support RDF

lib/domain/atom_feed.dart

@@ -41,7 +41,7 @@ class AtomFeed {
 
   factory AtomFeed.parse(String xmlString) {
     var document = XmlDocument.parse(xmlString);
-    var feedElement = findFirstElement(document, 'feed', recursive: true);
+    var feedElement = findFirstElement(document, 'feed');
     if (feedElement == null) {
       throw ArgumentError('feed not found');
     }

lib/domain/rss_feed.dart

@@ -59,7 +59,12 @@ class RssFeed {
 
   factory RssFeed.parse(String xmlString) {
     var document = XmlDocument.parse(xmlString);
-    var channelElement = findFirstElement(document, 'channel', recursive: true);
+    var rss = findFirstElement(document, 'rss');
+    var rdf = findFirstElement(document, 'rdf:RDF');
+    if (rss == null && rdf == null) {
+      throw ArgumentError('not a rss feed');
+    }
+    var channelElement = findFirstElement(rss ?? rdf, 'channel');
     if (channelElement == null) {
       throw ArgumentError('channel not found');
     }
@@ -68,11 +73,12 @@ class RssFeed {
       author: findFirstElement(channelElement, 'author')?.text,
       description: findFirstElement(channelElement, 'description')?.text,
       link: findFirstElement(channelElement, 'link')?.text,
-      items: channelElement
+      items: (rss != null ? channelElement : rdf)
           .findElements('item')
           .map((e) => RssItem.parse(e))
           .toList(),
-      image: RssImage.parse(findFirstElement(channelElement, 'image')),
+      image: RssImage.parse(
+          findFirstElement(rss != null ? channelElement : rdf, 'image')),
       cloud: RssCloud.parse(findFirstElement(channelElement, 'cloud')),
       categories: channelElement
           .findElements('category')

test/rss_test.dart

@@ -369,4 +369,20 @@ void main() {
     expect(item.itunes.title, 'awesome title');
     expect(item.itunes.block, false);
   });
+
+  test('parse RSS-RDF.xml', () {
+    var xmlString = File('test/xml/RSS-RDF.xml').readAsStringSync();
+
+    var feed = RssFeed.parse(xmlString);
+
+    expect(feed.title, 'Mozilla Dot Org');
+    expect(feed.link, 'http://www.mozilla.org');
+    expect(feed.description, 'the Mozilla Organization web site');
+    expect(feed.image.title, 'Mozilla');
+    expect(feed.image.url, 'http://www.mozilla.org/images/moz.gif');
+    expect(feed.image.link, 'http://www.mozilla.org');
+    expect(feed.items.length, 5);
+    expect(feed.items.first.title, 'New Status Updates');
+    expect(feed.items.first.link, 'http://www.mozilla.org/status/');
+  });
 }

test/xml/RSS-RDF.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0"?>
+<rdf:RDF
+        xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+        xmlns="http://channel.netscape.com/rdf/simple/0.9/">
+    <channel>
+        <title>Mozilla Dot Org</title>
+        <link>http://www.mozilla.org</link>
+        <description>the Mozilla Organization web site</description>
+    </channel>
+    <image>
+        <title>Mozilla</title>
+        <url>http://www.mozilla.org/images/moz.gif</url>
+        <link>http://www.mozilla.org</link>
+    </image>
+    <item>
+        <title>New Status Updates</title>
+        <link>http://www.mozilla.org/status/</link>
+    </item>
+    <item>
+        <title>Bugzilla Reorganized</title>
+        <link>http://www.mozilla.org/bugs/</link>
+    </item>
+    <item>
+        <title>Mozilla Party, 2.0!</title>
+        <link>http://www.mozilla.org/party/1999/</link>
+    </item>
+    <item>
+        <title>Unix Platform Parity</title>
+        <link>http://www.mozilla.org/build/unix.html</link>
+    </item>
+    <item>
+        <title>NPL 1.0M published</title>
+        <link>http://www.mozilla.org/NPL/NPL-1.0M.html</link>
+    </item>
+</rdf:RDF>