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|
-- | A store for stroing and retreiving items
--
module Hakyll.Core.Store
( Store
, makeStore
, storeSet
, storeGet
, wasModified
) where
import Control.Applicative ((<$>))
import System.FilePath ((</>))
import System.Directory (doesFileExist)
import Data.Binary (Binary, encodeFile, decodeFile)
import Hakyll.Core.Identifier
import Hakyll.Core.Util.File
import Hakyll.Core.ResourceProvider
-- | Data structure used for the store
--
data Store = Store
{ storeDirectory :: FilePath
}
-- | Initialize the store
--
makeStore :: FilePath -> IO Store
makeStore directory = return Store {storeDirectory = directory}
-- | Create a path
--
makePath :: Store -> String -> Identifier -> FilePath
makePath store name identifier =
storeDirectory store </> name </> toFilePath identifier
-- | Store an item
--
storeSet :: Binary a => Store -> String -> Identifier -> a -> IO ()
storeSet store name identifier value = do
makeDirectories path
encodeFile path value
where
path = makePath store name identifier
-- | Load an item
--
storeGet :: Binary a => Store -> String -> Identifier -> IO (Maybe a)
storeGet store name identifier = do
exists <- doesFileExist path
if exists then Just <$> decodeFile path
else return Nothing
where
path = makePath store name identifier
-- | Check if a resource was modified
--
wasModified :: Store -> ResourceProvider -> Identifier -> IO Bool
wasModified store provider identifier = do
-- Get the latest seen digest from the store
lastDigest <- storeGet store itemName identifier
-- Calculate the digest for the resource
newDigest <- resourceDigest provider identifier
-- Check digests
if Just newDigest == lastDigest
-- All is fine, not modified
then return False
-- Resource modified; store new digest
else do storeSet store itemName identifier newDigest
return True
where
itemName = "Hakyll.Core.Store.wasModified"
|
