it's a long story idiom
说来话长（用于别人向你询问某事时，表示你不想解释，因为要花很长时间）
something that you say when someone has asked you about something that has happened and you do not want to explain it to them because it would take too long
"So why was Carlo knocking on your door at midnight?" "It's a long story." “那为什么卡罗在午夜时分去敲你的房门呢？”“那可就说来话长了。”