Add basic pagination to news

Add:
- Pagination buttons to the template
- Custom IntegerConverter to Flask to support negative numbers
- Ability to select a certain range of newsentries (start~end)

Refs #2

sipa/app.py

@@ -28,8 +28,20 @@
 from sipa.utils.graph_utils import render_traffic_chart
 from sipa.utils.ldap_utils import User, authenticate
 
+from werkzeug.routing import IntegerConverter as BaseIntegerConverter
+
+
+class IntegerConverter(BaseIntegerConverter):
+    """Modification of the standard IntegerConverter which does not support
+    negative values. See
+    http://werkzeug.pocoo.org/docs/0.10/routing/#werkzeug.routing.IntegerConverter
+    """
+    regex = r'-?\d+'
+
 
 app = Flask('sipa')
+
+app.url_map.converters['int'] = IntegerConverter
 login_manager = LoginManager()
 
 

sipa/blueprints/news.py

@@ -5,21 +5,67 @@
 Blueprint providing features regarding the news entries.
 """
 
-from flask import Blueprint, render_template
+from flask import Blueprint, render_template, url_for, redirect
 from sipa.flatpages import cf_pages
 
 bp_news = Blueprint('news', __name__, url_prefix='/news')
 
 
 @bp_news.route("/")
-def display():
+@bp_news.route("/start/<int:start>")
+@bp_news.route("/end/<int:end>")
+# todo implement (gui) feature to select range
+@bp_news.route("/range/<int:start>:<int:end>")
+def display(start=None, end=None):
     """Get all markdown files from 'content/news/', parse them and put
     them in a list for the template.
     The formatting of these files is described in the readme.
     """
     cf_pages.reload()
-    latest = cf_pages.get_articles_of_category('news')
-    latest = sorted(latest, key=lambda a: a.date, reverse=True)
-    latest = latest[0:10]
-    return render_template("index.html", articles=latest)
+    news = cf_pages.get_articles_of_category('news')
+    news = sorted(news, key=lambda a: a.date, reverse=True)
 
+    default_step = 10
+    # calculating mod len() allows things like `end=-1` for the last article(s).
+    # this may lead to confusing behaviour because this allows values out of the
+    # range (|val|≥len(latest)), but this will only result in displaying
+    # articles instead of throwing an error.
+    # Apart from that, such values would just appear if edited manually.
+    if start is None:
+        if end is None:
+            start, end = 0, default_step
+        else:
+            end %= len(news)
+            start = max(end - default_step + 1, 0)
+    else:
+        start %= len(news)
+        if end is None:
+            end = min(start + default_step - 1, len(news) - 1)
+        else:
+            end %= len(news)
+
+    delta = end - start + 1
+    prev_range, next_range = None, None
+
+    if start > 0:
+        prev_range = {'start': max(start - delta, 0), 'end': start - 1}
+    if end < len(news) - 1:
+        next_range = {'start': end + 1, 'end': min(end + delta, len(news) - 1)}
+
+    return render_template("index.html", articles=news[start:end],
+                           previous_range=prev_range, next_range=next_range)
+
+
+@bp_news.route("/newest")
+def newest():
+    return redirect(url_for(".display"))
+
+
+@bp_news.route("/oldest")
+def oldest():
+    return redirect(url_for(".display", end=-1))
+
+
+@bp_news.route("/all")
+def display_all():
+    return redirect(url_for(".display", start=0, end=-1))

sipa/templates/index.html

@@ -22,4 +22,29 @@
             <div class="panel-footer">{{ _("geschrieben von") }} {{ art.author }}, {{ art.date }}</div>
         </div>
     {% endfor %}
+    <nav>
+        <ul class="pager">
+        {% if previous_range %}
+            <li class="previous">
+                <a href="{{ url_for(".display", start=previous_range.start, end=previous_range.end) }}">
+                <span aria-hidden="true">&larr;</span> {{ _("Neuer") }}</a>
+            </li>
+        {% else %}
+            <li class="previous disabled">
+                <a href="#">{{ _("Keine neueren Beiträge") }}</a>
+            </li>
+        {% endif %}
+
+        {% if next_range %}
+            <li class="next">
+                <a href="{{ url_for(".display", start=next_range.start, end=next_range.end) }}">
+                {{ _("Älter") }} <span aria-hidden="true">&rarr;</span></a>
+            </li>
+        {% else %}
+            <li class="next disabled">
+                <a href="#">{{ _("Keine älteren Beiträge") }}</a>
+            </li>
+        {% endif %}
+        </ul>
+    </nav>
 {% endblock %}