    >>> has_fit_parameter(SVC(), "sample_weight")
    True

    """
    return parameter in getargspec(estimator.fit)[0]
