Database.hs

-- | Standalone database functions for dealing with Groundhog types.
--
module TSN.Database ( insert_or_select )
where

import Database.Groundhog ( AutoKey, insertByAll )
import Database.Groundhog.Core ( PersistBackend, PersistEntity )


-- | Attempt to insert the given object returning its new primary
--   key. If any unique constraints would be violated, instead return
--   the primary key of the existing record that caused the collision.
insert_or_select :: (PersistBackend m, PersistEntity a)
                 => a
                 -> m (AutoKey a)
insert_or_select x = do
  tmp <- insertByAll x
  return $ (either id id) tmp