X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FXml.hs;h=d4ea4679cef1bafc974e7d9eede7249b39957491;hb=928a90109375caaa888ae4413151b560838948b7;hp=866ac4647fc258326cf8369ad5783f0a1ee375a6;hpb=4cdcdbe593c30f6434a25896951a1a4dfcc2b1ca;p=dead%2Fhtsn-import.git

diff --git a/src/Xml.hs b/src/Xml.hs
index 866ac46..d4ea467 100644
--- a/src/Xml.hs
+++ b/src/Xml.hs
@@ -1,32 +1,54 @@
+{-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TypeFamilies #-}
 
 -- | General XML stuff.
 --
 module Xml (
+  Child(..),
   DtdName(..),
   FromXml(..),
+  FromXmlFk(..),
+  ToDb(..),
   parse_opts,
+  parse_opts_novalidate,
   pickle_unpickle,
-  unpickleable )
+  unpickleable,
+  unsafe_read_document,
+  unsafe_read_invalid_document,
+  unsafe_unpickle )
 where
 
 -- System imports.
 import Control.Exception ( SomeException(..), catch )
+import Database.Groundhog.Core ( PersistEntity(..) )
 import Text.XML.HXT.Core (
   (>>>),
   (/>),
   PU,
   SysConfigList,
-  XmlPickler(..),
+  XmlTree,
   isElem,
+  no,
   readDocument,
   runX,
   withRemoveWS,
+  withSubstDTDEntities,
+  withValidate,
   xpickleVal,
+  xunpickleDocument,
   xunpickleVal,
   yes )
 
 
+
+-- | Common associated type shared by 'FromXml' and 'FromXmlFk'. This
+--   basically just forces the client to define the \"database
+--   version\" of his type.
+--
+class ToDb a where
+  -- | Each instance @a@ must declare its associated database type @Db a@.
+  type Db a :: *
+
 -- | 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 most XML thingies we're
@@ -38,14 +60,35 @@ import Text.XML.HXT.Core (
 --   to get the database type from the XML type that we have to define
 --   for HXT.
 --
-class FromXml a where
-  -- | Each instance @a@ must declare its associated database type @Db a@.
-  type Db a :: *
-
-  -- | And provide a function for getting a @Db a@ out of an @a@.
+class (ToDb a) => FromXml a where
+  -- | A function for getting a @Db a@ out of an @a@.
   from_xml :: a -> Db a
 
 
+-- | A class for XML representations which are children of other
+--   elements. The foal is to associate a child XML element with its
+--   parent element's database type. This is required to construct the
+--   database analogue of @a@ in 'FromXmlFk'.
+--
+class Child a where
+  -- | The type of our parent object, i.e. to the type to whom our
+  --   foreign key will point.
+  type Parent a :: *
+
+
+-- | Some database types cannot be constructed from the XML type
+--   alone; they must be supplied a foreign key to a parent object
+--   first. Members of this class can be converted from an XML
+--   representation to a database representation in this manner.
+--
+class (Child a, ToDb a) => FromXmlFk a where
+  -- | The function that produces a @Db a@ out of a foreign key and an
+  --   @a@. The parameter order makes it easier to map this function
+  --   over a bunch of things.
+  from_xml_fk :: DefaultKey (Parent a) -> a -> Db a
+
+
+
 -- | Represents the DTD filename (\"SYSTEM\") part of the DOCTYPE
 --   definition.
 newtype DtdName = DtdName String
@@ -55,7 +98,15 @@ newtype DtdName = DtdName String
 --   would have to parse whitespace in each (un)pickler.
 --
 parse_opts :: SysConfigList
-parse_opts = [ withRemoveWS yes ]
+parse_opts = [ withRemoveWS yes,
+               withSubstDTDEntities no ]
+
+-- | Like 'parse_opts' except we don't validate the document against
+--   its DTD. This is useful when we need to parse a document that we
+--   /know/ is invalid so that we can deliver a better error message.
+--
+parse_opts_novalidate :: SysConfigList
+parse_opts_novalidate = (withValidate no) : parse_opts
 
 
 -- | Given an @unpickler@ and a @filepath@, attempt to unpickle the
@@ -115,3 +166,26 @@ unpickleable filepath unpickler = do
     try_unpickle = runX $ readDocument parse_opts filepath
                           >>>
                           xunpickleVal unpickler
+
+
+-- | Unpickle from a 'FilePath' using the given pickler. Explode if it
+--   doesn't work.
+--
+unsafe_unpickle :: FilePath -> PU a -> IO a
+unsafe_unpickle filepath unpickler =
+  fmap head $ runX $ xunpickleDocument unpickler parse_opts filepath
+
+
+-- | Read an XML document from a 'FilePath' into an XmlTree. Explode if it
+--   doesn't work.
+--
+unsafe_read_document :: FilePath -> IO XmlTree
+unsafe_read_document filepath =
+  fmap head $ runX $ readDocument parse_opts filepath
+
+-- | The same as 'unsafe_read_document', except it allows you to read
+--   documents which don't validate against their DTDs.
+--
+unsafe_read_invalid_document :: FilePath -> IO XmlTree
+unsafe_read_invalid_document filepath =
+  fmap head $ runX $ readDocument parse_opts_novalidate filepath