import re
import unicodedata
import json

from django.core.exceptions import ImproperlyConfigured
from django.core.validators import validate_email, ValidationError
from django.core import urlresolvers
from django.contrib.sites.models import Site
from django.db.models import FieldDoesNotExist
from django.db.models.fields import (DateTimeField, DateField,
                                     EmailField, TimeField)
from django.utils import six, dateparse
from django.utils.datastructures import SortedDict
from django.core.serializers.json import DjangoJSONEncoder
try:
    from django.utils.encoding import force_text
except ImportError:
    from django.utils.encoding import force_unicode as force_text

try:
    import importlib
except:
    from django.utils import importlib


def _generate_unique_username_base(txts, regex=None):
    username = None
    regex = regex or '[^\w\s@+.-]'
    for txt in txts:
        if not txt:
            continue
        username = unicodedata.normalize('NFKD', force_text(txt))
        username = username.encode('ascii', 'ignore').decode('ascii')
        username = force_text(re.sub(regex, '', username).lower())
        # Django allows for '@' in usernames in order to accomodate for
        # project wanting to use e-mail for username. In allauth we don't
        # use this, we already have a proper place for putting e-mail
        # addresses (EmailAddress), so let's not use the full e-mail
        # address and only take the part leading up to the '@'.
        username = username.split('@')[0]
        username = username.strip()
        username = re.sub('\s+', '_', username)
        if username:
            break
    return username or 'user'


def get_username_max_length():
    from .account.app_settings import USER_MODEL_USERNAME_FIELD
    if USER_MODEL_USERNAME_FIELD is not None:
        User = get_user_model()
        max_length = User._meta.get_field(USER_MODEL_USERNAME_FIELD).max_length
    else:
        max_length = 0
    return max_length


def generate_unique_username(txts, regex=None):
    from .account.app_settings import USER_MODEL_USERNAME_FIELD
    username = _generate_unique_username_base(txts, regex)
    User = get_user_model()
    max_length = get_username_max_length()
    i = 0
    while True:
        try:
            if i:
                pfx = str(i + 1)
            else:
                pfx = ''
            ret = username[0:max_length - len(pfx)] + pfx
            query = {USER_MODEL_USERNAME_FIELD + '__iexact': ret}
            User.objects.get(**query)
            i += 1
        except User.MultipleObjectsReturned:
            i += 1
        except User.DoesNotExist:
            return ret


def valid_email_or_none(email):
    ret = None
    try:
        if email:
            validate_email(email)
            if len(email) <= EmailField().max_length:
                ret = email
    except ValidationError:
        pass
    return ret


def email_address_exists(email, exclude_user=None):
    from .account import app_settings as account_settings
    from .account.models import EmailAddress

    emailaddresses = EmailAddress.objects
    if exclude_user:
        emailaddresses = emailaddresses.exclude(user=exclude_user)
    ret = emailaddresses.filter(email__iexact=email).exists()
    if not ret:
        email_field = account_settings.USER_MODEL_EMAIL_FIELD
        if email_field:
            users = get_user_model().objects
            if exclude_user:
                users = users.exclude(pk=exclude_user.pk)
            ret = users.filter(**{email_field+'__iexact': email}).exists()
    return ret


def import_attribute(path):
    assert isinstance(path, six.string_types)
    pkg, attr = path.rsplit('.', 1)
    ret = getattr(importlib.import_module(pkg), attr)
    return ret


def import_callable(path_or_callable):
    if not hasattr(path_or_callable, '__call__'):
        ret = import_attribute(path_or_callable)
    else:
        ret = path_or_callable
    return ret

try:
    from django.contrib.auth import get_user_model
except ImportError:
    # To keep compatibility with Django 1.4
    def get_user_model():
        from . import app_settings
        from django.db.models import get_model

        try:
            app_label, model_name = app_settings.USER_MODEL.split('.')
        except ValueError:
            raise ImproperlyConfigured("AUTH_USER_MODEL must be of the"
                                       " form 'app_label.model_name'")
        user_model = get_model(app_label, model_name)
        if user_model is None:
            raise ImproperlyConfigured("AUTH_USER_MODEL refers to model"
                                       " '%s' that has not been installed"
                                       % app_settings.USER_MODEL)
        return user_model


def get_current_site(request=None):
    """Wrapper around ``Site.objects.get_current`` to handle ``Site`` lookups
    by request in Django >= 1.8.

    :param request: optional request object
    :type request: :class:`django.http.HttpRequest`
    """
    # >= django 1.8
    if request and hasattr(Site.objects, '_get_site_by_request'):
        site = Site.objects.get_current(request=request)
    else:
        site = Site.objects.get_current()

    return site


def resolve_url(to):
    """
    Subset of django.shortcuts.resolve_url (that one is 1.5+)
    """
    try:
        return urlresolvers.reverse(to)
    except urlresolvers.NoReverseMatch:
        # If this doesn't "feel" like a URL, re-raise.
        if '/' not in to and '.' not in to:
            raise
    # Finally, fall back and assume it's a URL
    return to


def serialize_instance(instance):
    """
    Since Django 1.6 items added to the session are no longer pickled,
    but JSON encoded by default. We are storing partially complete models
    in the session (user, account, token, ...). We cannot use standard
    Django serialization, as these are models are not "complete" yet.
    Serialization will start complaining about missing relations et al.
    """
    ret = dict([(k, v)
                for k, v in instance.__dict__.items()
                if not (k.startswith('_') or callable(v))])
    return json.loads(json.dumps(ret, cls=DjangoJSONEncoder))


def deserialize_instance(model, data):
    ret = model()
    for k, v in data.items():
        if v is not None:
            try:
                f = model._meta.get_field(k)
                if isinstance(f, DateTimeField):
                    v = dateparse.parse_datetime(v)
                elif isinstance(f, TimeField):
                    v = dateparse.parse_time(v)
                elif isinstance(f, DateField):
                    v = dateparse.parse_date(v)
            except FieldDoesNotExist:
                pass
        setattr(ret, k, v)
    return ret


def set_form_field_order(form, fields_order):
    if isinstance(form.fields, SortedDict):
        form.fields.keyOrder = fields_order
    else:
        # Python 2.7+
        from collections import OrderedDict
        assert isinstance(form.fields, OrderedDict)
        form.fields = OrderedDict((f, form.fields[f])
                                  for f in fields_order)


def build_absolute_uri(request, location, protocol=None):
    uri = request.build_absolute_uri(location)
    if protocol:
        uri = protocol + ':' + uri.partition(':')[2]
    return uri


def get_form_class(forms, form_id, default_form):
    form_class = forms.get(form_id, default_form)
    if isinstance(form_class, six.string_types):
        form_class = import_attribute(form_class)
    return form_class


def get_request_param(request, param, default=None):
    return request.POST.get(param) or request.GET.get(param, default)
