# Copyright 2011 OpenStack Foundation.
# All Rights Reserved.
#
#    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.

"""
System-level utilities and helper functions.
"""

import math
import re
import sys
import unicodedata

import six

from glance.openstack.common.gettextutils import _


UNIT_PREFIX_EXPONENT = {
    'k': 1,
    'K': 1,
    'Ki': 1,
    'M': 2,
    'Mi': 2,
    'G': 3,
    'Gi': 3,
    'T': 4,
    'Ti': 4,
}
UNIT_SYSTEM_INFO = {
    'IEC': (1024, re.compile(r'(^[-+]?\d*\.?\d+)([KMGT]i?)?(b|bit|B)$')),
    'SI': (1000, re.compile(r'(^[-+]?\d*\.?\d+)([kMGT])?(b|bit|B)$')),
}

TRUE_STRINGS = ('1', 't', 'true', 'on', 'y', 'yes')
FALSE_STRINGS = ('0', 'f', 'false', 'off', 'n', 'no')

SLUGIFY_STRIP_RE = re.compile(r"[^\w\s-]")
SLUGIFY_HYPHENATE_RE = re.compile(r"[-\s]+")


def int_from_bool_as_string(subject):
    """Interpret a string as a boolean and return either 1 or 0.

    Any string value in:

        ('True', 'true', 'On', 'on', '1')

    is interpreted as a boolean True.

    Useful for JSON-decoded stuff and config file parsing
    """
    return bool_from_string(subject) and 1 or 0


def bool_from_string(subject, strict=False, default=False):
    """Interpret a string as a boolean.

    A case-insensitive match is performed such that strings matching 't',
    'true', 'on', 'y', 'yes', or '1' are considered True and, when
    `strict=False`, anything else returns the value specified by 'default'.

    Useful for JSON-decoded stuff and config file parsing.

    If `strict=True`, unrecognized values, including None, will raise a
    ValueError which is useful when parsing values passed in from an API call.
    Strings yielding False are 'f', 'false', 'off', 'n', 'no', or '0'.
    """
    if not isinstance(subject, six.string_types):
        subject = six.text_type(subject)

    lowered = subject.strip().lower()

    if lowered in TRUE_STRINGS:
        return True
    elif lowered in FALSE_STRINGS:
        return False
    elif strict:
        acceptable = ', '.join(
            "'%s'" % s for s in sorted(TRUE_STRINGS + FALSE_STRINGS))
        msg = _("Unrecognized value '%(val)s', acceptable values are:"
                " %(acceptable)s") % {'val': subject,
                                      'acceptable': acceptable}
        raise ValueError(msg)
    else:
        return default


def safe_decode(text, incoming=None, errors='strict'):
    """Decodes incoming text/bytes string using `incoming` if they're not
       already unicode.

    :param incoming: Text's current encoding
    :param errors: Errors handling policy. See here for valid
        values http://docs.python.org/2/library/codecs.html
    :returns: text or a unicode `incoming` encoded
                representation of it.
    :raises TypeError: If text is not an instance of str
    """
    if not isinstance(text, (six.string_types, six.binary_type)):
        raise TypeError("%s can't be decoded" % type(text))

    if isinstance(text, six.text_type):
        return text

    if not incoming:
        incoming = (sys.stdin.encoding or
                    sys.getdefaultencoding())

    try:
        return text.decode(incoming, errors)
    except UnicodeDecodeError:
        # Note(flaper87) If we get here, it means that
        # sys.stdin.encoding / sys.getdefaultencoding
        # didn't return a suitable encoding to decode
        # text. This happens mostly when global LANG
        # var is not set correctly and there's no
        # default encoding. In this case, most likely
        # python will use ASCII or ANSI encoders as
        # default encodings but they won't be capable
        # of decoding non-ASCII characters.
        #
        # Also, UTF-8 is being used since it's an ASCII
        # extension.
        return text.decode('utf-8', errors)


def safe_encode(text, incoming=None,
                encoding='utf-8', errors='strict'):
    """Encodes incoming text/bytes string using `encoding`.

    If incoming is not specified, text is expected to be encoded with
    current python's default encoding. (`sys.getdefaultencoding`)

    :param incoming: Text's current encoding
    :param encoding: Expected encoding for text (Default UTF-8)
    :param errors: Errors handling policy. See here for valid
        values http://docs.python.org/2/library/codecs.html
    :returns: text or a bytestring `encoding` encoded
                representation of it.
    :raises TypeError: If text is not an instance of str
    """
    if not isinstance(text, (six.string_types, six.binary_type)):
        raise TypeError("%s can't be encoded" % type(text))

    if not incoming:
        incoming = (sys.stdin.encoding or
                    sys.getdefaultencoding())

    if isinstance(text, six.text_type):
        return text.encode(encoding, errors)
    elif text and encoding != incoming:
        # Decode text before encoding it with `encoding`
        text = safe_decode(text, incoming, errors)
        return text.encode(encoding, errors)
    else:
        return text


def string_to_bytes(text, unit_system='IEC', return_int=False):
    """Converts a string into an float representation of bytes.

    The units supported for IEC ::

        Kb(it), Kib(it), Mb(it), Mib(it), Gb(it), Gib(it), Tb(it), Tib(it)
        KB, KiB, MB, MiB, GB, GiB, TB, TiB

    The units supported for SI ::

        kb(it), Mb(it), Gb(it), Tb(it)
        kB, MB, GB, TB

    Note that the SI unit system does not support capital letter 'K'

    :param text: String input for bytes size conversion.
    :param unit_system: Unit system for byte size conversion.
    :param return_int: If True, returns integer representation of text
                       in bytes. (default: decimal)
    :returns: Numerical representation of text in bytes.
    :raises ValueError: If text has an invalid value.

    """
    try:
        base, reg_ex = UNIT_SYSTEM_INFO[unit_system]
    except KeyError:
        msg = _('Invalid unit system: "%s"') % unit_system
        raise ValueError(msg)
    match = reg_ex.match(text)
    if match:
        magnitude = float(match.group(1))
        unit_prefix = match.group(2)
        if match.group(3) in ['b', 'bit']:
            magnitude /= 8
    else:
        msg = _('Invalid string format: %s') % text
        raise ValueError(msg)
    if not unit_prefix:
        res = magnitude
    else:
        res = magnitude * pow(base, UNIT_PREFIX_EXPONENT[unit_prefix])
    if return_int:
        return int(math.ceil(res))
    return res


def to_slug(value, incoming=None, errors="strict"):
    """Normalize string.

    Convert to lowercase, remove non-word characters, and convert spaces
    to hyphens.

    Inspired by Django's `slugify` filter.

    :param value: Text to slugify
    :param incoming: Text's current encoding
    :param errors: Errors handling policy. See here for valid
        values http://docs.python.org/2/library/codecs.html
    :returns: slugified unicode representation of `value`
    :raises TypeError: If text is not an instance of str
    """
    value = safe_decode(value, incoming, errors)
    # NOTE(aababilov): no need to use safe_(encode|decode) here:
    # encodings are always "ascii", error handling is always "ignore"
    # and types are always known (first: unicode; second: str)
    value = unicodedata.normalize("NFKD", value).encode(
        "ascii", "ignore").decode("ascii")
    value = SLUGIFY_STRIP_RE.sub("", value).strip().lower()
    return SLUGIFY_HYPHENATE_RE.sub("-", value)
