{- git-annex "SHA1" backend
 -
 - Copyright 2010 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Backend.SHA1 (backend) where

import Control.Monad.State
import Data.String.Utils
import System.Cmd.Utils
import System.IO
import System.Directory

import qualified Backend.File
import TypeInternals
import Messages
import qualified Annex
import Locations
import Core

backend :: Backend
backend = Backend.File.backend {
	name = "SHA1",
	getKey = keyValue,
	fsckKey = Backend.File.checkKey checkKeySHA1
}

sha1 :: FilePath -> Annex String
sha1 file = do
	showNote "checksum..."
	liftIO $ pOpen ReadFromPipe "sha1sum" [file] $ \h -> do
		line <- hGetLine h
		let bits = split " " line
		if null bits
			then error "sha1sum parse error"
			else return $ head bits

-- A key is a sha1 of its contents.
keyValue :: FilePath -> Annex (Maybe Key)
keyValue file = do
	s <- sha1 file	
	return $ Just  $ Key (name backend, s)

-- A key's sha1 is checked during fsck.
checkKeySHA1 :: Key -> Annex Bool
checkKeySHA1 key = do
	g <- Annex.gitRepo
	let file = annexLocation g key
	present <- liftIO $ doesFileExist file
	if not present
		then return True
		else do
			s <- sha1 file
			if s == keyName key
				then return True
				else do
					dest <- moveBad key
					warning $ "Bad file content; moved to "++dest
					return False