Making API call for users(SPREE)

Hi All,

   Spree supports 7 API Calls:

=> Orders
=> LineItems
=> Shipments
=> InventoryUnits
=> Products
=> Countries
=> States

I want to make an API which can create users in Get Method and Respond
me back when the user is signed in.

& The same when I post the user name and password it should signup and
give me the API key through which I can access the data's .

Please Help me out in solving this problem. Anyone's help is
Appreciated.

Thanks In Advance
Santosh