Hi Rohan,
Embedded mode has a concept similar to BADI - custom planning functions. But since the whole approach is different sometimes BADI in Standard mode can be converted to delivered Planning Functions or FOX.
So, as everyone above, I'd suggest as a fist step take a look if standard functionality can help you to reach your goal; if it can't then consider FOX and only if it can't deliver those results then custom functions.
Regards,
Gersh