git-annex/Assistant/Monad.hs

{- git-annex assistant monad
 -
 - Copyright 2012 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU AGPL version 3 or higher.
 -}

{-# LANGUAGE GeneralizedNewtypeDeriving, MultiParamTypeClasses #-}

module Assistant.Monad (
	Assistant,
	AssistantData(..),
	newAssistantData,
	runAssistant,
	getAssistant,
	LiftAnnex,
	liftAnnex,
	(<~>),
	(<<~),
	asIO,
	asIO1,
	asIO2,
	ThreadName,
	debug,
) where

import "mtl" Control.Monad.Reader
import qualified Control.Monad.Fail as Fail

import Annex.Common hiding (debug)
import Assistant.Types.ThreadedMonad
import Assistant.Types.DaemonStatus
import Assistant.Types.ScanRemotes
import Assistant.Types.TransferQueue
import Assistant.Types.TransferSlots
import Assistant.Types.Pushes
import Assistant.Types.BranchChange
import Assistant.Types.Commits
import Assistant.Types.Changes
import Assistant.Types.RepoProblem
import Assistant.Types.ThreadName
import Assistant.Types.RemoteControl
import Assistant.Types.CredPairCache
import qualified Utility.Debug as Debug

newtype Assistant a = Assistant { mkAssistant :: ReaderT AssistantData IO a }
	deriving (
		Monad,
		MonadIO,
		MonadReader AssistantData,
		MonadCatch,
		MonadThrow,
		MonadMask,
		Fail.MonadFail,
		Functor,
		Applicative
	)

data AssistantData = AssistantData
	{ threadName :: ThreadName
	, threadState :: ThreadState
	, daemonStatusHandle :: DaemonStatusHandle
	, scanRemoteMap :: ScanRemoteMap
	, transferQueue :: TransferQueue
	, transferSlots :: TransferSlots
	, failedPushMap :: FailedPushMap
	, failedExportMap :: FailedPushMap
	, commitChan :: CommitChan
	, exportCommitChan :: CommitChan
	, changePool :: ChangePool
	, repoProblemChan :: RepoProblemChan
	, branchChangeHandle :: BranchChangeHandle
	, remoteControl :: RemoteControl
	, credPairCache :: CredPairCache
	}

newAssistantData :: ThreadState -> DaemonStatusHandle -> IO AssistantData
newAssistantData st dstatus = AssistantData
	<$> pure (ThreadName "main")
	<*> pure st
	<*> pure dstatus
	<*> newScanRemoteMap
	<*> newTransferQueue
	<*> newTransferSlots
	<*> newFailedPushMap
	<*> newFailedPushMap
	<*> newCommitChan
	<*> newCommitChan
	<*> newChangePool
	<*> newRepoProblemChan
	<*> newBranchChangeHandle
	<*> newRemoteControl
	<*> newCredPairCache

runAssistant :: AssistantData -> Assistant a -> IO a
runAssistant d a = runReaderT (mkAssistant a) d

getAssistant :: (AssistantData -> a) -> Assistant a
getAssistant = reader

{- Using a type class for lifting into the annex monad allows
 - easily lifting to it from multiple different monads. -}
class LiftAnnex m where
	liftAnnex :: Annex a -> m a

{- Runs an action in the git-annex monad. Note that the same monad state
 - is shared among all assistant threads, so only one of these can run at
 - a time. Therefore, long-duration actions should be avoided. -}
instance LiftAnnex Assistant where
	liftAnnex a = do
		st <- reader threadState
		liftIO $ runThreadState st a

{- Runs an IO action, passing it an IO action that runs an Assistant action. -}
(<~>) :: (IO a -> IO b) -> Assistant a -> Assistant b
io <~> a = do
	d <- reader id
	liftIO $ io $ runAssistant d a

{- Creates an IO action that will run an Assistant action when run. -}
asIO :: Assistant a -> Assistant (IO a)
asIO a = do
	d <- reader id
	return $ runAssistant d a

asIO1 :: (a -> Assistant b) -> Assistant (a -> IO b)
asIO1 a = do
	d <- reader id
	return $ \v -> runAssistant d $ a v

asIO2 :: (a -> b -> Assistant c) -> Assistant (a -> b -> IO c)
asIO2 a = do
	d <- reader id
	return $ \v1 v2 -> runAssistant d (a v1 v2)

{- Runs an IO action on a selected field of the AssistantData. -}
(<<~) :: (a -> IO b) -> (AssistantData -> a) -> Assistant b
io <<~ v = reader v >>= liftIO . io

debug :: [String] -> Assistant ()
debug ws = do
	ThreadName name <- getAssistant threadName
	liftIO $ Debug.debug (Debug.DebugSource (encodeBS name)) (unwords ws)