use a state monad

enormous reworking

Types.hs

@@ -1,20 +1,59 @@
 {- git-annex core data types -}
 
 module Types (
-	State(..),
+	Annex(..),
+	makeAnnexState,
+	runAnnexState,
+	gitAnnex,
+	gitAnnexChange,
+	backendsAnnex,
+	backendsAnnexChange,
+
+	AnnexState(..),
 	Key(..),
 	Backend(..)
 ) where
 
+import Control.Monad.State
 import Data.String.Utils
 import GitRepo
 
 -- git-annex's runtime state
-data State = State {
+data AnnexState = AnnexState {
 	repo :: GitRepo,
 	backends :: [Backend]
 } deriving (Show)
 
+-- git-annex's monad
+type Annex = StateT AnnexState IO
+
+-- constructor
+makeAnnexState :: GitRepo -> AnnexState
+makeAnnexState g = AnnexState { repo = g, backends = [] }
+
+-- performs an action in the Annex monad
+runAnnexState state action = runStateT (action) state
+
+-- state accessors
+gitAnnex :: Annex GitRepo
+gitAnnex = do
+	state <- get
+	return (repo state)
+gitAnnexChange :: GitRepo -> Annex ()
+gitAnnexChange r = do
+	state <- get
+	put state { repo = r }
+	return ()
+backendsAnnex :: Annex [Backend]
+backendsAnnex = do
+	state <- get
+	return (backends state)
+backendsAnnexChange :: [Backend] -> Annex ()
+backendsAnnexChange b = do
+	state <- get
+	put state { backends = b }
+	return ()
+
 -- annexed filenames are mapped into keys
 data Key = Key String deriving (Eq)
 
@@ -27,13 +66,13 @@ data Backend = Backend {
 	-- name of this backend
 	name :: String,
 	-- converts a filename to a key
-	getKey :: State -> FilePath -> IO (Maybe Key),
+	getKey :: FilePath -> Annex (Maybe Key),
 	-- stores a file's contents to a key
-	storeFileKey :: State -> FilePath -> Key -> IO Bool,
+	storeFileKey :: FilePath -> Key -> Annex Bool,
 	-- retrieves a key's contents to a file
-	retrieveKeyFile :: State -> Key -> FilePath -> IO Bool,
+	retrieveKeyFile :: Key -> FilePath -> Annex Bool,
 	-- removes a key
-	removeKey :: State -> Key -> IO Bool
+	removeKey :: Key -> Annex Bool
 }
 
 instance Show Backend where