What is the grammatical role of ḥubbaki in anna ḥubbaki qātilī?

Imruʾ al-Qays: Address to Fāṭimah, Parting, and the Arrows of the Eyes (Verses 19–22)

• The nominative predicate of anna
• A jussive conditional verb
• The accusative noun of anna
• An imperfect after a purpose-lām