# -*- coding: utf-8 -*-
"""
Natsort can sort strings with numbers in a natural order.
It provides the natsorted function to sort strings with
arbitrary numbers.

You can mix types with natsorted.  This can get around the new
'unorderable types' issue with Python 3. Natsort will recursively
descend into lists of lists so you can sort by the sublist contents.

See the README or the natsort homepage for more details.
"""
from __future__ import (
    print_function,
    division,
    unicode_literals,
    absolute_import
)

# Std lib. imports.
import re
from operator import itemgetter
from functools import partial
from warnings import warn

# Local imports.
from natsort.ns_enum import ns
from natsort.compat.py23 import u_format
from natsort.utils import (
    _natsort_key,
    _args_to_enum,
    _do_decoding,
)

# Make sure the doctest works for either python2 or python3
__doc__ = u_format(__doc__)


@u_format
def decoder(encoding):
    """
    Return a function that can be used to decode bytes to unicode.

    Parameters
    ----------
    encoding: str
        The codec to use for decoding. This must be a valid unicode codec.

    Returns
    -------
    decode_function:
        A function that takes a single argument and attempts to decode
        it using the supplied codec. Any `UnicodeErrors` are raised.
        If the argument was not of `bytes` type, it is simply returned
        as-is.

    See Also
    --------
    as_ascii
    as_utf8

    Examples
    --------

        >>> f = decoder('utf8')
        >>> f(b'bytes') == 'bytes'
        True
        >>> f(12345) == 12345
        True
        >>> natsorted([b'a10', b'a2'], key=decoder('utf8')) == [b'a2', b'a10']
        True
        >>> # On Python 3, without decoder this would return [b'a10', b'a2']
        >>> natsorted([b'a10', 'a2'], key=decoder('utf8')) == ['a2', b'a10']
        True
        >>> # On Python 3, without decoder this would raise a TypeError.

    """
    return partial(_do_decoding, encoding=encoding)


@u_format
def as_ascii(s):
    """
    Function to decode an input with the ASCII codec, or return as-is.

    Parameters
    ----------
    s:
        Any object.

    Returns
    -------
    output:
        If the input was of type `bytes`, the return value is a `str` decoded
        with the ASCII codec. Otherwise, the return value is identically the
        input.

    See Also
    --------
    decoder

    """
    return _do_decoding(s, 'ascii')


@u_format
def as_utf8(s):
    """
    Function to decode an input with the UTF-8 codec, or return as-is.

    Parameters
    ----------
    s:
        Any object.

    Returns
    -------
    output:
        If the input was of type `bytes`, the return value is a `str` decoded
        with the UTF-8 codec. Otherwise, the return value is identically the
        input.

    See Also
    --------
    decoder

    """
    return _do_decoding(s, 'utf-8')


def natsort_key(val, key=None, alg=0, **_kwargs):
    """Undocumented, kept for backwards-compatibility."""
    msg = "natsort_key is deprecated as of 3.4.0, please use natsort_keygen"
    warn(msg, DeprecationWarning)
    return _natsort_key(val, key, _args_to_enum(**_kwargs) | alg)


@u_format
def natsort_keygen(key=None, alg=0, **_kwargs):
    """\
    Generate a key to sort strings and numbers naturally.

    Generate a key to sort strings and numbers naturally,
    not lexicographically. This key is designed for use as the
    `key` argument to functions such as the `sorted` builtin.

    The user may customize the generated function with the
    arguments to `natsort_keygen`, including an optional
    `key` function which will be called before the `natsort_key`.

    Parameters
    ----------
    key : callable, optional
        A key used to manipulate the input value before parsing for
        numbers. It is **not** applied recursively.
        It should accept a single argument and return a single value.

    alg : ns enum, optional
        This option is used to control which algorithm `natsort`
        uses when sorting. For details into these options, please see
        the :class:`ns` class documentation. The default is `ns.INT`.

    Returns
    -------
    out : function
        A wrapped version of the `natsort_key` function that is
        suitable for passing as the `key` argument to functions
        such as `sorted`.

    See Also
    --------
    natsorted

    Examples
    --------
    `natsort_keygen` is a convenient way to create a custom key
    to sort lists in-place (for example). Calling with no objects
    will return a plain `natsort_key` instance::

        >>> a = ['num5.10', 'num-3', 'num5.3', 'num2']
        >>> a.sort(key=natsort_keygen(alg=ns.REAL))
        >>> a
        [{u}'num-3', {u}'num2', {u}'num5.10', {u}'num5.3']

    """
    return partial(_natsort_key, key=key, alg=_args_to_enum(**_kwargs) | alg)


@u_format
def natsorted(seq, key=None, reverse=False, alg=0, **_kwargs):
    """\
    Sorts a sequence naturally.

    Sorts a sequence naturally (alphabetically and numerically),
    not lexicographically. Returns a new copy of the sorted
    sequence as a list.

    Parameters
    ----------
    seq : iterable
        The sequence to sort.

    key : callable, optional
        A key used to determine how to sort each element of the sequence.
        It is **not** applied recursively.
        It should accept a single argument and return a single value.

    reverse : {{True, False}}, optional
        Return the list in reversed sorted order. The default is
        `False`.

    alg : ns enum, optional
        This option is used to control which algorithm `natsort`
        uses when sorting. For details into these options, please see
        the :class:`ns` class documentation. The default is `ns.INT`.

    Returns
    -------
    out: list
        The sorted sequence.

    See Also
    --------
    natsort_keygen : Generates the key that makes natural sorting possible.
    realsorted : A wrapper for ``natsorted(seq, alg=ns.REAL)``.
    humansorted : A wrapper for ``natsorted(seq, alg=ns.LOCALE)``.
    index_natsorted : Returns the sorted indexes from `natsorted`.

    Examples
    --------
    Use `natsorted` just like the builtin `sorted`::

        >>> a = ['num3', 'num5', 'num2']
        >>> natsorted(a)
        [{u}'num2', {u}'num3', {u}'num5']

    """
    alg = _args_to_enum(**_kwargs) | alg
    try:
        return sorted(seq, reverse=reverse, key=natsort_keygen(key, alg=alg))
    except TypeError as e:  # pragma: no cover
        # In the event of an unresolved "unorderable types" error
        # for string to number type comparisons (not str/bytes),
        # attempt to sort again, being careful to prevent this error.
        r = re.compile(r'(?:str|bytes)\(\) [<>] (?:str|bytes)\(\)')
        if 'unorderable types' in str(e) and not r.search(str(e)):
            return sorted(seq, reverse=reverse,
                          key=natsort_keygen(key,
                                             alg=alg | ns.TYPESAFE))
        else:
            # Re-raise if the problem was not "unorderable types"
            raise


@u_format
def versorted(seq, key=None, reverse=False, alg=0, **_kwargs):
    """\
    Identical to :func:`natsorted`.

    This function exists for backwards compatibility with `natsort`
    version < 4.0.0. Future development should use :func:`natsorted`.

    Please see the :func:`natsorted` documentation for use.

    See Also
    --------
    natsorted

    """
    return natsorted(seq, key, reverse, alg, **_kwargs)


@u_format
def humansorted(seq, key=None, reverse=False, alg=0):
    """\
    Convenience function to properly sort non-numeric characters.

    Convenience function to properly sort non-numeric characters
    in a locale-aware fashion (a.k.a "human sorting"). This is a
    wrapper around ``natsorted(seq, alg=ns.LOCALE)``.

    .. warning:: On BSD-based systems (like Mac OS X), the underlying
                 C library that Python's locale module uses is broken.
                 On these systems it is recommended that you install
                 `PyICU <https://pypi.python.org/pypi/PyICU>`_
                 if you wish to use ``humansorted``, especially if you need
                 to handle non-ASCII characters.  If you are on
                 one of systems and get unexpected results, please try
                 using `PyICU <https://pypi.python.org/pypi/PyICU>`_
                 before filing a bug report to `natsort`.

    Parameters
    ----------
    seq : iterable
        The sequence to sort.

    key : callable, optional
        A key used to determine how to sort each element of the sequence.
        It is **not** applied recursively.
        It should accept a single argument and return a single value.

    reverse : {{True, False}}, optional
        Return the list in reversed sorted order. The default is
        `False`.

    alg : ns enum, optional
        This option is used to control which algorithm `natsort`
        uses when sorting. For details into these options, please see
        the :class:`ns` class documentation. The default is `ns.LOCALE`.

    Returns
    -------
    out : list
        The sorted sequence.

    See Also
    --------
    index_humansorted : Returns the sorted indexes from `humansorted`.

    Notes
    -----
    You may find that if you do not explicitly set
    the locale your results may not be as you expect, although
    as of ``natsort`` version 4.0.0 the sorting algorithm has been
    updated to account for a buggy ``locale`` installation.
    In the below example 'en_US.UTF-8' is used, but you should use your
    locale::

        >>> import locale
        >>> # The 'str' call is only to get around a bug on Python 2.x
        >>> # where 'setlocale' does not expect unicode strings (ironic,
        >>> # right?)
        >>> locale.setlocale(locale.LC_ALL, str('en_US.UTF-8'))
        'en_US.UTF-8'

    It is preferred that you do this before importing `natsort`.
    If you use `PyICU <https://pypi.python.org/pypi/PyICU>`_ (see warning
    above) then you should not need to do explicitly set a locale.

    Examples
    --------
    Use `humansorted` just like the builtin `sorted`::

        >>> a = ['Apple', 'Banana', 'apple', 'banana']
        >>> natsorted(a)
        [{u}'Apple', {u}'Banana', {u}'apple', {u}'banana']
        >>> humansorted(a)
        [{u}'apple', {u}'Apple', {u}'banana', {u}'Banana']

    """
    return natsorted(seq, key, reverse, alg | ns.LOCALE)


@u_format
def realsorted(seq, key=None, reverse=False, alg=0):
    """\
    Convenience function to properly sort signed floats.

    Convenience function to properly sort signed floats within
    strings (i.e. "a-5.7"). This is a wrapper around
    ``natsorted(seq, alg=ns.REAL)``.

    The behavior of :func:`realsorted` for `natsort` version >= 4.0.0
    was the default behavior of :func:`natsorted` for `natsort`
    version < 4.0.0.

    Parameters
    ----------
    seq : iterable
        The sequence to sort.

    key : callable, optional
        A key used to determine how to sort each element of the sequence.
        It is **not** applied recursively.
        It should accept a single argument and return a single value.

    reverse : {{True, False}}, optional
        Return the list in reversed sorted order. The default is
        `False`.

    alg : ns enum, optional
        This option is used to control which algorithm `natsort`
        uses when sorting. For details into these options, please see
        the :class:`ns` class documentation. The default is `ns.REAL`.

    Returns
    -------
    out : list
        The sorted sequence.

    See Also
    --------
    index_realsorted : Returns the sorted indexes from `realsorted`.

    Examples
    --------
    Use `realsorted` just like the builtin `sorted`::

        >>> a = ['num5.10', 'num-3', 'num5.3', 'num2']
        >>> natsorted(a)
        [{u}'num2', {u}'num5.3', {u}'num5.10', {u}'num-3']
        >>> realsorted(a)
        [{u}'num-3', {u}'num2', {u}'num5.10', {u}'num5.3']

    """
    return natsorted(seq, key, reverse, alg | ns.REAL)


@u_format
def index_natsorted(seq, key=None, reverse=False, alg=0, **_kwargs):
    """\
    Return the list of the indexes used to sort the input sequence.

    Sorts a sequence naturally, but returns a list of sorted the
    indexes and not the sorted list. This list of indexes can be
    used to sort multiple lists by the sorted order of the given
    sequence.

    Parameters
    ----------
    seq : iterable
        The sequence to sort.

    key : callable, optional
        A key used to determine how to sort each element of the sequence.
        It is **not** applied recursively.
        It should accept a single argument and return a single value.

    reverse : {{True, False}}, optional
        Return the list in reversed sorted order. The default is
        `False`.

    alg : ns enum, optional
        This option is used to control which algorithm `natsort`
        uses when sorting. For details into these options, please see
        the :class:`ns` class documentation. The default is `ns.INT`.

    Returns
    -------
    out : tuple
        The ordered indexes of the sequence.

    See Also
    --------
    natsorted
    order_by_index

    Examples
    --------

    Use index_natsorted if you want to sort multiple lists by the
    sorted order of one list::

        >>> a = ['num3', 'num5', 'num2']
        >>> b = ['foo', 'bar', 'baz']
        >>> index = index_natsorted(a)
        >>> index
        [2, 0, 1]
        >>> # Sort both lists by the sort order of a
        >>> order_by_index(a, index)
        [{u}'num2', {u}'num3', {u}'num5']
        >>> order_by_index(b, index)
        [{u}'baz', {u}'foo', {u}'bar']

    """
    alg = _args_to_enum(**_kwargs) | alg
    if key is None:
        newkey = itemgetter(1)
    else:
        def newkey(x):
            return key(itemgetter(1)(x))
    # Pair the index and sequence together, then sort by element
    index_seq_pair = [[x, y] for x, y in enumerate(seq)]
    try:
        index_seq_pair.sort(reverse=reverse,
                            key=natsort_keygen(newkey, alg=alg))
    except TypeError as e:  # pragma: no cover
        # In the event of an unresolved "unorderable types" error
        # attempt to sort again, being careful to prevent this error.
        if 'unorderable types' in str(e):
            index_seq_pair.sort(reverse=reverse,
                                key=natsort_keygen(newkey,
                                                   alg=alg | ns.TYPESAFE))
        else:
            # Re-raise if the problem was not "unorderable types"
            raise
    return [x for x, _ in index_seq_pair]


@u_format
def index_versorted(seq, key=None, reverse=False, alg=0, **_kwargs):
    """\
    Identical to :func:`index_natsorted`.

    This function exists for backwards compatibility with
    ``index_natsort`` version < 4.0.0. Future development should use
    :func:`index_natsorted`.

    Please see the :func:`index_natsorted` documentation for use.

    See Also
    --------
    index_natsorted

    """
    return index_natsorted(seq, key, reverse, alg, **_kwargs)


@u_format
def index_humansorted(seq, key=None, reverse=False, alg=0):
    """\
    Return the list of the indexes used to sort the input sequence
    in a locale-aware manner.

    Sorts a sequence in a locale-aware manner, but returns a list
    of sorted the indexes and not the sorted list. This list of
    indexes can be used to sort multiple lists by the sorted order
    of the given sequence.

    This is a wrapper around ``index_natsorted(seq, alg=ns.LOCALE)``.
    Please see the ``humansorted`` documentation for caveats of
    using ``index_humansorted``.

    Parameters
    ----------
    seq: iterable
        The sequence to sort.

    key: callable, optional
        A key used to determine how to sort each element of the sequence.
        It is **not** applied recursively.
        It should accept a single argument and return a single value.

    reverse : {{True, False}}, optional
        Return the list in reversed sorted order. The default is
        `False`.

    alg : ns enum, optional
        This option is used to control which algorithm `natsort`
        uses when sorting. For details into these options, please see
        the :class:`ns` class documentation. The default is `ns.LOCALE`.

    Returns
    -------
    out : tuple
        The ordered indexes of the sequence.

    See Also
    --------
    humansorted
    order_by_index

    Notes
    -----
    You may find that if you do not explicitly set
    the locale your results may not be as you expect, although
    as of ``natsort`` version 4.0.0 the sorting algorithm has been
    updated to account for a buggy ``locale`` installation.
    In the below example 'en_US.UTF-8' is used, but you should use your
    locale::

        >>> import locale
        >>> # The 'str' call is only to get around a bug on Python 2.x
        >>> # where 'setlocale' does not expect unicode strings (ironic,
        >>> # right?)
        >>> locale.setlocale(locale.LC_ALL, str('en_US.UTF-8'))
        'en_US.UTF-8'

    It is preferred that you do this before importing `natsort`.
    If you use `PyICU <https://pypi.python.org/pypi/PyICU>`_ (see warning
    above) then you should not need to explicitly set a locale.

    Examples
    --------
    Use `index_humansorted` just like the builtin `sorted`::

        >>> a = ['Apple', 'Banana', 'apple', 'banana']
        >>> index_humansorted(a)
        [2, 0, 3, 1]

    """
    return index_natsorted(seq, key, reverse, alg | ns.LOCALE)


@u_format
def index_realsorted(seq, key=None, reverse=False, alg=0):
    """\
    Return the list of the indexes used to sort the input sequence
    in a locale-aware manner.

    Sorts a sequence in a locale-aware manner, but returns a list
    of sorted the indexes and not the sorted list. This list of
    indexes can be used to sort multiple lists by the sorted order
    of the given sequence.

    This is a wrapper around ``index_natsorted(seq, alg=ns.REAL)``.

    The behavior of :func:`index_realsorted` in `natsort` version >= 4.0.0
    was the default behavior of :func:`index_natsorted` for `natsort`
    version < 4.0.0.

    Parameters
    ----------
    seq: iterable
        The sequence to sort.

    key: callable, optional
        A key used to determine how to sort each element of the sequence.
        It is **not** applied recursively.
        It should accept a single argument and return a single value.

    reverse : {{True, False}}, optional
        Return the list in reversed sorted order. The default is
        `False`.

    alg : ns enum, optional
        This option is used to control which algorithm `natsort`
        uses when sorting. For details into these options, please see
        the :class:`ns` class documentation. The default is `ns.REAL`.

    Returns
    -------
    out : tuple
        The ordered indexes of the sequence.

    See Also
    --------
    realsorted
    order_by_index

    Examples
    --------
    Use `index_realsorted` just like the builtin `sorted`::

        >>> a = ['num5.10', 'num-3', 'num5.3', 'num2']
        >>> index_realsorted(a)
        [1, 3, 0, 2]

    """
    return index_natsorted(seq, key, reverse, alg | ns.REAL)


@u_format
def order_by_index(seq, index, iter=False):
    """\
    Order a given sequence by an index sequence.

    The output of `index_natsorted` and `index_versorted` is a
    sequence of integers (index) that correspond to how its input
    sequence **would** be sorted. The idea is that this index can
    be used to reorder multiple sequences by the sorted order of the
    first sequence. This function is a convenient wrapper to
    apply this ordering to a sequence.

    Parameters
    ----------
    seq : iterable
        The sequence to order.

    index : iterable
        The sequence that indicates how to order `seq`.
        It should be the same length as `seq` and consist
        of integers only.

    iter : {{True, False}}, optional
        If `True`, the ordered sequence is returned as a
        generator expression; otherwise it is returned as a
        list. The default is `False`.

    Returns
    -------
    out : {{list, generator}}
        The sequence ordered by `index`, as a `list` or as a
        generator expression (depending on the value of `iter`).

    See Also
    --------
    index_natsorted
    index_versorted
    index_humansorted
    index_realsorted

    Examples
    --------

    `order_by_index` is a convenience function that helps you apply
    the result of `index_natsorted` or `index_versorted`::

        >>> a = ['num3', 'num5', 'num2']
        >>> b = ['foo', 'bar', 'baz']
        >>> index = index_natsorted(a)
        >>> index
        [2, 0, 1]
        >>> # Sort both lists by the sort order of a
        >>> order_by_index(a, index)
        [{u}'num2', {u}'num3', {u}'num5']
        >>> order_by_index(b, index)
        [{u}'baz', {u}'foo', {u}'bar']

    """
    return (seq[i] for i in index) if iter else [seq[i] for i in index]
