add smart pagination

to avoid excessively long page lists

src/teamvault/apps/secrets/templates/secrets/secret_list.html

@@ -2,6 +2,7 @@
 {% load humanize %}
 {% load i18n %}
 {% load staticfiles %}
+{% load smart_pagination %}
 {% block "title" %}{% trans "Browse" %}{% endblock %}
 {% block "css" %}
 <link href="{% static 'css/secrets.css' %}" rel="stylesheet">
@@ -61,7 +62,7 @@ <h1>
 				{% else %}
 				<li class="disabled"><a href="#"><i class="fa fa-chevron-left"></i></a></li>
 				{% endif %}
-				{% for page in paginator.page_range %}
+				{% for page in paginator.page_range|smart_pages:page_obj.number %}
 				{% if page_obj.number == page %}
 				<li class="active"><a href="#">{{ page }} <span class="sr-only">(current)</span></a></li>
 				{% else %}

src/teamvault/apps/secrets/templatetags/smart_pagination.py

@@ -0,0 +1,20 @@
+from django import template
+
+register = template.Library()
+
+
+@register.filter
+def smart_pages(all_pages, current_page):
+    all_pages = list(all_pages)
+    smart_pages = set([
+        1,
+        all_pages[-1],
+        current_page,
+        max(min(current_page // 2, all_pages[-1]), 1),
+        max(min(current_page + ((all_pages[-1] - current_page) // 2), all_pages[-1]), 1),
+        max(min(current_page + 1, all_pages[-1]), 1),
+        max(min(current_page + 2, all_pages[-1]), 1),
+        max(min(current_page - 1, all_pages[-1]), 1),
+        max(min(current_page - 2, all_pages[-1]), 1),
+    ])
+    return sorted(smart_pages)