add generic pagination template (#14939)

README.txt

@@ -80,3 +80,8 @@ http://www.gnome.org/.
 gadjo/static/css/header-03.jpeg is copied from let's encrypt website, licensed
 under Mozilla Public License Version 2.0, see their repository at
 https://github.com/letsencrypt/website.git.
+
+The querystring template tag is originally from django-tables2, copyright (c)
+2011, Bradley Ayers, copyright (c) 2008, Michael Elsdörfer, published under
+the MIT license.
+https://raw.githubusercontent.com/jieter/django-tables2/master/LICENSE

gadjo/static/css/gadjo.scss

@@ -539,13 +539,13 @@ p.paginator span {
 }
 
 p.paginator span.this-page {
-	background: #0066CC;
-	border-color: #0066CC;
+	background: #5B616B;
+	border-color: #5B616B;
 	color: white;
 }
 
 p.paginator span.this-page + a {
-	border-left-color: #0066CC;
+	border-left-color: #5B616B;
 }
 
 p.paginator a:hover {

gadjo/templates/gadjo/pagination.html

@@ -0,0 +1,41 @@
+{% load gadjo %}
+{% comment %}
+Pagination bar
+
+Expected context variables:
+ - request: django request object
+ - page_obj: Paginator page object
+ - page_key (optional): name of page parameter (default: page)
+ - anchor (optional): anchor to use in links
+
+{% endcomment %}
+{% if page_obj.paginator.num_pages > 1 %}
+{% with page_key=page_key|default:"page" %}
+{% spaceless %}
+<p class="paginator">
+  {% if page_obj.number > 1 %}
+    {% if page_obj.previous_page_number != 1 %}
+      <a href="{% querystring page_key=1 %}{{ anchor }}">1</a>
+      …
+    {% endif %}
+  {% endif %}
+
+  {% if page_obj.has_previous %}
+    <a href="{% querystring page_key=page_obj.previous_page_number %}{{ anchor }}">{{ page_obj.previous_page_number }}</a>
+  {% endif %}
+
+  <span class="this-page">{{ page_obj.number }}</span>
+
+  {% if page_obj.has_next %}
+    <a href="{% querystring page_key=page_obj.next_page_number %}{{ anchor }}">{{ page_obj.next_page_number }}</a>
+  {% endif %}
+  {% if page_obj.number != page_obj.paginator.num_pages %}
+    {% if page_obj.next_page_number != page_obj.paginator.num_pages %}
+      …
+      <a href="{% querystring page_key=page_obj.paginator.num_pages %}{{ anchor }}">{{ page_obj.paginator.num_pages }}</a>
+    {% endif %}
+  {% endif %}
+</p>
+{% endspaceless %}
+{% endwith %}
+{% endif %}

gadjo/templatetags/gadjo.py

@@ -1,7 +1,13 @@
+from collections import OrderedDict
+import re
+
 from xstatic.main import XStatic
 
 from django import template
 from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+from django.utils.html import escape
+from django.utils.http import urlencode
 
 register = template.Library()
 
@@ -34,3 +40,71 @@ def xstatic(modname, filename):
                     return base_url.get(filename)
 
     return settings.STATIC_URL + 'xstatic/' + filename
+
+
+# {% querystring %} bits originally from django-tables2.
+kwarg_re = re.compile(r"(?:(.+)=)?(.+)")
+
+def token_kwargs(bits, parser):
+    """
+    Based on Django's `~django.template.defaulttags.token_kwargs`, but with a
+    few changes:
+
+    - No legacy mode.
+    - Both keys and values are compiled as a filter
+    """
+    if not bits:
+        return {}
+    kwargs = OrderedDict()
+    while bits:
+        match = kwarg_re.match(bits[0])
+        if not match or not match.group(1):
+            return kwargs
+        key, value = match.groups()
+        del bits[:1]
+        kwargs[parser.compile_filter(key)] = parser.compile_filter(value)
+    return kwargs
+
+class QuerystringNode(template.Node):
+    def __init__(self, updates, removals):
+        super(QuerystringNode, self).__init__()
+        self.updates = updates
+        self.removals = removals
+
+    def render(self, context):
+        if not 'request' in context:
+            raise ImproperlyConfigured('Missing django.core.context_processors.request')
+        params = dict(context['request'].GET)
+        for key, value in self.updates.items():
+            key = key.resolve(context)
+            value = value.resolve(context)
+            if key not in ("", None):
+                params[key] = value
+        for removal in self.removals:
+            params.pop(removal.resolve(context), None)
+        return escape("?" + urlencode(params, doseq=True))
+
+@register.tag
+def querystring(parser, token):
+    """
+    Creates a URL (containing only the querystring [including "?"]) derived
+    from the current URL's querystring, by updating it with the provided
+    keyword arguments.
+
+    Example (imagine URL is ``/abc/?gender=male&name=Brad``)::
+
+        {% querystring "name"="Ayers" "age"=20 %}
+        ?name=Ayers&gender=male&age=20
+        {% querystring "name"="Ayers" without "gender" %}
+        ?name=Ayers
+
+    """
+    bits = token.split_contents()
+    tag = bits.pop(0)
+    updates = token_kwargs(bits, parser)
+    # ``bits`` should now be empty of a=b pairs, it should either be empty, or
+    # have ``without`` arguments.
+    if bits and bits.pop(0) != "without":
+        raise TemplateSyntaxError("Malformed arguments to '%s'" % tag)
+    removals = [parser.compile_filter(bit) for bit in bits]
+    return QuerystringNode(updates, removals)