Split the (Parent a) associated type into a new Child class.

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

diff --git a/src/Xml.hs b/src/Xml.hs
index 780a64e6473815ecd0ec88d4257e4d1ce231373c..7cfe6eb19f169dbb544d80869f6d43acfc2a33e4 100644 (file)
--- a/src/Xml.hs
+++ b/src/Xml.hs
@@ -4,13 +4,16 @@
 -- | General XML stuff.
 --
 module Xml (
+  Child(..),
   DtdName(..),
   FromXml(..),
   FromXmlFk(..),
+  FromXmlFkTeams(..),
   ToDb(..),
   parse_opts,
   pickle_unpickle,
   unpickleable,
+  unsafe_read_document,
   unsafe_unpickle )
 where
 
@@ -22,6 +25,7 @@ import Text.XML.HXT.Core (
   (/>),
   PU,
   SysConfigList,
+  XmlTree,
   isElem,
   no,
   readDocument,
@@ -34,6 +38,11 @@ import Text.XML.HXT.Core (
   xunpickleVal,
   yes )
 
+
+-- Local imports.
+import TSN.Team ( Team(..) )
+
+
 -- | Common associated type shared by 'FromXml' and 'FromXmlFk'. This
 --   basically just forces the client to define the \"database
 --   version\" of his type.
@@ -58,22 +67,46 @@ class (ToDb a) => FromXml a where
   from_xml :: a -> Db 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.
+-- | 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 the 'FromXmlFk' and 'FromXmlFkTeams'
+--   classes.
 --
-class (ToDb a) => FromXmlFk a where
+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
 
 
+-- | A further refinement of 'FromXmlFk'. These types need not only a
+--   foreign key to a parent in order to make the XML -> DB
+--   conversion, but also two foreign keys to away/home teams (as
+--   represented in "TSN.Team").
+--
+class (Child a, ToDb a) => FromXmlFkTeams a where
+  -- | The function that produces a @Db a@ out of a parent foreign
+  -- key, two team foreign keys, and an @a@. The parameter order makes
+  -- it easier to map this function over a bunch of things.
+  from_xml_fk_teams :: DefaultKey (Parent a)
+                    -> DefaultKey Team -- ^ The away team FK
+                    -> DefaultKey Team -- ^ The home team FK
+                    -> a
+                    -> Db a
+
+
 -- | Represents the DTD filename (\"SYSTEM\") part of the DOCTYPE
 --   definition.
 newtype DtdName = DtdName String
@@ -153,3 +186,11 @@ unpickleable filepath unpickler = do
 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