2012-11-08 11:45:26 +00:00
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module Hakyll.Core.Resource.Modified
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( resourceModified
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, resourceModificationTime
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) where
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import Control.Applicative ((<$>), (<*>))
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import Control.Monad (when)
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import qualified Crypto.Hash.MD5 as MD5
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import qualified Data.ByteString as B
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import qualified Data.ByteString.Lazy as BL
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import Data.IORef
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import qualified Data.Map as M
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import Data.Time (UTCTime)
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import System.Directory (getModificationTime)
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--------------------------------------------------------------------------------
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import Hakyll.Core.Resource
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import Hakyll.Core.Resource.MetadataCache
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import Hakyll.Core.Resource.Provider.Internal
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import Hakyll.Core.Store (Store)
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import qualified Hakyll.Core.Store as Store
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--------------------------------------------------------------------------------
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-- | A resource is modified if it or its metadata has changed
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resourceModified :: ResourceProvider -> Resource -> IO Bool
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resourceModified rp r
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| not exists = return False
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| otherwise = do
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cache <- readIORef cacheRef
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case M.lookup r cache of
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Just m -> return m
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Nothing -> do
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-- Check if the actual file was modified, and do a recursive
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-- call to check if the metadata file was modified
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m <- (||)
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<$> fileDigestModified store (unResource r)
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<*> resourceModified rp (resourceMetadataResource r)
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modifyIORef cacheRef (M.insert r m)
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2012-11-08 12:50:08 +00:00
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-- Important! (But ugly)
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2012-11-08 11:45:26 +00:00
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when m $ resourceInvalidateMetadataCache rp r
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return m
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where
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exists = resourceExists rp r
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store = resourceStore rp
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cacheRef = resourceModifiedCache rp
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--------------------------------------------------------------------------------
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-- | Utility: Check if a the digest of a file was modified
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fileDigestModified :: Store -> FilePath -> IO Bool
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fileDigestModified store fp = do
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-- Get the latest seen digest from the store, and calculate the current
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-- digest for the
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lastDigest <- Store.get store key
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newDigest <- fileDigest fp
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if Store.Found newDigest == lastDigest
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-- All is fine, not modified
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then return False
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-- Resource modified; store new digest
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else do
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Store.set store key newDigest
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return True
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where
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key = ["Hakyll.Core.Resource.Provider.fileModified", fp]
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--------------------------------------------------------------------------------
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-- | Utility: Retrieve a digest for a given file
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fileDigest :: FilePath -> IO B.ByteString
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fileDigest = fmap MD5.hashlazy . BL.readFile
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--------------------------------------------------------------------------------
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resourceModificationTime :: Resource -> IO UTCTime
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resourceModificationTime = getModificationTime . unResource
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