Order sessions by recent use

src/database.rs

@@ -3,6 +3,7 @@ use diesel_migrations::{EmbeddedMigrations, MigrationHarness, embed_migrations};
 use std::collections::HashMap;
 use std::fs;
 use std::path::Path;
+use time::OffsetDateTime;
 
 use crate::schema::{a2ui_messages, messages, projects, sessions};
 
@@ -40,6 +41,7 @@ pub struct Session {
     /// Raw column value; read it through [`Session::state`].
     state: String,
     pub compacted_summary: Option<String>,
+    last_used: i64,
 }
 
 impl Session {
@@ -58,6 +60,7 @@ impl Session {
             last_tokens_per_second: None,
             state: state.as_id().to_owned(),
             compacted_summary: None,
+            last_used: 0,
         }
     }
 }
@@ -105,6 +108,7 @@ impl SessionState {
 struct NewSession<'a> {
     project_id: i32,
     title: &'a str,
+    last_used: i64,
 }
 
 #[derive(Clone, Debug, Identifiable, Queryable, Selectable)]
@@ -207,10 +211,15 @@ impl Database {
                 .or_default()
                 .push(session);
         }
-        // Pinned first, then ordinary, then archived; creation order within each
-        // group. A stable sort keeps the id ordering the query established.
+        // Preserve sidebar groups while matching DS4's newest-used-first order.
         for sessions in sessions_by_project.values_mut() {
-            sessions.sort_by_key(|session| session.state().rank());
+            sessions.sort_by(|left, right| {
+                left.state()
+                    .rank()
+                    .cmp(&right.state().rank())
+                    .then_with(|| right.last_used.cmp(&left.last_used))
+                    .then_with(|| right.id.cmp(&left.id))
+            });
         }
 
         Ok(project_rows
@@ -275,12 +284,20 @@ impl Database {
 
     pub fn create_session(&mut self, project_id: i32, title: &str) -> Result<Session, String> {
         diesel::insert_into(sessions::table)
-            .values(NewSession { project_id, title })
+            .values(NewSession {
+                project_id,
+                title,
+                last_used: OffsetDateTime::now_utc().unix_timestamp(),
+            })
             .returning(Session::as_returning())
             .get_result(&mut self.connection)
             .map_err(|error| error.to_string())
     }
 
+    pub fn touch_session(&mut self, session_id: i32) -> Result<(), String> {
+        touch_session(&mut self.connection, session_id).map_err(|error| error.to_string())
+    }
+
     pub fn rename_session(&mut self, session_id: i32, title: &str) -> Result<(), String> {
         let title = title.trim();
         if title.is_empty() {
@@ -431,6 +448,7 @@ impl Database {
     ) -> Result<Vec<StoredMessage>, String> {
         self.connection
             .transaction(|connection| {
+                touch_session(connection, session_id)?;
                 let mut stored = Vec::with_capacity(system_messages.len() + 2);
                 for content in system_messages {
                     stored.push(
@@ -497,6 +515,7 @@ impl Database {
     ) -> Result<Vec<StoredMessage>, String> {
         self.connection
             .transaction(|connection| {
+                touch_session(connection, session_id)?;
                 let mut stored = Vec::with_capacity(system_messages.len() + 3);
                 stored.push(
                     diesel::insert_into(messages::table)
@@ -686,6 +705,16 @@ impl Database {
     }
 }
 
+fn touch_session(
+    connection: &mut SqliteConnection,
+    session_id: i32,
+) -> Result<(), diesel::result::Error> {
+    diesel::update(sessions::table.find(session_id))
+        .set(sessions::last_used.eq(OffsetDateTime::now_utc().unix_timestamp()))
+        .execute(connection)
+        .map(|_| ())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -758,6 +787,46 @@ mod tests {
         fs::remove_file(path).unwrap();
     }
 
+    #[test]
+    fn sessions_are_ordered_by_recent_use_within_sidebar_groups() {
+        let id = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .unwrap()
+            .as_nanos();
+        let path = std::env::temp_dir().join(format!("ds4-session-order-{id}.sqlite3"));
+        let mut database = Database::open(&path).unwrap();
+        let project = database
+            .create_project("DS4", "/tmp/ds4-session-order")
+            .unwrap();
+        let older = database.create_session(project.id, "Older").unwrap();
+        let newer = database.create_session(project.id, "Newer").unwrap();
+        let pinned = database.create_session(project.id, "Pinned").unwrap();
+        database
+            .set_session_state(pinned.id, SessionState::Pinned)
+            .unwrap();
+        diesel::update(sessions::table.find(older.id))
+            .set(sessions::last_used.eq(100_i64))
+            .execute(&mut database.connection)
+            .unwrap();
+        diesel::update(sessions::table.find(newer.id))
+            .set(sessions::last_used.eq(200_i64))
+            .execute(&mut database.connection)
+            .unwrap();
+
+        let loaded = database.load_projects().unwrap();
+        assert_eq!(
+            loaded[0]
+                .sessions
+                .iter()
+                .map(|session| session.id)
+                .collect::<Vec<_>>(),
+            [pinned.id, newer.id, older.id]
+        );
+
+        drop(database);
+        fs::remove_file(path).unwrap();
+    }
+
     #[test]
     fn a2ui_dismissal_persists_a_fresh_surface_boundary() {
         let id = SystemTime::now()