Add Item abstraction

1 files changed, 62 insertions, 0 deletions

diff --git a/src/Hakyll/Core/Provider/MetadataCache.hs b/src/Hakyll/Core/Provider/MetadataCache.hs
new file mode 100644
index 0000000..cd67370
--- /dev/null
+++ b/src/Hakyll/Core/Provider/MetadataCache.hs
@@ -0,0 +1,62 @@
+--------------------------------------------------------------------------------
+module Hakyll.Core.Provider.MetadataCache
+    ( resourceMetadata
+    , resourceBody
+    , resourceInvalidateMetadataCache
+    ) where
+
+
+--------------------------------------------------------------------------------
+import           Hakyll.Core.Identifier
+import           Hakyll.Core.Metadata
+import           Hakyll.Core.Provider.Internal
+import           Hakyll.Core.Provider.Metadata
+import qualified Hakyll.Core.Store             as Store
+
+
+--------------------------------------------------------------------------------
+resourceMetadata :: Provider -> Identifier -> IO Metadata
+resourceMetadata p r = do
+    load p r
+    Store.Found md <- Store.get (providerStore p)
+        [name, toFilePath r, "metadata"]
+    return md
+
+
+--------------------------------------------------------------------------------
+resourceBody :: Provider -> Identifier -> IO String
+resourceBody p r = do
+    load p r
+    Store.Found bd <- Store.get (providerStore p)
+        [name, toFilePath r, "body"]
+    maybe (resourceString r) return bd
+
+
+--------------------------------------------------------------------------------
+resourceInvalidateMetadataCache :: Provider -> Identifier -> IO ()
+resourceInvalidateMetadataCache p r = do
+    Store.delete (providerStore p) [name, toFilePath r, "metadata"]
+    Store.delete (providerStore p) [name, toFilePath r, "body"]
+
+
+--------------------------------------------------------------------------------
+load :: Provider -> Identifier -> IO ()
+load p r = do
+    mmd <- Store.get store mdk :: IO (Store.Result Metadata)
+    case mmd of
+        -- Already loaded
+        Store.Found _  -> return ()
+        -- Not yet loaded
+        _ -> do
+            (metadata, body) <- loadMetadata p r
+            Store.set store mdk metadata
+            Store.set store bk  body
+  where
+    store = providerStore p
+    mdk   = [name, toFilePath r, "metadata"]
+    bk    = [name, toFilePath r, "body"]
+
+
+--------------------------------------------------------------------------------
+name :: String
+name = "Hakyll.Core.Resource.Provider.MetadataCache"