{- External special remote data types.
 -
 - Copyright 2013 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

{-# LANGUAGE FlexibleInstances, TypeSynonymInstances #-}

module Remote.External.Types (
	External(..),
	newExternal,
	ExternalType,
	ExternalLock,
	withExternalLock,
	ExternalState(..),
	PrepareStatus(..),
	parseMessage,
	Sendable(..),
	Receivable(..),
	Request(..),
	needsPREPARE,
	Response(..),
	RemoteRequest(..),
	RemoteResponse(..),
	AsyncMessage(..),
	ErrorMsg,
	Setting,
	ProtocolVersion,
	supportedProtocolVersions,
) where

import Common.Annex
import Annex.Exception
import Types.Key (file2key, key2file)
import Types.StandardGroups (PreferredContentExpression)
import Utility.Metered (BytesProcessed(..))
import Logs.Transfer (Direction(..))
import Config.Cost (Cost)
import Types.Remote (RemoteConfig)
import Types.Availability (Availability(..))

import Data.Char
import Control.Concurrent.STM

-- If the remote is not yet running, the ExternalState TMVar is empty.
-- The 
data External = External
	{ externalType :: ExternalType
	, externalUUID :: UUID
	-- Empty until the remote is running.
	, externalState :: TMVar ExternalState
	-- Empty when a remote is in use.
	, externalLock :: TMVar ExternalLock
	-- Never left empty.
	, externalConfig :: TMVar RemoteConfig
	}

newExternal :: ExternalType -> UUID -> RemoteConfig -> Annex External
newExternal externaltype u c = liftIO $ External
	<$> pure externaltype
	<*> pure u
	<*> atomically newEmptyTMVar
	<*> atomically (newTMVar ExternalLock)
	<*> atomically (newTMVar c)

type ExternalType = String

data ExternalState = ExternalState
	{ externalSend :: Handle
	, externalReceive :: Handle
	, externalPid :: ProcessHandle
	, externalPrepared :: PrepareStatus
	}

data PrepareStatus = Unprepared | Prepared | FailedPrepare ErrorMsg

-- Constructor is not exported, and only created by newExternal.
data ExternalLock = ExternalLock

withExternalLock :: External -> (ExternalLock -> Annex a) -> Annex a
withExternalLock external = bracketIO setup cleanup
  where
	setup = atomically $ takeTMVar v
	cleanup = atomically . putTMVar v
	v = externalLock external

-- Messages that git-annex can send.
class Sendable m where
	formatMessage :: m -> [String]

-- Messages that git-annex can receive.
class Receivable m where
	-- Passed the first word of the message, returns
	-- a Parser that can be be fed the rest of the message to generate
	-- the value.
	parseCommand :: String -> Parser m

parseMessage :: (Receivable m) => String -> Maybe m
parseMessage s = parseCommand command rest
  where
	(command, rest) = splitWord s

-- Messages that can be sent to the external remote to request it do something.
data Request 
	= PREPARE 
	| INITREMOTE
	| GETCOST
	| GETAVAILABILITY
	| TRANSFER Direction Key FilePath
	| CHECKPRESENT Key
	| REMOVE Key
	deriving (Show)

-- Does PREPARE need to have been sent before this request?
needsPREPARE :: Request -> Bool
needsPREPARE PREPARE = False
needsPREPARE INITREMOTE = False
needsPREPARE _ = True

instance Sendable Request where
	formatMessage PREPARE = ["PREPARE"]
	formatMessage INITREMOTE = ["INITREMOTE"]
	formatMessage GETCOST = ["GETCOST"]
	formatMessage GETAVAILABILITY = ["GETAVAILABILITY"]
	formatMessage (TRANSFER direction key file) =
		[ "TRANSFER", serialize direction, serialize key, serialize file ]
	formatMessage (CHECKPRESENT key) = [ "CHECKPRESENT", serialize key ]
	formatMessage (REMOVE key) = [ "REMOVE", serialize key ]

-- Responses the external remote can make to requests.
data Response
	= PREPARE_SUCCESS
	| PREPARE_FAILURE ErrorMsg
	| TRANSFER_SUCCESS Direction Key
	| TRANSFER_FAILURE Direction Key ErrorMsg
	| CHECKPRESENT_SUCCESS Key
	| CHECKPRESENT_FAILURE Key
	| CHECKPRESENT_UNKNOWN Key ErrorMsg
	| REMOVE_SUCCESS Key
	| REMOVE_FAILURE Key ErrorMsg
	| COST Cost
	| AVAILABILITY Availability
	| INITREMOTE_SUCCESS
	| INITREMOTE_FAILURE ErrorMsg
	| UNSUPPORTED_REQUEST
	deriving (Show)

instance Receivable Response where
	parseCommand "PREPARE-SUCCESS" = parse0 PREPARE_SUCCESS
	parseCommand "PREPARE-FAILURE" = parse1 PREPARE_FAILURE
	parseCommand "TRANSFER-SUCCESS" = parse2 TRANSFER_SUCCESS
	parseCommand "TRANSFER-FAILURE" = parse3 TRANSFER_FAILURE
	parseCommand "CHECKPRESENT-SUCCESS" = parse1 CHECKPRESENT_SUCCESS
	parseCommand "CHECKPRESENT-FAILURE" = parse1 CHECKPRESENT_FAILURE
	parseCommand "CHECKPRESENT-UNKNOWN" = parse2 CHECKPRESENT_UNKNOWN
	parseCommand "REMOVE-SUCCESS" = parse1 REMOVE_SUCCESS
	parseCommand "REMOVE-FAILURE" = parse2 REMOVE_FAILURE
	parseCommand "COST" = parse1 COST
	parseCommand "AVAILABILITY" = parse1 AVAILABILITY
	parseCommand "INITREMOTE-SUCCESS" = parse0 INITREMOTE_SUCCESS
	parseCommand "INITREMOTE-FAILURE" = parse1 INITREMOTE_FAILURE
	parseCommand "UNSUPPORTED-REQUEST" = parse0 UNSUPPORTED_REQUEST
	parseCommand _ = parseFail

-- Requests that the external remote can send at any time it's in control.
data RemoteRequest
	= VERSION ProtocolVersion
	| PROGRESS BytesProcessed
	| DIRHASH Key
	| SETCONFIG Setting String
	| GETCONFIG Setting
	| SETCREDS Setting String String
	| GETCREDS Setting
	| GETUUID
	| GETGITDIR
	| SETWANTED PreferredContentExpression
	| GETWANTED
	| SETSTATE Key String
	| GETSTATE Key
	| DEBUG String
	deriving (Show)

instance Receivable RemoteRequest where
	parseCommand "VERSION" = parse1 VERSION
	parseCommand "PROGRESS" = parse1 PROGRESS
	parseCommand "DIRHASH" = parse1 DIRHASH
	parseCommand "SETCONFIG" = parse2 SETCONFIG
	parseCommand "GETCONFIG" = parse1 GETCONFIG
	parseCommand "SETCREDS" = parse3 SETCREDS
	parseCommand "GETCREDS" = parse1 GETCREDS
	parseCommand "GETUUID" = parse0 GETUUID
	parseCommand "GETGITDIR" = parse0 GETGITDIR
	parseCommand "SETWANTED" = parse1 SETWANTED
	parseCommand "GETWANTED" = parse0 GETWANTED
	parseCommand "SETSTATE" = parse2 SETSTATE
	parseCommand "GETSTATE" = parse1 GETSTATE
	parseCommand "DEBUG" = parse1 DEBUG
	parseCommand _ = parseFail

-- Responses to RemoteRequest.
data RemoteResponse
	= VALUE String
	| CREDS String String
	deriving (Show)

instance Sendable RemoteResponse where
	formatMessage (VALUE s) = [ "VALUE", serialize s ]
	formatMessage (CREDS login password) = [ "CREDS", serialize login, serialize password ]

-- Messages that can be sent at any time by either git-annex or the remote.
data AsyncMessage
	= ERROR ErrorMsg
	deriving (Show)

instance Sendable AsyncMessage where
	formatMessage (ERROR err) = [ "ERROR", serialize err ]

instance Receivable AsyncMessage where
	parseCommand "ERROR" = parse1 ERROR
	parseCommand _ = parseFail

-- Data types used for parameters when communicating with the remote.
-- All are serializable.
type ErrorMsg = String
type Setting = String
type ProtocolVersion = Int

supportedProtocolVersions :: [ProtocolVersion]
supportedProtocolVersions = [1]

class ExternalSerializable a where
	serialize :: a -> String
	deserialize :: String -> Maybe a

instance ExternalSerializable Direction where
	serialize Upload = "STORE"
	serialize Download = "RETRIEVE"

	deserialize "STORE" = Just Upload
	deserialize "RETRIEVE" = Just Download
	deserialize _ = Nothing

instance ExternalSerializable Key where
	serialize = key2file
	deserialize = file2key

instance ExternalSerializable [Char] where
	serialize = id
	deserialize = Just

instance ExternalSerializable ProtocolVersion where
	serialize = show
	deserialize = readish

instance ExternalSerializable Cost where
	serialize = show
	deserialize = readish

instance ExternalSerializable Availability where
	serialize GloballyAvailable = "GLOBAL"
	serialize LocallyAvailable = "LOCAL"

	deserialize "GLOBAL" = Just GloballyAvailable
	deserialize "LOCAL" = Just LocallyAvailable
	deserialize _ = Nothing

instance ExternalSerializable BytesProcessed where
	serialize (BytesProcessed n) = show n
	deserialize = BytesProcessed <$$> readish

{- Parsing the parameters of messages. Using the right parseN ensures
 - that the string is split into exactly the requested number of words,
 - which allows the last parameter of a message to contain arbitrary
 - whitespace, etc, without needing any special quoting.
 -}
type Parser a = String -> Maybe a

parseFail :: Parser a
parseFail _ = Nothing

parse0 :: a -> Parser a
parse0 mk "" = Just mk
parse0 _ _ = Nothing

parse1 :: ExternalSerializable p1 => (p1 -> a) -> Parser a
parse1 mk p1 = mk <$> deserialize p1

parse2 :: (ExternalSerializable p1, ExternalSerializable p2) => (p1 -> p2 -> a) -> Parser a
parse2 mk s = mk <$> deserialize p1 <*> deserialize p2
  where
	(p1, p2) = splitWord s

parse3 :: (ExternalSerializable p1, ExternalSerializable p2, ExternalSerializable p3) => (p1 -> p2 -> p3 -> a) -> Parser a
parse3 mk s = mk <$> deserialize p1 <*> deserialize p2 <*> deserialize p3
  where
	(p1, rest) = splitWord s
	(p2, p3) = splitWord rest

splitWord :: String -> (String, String)
splitWord = separate isSpace