#===============================================================================
# Copyright 2014-2021 Intel Corporation
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#===============================================================================

import numpy as np
import daal4py as d4p
from sklearn import get_config as _get_config
from sklearn.utils.fixes import _object_dtype_isnan
import warnings
from contextlib import suppress
import scipy.sparse as sp
from numpy.core.numeric import ComplexWarning
from sklearn.utils.validation import (_num_samples, _ensure_no_complex_data,
                                      _ensure_sparse_format, column_or_1d,
                                      check_consistent_length)
from .._utils import is_DataFrame, get_dtype, get_number_of_types


def _daal_assert_all_finite(X, allow_nan=False, msg_dtype=None):
    """Like assert_all_finite, but only for ndarray."""
    # validation is also imported in extmath
    from sklearn.utils.extmath import _safe_accumulator_op

    if _get_config()['assume_finite']:
        return

    is_df = is_DataFrame(X)
    num_of_types = get_number_of_types(X)

    # if X is heterogeneous pandas.DataFrame then
    # covert it to a list of arrays
    if is_df and num_of_types > 1:
        lst = []
        for idx in X:
            arr = X[idx].to_numpy()
            lst.append(arr if arr.flags['C_CONTIGUOUS'] else np.ascontiguousarray(arr))
    else:
        X = np.asanyarray(X)
        is_df = False

    dt = np.dtype(get_dtype(X))
    is_float = dt.kind in 'fc'

    msg_err = "Input contains {} or a value too large for {!r}."
    type_err = 'infinity' if allow_nan else 'NaN, infinity'
    err = msg_err.format(type_err, msg_dtype if msg_dtype is not None else dt)

    if X.ndim in [1, 2] and not np.any(np.equal(X.shape, 0)) and \
            dt in [np.float32, np.float64]:
        if X.ndim == 1:
            X = X.reshape((-1, 1))

        x_for_daal = lst if is_df and num_of_types > 1 else X

        if dt == np.float64:
            if not d4p.daal_assert_all_finite(x_for_daal, allow_nan, 0):
                raise ValueError(err)
        elif dt == np.float32:
            if not d4p.daal_assert_all_finite(x_for_daal, allow_nan, 1):
                raise ValueError(err)
    # 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. The sum is also calculated
    # safely to reduce dtype induced overflows.
    elif is_float and (np.isfinite(_safe_accumulator_op(np.sum, X))):
        pass
    elif is_float:
        if allow_nan and np.isinf(X).any() or \
                not allow_nan and not np.isfinite(X).all():
            raise ValueError(err)
    # for object dtype data, we only check for NaNs (GH-13254)
    elif dt == np.dtype('object') and not allow_nan:
        if _object_dtype_isnan(X).any():
            raise ValueError("Input contains NaN")


def _pandas_check_array(array, array_orig, force_all_finite, ensure_min_samples,
                        ensure_min_features, copy, context):
    if force_all_finite:
        _daal_assert_all_finite(array, allow_nan=force_all_finite == 'allow-nan')

    if ensure_min_samples > 0:
        n_samples = _num_samples(array)
        if n_samples < ensure_min_samples:
            raise ValueError("Found array with %d sample(s) (shape=%s) while a"
                             " minimum of %d is required%s."
                             % (n_samples, array.shape, ensure_min_samples,
                                context))

    if ensure_min_features > 0:
        n_features = array.shape[1]
        if n_features < ensure_min_features:
            raise ValueError("Found array with %d feature(s) (shape=%s) while"
                             " a minimum of %d is required%s."
                             % (n_features, array.shape, ensure_min_features,
                                context))

    if copy and np.may_share_memory(array, array_orig):
        array = array.copy()

    return array


def _daal_check_array(array, accept_sparse=False, *, accept_large_sparse=True,
                      dtype="numeric", order=None, copy=False, force_all_finite=True,
                      ensure_2d=True, allow_nd=False, ensure_min_samples=1,
                      ensure_min_features=1, estimator=None):

    """Input validation on an array, list, sparse matrix or similar.

    By default, the input is checked to be a non-empty 2D array containing
    only finite values. If the dtype of the array is object, attempt
    converting to float, raising on failure.

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

    accept_sparse : string, boolean or list/tuple of strings (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=False will cause it to be accepted
        only if its indices are stored with a 32-bit dtype.

        .. versionadded:: 0.20

    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.
        When order is None (default), then if copy=False, nothing is ensured
        about the memory layout of the output array; otherwise (copy=True)
        the memory layout of the returned array is kept as close as possible
        to the original array.

    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 array. The
        possibilities are:

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

        .. versionadded:: 0.20
           ``force_all_finite`` accepts the string ``'allow-nan'``.

        .. versionchanged:: 0.23
           Accepts `pd.NA` and converts it into `np.nan`

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

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

    ensure_min_samples : int (default=1)
        Make sure that the array has a minimum number of samples in its first
        axis (rows for a 2D array). Setting to 0 disables this check.

    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 the input data has effectively 2
        dimensions or is originally 1D and ``ensure_2d`` is True. Setting to 0
        disables this check.

    estimator : str or estimator instance (default=None)
        If passed, include the name of the estimator in warning messages.

    Returns
    -------
    array_converted : object
        The converted and validated array.
    """
    if force_all_finite not in (True, False, 'allow-nan'):
        raise ValueError('force_all_finite should be a bool or "allow-nan"'
                         '. Got {!r} instead'.format(force_all_finite))

    if estimator is not None:
        if isinstance(estimator, str):
            estimator_name = estimator
        else:
            estimator_name = estimator.__class__.__name__
    else:
        estimator_name = "Estimator"
    context = " by %s" % estimator_name if estimator is not None else ""

    array_orig = array

    # a branch for heterogeneous pandas.DataFrame
    if is_DataFrame(array) and get_number_of_types(array) > 1:
        from pandas.api.types import is_sparse
        if hasattr(array, 'sparse') or \
                not array.dtypes.apply(is_sparse).any():
            return _pandas_check_array(array, array_orig, force_all_finite,
                                       ensure_min_samples, ensure_min_features,
                                       copy, context)

    # store whether originally we wanted numeric dtype
    dtype_numeric = isinstance(dtype, str) and dtype == "numeric"

    dtype_orig = getattr(array, "dtype", None)
    if not hasattr(dtype_orig, 'kind'):
        # not a data type (e.g. a column named dtype in a pandas DataFrame)
        dtype_orig = None

    # check if the object contains several dtypes (typically a pandas
    # DataFrame), and store them. If not, store None.
    dtypes_orig = None
    has_pd_integer_array = False
    if hasattr(array, "dtypes") and hasattr(array.dtypes, '__array__'):
        # throw warning if columns are sparse. If all columns are sparse, then
        # array.sparse exists and sparsity will be perserved (later).
        with suppress(ImportError):
            from pandas.api.types import is_sparse
            if not hasattr(array, 'sparse') and \
                    array.dtypes.apply(is_sparse).any():
                warnings.warn(
                    "pandas.DataFrame with sparse columns found."
                    "It will be converted to a dense numpy array."
                )

        dtypes_orig = list(array.dtypes)
        # pandas boolean dtype __array__ interface coerces bools to objects
        for i, dtype_iter in enumerate(dtypes_orig):
            if dtype_iter.kind == 'b':
                dtypes_orig[i] = np.dtype(np.object)
            elif dtype_iter.name.startswith(("Int", "UInt")):
                # name looks like an Integer Extension Array, now check for
                # the dtype
                with suppress(ImportError):
                    from pandas import (Int8Dtype, Int16Dtype,
                                        Int32Dtype, Int64Dtype,
                                        UInt8Dtype, UInt16Dtype,
                                        UInt32Dtype, UInt64Dtype)
                    if isinstance(dtype_iter, (Int8Dtype, Int16Dtype,
                                               Int32Dtype, Int64Dtype,
                                               UInt8Dtype, UInt16Dtype,
                                               UInt32Dtype, UInt64Dtype)):
                        has_pd_integer_array = True

        if all(isinstance(dtype, np.dtype) for dtype in dtypes_orig):
            dtype_orig = np.result_type(*dtypes_orig)

    if dtype_numeric:
        if dtype_orig is not None and dtype_orig.kind == "O":
            # if input is object, convert to float.
            dtype = np.float64
        else:
            dtype = None

    if isinstance(dtype, (list, tuple)):
        if dtype_orig is not None and dtype_orig in dtype:
            # no dtype conversion required
            dtype = None
        else:
            # dtype conversion required. Let's select the first element of the
            # list of accepted types.
            dtype = dtype[0]

    if has_pd_integer_array:
        # If there are any pandas integer extension arrays,
        array = array.astype(dtype)

    # When all dataframe columns are sparse, convert to a sparse array
    if hasattr(array, 'sparse') and array.ndim > 1:
        # DataFrame.sparse only supports `to_coo`
        array = array.sparse.to_coo()

    if sp.issparse(array):
        _ensure_no_complex_data(array)
        array = _ensure_sparse_format(array, accept_sparse=accept_sparse,
                                      dtype=dtype, copy=copy,
                                      force_all_finite=force_all_finite,
                                      accept_large_sparse=accept_large_sparse)
    else:
        # If np.array(..) gives ComplexWarning, then we convert the warning
        # to an error. This is needed because specifying a non complex
        # dtype to the function converts complex to real dtype,
        # thereby passing the test made in the lines following the scope
        # of warnings context manager.
        with warnings.catch_warnings():
            try:
                warnings.simplefilter('error', ComplexWarning)
                if dtype is not None and np.dtype(dtype).kind in 'iu':
                    # Conversion float -> int should not contain NaN or
                    # inf (numpy#14412). We cannot use casting='safe' because
                    # then conversion float -> int would be disallowed.
                    array = np.asarray(array, order=order)
                    if array.dtype.kind == 'f':
                        _daal_assert_all_finite(array, allow_nan=False,
                                                msg_dtype=dtype)
                    array = array.astype(dtype, casting="unsafe", copy=False)
                else:
                    array = np.asarray(array, order=order, dtype=dtype)
            except ComplexWarning:
                raise ValueError("Complex data not supported\n"
                                 "{}\n".format(array))

        # It is possible that the np.array(..) gave no warning. This happens
        # when no dtype conversion happened, for example dtype = None. The
        # result is that np.array(..) produces an array of complex dtype
        # and we need to catch and raise exception for such cases.
        _ensure_no_complex_data(array)  # doing nothing for DataFrame

        if ensure_2d:
            # If input is scalar raise error
            if array.ndim == 0:
                raise ValueError(
                    "Expected 2D array, got scalar array instead:\narray={}.\n"
                    "Reshape your data either using array.reshape(-1, 1) if "
                    "your data has a single feature or array.reshape(1, -1) "
                    "if it contains a single sample.".format(array))
            # If input is 1D raise error
            if array.ndim == 1:
                raise ValueError(
                    "Expected 2D array, got 1D array instead:\narray={}.\n"
                    "Reshape your data either using array.reshape(-1, 1) if "
                    "your data has a single feature or array.reshape(1, -1) "
                    "if it contains a single sample.".format(array))

        # in the future np.flexible dtypes will be handled like object dtypes
        if dtype_numeric and np.issubdtype(array.dtype, np.flexible):
            warnings.warn(
                "Beginning in version 0.22, arrays of bytes/strings will be "
                "converted to decimal numbers if dtype='numeric'. "
                "It is recommended that you convert the array to "
                "a float dtype before using it in scikit-learn, "
                "for example by using "
                "your_array = your_array.astype(np.float64).",
                FutureWarning, stacklevel=2)

        # make sure we actually converted to numeric:
        if dtype_numeric and array.dtype.kind == "O":
            array = array.astype(np.float64)
        if not allow_nd and array.ndim >= 3:
            raise ValueError("Found array with dim %d. %s expected <= 2."
                             % (array.ndim, estimator_name))

        if force_all_finite:
            _daal_assert_all_finite(array,
                                    allow_nan=force_all_finite == 'allow-nan')

    if ensure_min_samples > 0:
        n_samples = _num_samples(array)
        if n_samples < ensure_min_samples:
            raise ValueError("Found array with %d sample(s) (shape=%s) while a"
                             " minimum of %d is required%s."
                             % (n_samples, array.shape, ensure_min_samples,
                                context))

    if ensure_min_features > 0 and array.ndim == 2:
        n_features = array.shape[1]
        if n_features < ensure_min_features:
            raise ValueError("Found array with %d feature(s) (shape=%s) while"
                             " a minimum of %d is required%s."
                             % (n_features, array.shape, ensure_min_features,
                                context))

    if copy and np.may_share_memory(array, array_orig):
        array = np.array(array, dtype=dtype, order=order)

    return array


def _daal_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,
                    estimator=None):
    """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.

        .. versionadded:: 0.20

    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.

        .. versionadded:: 0.20
           ``force_all_finite`` accepts the string ``'allow-nan'``.

        .. versionchanged:: 0.23
           Accepts `pd.NA` and converts it into `np.nan`

    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.

    estimator : str or estimator instance (default=None)
        If passed, include the name of the estimator in warning messages.

    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 = _daal_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,
        estimator=estimator
    )
    if multi_output:
        y = _daal_check_array(y, accept_sparse='csr', force_all_finite=True,
                              ensure_2d=False, dtype=None)
    else:
        y = column_or_1d(y, warn=True)
        _daal_assert_all_finite(y)
    if y_numeric and hasattr(y, 'dtype') and y.dtype.kind == 'O':
        y = y.astype(np.float64)

    check_consistent_length(X, y)

    return X, y
