From 1319bbfe4ab3ddd321bcbb902bba7392ad868324 Mon Sep 17 00:00:00 2001
From: Jasper Van der Jeugt <m@jaspervdj.be>
Date: Fri, 9 Nov 2012 16:34:45 +0100
Subject: Remove Resource type

---
 src/Hakyll/Core/ResourceProvider/Modified.hs | 83 ++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 src/Hakyll/Core/ResourceProvider/Modified.hs

(limited to 'src/Hakyll/Core/ResourceProvider/Modified.hs')

diff --git a/src/Hakyll/Core/ResourceProvider/Modified.hs b/src/Hakyll/Core/ResourceProvider/Modified.hs
new file mode 100644
index 0000000..837bc8c
--- /dev/null
+++ b/src/Hakyll/Core/ResourceProvider/Modified.hs
@@ -0,0 +1,83 @@
+--------------------------------------------------------------------------------
+module Hakyll.Core.ResourceProvider.Modified
+    ( resourceModified
+    , resourceModificationTime
+    ) where
+
+
+--------------------------------------------------------------------------------
+import           Control.Applicative                        ((<$>), (<*>))
+import           Control.Monad                              (when)
+import qualified Crypto.Hash.MD5                            as MD5
+import qualified Data.ByteString                            as B
+import qualified Data.ByteString.Lazy                       as BL
+import           Data.IORef
+import qualified Data.Map                                   as M
+import           Data.Time                                  (UTCTime)
+import           System.Directory                           (getModificationTime)
+
+
+--------------------------------------------------------------------------------
+import           Hakyll.Core.Identifier
+import           Hakyll.Core.ResourceProvider.Internal
+import           Hakyll.Core.ResourceProvider.MetadataCache
+import           Hakyll.Core.Store                          (Store)
+import qualified Hakyll.Core.Store                          as Store
+
+
+--------------------------------------------------------------------------------
+-- | A resource is modified if it or its metadata has changed
+resourceModified :: ResourceProvider -> Identifier a -> IO Bool
+resourceModified rp r
+    | not exists = return False
+    | otherwise  = do
+        cache <- readIORef cacheRef
+        case M.lookup normalized cache of
+            Just m  -> return m
+            Nothing -> do
+                -- Check if the actual file was modified, and do a recursive
+                -- call to check if the metadata file was modified
+                m <- (||)
+                    <$> fileDigestModified store (toFilePath r)
+                    <*> resourceModified rp (resourceMetadataResource r)
+                modifyIORef cacheRef (M.insert normalized m)
+
+                -- Important! (But ugly)
+                when m $ resourceInvalidateMetadataCache rp r
+
+                return m
+  where
+    normalized = castIdentifier $ setGroup Nothing r
+    exists     = resourceExists rp r
+    store      = resourceStore rp
+    cacheRef   = resourceModifiedCache rp
+
+
+--------------------------------------------------------------------------------
+-- | Utility: Check if a the digest of a file was modified
+fileDigestModified :: Store -> FilePath -> IO Bool
+fileDigestModified store fp = do
+    -- Get the latest seen digest from the store, and calculate the current
+    -- digest for the
+    lastDigest <- Store.get store key
+    newDigest  <- fileDigest fp
+    if Store.Found newDigest == lastDigest
+        -- All is fine, not modified
+        then return False
+        -- Resource modified; store new digest
+        else do
+            Store.set store key newDigest
+            return True
+  where
+    key = ["Hakyll.Core.Resource.Provider.fileModified", fp]
+
+
+--------------------------------------------------------------------------------
+-- | Utility: Retrieve a digest for a given file
+fileDigest :: FilePath -> IO B.ByteString
+fileDigest = fmap MD5.hashlazy . BL.readFile
+
+
+--------------------------------------------------------------------------------
+resourceModificationTime :: Identifier a -> IO UTCTime
+resourceModificationTime = getModificationTime . toFilePath
-- 
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