# 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.

from django.core import urlresolvers
from django.forms import fields
from django.forms import widgets


class DynamicMultiSelectWidget(widgets.SelectMultiple):

    """A subclass of the ``Select`` widget which renders extra attributes for
    use in callbacks to handle dynamic changes to the available choices.
    """
    _data_add_url_attr = "data-add-item-url"

    def render(self, *args, **kwargs):
        add_item_url = self.get_add_item_url()
        if add_item_url is not None:
            self.attrs[self._data_add_url_attr] = add_item_url
        return super(DynamicMultiSelectWidget, self).render(*args, **kwargs)

    def get_add_item_url(self):
        if callable(self.add_item_link):
            return self.add_item_link()
        try:
            if self.add_item_link_args:
                return urlresolvers.reverse(self.add_item_link,
                                            args=self.add_item_link_args)
            else:
                return urlresolvers.reverse(self.add_item_link)
        except urlresolvers.NoReverseMatch:
            return self.add_item_link


class DynamicMultiChoiceField(fields.MultipleChoiceField):

    """A subclass of ``ChoiceField`` with additional properties that make
    dynamically updating its elements easier.

    Notably, the field declaration takes an extra argument, ``add_item_link``
    which may be a string or callable defining the URL that should be used
    for the "add" link associated with the field.
    """
    widget = DynamicMultiSelectWidget

    def __init__(self,
                 add_item_link=None,
                 add_item_link_args=None,
                 *args,
                 **kwargs):
        super(DynamicMultiChoiceField, self).__init__(*args, **kwargs)
        self.widget.add_item_link = add_item_link
        self.widget.add_item_link_args = add_item_link_args


class CustomMultiChoiceField(DynamicMultiChoiceField):
    def validate(self, *args, **kwargs):
        return True
