laravel model "case" or if statement

so i'm newer to laravel models and have searched pretty extensively and wondering how to do the following in the model.

i have a master table (primary key=id) with a fields of type and type_id.

if the value of type=1, i want to reference table1 and the records master.type_id=table1.primarykey. this table has field abc

if the value of type=2, i want to reference table2 and the records master.type_id=table2.primarykey. this table has field def

i'm wondering what the model is that would do this and i'd be able to reference fields abc and def.

thanks for your help