# Original authors from Sckit-Learn:
#          Olivier Grisel
#          Gael Varoquaux
#          Andreas Mueller
#          Lars Buitinck
#          Alexandre Gramfort
#          Nicolas Tresegnie
#          Sylvain Marie
# License: BSD 3 clause


# This code originates from the Scikit-Learn library,
# it was since modified to allow GPU acceleration.
# This code is under BSD 3 clause license.
# Authors mentioned above do not endorse or promote this production.


from ....thirdparty_adapters import check_array
from ....common.exceptions import NotFittedError
from inspect import isclass
from cuml.internals.safe_imports import gpu_only_import
import numbers
from cuml.internals.safe_imports import cpu_only_import
np = cpu_only_import('numpy')
cp = gpu_only_import('cupy')
sp = gpu_only_import('cupyx.scipy.sparse')


FLOAT_DTYPES = (np.float64, np.float32, np.float16)


def check_X_y(X, y, accept_sparse=False, *, accept_large_sparse=True,
              dtype="numeric", order=None, copy=False, force_all_finite=True,
              ensure_2d=True, allow_nd=False, multi_output=False,
              ensure_min_samples=1, ensure_min_features=1, y_numeric=False):
    """Input validation for standard estimators.

    Checks X and y for consistent length, enforces X to be 2D and y 1D. By
    default, X is checked to be non-empty and containing only finite values.
    Standard input checks are also applied to y, such as checking that y
    does not have np.nan or np.inf targets. For multi-label y, set
    multi_output=True to allow 2D and sparse y. If the dtype of X is
    object, attempt converting to float, raising on failure.

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

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

    accept_sparse : string, boolean or list of string (default=False)
        String[s] representing allowed sparse matrix formats, such as 'csc',
        'csr', etc. If the input is sparse but not in the allowed format,
        it will be converted to the first listed format. True allows the input
        to be any format. False means that a sparse matrix input will
        raise an error.

    accept_large_sparse : bool (default=True)
        If a CSR, CSC, COO or BSR sparse matrix is supplied and accepted by
        accept_sparse, accept_large_sparse will cause it to be accepted only
        if its indices are stored with a 32-bit dtype.

    dtype : string, type, list of types or None (default="numeric")
        Data type of result. If None, the dtype of the input is preserved.
        If "numeric", dtype is preserved unless array.dtype is object.
        If dtype is a list of types, conversion on the first type is only
        performed if the dtype of the input is not in the list.

    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 or 'allow-nan', (default=True)
        Whether to raise an error on np.inf, np.nan, pd.NA in X. This parameter
        does not influence whether y can have np.inf, np.nan, pd.NA values.
        The possibilities are:

        - True: Force all values of X to be finite.
        - False: accepts np.inf, np.nan, pd.NA in X.
        - 'allow-nan': accepts only np.nan or pd.NA values in X. Values cannot
          be infinite.

    ensure_2d : boolean (default=True)
        Whether to raise a value error if X is not 2D.

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

    multi_output : boolean (default=False)
        Whether to allow 2D y (array or sparse matrix). If false, y will be
        validated as a vector. y cannot have np.nan or np.inf values if
        multi_output=True.

    ensure_min_samples : int (default=1)
        Make sure that X has a minimum number of samples in its first
        axis (rows for a 2D array).

    ensure_min_features : int (default=1)
        Make sure that the 2D array has some minimum number of features
        (columns). The default value of 1 rejects empty datasets.
        This check is only enforced when X has effectively 2 dimensions or
        is originally 1D and ``ensure_2d`` is True. Setting to 0 disables
        this check.

    y_numeric : boolean (default=False)
        Whether to ensure that y has a numeric type. If dtype of y is object,
        it is converted to float64. Should only be used for regression
        algorithms.

    Returns
    -------
    X_converted : object
        The converted and validated X.

    y_converted : object
        The converted and validated y.
    """
    if y is None:
        raise ValueError("y cannot be None")

    X = check_array(X, accept_sparse=accept_sparse,
                    accept_large_sparse=accept_large_sparse,
                    dtype=dtype, order=order, copy=copy,
                    force_all_finite=force_all_finite,
                    ensure_2d=ensure_2d, allow_nd=allow_nd,
                    ensure_min_samples=ensure_min_samples,
                    ensure_min_features=ensure_min_features)

    y = check_array(y, accept_sparse='csr', force_all_finite=True,
                    ensure_2d=False, dtype='numeric' if y_numeric else None)

    if not multi_output and y.ndim > 1:
        if y.shape[1] > 1:
            raise ValueError(
                "y should be a 1d array, "
                "got an array of shape {} instead.".format(y.shape))

    if X.shape[0] != y.shape[0]:
        raise ValueError("Found input variables with inconsistent numbers of"
                         " samples")

    return X, y


def check_random_state(seed):
    """Turn seed into a np.random.RandomState instance
    Parameters
    ----------
    seed : None | int | instance of RandomState
        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):
        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 check_is_fitted(estimator, attributes=None, *, msg=None, all_or_any=all):
    """Perform is_fitted validation for estimator.

    Checks if the estimator is fitted by verifying the presence of
    fitted attributes (ending with a trailing underscore) and otherwise
    raises a NotFittedError with the given message.

    This utility is meant to be used internally by estimators themselves,
    typically in their own predict / transform methods.

    Parameters
    ----------
    estimator : estimator instance.
        estimator instance for which the check is performed.

    attributes : str, list or tuple of str, default=None
        Attribute name(s) given as string or a list/tuple of strings
        Eg.: ``["coef_", "estimator_", ...], "coef_"``

        If `None`, `estimator` is considered fitted if there exist an
        attribute that ends with a underscore and does not start with double
        underscore.

    msg : string
        The default error message is, "This %(name)s instance is not fitted
        yet. Call 'fit' with appropriate arguments before using this
        estimator."

        For custom messages if "%(name)s" is present in the message string,
        it is substituted for the estimator name.

        Eg. : "Estimator, %(name)s, must be fitted before sparsifying".

    all_or_any : callable, {all, any}, default all
        Specify whether all or any of the given attributes must exist.

    Returns
    -------
    None

    Raises
    ------
    NotFittedError
        If the attributes are not found.
    """
    if isclass(estimator):
        raise TypeError("{} is a class, not an instance.".format(estimator))
    if msg is None:
        msg = ("This %(name)s instance is not fitted yet. Call 'fit' with "
               "appropriate arguments before using this estimator.")

    if not hasattr(estimator, 'fit'):
        raise TypeError("%s is not an estimator instance." % (estimator))

    if attributes is not None:
        if not isinstance(attributes, (list, tuple)):
            attributes = [attributes]
        attrs = all_or_any([hasattr(estimator, attr) for attr in attributes])
    else:
        attrs = [v for v in vars(estimator)
                 if v.endswith("_") and not v.startswith("__")]

    if not attrs:
        raise NotFittedError(msg % {'name': type(estimator).__name__})


def _allclose_dense_sparse(x, y, rtol=1e-7, atol=1e-9):
    """Check allclose for sparse and dense data.

    Both x and y need to be either sparse or dense, they
    can't be mixed.

    Parameters
    ----------
    x : array-like or sparse matrix
        First array to compare.

    y : array-like or sparse matrix
        Second array to compare.

    rtol : float, optional
        relative tolerance; see numpy.allclose

    atol : float, optional
        absolute tolerance; see numpy.allclose. Note that the default here is
        more tolerant than the default for numpy.testing.assert_allclose, where
        atol=0.
    """
    if sp.issparse(x) and sp.issparse(y):
        x = x.tocsr()
        y = y.tocsr()
        x.sum_duplicates()
        y.sum_duplicates()
        return (cp.array_equal(x.indices, y.indices) and
                cp.array_equal(x.indptr, y.indptr) and
                cp.allclose(x.data, y.data, rtol=rtol, atol=atol))
    elif not sp.issparse(x) and not sp.issparse(y):
        return cp.allclose(x, y, rtol=rtol, atol=atol)
    raise ValueError("Can only compare two sparse matrices, not a sparse "
                     "matrix and an array")
