feat(interests): keep our own list and send it again each login

The server holds interests only for the session that set them, so a client
that does not re-send its list comes back from a reconnect with none. That
is why Nicotine+ sends its whole list at every login, and why it lowercases
each item before sending — the server matches them case-insensitively, so
two spellings would otherwise be held as two interests.

Ours now keeps the list, in one spelling, and puts it back on the wire when
a session starts; an interest set before there is a connection is kept
rather than dropped. A room's ticker board is also let go when we leave the
room, since the server sends the whole board again on the next join.

soulseek-rs-lib/src/client/social.rs

@@ -265,10 +265,16 @@ impl Client {
     /// Add an interest (code 51). Interests are what the recommendation and
     /// similar-user queries below are computed from.
     ///
+    /// The server holds interests only for the session that set them, so the
+    /// list is kept here and sent again after every login. An interest added
+    /// before there is a connection is kept all the same — the error says
+    /// only that it could not go out yet, not that it was dropped.
+    ///
     /// # Errors
     /// [`crate::SoulseekRs::NotConnected`] when there is no server connection.
     pub fn add_interest(&self, item: &str) -> Result<()> {
-        self.send_server_message(MessageFactory::build_add_thing_i_like(item))
+        let item = self.context.write_safe()?.add_own_interest(item, true);
+        self.send_server_message(MessageFactory::build_add_thing_i_like(&item))
     }
 
     /// Drop an interest (code 52).
@@ -276,8 +282,9 @@ impl Client {
     /// # Errors
     /// [`crate::SoulseekRs::NotConnected`] when there is no server connection.
     pub fn remove_interest(&self, item: &str) -> Result<()> {
+        let item = self.context.write_safe()?.remove_own_interest(item, true);
         self.send_server_message(MessageFactory::build_remove_thing_i_like(
-            item,
+            &item,
         ))
     }
 
@@ -286,7 +293,8 @@ impl Client {
     /// # Errors
     /// [`crate::SoulseekRs::NotConnected`] when there is no server connection.
     pub fn add_dislike(&self, item: &str) -> Result<()> {
-        self.send_server_message(MessageFactory::build_add_thing_i_hate(item))
+        let item = self.context.write_safe()?.add_own_interest(item, false);
+        self.send_server_message(MessageFactory::build_add_thing_i_hate(&item))
     }
 
     /// Drop a dislike (code 118).
@@ -294,8 +302,9 @@ impl Client {
     /// # Errors
     /// [`crate::SoulseekRs::NotConnected`] when there is no server connection.
     pub fn remove_dislike(&self, item: &str) -> Result<()> {
+        let item = self.context.write_safe()?.remove_own_interest(item, false);
         self.send_server_message(MessageFactory::build_remove_thing_i_hate(
-            item,
+            &item,
         ))
     }
 
@@ -318,6 +327,20 @@ impl Client {
         self.send_server_message(MessageFactory::build_global_recommendations())
     }
 
+    /// What we ourselves like and hate, as set through this client. The
+    /// server forgets these when the session ends, so they are re-sent after
+    /// each login.
+    #[must_use]
+    pub fn own_interests(&self) -> UserInterests {
+        match self.context.read_safe() {
+            Ok(ctx) => ctx.own_interests(),
+            Err(e) => {
+                error!("[client] own_interests: {}", e);
+                UserInterests::default()
+            }
+        }
+    }
+
     /// The last reply to [`Client::request_recommendations`] as
     /// (recommended, recommended-against), or `None` until one arrives.
     #[must_use]