Imam Mahdi(as) and Sharia

[Lion of Shia]

as salaam alakim!!!

I know in hadiths it says when Imam Mahdi comes he will establish islam, but in certain hadiths it says he'll rule people by their books, but will he rule by islamic laws? i know in sunni hadiths it says him and Isa(عليه السلام) will establish islam, but in shia it syas he'll rule by the books of the people of the book and islam. So how will ImamMahdi(عليه السلام) rule according to Shia islam(i mean will hell rue also by the Sharia(shia)?

[Ashvazdanghe]

Salam it said that original books of Torah & Bible are with him that at first he will use these books to convince people of book for joining to him that can be judgment based on their original books that after converting whole of people to Islam by him he will use combination of whole divine books & scriptures in addition of holy Quran  for ruling whole of people that whole of Sharia rule according Shia Islam means holy Quran  in addition of whole of original divine boos & scriptures that are with Imam Mahdi (aj).