Simple key-value store

src/Hakyll/Core/Store.hs

@@ -0,0 +1,53 @@
+-- | A store for stroing and retreiving items
+--
+module Hakyll.Core.Store
+    ( Store
+    , makeStore
+    , storeSet
+    , storeGet
+    ) where
+
+import Control.Applicative ((<$>))
+import System.FilePath ((</>))
+import System.Directory (doesFileExist)
+
+import Data.Binary (Binary, encodeFile, decodeFile)
+
+import Hakyll.Core.Identifier
+import Hakyll.Core.Util.File
+
+-- | Data structure used for the store
+--
+data Store = Store
+    { storeDirectory :: FilePath
+    }
+
+-- | Initialize the store
+--
+makeStore :: FilePath -> IO Store
+makeStore directory = return Store {storeDirectory = directory}
+
+-- | Create a path
+--
+makePath :: Store -> String -> Identifier -> FilePath
+makePath store name identifier =
+    storeDirectory store </> name </> toFilePath identifier
+
+-- | Store an item
+--
+storeSet :: Binary a => Store -> String -> Identifier -> a -> IO ()
+storeSet store name identifier value = do
+    makeDirectories path
+    encodeFile path value
+  where
+    path = makePath store name identifier
+
+-- | Load an item
+--
+storeGet :: Binary a => Store -> String -> Identifier -> IO (Maybe a)
+storeGet store name identifier = do
+    exists <- doesFileExist path
+    if exists then Just <$> decodeFile path
+              else return Nothing
+  where
+    path = makePath store name identifier