From f33754169fe99ab667271666efc2b2eb424ba8c9 Mon Sep 17 00:00:00 2001
From: Lakshmi Vyasarajan <lakshmi.vyas@gmail.com>
Date: Fri, 7 Jan 2011 10:25:41 +0530
Subject: [PATCH] Added next prev support to sorter

---
 hyde/ext/plugins/sorter.py    | 19 ++++++++++++++++++-
 hyde/tests/ext/test_sorter.py | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/hyde/ext/plugins/sorter.py b/hyde/ext/plugins/sorter.py
index f9d63f5..d993cc8 100644
--- a/hyde/ext/plugins/sorter.py
+++ b/hyde/ext/plugins/sorter.py
@@ -7,7 +7,7 @@ from hyde.plugin import Plugin
 from hyde.site import Node, Resource
 
 from functools import partial
-from itertools import ifilter
+from itertools import ifilter, izip, tee
 from operator import attrgetter
 
 import logging
@@ -15,6 +15,10 @@ from logging import NullHandler
 logger = logging.getLogger('hyde.engine')
 logger.addHandler(NullHandler())
 
+def pairwalk(iterable):
+    a, b = tee(iterable)
+    next(b, None)
+    return izip(a, b)
 
 def filter_method(item, settings=None):
     """
@@ -104,3 +108,16 @@ class SorterPlugin(Plugin):
             add_method(Node, sort_method_name, sort_method, settings)
             match_method_name = 'is_%s' % name
             add_method(Resource, match_method_name, filter_method, settings)
+
+            prev_att = 'prev_by_%s' % name
+            next_att = 'next_by_%s' % name
+
+            setattr(Resource, prev_att, None)
+            setattr(Resource, next_att, None)
+
+            walker = getattr(self.site.content,
+                                sort_method_name,
+                                self.site.content.walk_resources)
+            for prev, next in pairwalk(walker()):
+                setattr(prev, next_att, next)
+                setattr(next, prev_att, prev)
diff --git a/hyde/tests/ext/test_sorter.py b/hyde/tests/ext/test_sorter.py
index 805d526..6b83857 100644
--- a/hyde/tests/ext/test_sorter.py
+++ b/hyde/tests/ext/test_sorter.py
@@ -73,6 +73,40 @@ class TestMeta(object):
 
         assert pages == sorted(expected)
 
+    def test_prev_next(self):
+        s = Site(TEST_SITE)
+        cfg = """
+        plugins:
+            - hyde.ext.sorter.SorterPlugin
+        sorter:
+            kind2:
+                filters:
+                    source_file.kind: html
+        """
+        s.config = Config(TEST_SITE, config_dict=yaml.load(cfg))
+        s.load()
+        SorterPlugin(s).begin_site()
+
+        p_404 = s.content.resource_from_relative_path('404.html')
+        p_about = s.content.resource_from_relative_path('about.html')
+        p_mc = s.content.resource_from_relative_path(
+                            'blog/2010/december/merry-christmas.html')
+
+        assert hasattr(p_404, 'prev_by_kind2')
+        assert not p_404.prev_by_kind2
+        assert hasattr(p_404, 'next_by_kind2')
+        assert p_404.next_by_kind2 == p_about
+
+        assert hasattr(p_about, 'prev_by_kind2')
+        assert p_about.prev_by_kind2 == p_404
+        assert hasattr(p_about, 'next_by_kind2')
+        assert p_about.next_by_kind2 == p_mc
+
+        assert hasattr(p_mc, 'prev_by_kind2')
+        assert p_mc.prev_by_kind2 == p_about
+        assert hasattr(p_mc, 'next_by_kind2')
+        assert not p_mc.next_by_kind2
+
     def test_walk_resources_sorted_using_generator(self):
            s = Site(TEST_SITE)
            cfg = """