{- Magic Wormhole integration
 -
 - Copyright 2016 Joey Hess <id@joeyh.name>
 -
 - License: BSD-2-clause
 -}

module Utility.MagicWormHole (
	Code,
	mkCode,
	validCode,
	CodeObserver,
	CodeProducer,
	mkCodeObserver,
	mkCodeProducer,
	waitCode,
	sendCode,
	WormHoleParams,
	sendFile,
	receiveFile,
) where

import Utility.Process
import Utility.SafeCommand
import Utility.Monad
import Utility.Misc
import Utility.FileSystemEncoding
import Utility.Env

import System.IO
import System.Exit
import Control.Concurrent
import Control.Exception
import Data.Char

-- | A Magic Wormhole code.
newtype Code = Code String

-- | Smart constructor for Code
mkCode :: String -> Maybe Code
mkCode s
	| validCode s = Just (Code s)
	| otherwise = Nothing

-- | Codes have the form number-word-word and may contain 2 or more words.
validCode :: String -> Bool
validCode s = 
	let (n, r) = separate (== '-') s
	    (w1, w2) = separate (== '-') r
	in and
		[ not (null n)
		, all isDigit n
		, not (null w1)
		, not (null w2)
		, not $ any isSpace s
		]

newtype CodeObserver = CodeObserver (MVar Code)

newtype CodeProducer = CodeProducer (MVar Code)

mkCodeObserver :: IO CodeObserver
mkCodeObserver = CodeObserver <$> newEmptyMVar

mkCodeProducer :: IO CodeProducer
mkCodeProducer = CodeProducer <$> newEmptyMVar

waitCode :: CodeObserver -> IO Code
waitCode (CodeObserver o) = takeMVar o

sendCode :: CodeProducer -> Code -> IO ()
sendCode (CodeProducer p) = putMVar p

type WormHoleParams = [CommandParam]

-- | Sends a file. Once the send is underway, and the Code has been
-- generated, it will be sent to the CodeObserver. (This may not happen,
-- eg if there's a network problem).
--
-- Currently this has to parse the output of wormhole to find the code.
-- To make this as robust as possible, avoids looking for any particular
-- output strings, and only looks for the form of a wormhole code
-- (number-word-word). 
--
-- Note that, if the filename looks like "foo 1-wormhole-code bar", when
-- that is output by wormhole, it will look like it's output a wormhole code.
--
-- A request to make the code available in machine-parsable form is here:
-- https://github.com/warner/magic-wormhole/issues/104
sendFile :: FilePath -> CodeObserver -> WormHoleParams -> IO Bool
sendFile f (CodeObserver observer) ps = do
	-- Work around stupid stdout buffering behavior of python.
	-- See https://github.com/warner/magic-wormhole/issues/108
	environ <- addEntry "PYTHONUNBUFFERED" "1" <$> getEnvironment
	runWormHoleProcess p { env = Just environ} $ \_hin hout -> do
		fileEncoding hout
		findcode =<< words <$> hGetContents hout
  where
	p = wormHoleProcess (Param "send" : ps ++ [File f])
	findcode [] = return False
	findcode (w:ws) = case mkCode w of
		Just code -> do
			putMVar observer code
			return True
		Nothing -> findcode ws

-- | Receives a file. Once the receive is under way, the Code will be
-- read from the CodeProducer, and fed to wormhole on stdin.
receiveFile :: FilePath -> CodeProducer -> WormHoleParams -> IO Bool
receiveFile f (CodeProducer producer) ps = runWormHoleProcess p $ \hin _hout -> do
	Code c <- takeMVar producer
	hPutStrLn hin c
	hFlush hin
	return True
  where
	p = wormHoleProcess $
		[ Param "receive"
		, Param "--accept-file"
		, Param "--output-file"
		, File f
		] ++ ps

wormHoleProcess :: WormHoleParams -> CreateProcess
wormHoleProcess = proc "wormhole" . toCommand

runWormHoleProcess :: CreateProcess -> (Handle -> Handle -> IO Bool) ->  IO Bool
runWormHoleProcess p consumer = bracketOnError setup cleanup go
  where
	setup = do
		(Just hin, Just hout, Nothing, pid)
			<- createProcess p
				{ std_in = CreatePipe
				, std_out = CreatePipe
				}
		return (hin, hout, pid)
	cleanup (hin, hout, pid) = do
		r <- waitForProcess pid
		hClose hin
		hClose hout
		return $ case r of
			ExitSuccess -> True
			ExitFailure _ -> False
	go h@(hin, hout, _) = consumer hin hout <&&> cleanup h