Improve pagination for recipe list

Use a Django snippet to make pagination display a bit nicer (compressed
form instead of showing all page numbers). In order to interact properly
with GET requests, an additional snippet was required to add parameters
to the URL (why doesn't Django provide this out of the box?).

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

layerindex/index.html

@@ -99,27 +99,8 @@
     </div>
 
     {% if is_paginated %}
-        <div class="pagination pagination-centered">
+        {% load pagination %}
-            <ul>
+        {% pagination page_obj %}
-            {% if page_obj.has_previous %}
-                <li><a href="?page={{ page_obj.previous_page_number }}">prev</a></li>
-            {% else %}
-                <li class="disabled"><a href="#">prev</a></li>
-            {% endif %}
-            {% for i in paginator.page_range %}
-                {% if i == page_obj.number %}
-                <li class="active"><a href="#">{{ page_obj.number }}</a></li>
-                {% else %}
-                <li><a href="?page={{i}}">{{i}}</a></li>
-                {% endif %}
-            {% endfor %}
-            {% if page_obj.has_next %}
-                <li><a href="?page={{ page_obj.next_page_number }}">next</a></li>
-            {% else %}
-                <li class="disabled"><a href="#">next</a></li>
-            {% endif %}
-            </ul>
-        </div>
     {% endif %}
 {% else %}
     <p>No matching layers in database.</p>

layerindex/recipes.html

@@ -62,27 +62,8 @@
                 </table>
 
     {% if is_paginated %}
-        <div class="pagination pagination-centered">
+        {% load pagination %}
-            <ul>
+        {% pagination page_obj %}
-            {% if page_obj.has_previous %}
-                <li><a href="?page={{ page_obj.previous_page_number }}">prev</a></li>
-            {% else %}
-                <li class="disabled"><a href="#">prev</a></li>
-            {% endif %}
-            {% for i in paginator.page_range %}
-                {% if i == page_obj.number %}
-                <li class="active"><a href="#">{{ page_obj.number }}</a></li>
-                {% else %}
-                <li><a href="?page={{i}}">{{i}}</a></li>
-                {% endif %}
-            {% endfor %}
-            {% if page_obj.has_next %}
-                <li><a href="?page={{ page_obj.next_page_number }}">next</a></li>
-            {% else %}
-                <li class="disabled"><a href="#">next</a></li>
-            {% endif %}
-            </ul>
-        </div>
     {% endif %}
 {% else %}
     {% if search_keyword %}

layerindex/templatetags/addurlparameter.py

@@ -0,0 +1,29 @@
+# Borrowed from http://djangosnippets.org/snippets/361/
+# Original author: johan de taeye
+# With modifications from Ludwik Trammer
+#
+# Adds GET parameters to the current URL
+
+from django.template import Library, Node, resolve_variable, TemplateSyntaxError, Variable
+
+register = Library()
+
+class AddParameter(Node):
+    def __init__(self, varname, value):
+        self.varname = Variable(varname)
+        self.value = Variable(value)
+
+    def render(self, context):
+        req = Variable('request').resolve(context)
+        params = req.GET.copy()
+        params[self.varname.resolve(context)] = self.value.resolve(context)
+        return '%s?%s' % (req.path, params.urlencode())
+
+def addurlparameter(parser, token):
+    from re import split
+    bits = split(r'\s+', token.contents, 2)
+    if len(bits) < 2:
+        raise TemplateSyntaxError, "'%s' tag requires two arguments" % bits[0]
+    return AddParameter(bits[1],bits[2])
+
+register.tag('addurlparameter', addurlparameter)

layerindex/templatetags/pagination.py

@@ -0,0 +1,52 @@
+# Borrowed from http://djangosnippets.org/snippets/2199/
+#
+# Digg-like page numbering using inclusion tag
+
+from django import template
+
+register = template.Library()
+
+@register.inclusion_tag('pagination.html', takes_context=True)
+def pagination(context, page, begin_pages=2, end_pages=2, before_current_pages=4, after_current_pages=4):
+    # Digg-like pages
+    before = max(page.number - before_current_pages - 1, 0)
+    after = page.number + after_current_pages
+
+    begin = page.paginator.page_range[:begin_pages]
+    middle = page.paginator.page_range[before:after]
+    end = page.paginator.page_range[-end_pages:]
+    last_page_number = end[-1]
+
+    def collides(firstlist, secondlist):
+        """ Returns true if lists collides (have same entries)
+
+        >>> collides([1,2,3,4],[3,4,5,6,7])
+        True
+        >>> collides([1,2,3,4],[5,6,7])
+        False
+        """
+        return any(item in secondlist for item in firstlist)
+
+    # If middle and end has same entries, then end is what we want
+    if collides(middle, end):
+        end = range(max(page.number-before_current_pages, 1), last_page_number+1)
+
+        middle = []
+
+    # If begin and middle ranges has same entries, then begin is what we want
+    if collides(begin, middle):
+        begin = range(1, min(page.number + after_current_pages, last_page_number)+1)
+
+        middle = []
+
+    # If begin and end has same entries then begin is what we want
+    if collides(begin, end):
+        begin = range(1, last_page_number+1)
+        end = []
+
+    context.update({'page' : page,
+                    'begin' : begin,
+                    'middle' : middle,
+                    'end' : end})
+
+    return context

pagination.html

@@ -0,0 +1,57 @@
+{% comment %}
+
+  layerindex-web - pagination template
+
+  Copyright (C) 2013 Intel Corporation
+  Licensed under the MIT license, see COPYING.MIT for details
+
+{% endcomment %}
+
+{% load addurlparameter %}
+
+<div class="pagination pagination-centered">
+    <ul>
+    {% if page.has_previous %}
+        <li><a href="{% addurlparameter 'page' page.previous_page_number %}">prev</a></li>
+    {% else %}
+        <li class="disabled"><span>prev</span></li>
+    {% endif %}
+
+
+    {% for pnum in begin %}
+        {% if pnum == page.number %}
+        <li class="active"><a href="#">{{ page.number }}</a></li>
+        {% else %}
+        <li><a href="{% addurlparameter 'page' pnum %}">{{ pnum }}</a></li>
+        {% endif %}
+    {% endfor %}
+
+    {% if middle %}
+        <li class="disabled"><span>...</span></li>
+        {% for pnum in middle %}
+            {% if pnum == page.number %}
+            <li class="active"><span>{{ page.number }}</span></li>
+            {% else %}
+            <li><a href="{% addurlparameter 'page' pnum %}">{{ pnum }}</a></li>
+            {% endif %}
+        {% endfor %}
+    {% endif %}
+
+    {% if end %}
+        <li class="disabled"><span>...</span></li>
+        {% for pnum in end %}
+            {% if pnum == page.number %}
+            <li class="active"><span>{{ page.number }}</span></li>
+            {% else %}
+            <li><a href="{% addurlparameter 'page' pnum %}">{{ pnum }}</a></li>
+            {% endif %}
+        {% endfor %}
+    {% endif %}
+
+    {% if page.has_next %}
+        <li><a href="{% addurlparameter 'page' page.next_page_number %}">next</a></li>
+    {% else %}
+        <li class="disabled"><span>next</span></li>
+    {% endif %}
+    </ul>
+</div>

settings.py

@@ -108,6 +108,11 @@ MIDDLEWARE_CLASSES = (
     'reversion.middleware.RevisionMiddleware',
 )
 
+from django.conf.global_settings import TEMPLATE_CONTEXT_PROCESSORS as TCP
+TEMPLATE_CONTEXT_PROCESSORS = TCP + (
+    'django.core.context_processors.request',
+)
+
 ROOT_URLCONF = 'urls'
 
 TEMPLATE_DIRS = (