Rewrite everything to use XmlImport/DbImport classes making things much more easy...

[dead/htsn-import.git] / src / Xml.hs

diff --git a/src/Xml.hs b/src/Xml.hs
index c4d4049e2f5ec4fc62d93d80ab31d83e8d07c764..95eddc0e51f949acbb287003dfb98c22ff244cb4 100644 (file)
--- a/src/Xml.hs
+++ b/src/Xml.hs
@@ -4,14 +4,13 @@
 --
 module Xml (
   DtdName(..),
-  ToFromXml(..),
+  FromXml(..),
   parse_opts,
   pickle_unpickle,
   unpickleable )
 where
 
 import Control.Exception ( SomeException(..), catch )
-import Database.Groundhog ( AutoKey )
 import Text.XML.HXT.Core (
   (>>>),
   (/>),
@@ -27,37 +26,21 @@ import Text.XML.HXT.Core (
   yes )
 
 
--- | A typeclass for types which can be converted into an associated
---   XML type. The story behind this is long, but basically, we need
+-- | A typeclass for XML types that can be converted into an associated
+--   database type. The story behind this is long, but basically, we need
 --   to different types for each XML thingie we're going to import: a
 --   database type and an XML type. Both Groundhog and HXT are very
 --   particular about the types that they can use, and there's no way
 --   to reuse e.g. a type that HXT can pickle in Groundhog. So this
---   typeclass gives us a way to get the XML type from the Groundhog
---   type.
+--   typeclass gives us a way to get the database type from the XML
+--   type that we have to define for HXT.
 --
---   At first there appears to be an equally-valid approach, getting the
---   Groundhog type from the XML one. But Groundhog won't use type family
---   instances, so here we are.
---
-class ToFromXml a where
-  -- | Each instance a must declare its associated XML type (Xml a)
-  type Xml a :: *
-  type Container a :: *
-
-  -- | And provide a function for getting an (Xml a) out of an "a."
-  to_xml :: a -> Xml a
-
-  -- | And provide a function for getting an "a" out of an (Xml a).
-  from_xml :: Xml a -> a
+class FromXml a where
+  -- | Each instance a must declare its associated database type (Db a)
+  type Db a :: *
 
-  -- | Often we need to provide a key to use as a foreign key into
-  --   some container. If the instance "belongs" to some other object,
-  --   then it might need to be passed a key before it can un-XML
-  --   itself. For example, the XML version of 'NewsTeam' doesn't
-  --   contain a message ID which is part of its database type.
-  from_xml_fk :: AutoKey (Container a) -> Xml a -> a
-  from_xml_fk _ = from_xml
+  -- | And provide a function for getting a (Db a) out of an "a".
+  from_xml :: a -> Db a
 
 
 -- | Represents the DTD filename ("SYSTEM") part of the DOCTYPE