Rewrite TSN.DbImport.run_dbmigrate for groundhog-0.7.

[dead/htsn-import.git] / src / TSN / DbImport.hs

diff --git a/src/TSN/DbImport.hs b/src/TSN/DbImport.hs
index 8884a9eef4708597aaca4b2ac22b6d5530f7391c..066b5a0c36e7e8ec2a72dfc687224a03ff3b1b79 100644 (file)
--- a/src/TSN/DbImport.hs
+++ b/src/TSN/DbImport.hs
@@ -1,21 +1,40 @@
 -- | Definition of the DbImport typeclass.
+--
+--   When we parse an XML tree, there are two functions that we would
+--   like to call on the result independent of its type. First, we
+--   would like to be able to run the database migrations for that
+--   type. The migrations are kept separate from insertion because, at
+--   some later point, it make make sense to disable automatic
+--   migrations.
+--
+--   Next we want to import the thing.
+--
+--   Neither of these should depend on the type -- we should just be
+--   able to call 'dbmigrate' followed by 'dbimport' on the
+--   datastructure and have the right thing happen. That is the
+--   purpose of the 'DbImport' typeclass. It allows the XML types to
+--   define their own \"migrate me\" and \"insert me\" functions that
+--   the rest of the application doesn't have to care about.
+--
 module TSN.DbImport (
   DbImport(..),
   ImportResult(..),
-  dbimport_generic,
   run_dbmigrate )
 where
 
 -- System imports
-import Control.Monad.IO.Class ( MonadIO )
-import Database.Groundhog (
-  runMigration )
+import Control.Monad ( forM_ )
+import Control.Monad.IO.Class ( MonadIO( liftIO ) )
+import qualified Data.Map as Map ( elems )
+import Database.Groundhog ( executeRaw )
+import Database.Groundhog.Core ( NamedMigrations )
+import Database.Groundhog.Generic (
+  createMigration,
+  getQueries,
+  mergeMigrations )
 import Database.Groundhog.Core ( Migration, PersistBackend )
 import Network.Services.TSN.Report ( report_info )
 
--- Local imports
-import TSN.XmlImport ( XmlImport(..) )
-
 
 -- | The type that will be returned from every file import attempt.
 --
@@ -31,32 +50,31 @@ data ImportResult =
                              --   The second field should contain info.
 
 
--- | Instances of this type know how to insert themselves into a
---   Groundhog database.
+-- | Instances of this type know how to run their own database
+--   migrations and insert themselves into a database.
 --
 class DbImport a where
   -- | Import an instance of type @a@.
   dbimport :: (PersistBackend m) => a -> m ImportResult
 
   -- | This must migrate *all* stuffs that can potentially be
-  -- created/used by the type @a@.
+  --   created/used by the type @a@.
   dbmigrate :: (MonadIO m, PersistBackend m) => a -> m ()
 
 
--- | The simplest possible implementation of 'dbimport', for types
---   which happen to be members of the XmlImport typeclass.
---
-dbimport_generic :: (XmlImport a, MonadIO m, PersistBackend m)
-                 => a
-                 -> m ImportResult
-dbimport_generic x = insert_xml x >> return ImportSucceeded
-
-
 -- | A migration runner that will use our normal info reporting
---   mechanism.
+--   mechanism. The top-level code was stolen from 'runMigration' in
+--   "Data.Groundhog.Generic" and the 'execute_pretty' code was stolen
+--   from 'executeMigration'' in the same module.
+--
 run_dbmigrate :: (MonadIO m, PersistBackend m) => Migration m -> m ()
-run_dbmigrate =
-  runMigration pretty_migration_logger
+run_dbmigrate migration = createMigration migration >>= execute_pretty
   where
-    pretty_migration_logger x =
-      report_info ("Migration: " ++ x ++ ";")
+    execute_pretty :: (PersistBackend m, MonadIO m) => NamedMigrations -> m ()
+    execute_pretty m = do
+      let migs = getQueries False $ mergeMigrations $ Map.elems m
+      case migs of
+        Left errs -> fail $ unlines errs
+        Right qs -> forM_ qs $ \q -> do
+                         liftIO $ report_info ("Migration: " ++ q ++ ";")
+                         executeRaw False q []