src/TSN/DbImport.hs

   1 -- | Definition of the DbImport typeclass.
   2 module TSN.DbImport
   3 where
   4
   5 import Control.Monad.IO.Class ( MonadIO )
   6 import Database.Groundhog.Core ( PersistBackend )
   7
   8 import TSN.XmlImport ( XmlImport(..) )
   9
  10 -- | The type that will be returned from every file import attempt.
  11 --
  12 data ImportResult =
  13   ImportFailed String -- ^ Failure with an error message.
  14     | ImportSkipped String -- ^ We processed the file, but didn't import it.
  15                            --   The reason is contained in the second field.
  16     | ImportSucceeded      -- ^ We did import records.
  17     | ImportUnsupported String -- ^ We didn't know how to process this file.
  18                                --   The second field should contain info.
  19
  20 -- | Instances of this type know how to insert themselves into a
  21 --   Groundhog database.
  22 --
  23 class DbImport a where
  24   -- | Import an instance of type @a@.
  25   dbimport :: (PersistBackend m) => a -> m ImportResult
  26
  27   -- | This must migrate *all* stuffs that can potentially be
  28   -- created/used by the type @a@.
  29   dbmigrate :: (MonadIO m, PersistBackend m) => a -> m ()
  30
  31 dbimport_generic :: (XmlImport a, MonadIO m, PersistBackend m)
  32                  => a
  33                  -> m ImportResult
  34 dbimport_generic x = insert_xml x >> return ImportSucceeded