# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2012 Nebula, Inc.
#
#    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, widgets


class DynamicSelectWidget(widgets.Select):
    """
    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.update({self._data_add_url_attr: add_item_url})
        return super(DynamicSelectWidget, self).render(*args, **kwargs)

    def get_add_item_url(self):
        if callable(self.add_item_link):
            return self.add_item_link()
        try:
            return urlresolvers.reverse(self.add_item_link)
        except urlresolvers.NoReverseMatch:
            return self.add_item_link


class DynamicChoiceField(fields.ChoiceField):
    """
    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 = DynamicSelectWidget

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


class DynamicTypedChoiceField(DynamicChoiceField, fields.TypedChoiceField):
    """ Simple mix of ``DynamicChoiceField`` and ``TypedChoiceField``. """
    pass
