AlphabeticalPaginationMixin.

shared/utils/views/alphabetical_pagination.py

@@ -0,0 +1,48 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db.models import F, Func, Value
+
+
+class AlphabeticalPaginationMixin(object):
+    alphabetical_pagination_field = 'name'
+
+    def get_alphabetical_pagination_field(self):
+        return self.alphabetical_pagination_field
+
+    def get_selected_letter(self):
+        return self.request.GET.get('letter', 'a')
+
+    def get_base_queryset(self):
+        """
+        Queryset before applying pagination filters.
+        """
+        qs = super(AlphabeticalPaginationMixin, self).get_queryset().exclude(
+            **{self.get_alphabetical_pagination_field(): ''}
+        )
+        return qs
+
+    def get_queryset(self):
+        qs = self.get_base_queryset()
+        # FIXME Select Umlauts (using downgrade and also downgrade sort_name field?)
+        # FIXME Select on TRIM/LEFT as in get_letter_choices
+        filter = {
+            "{}__istartswith".format(self.get_alphabetical_pagination_field()):
+            self.get_selected_letter()}
+        return qs.filter(**filter)
+
+    def get_letter_choices(self):
+        return self.get_base_queryset().annotate(name_lower=Func(
+            Func(
+                Func(
+                    F(self.get_alphabetical_pagination_field()), function='LOWER'),
+                function='TRIM'),
+            Value("1"), function='LEFT')).order_by(
+                'name_lower').distinct('name_lower').values_list('name_lower', flat=True)
+
+    def get_context_data(self, **kwargs):
+        context = super(AlphabeticalPaginationMixin, self).get_context_data(**kwargs)
+        context['selected_letter'] = self.get_selected_letter()
+        context['alphabet'] = self.get_letter_choices()
+        return context
+