List feeds in the Directory before anyone subscribes, and clear out dead ones (#107)

The Directory showed a catalogue feed only once someone subscribed, and a feed left the
catalogue with its last subscriber, so nothing could be put there for others to find.

- A feed has a listed flag, set by ipx add --list (with --category for the Directory's chip).
  The web page keeps a listed feed in the catalogue when its last subscriber leaves.
- The Directory lists every catalogue feed; Popular still only what people subscribe to.
  popular() reads titles, artwork and categories through Db::feed_list, not three queries a
  feed. Subscribing from the Directory scans the feed at once.
- A feed nobody subscribes to is checked once a day at most.
- clean_directory, in the sweep before each scan, removes from the catalogue and the database
  a feed nobody subscribes to, with no file on disk and not from an OPML, that has failed for
  30 days or published nothing in a year. Run against production first: it removes nothing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/db.rs

@@ -778,13 +778,47 @@ impl Db {
             .map(|r| Ok(r.try_get("", "id")?))
             .collect::<Result<_>>()?;
         for id in &gone {
-            for table in ["enclosures", "entry_state", "hidden", "blocklists", "entries"] {
-                self.exec(&format!("DELETE FROM {table} WHERE feed_id = $1"), vec![id.clone().into()]).await?;
-            }
+            self.forget_rows(id).await?;
         }
         Ok(gone)
     }
 
+    /// Everything stored about a feed but its row: items, file rows, read state, block list.
+    async fn forget_rows(&self, id: &str) -> Result<()> {
+        for table in ["enclosures", "entry_state", "hidden", "blocklists", "entries"] {
+            self.exec(&format!("DELETE FROM {table} WHERE feed_id = $1"), vec![id.into()]).await?;
+        }
+        Ok(())
+    }
+
+    /// Forgets a feed and everything stored about it.
+    pub async fn forget_feed(&self, id: &str) -> Result<()> {
+        self.forget_rows(id).await?;
+        self.exec("DELETE FROM feeds WHERE id = $1", vec![id.into()]).await?;
+        Ok(())
+    }
+
+    /// Feeds nobody subscribes to that are dead, failing since before `dead_before`, or quiet,
+    /// their newest item from before `quiet_before`: what keeps the Directory to feeds worth
+    /// taking. One with a file on disk stays, and so does one an OPML subscription lists, which
+    /// comes back with the OPML anyway. A feed with no items yet is not quiet, only new.
+    pub async fn stale_unsubscribed(&self, dead_before: i64, quiet_before: i64) -> Result<Vec<String>> {
+        self.rows(
+            "SELECT f.id FROM feeds f
+              WHERE NOT EXISTS (SELECT 1 FROM subscriptions s WHERE s.feed_id = f.id)
+                AND NOT EXISTS (SELECT 1 FROM enclosures x WHERE x.feed_id = f.id AND x.path IS NOT NULL)
+                AND f.group_id IS NULL AND NOT coalesce(f.managed, false)
+                AND ((f.error_since IS NOT NULL AND f.error_since < $1)
+                     OR (SELECT max(coalesce(e.published, e.first_seen)) FROM entries e
+                          WHERE e.feed_id = f.id) < $2)",
+            vec![dead_before.into(), quiet_before.into()],
+        )
+        .await?
+        .iter()
+        .map(|r| Ok(r.try_get("", "id")?))
+        .collect()
+    }
+
     pub async fn prune_entries(&self, older_than: i64) -> Result<usize> {
         let n = self
             .exec(
@@ -1998,6 +2032,32 @@ mod tests {
         assert_eq!((list["f"].unread, list["g"].unread), (1, 1)); // a read, c hidden; sam's read is sam's
     }
 
+    #[tokio::test]
+    async fn stale_feeds_nobody_subscribes_to_are_found_and_the_rest_left() {
+        let db = Db::memory().await.unwrap();
+        db.exec_for_test(
+            "INSERT INTO users (id, name, is_admin) VALUES (1,'ray',true);
+             INSERT INTO feeds (id, url, error_since, managed, group_id) VALUES
+                ('dead','a',100,false,null),('quiet','b',null,false,null),('news','c',null,false,null),
+                ('new','d',null,false,null),('wanted','e',100,false,null),('kept','f',100,false,null),
+                ('child','g',100,true,'opml'),('lately','h',900,false,null);
+             INSERT INTO subscriptions (user_id, feed_id) VALUES (1,'wanted');
+             INSERT INTO entries (feed_id, guid, first_seen, published) VALUES
+                ('quiet','q',0,100),('news','n',0,950),('dead','d',0,950),('kept','k',0,100);
+             INSERT INTO enclosures (id, feed_id, guid, url, path, state) VALUES (1,'kept','k','u','/tmp/k','done');",
+        ).await
+        .unwrap();
+        // Dead before 500, or nothing newer than 500: dead fails since 100, quiet's newest is 100.
+        // news published lately, new has no items yet, wanted has a subscriber, kept a file,
+        // child comes from an OPML, lately began failing after the cutoff.
+        let mut stale = db.stale_unsubscribed(500, 500).await.unwrap();
+        stale.sort();
+        assert_eq!(stale, ["dead", "quiet"]);
+        db.forget_feed("dead").await.unwrap();
+        assert_eq!(db.feed_summary("dead").await.unwrap().entries, 0);
+        assert!(!db.feed_urls().await.unwrap().iter().any(|(id, _)| id == "dead"));
+    }
+
     #[tokio::test]
     async fn a_failing_feed_nobody_subscribes_to_is_forgotten() {
         let db = Db::memory().await.unwrap();