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6 changed files with 79 additions and 30 deletions
55
Backend.hs
55
Backend.hs
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@ -18,24 +18,60 @@
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module Backend where
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import GitRepo
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import System.Directory
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import GitRepo
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import Utility
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type Key = String
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data Backend = Backend {
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name :: String, -- name of this backend
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keyvalue :: FilePath -> Maybe String, -- maps from key to value
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retrievekey :: IO String -> IO (Bool) -- retrieves value given key
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-- name of this backend
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name :: String,
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-- converts a filename to a key
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getKey :: FilePath -> IO (Maybe Key),
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-- stores a file's contents to a key
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storeFileKey :: FilePath -> Key -> IO (Bool),
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-- retrieves a key's contents to a file
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retrieveKeyFile :: IO Key -> FilePath -> IO (Bool)
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}
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instance Show Backend where
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show backend = "Backend { name =\"" ++ (name backend) ++ "\" }"
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{- Name of state file that holds the key for an annexed file,
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- using a given backend. -}
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backendFile :: Backend -> GitRepo -> FilePath -> String
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backendFile backend repo file = gitStateDir repo ++
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(gitRelative repo file) ++ "." ++ (name backend)
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{- Attempts to Stores a file in one of the backends. -}
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storeFile :: [Backend] -> GitRepo -> FilePath -> IO (Bool)
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storeFile [] _ _ = return False
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storeFile (b:bs) repo file = do
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try <- (getKey b) (gitRelative repo file)
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case (try) of
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Nothing -> storeFile bs repo file
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Just key -> do
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(storeFileKey b) file key
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createDirectoryIfMissing True (parentDir backendfile)
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writeFile backendfile key
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return True
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where backendfile = backendFile b repo file
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{- Attempts to retrieve an file from one of the backends, saving it to
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- a specified location. -}
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retrieveFile :: [Backend] -> GitRepo -> FilePath -> FilePath -> IO (Bool)
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retrieveFile backends repo file dest = do
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result <- lookupBackend backends repo file
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case (result) of
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Nothing -> return False
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Just b -> (retrieveKeyFile b) key dest
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where
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key = readFile (backendFile b repo file)
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{- Looks up the backend used for an already annexed file. -}
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lookupBackend :: [Backend] -> GitRepo -> FilePath -> IO (Maybe Backend)
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lookupBackend [] repo file = return Nothing
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lookupBackend [] _ _ = return Nothing
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lookupBackend (b:bs) repo file = do
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present <- checkBackend b repo file
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if present
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@ -47,12 +83,3 @@ lookupBackend (b:bs) repo file = do
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{- Checks if a file is available via a given backend. -}
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checkBackend :: Backend -> GitRepo -> FilePath -> IO (Bool)
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checkBackend backend repo file = doesFileExist $ backendFile backend repo file
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{- Attempts to retrieve an annexed file from one of the backends. -}
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retrieveFile :: [Backend] -> GitRepo -> FilePath -> IO (Bool)
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retrieveFile backends repo file = do
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result <- lookupBackend backends repo file
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case (result) of
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Nothing -> return False
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Just b -> (retrievekey b) key
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where key = readFile (backendFile b repo file)
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