handle bad page inputs

sanitize page input, like OPDS
catch errors when page parameter is invalid
correct documentation

api/onix.py

@@ -3,7 +3,7 @@ import pytz
 import re
 from lxml import etree
 
-from django.core.paginator import Paginator
+from django.core.paginator import Paginator, InvalidPage
 
 from regluit.core import models
 from regluit.core.cc import ccinfo
@@ -26,8 +26,11 @@ def onix_feed(facet, max=None, page_number=None):
     works = facet.works[0:max] if max else facet.works
 
     if page_number is not None:
+        try:
             p = Paginator(works, WORKS_PER_PAGE)
             works = p.page(page_number)
+        except InvalidPage:
+            works = []
 
     for work in works:
         editions = models.Edition.objects.filter(work=work,ebooks__isnull=False)

api/templates/api_help.html

@@ -89,11 +89,13 @@ XML: <a href="/api/v1/identifier/?format=xml&amp;api_key={{api_key}}&amp;usernam
     <dd><code><a href="{% url 'opds_acqusition' 'kw.fiction' %}">{{base_url}}{% url 'opds_acqusition' 'kw.fiction' %}</a></code></dd>
     <dt>filtered by ungluer</dt>
     <dd><code><a href="{% url 'opds_acqusition' '@eric' %}">{{base_url}}{% url 'opds_acqusition' '@eric' %}</a></code></dd>
+    <dt>filtered by having a Project Gutenberg or DOAB identifier (doab, gtbg)</dt>
+    <dd><code><a href="{% url 'opds_acqusition' 'doab/-gtbg' %}">{{base_url}}{% url 'opds_acqusition' 'doab/-gtbg' %}</a></code></dd>
     </p>
         <p>There's also an OPDS record available for every work on unglue.it. For example, requesting, <code><a href="{% url 'opds_acqusition' 'all'%}?work=13950">{{base_url}}{% url 'opds_acqusition' 'all'%}?work=13950</a></code> get you to the web page or opds record for <i>A Christmas Carol</i>.</p>
    
     <h3>ONIX Catalog Feeds</h3>
-    <p>There is an <a href="http://www.editeur.org/12/about-release-3.0/">ONIX 3.0</a> feed corresponding to every facet of our <a href="{% url 'free' %}">free ebook lists</a>. You don't need a key to use them. There is a maximum of 100 books per result you can change with the max parameter. For example, here are the <a href="{% url 'onix' 'by-nc-nd/epub' %}">first hundred CC BY-ND-ND licensed books available in EPUB.</a> Pagination is available via the page_number parameter.</p>
+    <p>There is an <a href="http://www.editeur.org/12/about-release-3.0/">ONIX 3.0</a> feed corresponding to every facet of our <a href="{% url 'free' %}">free ebook lists</a>. You don't need a key to use them. There is a maximum of 100 books per result you can change with the <code>max</code> parameter. For example, here are the <a href="{% url 'onix' 'by-nc-nd/epub' %}?max=20">first twenty CC BY-ND-ND licensed books available in EPUB.</a> Pages of 30 records each are available via the <code>page</code> parameter. Here's the <a href="{% url 'onix' 'doab' %}?page=1">first page of books from the Directory of Open Access Books.</a></p>
     <p>There's also an ONIX record available for every free ebook on unglue.it.  For example, here is <a href="{% url 'onix_all' %}?work=140086"><i>Issues in Open Research Data</i></a>.</p>
     
     <h3>Identifiers with Content type negotiation</h3>

api/views.py

@@ -239,8 +239,12 @@ class OnixView(View):
             max_records = None
 
         facet_class = opds.get_facet_class(facet)()
-        page_number = request.GET.get('page')
+        page = request.GET.get('page', None)
+        try:
+            page = int(page)
+        except:
+            page = None
 
-        feed = onix.onix_feed(facet_class, max_records, page_number=page_number)
+        feed = onix.onix_feed(facet_class, max_records, page_number=page)
         return HttpResponse(feed, content_type="text/xml")