{- Construction of Git Repo objects
 -
 - Copyright 2010-2012 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Git.Construct (
	fromCwd,
	fromAbsPath,
	fromPath,
	fromUrl,
	fromUnknown,
	localToUrl,
	remoteNamed,
	remoteNamedFromKey,
	fromRemotes,
	fromRemoteLocation,
	repoAbsPath,
) where

import System.Posix.User
import qualified Data.Map as M hiding (map, split)
import Network.URI

import Common
import Git.Types
import Git
import qualified Git.Url as Url

{- Finds the git repository used for the cwd, which may be in a parent
 - directory. -}
fromCwd :: IO Repo
fromCwd = getCurrentDirectory >>= seekUp checkForRepo
	where
		norepo = error "Not in a git repository."
		seekUp check dir = do
			r <- check dir
			case r of
				Nothing -> case parentDir dir of
					"" -> norepo
					d -> seekUp check d
				Just loc -> newFrom loc

{- Local Repo constructor, accepts a relative or absolute path. -}
fromPath :: FilePath -> IO Repo
fromPath dir = fromAbsPath =<< absPath dir

{- Local Repo constructor, requires an absolute path to the repo be
 - specified. -}
fromAbsPath :: FilePath -> IO Repo
fromAbsPath dir
	| "/" `isPrefixOf` dir =
		ifM (doesDirectoryExist dir') ( ret dir' , hunt )
	| otherwise =
		error $ "internal error, " ++ dir ++ " is not absolute"
	where
		ret = newFrom . LocalUnknown
 		{- Git always looks for "dir.git" in preference to
		 - to "dir", even if dir ends in a "/". -}
		canondir = dropTrailingPathSeparator dir
		dir' = canondir ++ ".git"
		{- When dir == "foo/.git", git looks for "foo/.git/.git",
		 - and failing that, uses "foo" as the repository. -}
		hunt
			| "/.git" `isSuffixOf` canondir =
				ifM (doesDirectoryExist $ dir </> ".git")
					( ret dir
					, ret $ takeDirectory canondir
					)
			| otherwise = ret dir

{- Remote Repo constructor. Throws exception on invalid url.
 -
 - Git is somewhat forgiving about urls to repositories, allowing
 - eg spaces that are not normally allowed unescaped in urls.
 -}
fromUrl :: String -> IO Repo
fromUrl url
	| not (isURI url) = fromUrlStrict $ escapeURIString isUnescapedInURI url
	| otherwise = fromUrlStrict url

fromUrlStrict :: String -> IO Repo
fromUrlStrict url
	| startswith "file://" url = fromAbsPath $ uriPath u
	| otherwise = newFrom $ Url u
	where
		u = fromMaybe bad $ parseURI url
		bad = error $ "bad url " ++ url

{- Creates a repo that has an unknown location. -}
fromUnknown :: IO Repo
fromUnknown = newFrom Unknown

{- Converts a local Repo into a remote repo, using the reference repo
 - which is assumed to be on the same host. -}
localToUrl :: Repo -> Repo -> Repo
localToUrl reference r
	| not $ repoIsUrl reference = error "internal error; reference repo not url"
	| repoIsUrl r = r
	| otherwise = r { location = Url $ fromJust $ parseURI absurl }
	where
		absurl =
			Url.scheme reference ++ "//" ++
			Url.authority reference ++
			repoPath r

{- Calculates a list of a repo's configured remotes, by parsing its config. -}
fromRemotes :: Repo -> IO [Repo]
fromRemotes repo = mapM construct remotepairs
	where
		filterconfig f = filter f $ M.toList $ config repo
		filterkeys f = filterconfig (\(k,_) -> f k)
		remotepairs = filterkeys isremote
		isremote k = startswith "remote." k && endswith ".url" k
		construct (k,v) = remoteNamedFromKey k $ fromRemoteLocation v repo

{- Sets the name of a remote when constructing the Repo to represent it. -}
remoteNamed :: String -> IO Repo -> IO Repo
remoteNamed n constructor = do
	r <- constructor
	return $ r { remoteName = Just n }

{- Sets the name of a remote based on the git config key, such as
   "remote.foo.url". -}
remoteNamedFromKey :: String -> IO Repo -> IO Repo
remoteNamedFromKey k = remoteNamed basename
	where
		basename = join "." $ reverse $ drop 1 $
				reverse $ drop 1 $ split "." k

{- Constructs a new Repo for one of a Repo's remotes using a given
 - location (ie, an url). -}
fromRemoteLocation :: String -> Repo -> IO Repo
fromRemoteLocation s repo = gen $ calcloc s
	where
		gen v	
			| scpstyle v = fromUrl $ scptourl v
			| urlstyle v = fromUrl v
			| otherwise = fromRemotePath v repo
		-- insteadof config can rewrite remote location
		calcloc l
			| null insteadofs = l
			| otherwise = replacement ++ drop (length bestvalue) l
			where
				replacement = drop (length prefix) $
					take (length bestkey - length suffix) bestkey
				(bestkey, bestvalue) = maximumBy longestvalue insteadofs
				longestvalue (_, a) (_, b) = compare b a
				insteadofs = filterconfig $ \(k, v) -> 
					startswith prefix k &&
					endswith suffix k &&
					startswith v l
				filterconfig f = filter f $
					concatMap splitconfigs $
						M.toList $ fullconfig repo
				splitconfigs (k, vs) = map (\v -> (k, v)) vs
				(prefix, suffix) = ("url." , ".insteadof")
		urlstyle v = isURI v || ":" `isInfixOf` v && "//" `isInfixOf` v
		-- git remotes can be written scp style -- [user@]host:dir
		scpstyle v = ":" `isInfixOf` v && not ("//" `isInfixOf` v)
		scptourl v = "ssh://" ++ host ++ slash dir
			where
				(host, dir) = separate (== ':') v
				slash d	| d == "" = "/~/" ++ d
					| "/" `isPrefixOf` d = d
					| "~" `isPrefixOf` d = '/':d
					| otherwise = "/~/" ++ d

{- Constructs a Repo from the path specified in the git remotes of
 - another Repo. -}
fromRemotePath :: FilePath -> Repo -> IO Repo
fromRemotePath dir repo = do
	dir' <- expandTilde dir
	fromAbsPath $ repoPath repo </> dir'

{- Git remotes can have a directory that is specified relative
 - to the user's home directory, or that contains tilde expansions.
 - This converts such a directory to an absolute path.
 - Note that it has to run on the system where the remote is.
 -}
repoAbsPath :: FilePath -> IO FilePath
repoAbsPath d = do
	d' <- expandTilde d
	h <- myHomeDir
	return $ h </> d'

expandTilde :: FilePath -> IO FilePath
expandTilde = expandt True
	where
		expandt _ [] = return ""
		expandt _ ('/':cs) = do
			v <- expandt True cs
			return ('/':v)
		expandt True ('~':'/':cs) = do
			h <- myHomeDir
			return $ h </> cs
		expandt True ('~':cs) = do
			let (name, rest) = findname "" cs
			u <- getUserEntryForName name
			return $ homeDirectory u </> rest
		expandt _ (c:cs) = do
			v <- expandt False cs
			return (c:v)
		findname n [] = (n, "")
		findname n (c:cs)
			| c == '/' = (n, cs)
			| otherwise = findname (n++[c]) cs

checkForRepo :: FilePath -> IO (Maybe RepoLocation)
checkForRepo dir = 
	check isRepo $
		check gitDirFile $
			check isBareRepo $
				return Nothing
	where
		check test cont = maybe cont (return . Just) =<< test
		checkdir c = ifM c
			( return $ Just $ LocalUnknown dir
			, return Nothing
			)
		isRepo = checkdir $ gitSignature $ ".git" </> "config"
		isBareRepo = checkdir $ gitSignature "config"
			<&&> doesDirectoryExist (dir </> "objects")
		gitDirFile = do
			c <- firstLine <$>
				catchDefaultIO "" (readFile $ dir </> ".git")
			return $ if gitdirprefix `isPrefixOf` c
				then Just $ Local 
					{ gitdir = drop (length gitdirprefix) c
					, worktree = Just dir
					}
				else Nothing
			where
				gitdirprefix = "gitdir: "
		gitSignature file = doesFileExist $ dir </> file

newFrom :: RepoLocation -> IO Repo
newFrom l = return Repo
	{ location = l
	, config = M.empty
	, fullconfig = M.empty
	, remotes = []
	, remoteName = Nothing
	, gitEnv = Nothing
	}