from django.contrib.admin.util import NestedObjects

from django.utils.html import format_html

from django.utils.text import capfirst

class RelatedCollectorMixin(object):

    """

    Implements model mixin for easily obtainning related items of a model

    instance.

    The mixin can be used for obtaining all model objects that are directly or

    indirectly linked to the calling model object (through foreign key

    relationships).

    This mixin is very useful in delete views for warning the user about all of

    the related items that will be deleted if the calling item is deleted as

    well.

    """

    def get_dependant_objects(self):

        """

        Creates a list of model objects that depend (reference), both directly

        and indirectly, on calling model object. The calling model object is

        included as the first element of the list. This method call can be used

        in order to obtain a list of model objects that would get deleted in

        case the calling model object gets deleted.

        Returns:

          Nested list of model objects that depend (reference) calling model

          object.

        """

        collector = NestedObjects(using='default')

        collector.collect([self])

        return collector.nested()

    def get_dependant_objects_representation(self):

        """

        Creates a nested list of object representations that depend (reference),

        both directly and indirectly, calling model object. This method call can

        be used in order to obtain a list of string representations of model

        objects that would get deleted in case the calling model object gets

        deleted.

        The resulting nested list can be shown to the user for

        warning/notification purposes using the unordered_list template tag.

        Each non-list element will be a string of format:

        MODEL_NAME: OBJECT_REPRESENTATION

        If object has a callable get_absolute_url method, the object

        representation will be surrouned by HTML anchor tag (<a></a>) where

        target (href) is set to the value of get_absolute_url() method call.

        Returns:

          Nested list of representations of model objects that depend

          (reference) calling model object.

        """

        collector = NestedObjects(using='default')

        collector.collect([self])

        def formatter_callback(obj):

            """

            Creates model object representation in format:

            MODEL_NAME: OBJECT_REPRESENTATION

            If passed object has a callable get_absolute_url method, the

            instance representation will be surrouned by an HTML anchor

            (<a></a>) where target is set to value of the get_absolute_url()

            method call.

            Arguments:

              obj - Model object whose representation should be returned.

            Returns:

              String represenation of passed model object.

            """

            try:

                return format_html('<strong>{0}</strong>: <a href="{1}">{2}</a>', capfirst(obj._meta.verbose_name), obj.get_absolute_url(), str(obj))

            except AttributeError:

                return format_html('<strong>{0}</strong>: {1}', capfirst(obj._meta.verbose_name), str(obj))

        return collector.nested(formatter_callback)

class Project(RelatedCollectorMixin, models.Model):

    deletion_collect_models = ["Entity", "Interface"] 

class Location(RelatedCollectorMixin, models.Model):

class Entity(RelatedCollectorMixin, models.Model):

class Interface(RelatedCollectorMixin, models.Model):

class Communication(RelatedCollectorMixin, models.Model):

        The following entries will be removed:

        <ul>

          {{ related_items|unordered_list }}

        </ul>

        Are you sure you want to remove them?

from django.db.models.deletion import Collector

class RelatedItemsMixin(object):

    """

    View mixin that adds related items of a referenced model object to context

    data in form of a nested list, including the reference model object as the

    first element of a list.

    The context data will be passed using the "related_items" key.

    This data can be used in the template by passing it through the

    unordered_list template tag.

    The reference object is accessed via "object" property of calling view

    (i.e. self.object).

    For more details on implementation, see:

    RelatedCollectorMixin.get_dependant_objects_representation method

    """

    def get_context_data(self, **kwargs):

        """

        Adds the related items of a reference model object to context data.

        Returns:

          Context data.

        """

        # Set the context using the parent class.

        context = super(RelatedItemsMixin, self).get_context_data(**kwargs)

        # Add to context the nested list of string representations of related

        # items.

        context["related_items"] = self.object.get_dependant_objects_representation()

        return context

class ProjectDeleteView(RelatedItemsMixin, RedirectToNextMixin, SetHeadlineMixin, MultiplePermissionsRequiredMixin, DeleteView):

class LocationDeleteView(RelatedItemsMixin, RedirectToNextMixin, SetHeadlineMixin, MultiplePermissionsRequiredMixin, DeleteView):

class EntityDeleteView(RelatedItemsMixin, RedirectToNextMixin, SetHeadlineMixin, MultiplePermissionsRequiredMixin, DeleteView):

class InterfaceDeleteView(RelatedItemsMixin, RedirectToNextMixin, SetHeadlineMixin, MultiplePermissionsRequiredMixin, DeleteView):

class CommunicationDeleteView(RelatedItemsMixin, RedirectToNextMixin, SetHeadlineMixin, MultiplePermissionsRequiredMixin, DeleteView):