Sort appcast items by version

Ensure that the highest (compatible) version is used regardless of
appcast feed's order.

Fixes #273.

src/appcast.cpp

@@ -347,9 +347,6 @@ void XMLCALL OnEndElement(void *data, const char *name)
             if (item.IsValid() && is_compatible_with_windows_version(item))
             {
                 ctxt.all_items.push_back(item);
-
-                // FIXME: this is premature, we should sort appcast items by date and pick the newest (as Sparkle does)
-                XML_StopParser(ctxt.parser, XML_TRUE);
             }
         }
     }
@@ -411,7 +408,7 @@ void XMLCALL OnText(void *data, const char *s, int len)
                                Appcast class
  *--------------------------------------------------------------------------*/
 
-Appcast Appcast::Load(const std::string& xml)
+std::vector<Appcast> Appcast::Load(const std::string& xml)
 {
     XML_Parser p = XML_ParserCreateNS(NULL, NS_SEP);
     if ( !p )
@@ -436,11 +433,11 @@ Appcast Appcast::Load(const std::string& xml)
     XML_ParserFree(p);
 
     if (ctxt.all_items.empty())
-        return Appcast(); // invalid
+        return {}; // invalid
 
 	// the items were already filtered to only include those compatible with the current OS + arch
 	// and meeting minimum OS version requirements, so we can just return the first one
-	return ctxt.all_items.front();
+	return std::move(ctxt.all_items);
 }
 
 } // namespace winsparkle

src/appcast.h

@@ -27,6 +27,8 @@
 #define _appcast_h_
 
 #include <string>
+#include <vector>
+
 
 namespace winsparkle
 {
@@ -79,18 +81,20 @@ struct Appcast
 
 
     /**
-        Initializes the struct with data from XML appcast feed.
+        Loads all updates from XML appcast feed.
+
+		The list is in the order of the feed, without any additional sorting.
 
-        If the feed contains multiple entries, only the latest one is read,
-        the rest is ignored. Entries that are not appliable (e.g. for different
-        OS) are likewise skipped.
+        Entries that are not appliable (e.g. for different OS) are skipped.
 
         Throws on error.
-        Returns NULL if no error ocurred, but there was no update in the appcast.
+
+        Returns emty list if no error ocurred, but there was no usable update
+        in the appcast.
 
         @param xml Appcast feed data.
      */
-    static Appcast Load(const std::string& xml);
+    static std::vector<Appcast> Load(const std::string& xml);
 
     /// Returns true if the struct constains valid data.
     bool IsValid() const { return !Version.empty() && (HasDownload() || !WebBrowserURL.empty()); }

src/updatechecker.cpp

@@ -230,7 +230,24 @@ void UpdateChecker::PerformUpdateCheck()
         StringDownloadSink appcast_xml;
         DownloadFile(url, &appcast_xml, this, Settings::GetHttpHeadersString(), Download_BypassProxies);
 
-        Appcast appcast = Appcast::Load(appcast_xml.data);
+        auto all = Appcast::Load(appcast_xml.data);
+
+        if (all.empty())
+        {
+            // No applicable updates in the feed.
+            UI::NotifyNoUpdates(ShouldAutomaticallyInstall());
+            return;
+        }
+
+        // Sort by version number and pick the latest:
+		std::stable_sort
+        (
+            all.begin(), all.end(),
+            [](const Appcast& a, const Appcast& b) { return CompareVersions(a.Version, b.Version) > 0; }
+        );
+
+        auto appcast = all.front();
+
         if (!appcast.ReleaseNotesURL.empty())
             CheckForInsecureURL(appcast.ReleaseNotesURL, "release notes");
         if (!appcast.enclosure.DownloadURL.empty())