Pagination: Add custom pure pagination subclasses

Add Paginator and Page subclasses that supports custom page
querystring keys.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

HISTORY.rst

@@ -2,6 +2,8 @@
 ================
 - Pagination: Fix page AJAX reload when clicking on pagination active page
   link.
+- Pagination: Add pure pagination subclass that supports custom page
+  querystring keys
 
 3.1.9 (2018-11-01)
 ==================

mayan/apps/common/paginator.py

@@ -0,0 +1,68 @@
+from __future__ import absolute_import, unicode_literals
+
+from pure_pagination import Paginator
+from pure_pagination.paginator import Page, PageRepresentation
+
+
+class PurePage(Page):
+    """
+    Subclass of pure_pagination Page class to support configurable page
+    querystring keys
+    """
+    def __init__(self, object_list, number, paginator, page_kwarg='page'):
+        self.object_list = object_list
+        self.page_kwarg = page_kwarg
+        self.paginator = paginator
+        if paginator.request:
+            # Reason: I just want to perform this operation once, and not once per page
+            self.base_queryset = self.paginator.request.GET.copy()
+            # self.base_queryset['page'] = 'page'
+            # self.base_queryset = self.base_queryset.urlencode().replace(
+            # '%', '%%').replace('page=page', 'page=%s')
+
+        self.number = PageRepresentation(number, self._other_page_querystring(number))
+
+    def _other_page_querystring(self, page_number):
+        """
+        Returns a query string for the given page, preserving any
+        GET parameters present.
+        """
+        if self.paginator.request:
+            self.base_queryset[self.page_kwarg] = page_number
+            return self.base_queryset.urlencode()
+
+        # raise Warning("You must supply Paginator() with the request object
+        # for a proper querystring.")
+        return '{}={}'.format(self.page_kwarg, page_number)
+
+
+class PurePaginator(Paginator):
+    """
+    Subclass of pure_pagination Paaginator class to support configurable page
+    querystring keys
+    """
+    page_class = PurePage
+
+    def __init__(self, object_list, per_page, allow_empty_first_page=True, orphans=0, page_kwarg='page', request=None):
+        self._num_pages = self._count = None
+        self.allow_empty_first_page = allow_empty_first_page
+        self.object_list = object_list
+        self.orphans = orphans
+        self.per_page = per_page
+        self.page_kwarg = page_kwarg
+        self.request = request
+
+    def page(self, number):
+        """
+        Returns a Page object for the given 1-based page number.
+        """
+        number = self.validate_number(number)
+        bottom = (number - 1) * self.per_page
+        top = bottom + self.per_page
+        if top + self.orphans >= self.count:
+            top = self.count
+
+        return self.page_class(
+            object_list=self.object_list[bottom:top], number=number,
+            paginator=self, page_kwarg=self.page_kwarg
+        )