Don't mark old episodes as new on update (bug 340)

Another attempt at finally fixing bug 340, but this time I'm pretty sure
that it works, because we are more selective now.

Whenever a new episode appears in the feed, its date is compared to the
date of the newest-known episode in the same feed. If it's more than one
week older than the newest-known episode, it's marked as old by default.

The "one week" value is just a randomly-chosen one to allow for border
cases (like a daily podcast re-issuing an episode of the last few days)
to work correctly and not cause "missing episodes".

src/gpodder/dbsqlite.py

@@ -603,6 +603,16 @@ class Database(object):
             self.log("find_channel_id(%s)", url)
             return self.__get__("SELECT id FROM channels WHERE url = ?", (url, ))
 
+    def get_last_pubdate(self, channel):
+        """
+        Look up the highest "pubDate" value for
+        all episodes of the given podcast.
+        """
+        return self.__get__("""
+                SELECT MAX(pubDate) FROM episodes
+                WHERE channel_id = ?
+                """, (channel.id, ))
+
     def force_last_new(self, channel):
         old = self.__get__("""SELECT COUNT(*) FROM episodes WHERE channel_id = ?
             AND state IN (?, ?)""", (channel.id, gpodder.STATE_DOWNLOADED,

src/gpodder/model.py

@@ -117,6 +117,7 @@ class PodcastModelObject(object):
 class PodcastChannel(PodcastModelObject):
     """holds data for a complete channel"""
     MAX_FOLDERNAME_LENGTH = 150
+    SECONDS_PER_WEEK = 7*24*60*60
 
     feed_fetcher = gPodderFetcher()
 
@@ -224,6 +225,9 @@ class PodcastChannel(PodcastModelObject):
         # GUID-based existing episode list
         existing_guids = dict((e.guid, e) for e in existing)
 
+        # Get most recent pubDate of all episodes
+        last_pubdate = self.db.get_last_pubdate(self) or 0
+
         # Search all entries for new episodes
         for entry in entries:
             try:
@@ -252,8 +256,15 @@ class PodcastChannel(PodcastModelObject):
                     existing_episode.save()
                     continue
 
-            # Otherwise we have found a new episode to store in the DB
-            self.count_new += 1
+            # Workaround for bug 340: If the episode has been
+            # published earlier than one week before the most
+            # recent existing episode, do not mark it as new.
+            if episode.pubDate < last_pubdate - self.SECONDS_PER_WEEK:
+                log('Episode with old date: %s', episode.title, sender=self)
+                episode.is_played = True
+            else:
+                self.count_new += 1
+
             episode.save()
 
         # Remove "unreachable" episodes - episodes that have not been
@@ -365,7 +376,6 @@ class PodcastChannel(PodcastModelObject):
         self.image = None
         self.pubDate = 0
         self.parse_error = None
-        self.newest_pubdate_cached = None
         self.foldername = None
         self.auto_foldername = 1 # automatically generated foldername