moon over someone/something        
phrasal verb with moon verb [ I or T  ]  informal uk/muːn/ us/muːn/
 无望地思念
to spend time thinking about someone or something that you love, in a silly way that does not achieve anything
  He spends all his time mooning over a girl at school. 他把所有时间都用来无望地思念学校里的一个女孩子。