Don't require Writable for storing things

2 files changed, 14 insertions, 11 deletions

diff --git a/src/Hakyll/Core/CompiledItem.hs b/src/Hakyll/Core/CompiledItem.hs
index 2e492a2..e40ab56 100644
--- a/src/Hakyll/Core/CompiledItem.hs
+++ b/src/Hakyll/Core/CompiledItem.hs
@@ -7,7 +7,7 @@
 --
 -- * we need a 'Writable' instance so the results can be saved.
 --
-{-# LANGUAGE ExistentialQuantification #-}
+{-# LANGUAGE ExistentialQuantification, DeriveDataTypeable #-}
 module Hakyll.Core.CompiledItem
     ( CompiledItem (..)
     , compiledItem
@@ -24,6 +24,7 @@ import Hakyll.Core.Writable
 --
 data CompiledItem =  forall a.  (Binary a, Typeable a, Writable a)
                   => CompiledItem a
+                  deriving (Typeable)
 
 instance Writable CompiledItem where
     write p (CompiledItem x) = write p x
diff --git a/src/Hakyll/Core/Store.hs b/src/Hakyll/Core/Store.hs
index 12e33a7..50ffa90 100644
--- a/src/Hakyll/Core/Store.hs
+++ b/src/Hakyll/Core/Store.hs
@@ -1,5 +1,6 @@
 -- | A store for stroing and retreiving items
 --
+{-# LANGUAGE ExistentialQuantification #-}
 module Hakyll.Core.Store
     ( Store
     , makeStore
@@ -14,20 +15,22 @@ import Data.Map (Map)
 import qualified Data.Map as M
 
 import Data.Binary (Binary, encodeFile, decodeFile)
-import Data.Typeable (Typeable)
+import Data.Typeable (Typeable, cast)
 
-import Hakyll.Core.CompiledItem
-import Hakyll.Core.Writable
 import Hakyll.Core.Identifier
 import Hakyll.Core.Util.File
 
+-- | Items we can store
+--
+data Storable = forall a. (Binary a, Typeable a) => Storable a
+
 -- | Data structure used for the store
 --
 data Store = Store
     { -- | All items are stored on the filesystem
       storeDirectory :: FilePath
     , -- | And some items are also kept in-memory
-      storeMap :: MVar (Map FilePath CompiledItem)
+      storeMap :: MVar (Map FilePath Storable)
     }
 
 -- | Initialize the store
@@ -42,10 +45,9 @@ makeStore directory = do
 
 -- | Auxiliary: add an item to the map
 --
-addToMap :: (Binary a, Typeable a, Writable a)
-         => Store -> FilePath -> a -> IO ()
+addToMap :: (Binary a, Typeable a) => Store -> FilePath -> a -> IO ()
 addToMap store path value =
-    modifyMVar_ (storeMap store) $ return . M.insert path (compiledItem value)
+    modifyMVar_ (storeMap store) $ return . M.insert path (Storable value)
 
 -- | Create a path
 --
@@ -55,7 +57,7 @@ makePath store name identifier =
 
 -- | Store an item
 --
-storeSet :: (Binary a, Typeable a, Writable a)
+storeSet :: (Binary a, Typeable a)
          => Store -> String -> Identifier -> a -> IO ()
 storeSet store name identifier value = do
     makeDirectories path
@@ -66,14 +68,14 @@ storeSet store name identifier value = do
 
 -- | Load an item
 --
-storeGet :: (Binary a, Typeable a, Writable a)
+storeGet :: (Binary a, Typeable a)
          => Store -> String -> Identifier -> IO (Maybe a)
 storeGet store name identifier = do
     -- First check the in-memory map
     map' <- readMVar $ storeMap store
     case M.lookup path map' of
         -- Found in the in-memory map
-        Just c -> return $ Just $ unCompiledItem c
+        Just (Storable s) -> return $ cast s
         -- Not found in the map, try the filesystem
         Nothing -> do
             exists <- doesFileExist path