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+{- Types for Storer and Retriever actions for remotes.
+ -
+ - Copyright 2014 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+{-# LANGUAGE Rank2Types #-}
+
+module Types.StoreRetrieve where
+
+import Common.Annex
+import Utility.Metered
+
+import qualified Data.ByteString.Lazy as L
+
+-- Prepares for and then runs an action that will act on a Key's
+-- content, passing it a helper when the preparation is successful.
+type Preparer helper = forall a. Key -> (Maybe helper -> Annex a) -> Annex a
+
+-- A source of a Key's content.
+data ContentSource
+	= FileContent FilePath
+	| ByteContent L.ByteString
+
+isByteContent :: ContentSource -> Bool
+isByteContent (ByteContent _) = True
+isByteContent (FileContent _) = False
+
+-- Action that stores a Key's content on a remote.
+-- Can throw exceptions.
+type Storer = Key -> ContentSource -> MeterUpdate -> Annex Bool
+
+-- Action that retrieves a Key's content from a remote, passing it to a
+-- callback.
+-- Throws exception if key is not present, or remote is not accessible.
+type Retriever = Key -> MeterUpdate -> (ContentSource -> Annex Bool) -> Annex Bool