Rule reminder
Modal verbs (potere, dovere, volere) can appear in both the protasis (se-clause) and apodosis (result clause). In type 2/3 conditionals: 'Se potessi farlo, lo farei' (type 2); 'Se avessi potuto farlo, lo avrei fatto' (type 3). The modal itself must also be conjugated in the appropriate subjunctive or conditional form.
Se _____ venire alla festa, ti _____ avvisare prima.