أعراب أمضيت وقتي داخل المكتبة

The sentence (أمضيت وقتي داخل المكتبة) can be analyzed as follows: أمضيت is a past verb in the active voice with the subject marker تاء الفاعل indicating a pronoun in the nominative case. وقتي is the accusative object with a fatha vowel indicating its case. داخل is a preposition indicating location with a fatha vowel indicating its case. المكتبة is a genitive noun with a kasra vowel indicating its case.