import re
import sys
import unicodedata
import collections
import six

import social

from social.p3 import urlparse, urlunparse, urlencode, \
                      parse_qs as battery_parse_qs


SETTING_PREFIX = 'SOCIAL_AUTH'


def import_module(name):
    __import__(name)
    return sys.modules[name]


def module_member(name):
    mod, member = name.rsplit('.', 1)
    module = import_module(mod)
    return getattr(module, member)


def user_agent():
    """Builds a simple User-Agent string to send in requests"""
    return 'python-social-auth-' + social.__version__


def url_add_parameters(url, params):
    """Adds parameters to URL, parameter will be repeated if already present"""
    if params:
        fragments = list(urlparse(url))
        value = parse_qs(fragments[4])
        value.update(params)
        fragments[4] = urlencode(value)
        url = urlunparse(fragments)
    return url


def to_setting_name(*names):
    return '_'.join([name.upper().replace('-', '_') for name in names if name])


def setting_name(*names):
    return to_setting_name(*((SETTING_PREFIX,) + names))


def sanitize_redirect(host, redirect_to):
    """
    Given the hostname and an untrusted URL to redirect to,
    this method tests it to make sure it isn't garbage/harmful
    and returns it, else returns None, similar as how's it done
    on django.contrib.auth.views.
    """
    if redirect_to:
        try:
            # Don't redirect to a different host
            netloc = urlparse(redirect_to)[1] or host
        except (TypeError, AttributeError):
            pass
        else:
            if netloc == host:
                return redirect_to


def user_is_authenticated(user):
    if user and hasattr(user, 'is_authenticated'):
        if isinstance(user.is_authenticated, collections.Callable):
            authenticated = user.is_authenticated()
        else:
            authenticated = user.is_authenticated
    elif user:
        authenticated = True
    else:
        authenticated = False
    return authenticated


def user_is_active(user):
    if user and hasattr(user, 'is_active'):
        if isinstance(user.is_active, collections.Callable):
            is_active = user.is_active()
        else:
            is_active = user.is_active
    elif user:
        is_active = True
    else:
        is_active = False
    return is_active


# This slugify version was borrowed from django revision a61dbd6
def slugify(value):
    """Converts to lowercase, removes non-word characters (alphanumerics
    and underscores) and converts spaces to hyphens. Also strips leading
    and trailing whitespace."""
    value = unicodedata.normalize('NFKD', value) \
                       .encode('ascii', 'ignore') \
                       .decode('ascii')
    value = re.sub('[^\w\s-]', '', value).strip().lower()
    return re.sub('[-\s]+', '-', value)


def first(func, items):
    """Return the first item in the list for what func returns True"""
    for item in items:
        if func(item):
            return item


def parse_qs(value):
    """Like urlparse.parse_qs but transform list values to single items"""
    return drop_lists(battery_parse_qs(value))


def drop_lists(value):
    out = {}
    for key, val in value.items():
        val = val[0]
        if isinstance(key, six.binary_type):
            key = six.text_type(key, 'utf-8')
        if isinstance(val, six.binary_type):
            val = six.text_type(val, 'utf-8')
        out[key] = val
    return out


def partial_pipeline_data(backend, user=None, *args, **kwargs):
    partial = backend.strategy.session_get('partial_pipeline', None)
    if partial:
        idx, backend_name, xargs, xkwargs = \
            backend.strategy.partial_from_session(partial)
        if backend_name == backend.name:
            kwargs.setdefault('pipeline_index', idx)
            if user:  # don't update user if it's None
                kwargs.setdefault('user', user)
            kwargs.setdefault('request', backend.strategy.request_data())
            xkwargs.update(kwargs)
            return xargs, xkwargs
        else:
            backend.strategy.clean_partial_pipeline()


def build_absolute_uri(host_url, path=None):
    """Build absolute URI with given (optional) path"""
    path = path or ''
    if path.startswith('http://') or path.startswith('https://'):
        return path
    if host_url.endswith('/') and path.startswith('/'):
        path = path[1:]
    return host_url + path


def constant_time_compare(val1, val2):
    """
    Returns True if the two strings are equal, False otherwise.
    The time taken is independent of the number of characters that match.
    This code was borrowed from Django 1.5.4-final
    """
    if len(val1) != len(val2):
        return False
    result = 0
    if six.PY3 and isinstance(val1, bytes) and isinstance(val2, bytes):
        for x, y in zip(val1, val2):
            result |= x ^ y
    else:
        for x, y in zip(val1, val2):
            result |= ord(x) ^ ord(y)
    return result == 0


def is_url(value):
    return value and \
           (value.startswith('http://') or
            value.startswith('https://') or
            value.startswith('/'))


def setting_url(backend, *names):
    for name in names:
        if is_url(name):
            return name
        else:
            value = backend.setting(name)
            if is_url(value):
                return value