From 5b2147958b107c35f54c11c2d0b0b43a71855ad8 Mon Sep 17 00:00:00 2001
From: eric <eric@hellman.net>
Date: Mon, 3 Nov 2014 19:36:26 -0500
Subject: [PATCH] paginate feeds

---
 api/opds.py  | 45 +++++++++++++++++++++++++++++++++------------
 api/views.py |  7 ++++++-
 2 files changed, 39 insertions(+), 13 deletions(-)

diff --git a/api/opds.py b/api/opds.py
index dfc784e6..ade9e561 100644
--- a/api/opds.py
+++ b/api/opds.py
@@ -19,6 +19,7 @@ FORMAT_TO_MIMETYPE = {'pdf':"application/pdf",
 facets = ["creative_commons","active_campaigns"]
 
 UNGLUEIT_URL= 'https://unglue.it'
+NAVIGATION = "application/atom+xml;profile=opds-catalog;kind=navigation"
 def feeds():
     for facet in facets:
         yield globals()[facet]()
@@ -117,8 +118,8 @@ class Facet:
     feed_path = ''
     description = ''
         
-    def feed(self):
-        return opds_feed_for_works(self.works, self.feed_path, title=self.title)
+    def feed(self, page=None):
+        return opds_feed_for_works(self.works, self.feed_path, title=self.title, page=page)
         
     def updated(self):
         # return the creation date for most recently added item
@@ -145,7 +146,7 @@ class active_campaigns(Facet):
                                editions__ebooks__isnull=False).distinct().order_by('-created')
     description= "With your help we're raising money to make these books free to the world."
 
-def opds_feed_for_works(works, feed_path, title="Unglue.it Catalog"):
+def opds_feed_for_works(works, feed_path, title="Unglue.it Catalog", page=None):
 
     feed_xml = """<feed xmlns:dcterms="http://purl.org/dc/terms/" 
       xmlns:opds="http://opds-spec.org/"
@@ -183,17 +184,37 @@ def opds_feed_for_works(works, feed_path, title="Unglue.it Catalog"):
     # links:  start, self, next/prev (depending what's necessary -- to start with put all CC books)
     
     # start link
+    append_navlink(feed, 'start', feed_path, None )
     
-    start_link = etree.Element("link")
-    start_link.attrib.update({"rel":"start",
-     "href":"https://unglue.it/api/opds/",
-     "type":"application/atom+xml;profile=opds-catalog;kind=navigation",
-    })
-    feed.append(start_link)
-
+    # next link
     
-    for work in islice(works,None):
+    if not page:
+        page =0
+    else:
+        try:
+            page=int(page)
+        except TypeError:
+            page=0
+    
+    try:
+        works[10 * page + 10]
+        append_navlink(feed, 'next', feed_path, page+1 )
+    except IndexError:
+        pass
+                
+    works = islice(works,  10 * page, 10 * page + 10)
+    if page > 0:
+        append_navlink(feed, 'previous', feed_path, page-1)
+    for work in works:
         node = work_node(work)
         feed.append(node)
     
-    return etree.tostring(feed, pretty_print=True)
\ No newline at end of file
+    return etree.tostring(feed, pretty_print=True)
+
+def append_navlink(feed, rel, path, page):
+    link = etree.Element("link")
+    link.attrib.update({"rel":rel,
+             "href": UNGLUEIT_URL + "/api/opds/" + path + ('/?page=' + unicode(page) if page!=None else '/'),
+             "type": NAVIGATION,
+            })
+    feed.append(link)
\ No newline at end of file
diff --git a/api/views.py b/api/views.py
index fb3bd18d..b742f303 100755
--- a/api/views.py
+++ b/api/views.py
@@ -101,9 +101,14 @@ class OPDSAcquisitionView(View):
 
     def get(self, request, *args, **kwargs):
         facet = kwargs.get('facet')
+        page = request.GET.get('page', None)
+        try:
+            page = int(page)
+        except:
+            page = None
         if facet in opds.facets:
             facet_class = getattr(opds, facet)()
-            return HttpResponse(facet_class.feed(),
+            return HttpResponse(facet_class.feed(page),
                             content_type="application/atom+xml;profile=opds-catalog;kind=acquisition")
         else:
             return HttpResponseNotFound("invalid facet")