Pin a feed to the top of the feed list

subscriptions.pinned, per person, set by PATCH /api/feeds/{id} {pinned} and
returned as FeedRow.pinned. Kept out of Sub, which the scanner merges into its
policy; set_subscription names its columns, so saving a feed's settings leaves
the pin alone (tested).

Pinned feeds come first in the list, a pin before the name and a rule under the
block: a pinned folder with its feeds under it, a feed from inside one lifted out
of it. The pin button is on both the feed and the folder page.

Closes #33.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/db.rs

@@ -96,6 +96,8 @@ CREATE TABLE IF NOT EXISTS subscriptions (
     auto_download     INTEGER,
     allow_explicit    INTEGER,
     max_new_per_check INTEGER,
+    -- Pinned to the top of this person's feed list, a feed inside a folder included.
+    pinned            INTEGER NOT NULL DEFAULT 0,
     PRIMARY KEY (user_id, feed_id)
 );
 
@@ -182,6 +184,7 @@ fn migrate(conn: &Connection) -> Result<()> {
         // Kept per account so a theme follows you to another browser; it was in localStorage.
         ("users", "theme", "TEXT"),
         ("users", "theme_mode", "TEXT"),
+        ("subscriptions", "pinned", "INTEGER NOT NULL DEFAULT 0"),
     ];
     let retired: &[(&str, &str)] = &[
         // Read state from before accounts, long since moved to entry_state. Two bugs came from
@@ -1060,6 +1063,24 @@ impl Db {
         Ok(())
     }
 
+    /// The feeds this person pinned to the top of their list. Kept apart from `Sub`, which is
+    /// what the scanner merges into its policy, and which a pin has nothing to do with.
+    pub fn pinned_feeds(&self, user_id: i64) -> Result<std::collections::HashSet<String>> {
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn.prepare("SELECT feed_id FROM subscriptions WHERE user_id = ?1 AND pinned")?;
+        let ids = stmt.query_map([user_id], |r| r.get(0))?.collect::<rusqlite::Result<_>>()?;
+        Ok(ids)
+    }
+
+    /// False when they do not subscribe to it, since there is then no row in their list to pin.
+    pub fn set_pinned(&self, user_id: i64, feed_id: &str, on: bool) -> Result<bool> {
+        let conn = self.conn.lock().unwrap();
+        Ok(conn.execute(
+            "UPDATE subscriptions SET pinned = ?3 WHERE user_id = ?1 AND feed_id = ?2",
+            params![user_id, feed_id, on as i64],
+        )? > 0)
+    }
+
     pub fn unsubscribe(&self, user_id: i64, feed_id: &str) -> Result<()> {
         let conn = self.conn.lock().unwrap();
         conn.execute(
@@ -2029,6 +2050,21 @@ mod tests {
         assert_eq!(after.error_since, None, "a clean check ends the run of failures");
     }
 
+    #[test]
+    fn a_pin_survives_saving_the_feeds_settings_and_needs_a_subscription() {
+        let db = Db::memory().unwrap();
+        let me = db.create_user("pat", None, false).unwrap();
+        assert!(!db.set_pinned(me, "f", true).unwrap(), "not subscribed: nothing to pin");
+        db.subscribe(me, "f").unwrap();
+        assert!(db.set_pinned(me, "f", true).unwrap());
+        // set_subscription writes the rest of the row; it must leave the pin alone.
+        db.set_subscription(me, &Sub { feed_id: "f".into(), auto_download: Some(false), ..Default::default() })
+            .unwrap();
+        assert!(db.pinned_feeds(me).unwrap().contains("f"));
+        db.set_pinned(me, "f", false).unwrap();
+        assert!(db.pinned_feeds(me).unwrap().is_empty());
+    }
+
     #[test]
     fn enclosure_url_is_the_dedupe_key() {
         let db = Db::memory().unwrap();