add prev/next links to articles

Signed-off-by: Sebastian Krzyszkowiak <dos@dosowisko.net>

5 files changed, 167 insertions, 1 deletions

diff --git a/pelicanconf.py b/pelicanconf.py
index d5c85a2..32ce4e2 100644
--- a/pelicanconf.py
+++ b/pelicanconf.py
@@ -39,4 +39,7 @@ ARTICLE_URL = "news/{slug}"
 ARTICLE_SAVE_AS = "news/{slug}.html"
 
 PAGE_URL = "{slug}"
-PAGE_SAVE_AS = "{slug}.html"
\ No newline at end of file
+PAGE_SAVE_AS = "{slug}.html"
+
+PLUGIN_PATH = 'plugins'
+PLUGINS = ['neighbors']
diff --git a/plugins/neighbors/Readme.rst b/plugins/neighbors/Readme.rst
new file mode 100644
index 0000000..573b914
--- /dev/null
+++ b/plugins/neighbors/Readme.rst
@@ -0,0 +1,97 @@
+Neighbor Articles Plugin for Pelican
+====================================
+
+This plugin adds ``next_article`` (newer) and ``prev_article`` (older) 
+variables to the article's context.
+
+Also adds ``next_article_in_category`` and ``prev_article_in_category``.
+
+
+Usage
+-----
+
+.. code-block:: html+jinja
+
+    <ul>
+    {% if article.prev_article %}
+        <li>
+            <a href="{{ SITEURL }}/{{ article.prev_article.url}}">
+                {{ article.prev_article.title }}
+            </a>
+        </li>
+    {% endif %}
+    {% if article.next_article %}
+        <li>
+            <a href="{{ SITEURL }}/{{ article.next_article.url}}">
+                {{ article.next_article.title }}
+            </a>
+        </li>
+    {% endif %}
+   </ul>    
+   <ul>
+    {% if article.prev_article_in_category %}
+        <li>
+            <a href="{{ SITEURL }}/{{ article.prev_article_in_category.url}}">
+                {{ article.prev_article_in_category.title }}
+            </a>
+        </li>
+    {% endif %}
+    {% if article.next_article %}
+        <li>
+            <a href="{{ SITEURL }}/{{ article.next_article_in_category.url}}">
+                {{ article.next_article_in_category.title }}
+            </a>
+        </li>
+    {% endif %}
+    </ul> 
+
+Usage with the Subcategory plugin
+---------------------------------
+
+If you want to get the neigbors within a subcategory it's a little different.
+Since an article can belong to more than one subcategory, subcategories are
+stored in a list. If you have an article with subcategories like 
+
+``Category/Foo/Bar``
+
+it will belong to both subcategory Foo, and Foo/Bar. Subcategory neighbors are
+added to an article as ``next_article_in_subcategory#`` and 
+``prev_article_in_subcategory#`` where ``#`` is the level of subcategory. So using
+the example from above, subcategory1 will be Foo, and subcategory2 Foo/Bar. 
+Therefor the usage with subcategories is:
+
+.. code-block:: html+jinja
+
+    <ul>
+    {% if article.prev_article_subcategory1 %}
+        <li>
+            <a href="{{ SITEURL }}/{{ article.prev_article_in_subcategory1.url}}">
+                {{ article.prev_article_in_subcategory1.title }}
+            </a>
+        </li>
+    {% endif %}
+    {% if article.next_article %}
+        <li>
+            <a href="{{ SITEURL }}/{{ article.next_article_subcategory1.url}}">
+                {{ article.next_article_subcategory1.title }}
+            </a>
+        </li>
+    {% endif %}
+   </ul>    
+   <ul>
+    {% if article.prev_article_in_subcategory2 %}
+        <li>
+            <a href="{{ SITEURL }}/{{ article.prev_article_in_subcategory2.url}}">
+                {{ article.prev_article_in_subcategory2.title }}
+            </a>
+        </li>
+    {% endif %}
+    {% if article.next_article %}
+        <li>
+            <a href="{{ SITEURL }}/{{ article.next_article_in_subcategory2.url}}">
+                {{ article.next_article_in_subcategory2.title }}
+            </a>
+        </li>
+    {% endif %}
+    </ul> 
+
diff --git a/plugins/neighbors/__init__.py b/plugins/neighbors/__init__.py
new file mode 100644
index 0000000..9038d7e
--- /dev/null
+++ b/plugins/neighbors/__init__.py
@@ -0,0 +1 @@
+from .neighbors import *
diff --git a/plugins/neighbors/neighbors.py b/plugins/neighbors/neighbors.py
new file mode 100755
index 0000000..b65fcfe
--- /dev/null
+++ b/plugins/neighbors/neighbors.py
@@ -0,0 +1,58 @@
+# -*- coding: utf-8 -*-
+"""
+Neighbor Articles Plugin for Pelican
+====================================
+
+This plugin adds ``next_article`` (newer) and ``prev_article`` (older) 
+variables to the article's context
+"""
+from pelican import signals
+
+def iter3(seq):
+    it = iter(seq)
+    nxt = None
+    cur = next(it)
+    for prv in it:
+        yield nxt, cur, prv
+        nxt, cur = cur, prv
+    yield nxt, cur, None
+
+def get_translation(article, prefered_language):
+    if not article:
+        return None
+    for translation in article.translations:
+        if translation.lang == prefered_language:
+            return translation
+    return article
+
+def set_neighbors(articles, next_name, prev_name):
+    for nxt, cur, prv in iter3(articles):
+        exec("cur.{} = nxt".format(next_name))
+        exec("cur.{} = prv".format(prev_name))
+
+        for translation in cur.translations:
+            exec(
+            "translation.{} = get_translation(nxt, translation.lang)".format(
+                next_name))
+            exec(
+            "translation.{} = get_translation(prv, translation.lang)".format(
+                prev_name))
+      
+def neighbors(generator):
+    set_neighbors(generator.articles, 'next_article', 'prev_article')
+    
+    for category, articles in generator.categories:
+        articles.sort(key=(lambda x: x.date), reverse=(True))
+        set_neighbors(
+            articles, 'next_article_in_category', 'prev_article_in_category')
+
+    if hasattr(generator, 'subcategories'):
+        for subcategory, articles in generator.subcategories:
+            articles.sort(key=(lambda x: x.date), reverse=(True))
+            index = subcategory.name.count('/')
+            next_name = 'next_article_in_subcategory{}'.format(index)
+            prev_name = 'prev_article_in_subcategory{}'.format(index)
+            set_neighbors(articles, next_name, prev_name)
+
+def register():
+    signals.article_generator_finalized.connect(neighbors)
diff --git a/theme/templates/article.html b/theme/templates/article.html
index 8481d80..095718a 100644
--- a/theme/templates/article.html
+++ b/theme/templates/article.html
@@ -69,6 +69,13 @@
                 </div>
                 {% endif %}
 
+                {% if article.next_article %}
+                <p style="float: right"><a href="/{{article.next_article.url}}">{{article.next_article.title}} &raquo;</a></p>
+                {% endif %}
+                {% if article.prev_article %}
+                <p><a href="/{{article.prev_article.url}}">&laquo; {{article.prev_article.title}}</a></p>
+                {% endif %}
+
                 <hr />
 
                 <a style="float: right; margin: 3px 35px" href="http://neo900.org/" class="btn btn-default">Learn more</a>