Add Template Haskell code for constant generation

Add Template Haskell functions that generate a list in Haskell
containing all the constants to be generated in Python.  This list is
an association list mapping the constant name to its Python value,
which is stored as a string.
Signed-off-by: Jose A. Lopes <jabolopes@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

Makefile.am

@@ -630,6 +630,7 @@ HS_LIB_SRCS = \
 	src/Ganeti/Hypervisor/Xen/XmParser.hs \
 	src/Ganeti/Hypervisor/Xen/Types.hs \
 	src/Ganeti/Hash.hs \
+	src/Ganeti/Hs2Py/GenConstants.hs \
 	src/Ganeti/Hs2Py/GenOpCodes.hs \
 	src/Ganeti/Hs2Py/OpDoc.hs \
 	src/Ganeti/JQueue.hs \

src/Ganeti/Hs2Py/GenConstants.hs

+{-| Template Haskell code for Haskell to Python constants.
+
+-}
+
+{-
+
+Copyright (C) 2013 Google Inc.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.
+
+-}
+{-# LANGUAGE TemplateHaskell #-}
+module Ganeti.Hs2Py.GenConstants (genPyConstants) where
+
+import Language.Haskell.TH
+
+import Ganeti.THH
+
+genList :: Name -> [Name] -> Q [Dec]
+genList name consNames = do
+  let cons = listE $ map (\n -> tupE [mkString n, mkPyValueEx n]) consNames
+  sig <- sigD name [t| [(String, String)] |]
+  fun <- funD name [clause [] (normalB cons) []]
+  return [sig, fun]
+  where mkString n = stringE (deCamelCase (nameBase n))
+        mkPyValueEx n = [| showValue $(varE n) |]
+
+genPyConstants :: String -> [Name] -> Q [Dec]
+genPyConstants name = genList (mkName name)

src/Ganeti/THH.hs

@@ -32,6 +32,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 module Ganeti.THH ( declareSADT
                   , declareIADT
                   , makeJSONInstance
+                  , deCamelCase
                   , genOpID
                   , genAllConstr
                   , genAllOpIDs