Load the lead's scrollback 50 turns at a time

internal/store/store.go

@@ -1297,6 +1297,33 @@ func (s *Store) LeadEvents(ctx context.Context, owner string, after int64, limit
 	return scanEvents(rows)
 }
 
+func (s *Store) LeadEventsPage(ctx context.Context, owner string, before int64, turns int) (api.EventPage, error) {
+	from := int64(0)
+	more := true
+	err := s.db.QueryRowContext(ctx, `
+		SELECT seq FROM events WHERE owner = ? AND agent_session_id IS NOT NULL AND kind = 'turn.ended' AND seq < ?
+		ORDER BY seq DESC LIMIT 1 OFFSET ?
+	`, owner, before, turns).Scan(&from)
+	if errors.Is(err, sql.ErrNoRows) {
+		more = false
+	} else if err != nil {
+		return api.EventPage{}, err
+	}
+
+	rows, err := s.db.QueryContext(ctx, `
+		SELECT `+eventColumns+`
+		FROM events WHERE owner = ? AND agent_session_id IS NOT NULL AND seq > ? AND seq < ? ORDER BY seq
+	`, owner, from, before)
+	if err != nil {
+		return api.EventPage{}, err
+	}
+	events, err := scanEvents(rows)
+	if err != nil {
+		return api.EventPage{}, err
+	}
+	return api.EventPage{Events: events, More: more}, nil
+}
+
 func scanEvents(rows *sql.Rows) ([]api.Event, error) {
 	defer rows.Close()