{- git repository handling 
 -
 - This is written to be completely independant of git-annex and should be
 - suitable for other uses.
 -
 - Copyright 2010 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module GitRepo (
	Repo,
	repoFromCwd,
	repoFromPath,
	repoFromUrl,
	repoIsUrl,
	repoIsSsh,
	repoDescribe,
	workTree,
	gitDir,
	relative,
	urlPath,
	urlHost,
	configGet,
	configMap,
	configRead,
	configTrue,
	gitCommandLine,
	run,
	pipeRead,
	hPipeRead,
	attributes,
	remotes,
	remotesAdd,
	repoRemoteName,
	inRepo,
	notInRepo,
	stagedFiles,
	checkAttr,
	decodeGitFile,
	encodeGitFile,
	typeChangedFiles,
	typeChangedStagedFiles,

	prop_idempotent_deencode
) where

import Control.Monad (unless)
import System.Directory
import System.Posix.Directory
import System.Path
import System.Cmd.Utils
import IO (bracket_)
import Data.String.Utils
import System.IO
import qualified Data.Map as Map hiding (map, split)
import Network.URI
import Data.Maybe
import Data.Char
import Data.Word (Word8)
import Codec.Binary.UTF8.String (encode)
import Text.Printf

import Utility

{- There are two types of repositories; those on local disk and those
 - accessed via an URL. -}
data RepoLocation = Dir FilePath | Url URI
	deriving (Show, Eq)

data Repo = Repo {
	location :: RepoLocation,
	config :: Map.Map String String,
	remotes :: [Repo],
	-- remoteName holds the name used for this repo in remotes
	remoteName :: Maybe String 
} deriving (Show, Eq)

newFrom :: RepoLocation -> Repo
newFrom l = 
	Repo {
		location = l,
		config = Map.empty,
		remotes = [],
		remoteName = Nothing
	}

{- Local Repo constructor. -}
repoFromPath :: FilePath -> Repo
repoFromPath dir = newFrom $ Dir dir

{- Remote Repo constructor. Throws exception on invalid url. -}
repoFromUrl :: String -> Repo
repoFromUrl url
	| startswith "file://" url = repoFromPath $ uriPath u
	| otherwise = newFrom $ Url u
		where u = fromJust $ parseURI url

{- User-visible description of a git repo. -}
repoDescribe :: Repo -> String
repoDescribe Repo { remoteName = Just name } = name
repoDescribe Repo { location = Url url } = show url
repoDescribe Repo { location = Dir dir } = dir

{- Constructs and returns an updated version of a repo with
 - different remotes list. -}
remotesAdd :: Repo -> [Repo] -> Repo
remotesAdd repo rs = repo { remotes = rs }

{- Returns the name of the remote that corresponds to the repo, if 
 - it is a remote. Otherwise, "" -}
repoRemoteName :: Repo -> String
repoRemoteName Repo { remoteName = Just name } = name
repoRemoteName _ = ""

{- Some code needs to vary between URL and normal repos,
 - or bare and non-bare, these functions help with that. -}
repoIsUrl :: Repo -> Bool
repoIsUrl Repo { location = Url _ } = True
repoIsUrl _ = False

repoIsSsh :: Repo -> Bool
repoIsSsh Repo { location = Url url } 
	| uriScheme url == "ssh:" = True
	| otherwise = False
repoIsSsh _ = False

assertLocal :: Repo -> a -> a
assertLocal repo action = 
	if (not $ repoIsUrl repo)
		then action
		else error $ "acting on URL git repo " ++  repoDescribe repo ++ 
				" not supported"
assertUrl :: Repo -> a -> a
assertUrl repo action = 
	if (repoIsUrl repo)
		then action
		else error $ "acting on local git repo " ++  repoDescribe repo ++ 
				" not supported"
assertSsh :: Repo -> a -> a
assertSsh repo action =
	if (repoIsSsh repo)
		then action
		else error $ "unsupported url in repo " ++ repoDescribe repo
bare :: Repo -> Bool
bare repo = case Map.lookup "core.bare" $ config repo of
	Just v -> configTrue v
	Nothing -> error $ "it is not known if git repo " ++
			repoDescribe repo ++
			" is a bare repository; config not read"

{- Path to a repository's gitattributes file. -}
attributes :: Repo -> String
attributes repo
	| bare repo = workTree repo ++ "/info/.gitattributes"
	| otherwise = workTree repo ++ "/.gitattributes"

{- Path to a repository's .git directory, relative to its workTree. -}
gitDir :: Repo -> String
gitDir repo
	| bare repo = ""
	| otherwise = ".git"

{- Path to a repository's --work-tree, that is, its top.
 -
 - Note that for URL repositories, this is the path on the remote host. -}
workTree :: Repo -> FilePath
workTree r@(Repo { location = Url _ }) = urlPath r
workTree (Repo { location = Dir d }) = d

{- Given a relative or absolute filename in a repository, calculates the
 - name to use to refer to the file relative to a git repository's top.
 - This is the same form displayed and used by git. -}
relative :: Repo -> String -> String
relative repo@(Repo { location = Dir d }) file = drop (length absrepo) absfile
	where
		-- normalize both repo and file, so that repo
		-- will be substring of file
		absrepo = case (absNormPath "/" d) of
			Just f -> f ++ "/"
			Nothing -> error $ "bad repo" ++ repoDescribe repo
		absfile = case (secureAbsNormPath absrepo file) of
			Just f -> f
			Nothing -> error $ file ++ " is not located inside git repository " ++ absrepo
relative repo _ = assertLocal repo $ error "internal"

{- Hostname of an URL repo. (May include a username and/or port too.) -}
urlHost :: Repo -> String
urlHost Repo { location = Url u } = uriUserInfo a ++ uriRegName a ++ uriPort a
	where a = fromJust $ uriAuthority u
urlHost repo = assertUrl repo $ error "internal"

{- Path of an URL repo. -}
urlPath :: Repo -> String
urlPath Repo { location = Url u } = uriPath u
urlPath repo = assertUrl repo $ error "internal"

{- Constructs a git command line operating on the specified repo. -}
gitCommandLine :: Repo -> [String] -> [String]
gitCommandLine repo@(Repo { location = Dir d} ) params =
	-- force use of specified repo via --git-dir and --work-tree
	["--git-dir="++d++"/"++(gitDir repo), "--work-tree="++d] ++ params
gitCommandLine repo _ = assertLocal repo $ error "internal"

{- Runs git in the specified repo, throwing an error if it fails. -}
run :: Repo -> [String] -> IO ()
run repo params = assertLocal repo $ do
	ok <- boolSystem "git" (gitCommandLine repo params)
	unless (ok) $ error $ "git " ++ show params ++ " failed"

{- Runs a git subcommand and returns its output. -}
pipeRead :: Repo -> [String] -> IO String
pipeRead repo params = assertLocal repo $ do
	pOpen ReadFromPipe "git" (gitCommandLine repo params) $ \h -> do
		hGetContentsStrict h

{- Like pipeRead, but does not read output strictly; recommended
 - for git commands that produce a lot of output that will be processed
 - lazily. 
 -
 - ONLY AFTER the string has been read completely, You must call either
 - getProcessStatus or forceSuccess on the PipeHandle. Zombies will result
 - otherwise.-}
hPipeRead :: Repo -> [String] -> IO (PipeHandle, String)
hPipeRead repo params = assertLocal repo $ do
	pipeFrom "git" (gitCommandLine repo params)

{- Passed a location, recursively scans for all files that
 - are checked into git at that location. -}
inRepo :: Repo -> FilePath -> IO [FilePath]
inRepo repo l = pipeNullSplit repo
	["ls-files", "--cached", "--exclude-standard", "-z", "--", l]

{- Passed a location, recursively scans for all files that are not checked
 - into git, and not gitignored. -}
notInRepo :: Repo -> FilePath -> IO [FilePath]
notInRepo repo l = pipeNullSplit repo
	["ls-files", "--others", "--exclude-standard", "-z", "--", l]

{- Passed a location, returns a list of the files, staged for
 - commit, that are being added, moved, or changed (but not deleted). -}
stagedFiles :: Repo -> FilePath -> IO [FilePath]
stagedFiles repo l = pipeNullSplit repo
	["diff", "--cached", "--name-only", "--diff-filter=ACMRT", "-z", 
		"--", l]

{- Passed a location, returns a list of the files, staged for
 - commit, whose type has changed. -}
typeChangedStagedFiles :: Repo -> FilePath -> IO [FilePath]
typeChangedStagedFiles repo l = typeChangedFiles' repo l ["--cached"]

{- Passed a location, returns a list of the files whose type has changed. 
 - Files only staged for commit will not be included. -}
typeChangedFiles :: Repo -> FilePath -> IO [FilePath]
typeChangedFiles repo l = typeChangedFiles' repo l []

typeChangedFiles' :: Repo -> FilePath -> [String] -> IO [FilePath]
typeChangedFiles' repo l middle = pipeNullSplit repo $ start ++ middle ++ end
	where
		start = ["diff", "--name-only", "--diff-filter=T", "-z"]
		end = ["--", l]
	

{- Reads null terminated output of a git command (as enabled by the -z 
 - parameter), and splits it into a list of files. -}
pipeNullSplit :: Repo -> [String] -> IO [FilePath]
pipeNullSplit repo params = do
	-- XXX handle is left open, this is ok for git-annex, but may need
	-- to be cleaned up for other uses.
	(_, fs0) <- hPipeRead repo params
	return $ split0 fs0
	where
		split0 s = filter (not . null) $ split "\0" s

{- Runs git config and populates a repo with its config. 
 -
 - For a ssh repository, a list of ssh options may optionally be specified. -}
configRead :: Repo -> Maybe [String] -> IO Repo
configRead repo@(Repo { location = Dir d }) _ = do
	{- Cannot use pipeRead because it relies on the config having
	   been already read. Instead, chdir to the repo. -}
	cwd <- getCurrentDirectory
	bracket_ (changeWorkingDirectory d)
		(\_ -> changeWorkingDirectory cwd) $
			pOpen ReadFromPipe "git" ["config", "--list"] $
				hConfigRead repo
configRead repo sshopts = assertSsh repo $ do
	pOpen ReadFromPipe "ssh" params $ hConfigRead repo
	where
		params = case sshopts of
				Nothing -> [urlHost repo, command]
				Just l -> l ++ [urlHost repo, command]
		command = "cd " ++ (shellEscape $ urlPath repo) ++
				" && git config --list"
hConfigRead :: Repo -> Handle -> IO Repo
hConfigRead repo h = do
	val <- hGetContentsStrict h
	let r = repo { config = configParse val }
	return r { remotes = configRemotes r }	

{- Checks if a string fron git config is a true value. -}
configTrue :: String -> Bool
configTrue s = map toLower s == "true"

{- Calculates a list of a repo's configured remotes, by parsing its config. -}
configRemotes :: Repo -> [Repo]
configRemotes repo = map construct remotepairs
	where
		remotepairs = Map.toList $ filterremotes $ config repo
		filterremotes = Map.filterWithKey (\k _ -> isremote k)
		isremote k = (startswith "remote." k) && (endswith ".url" k)
		remotename k = (split "." k) !! 1
		construct (k,v) = (gen v) { remoteName = Just $ remotename k }
		gen v	| isURI v = repoFromUrl v
			| otherwise = repoFromPath v

{- Parses git config --list output into a config map. -}
configParse :: String -> Map.Map String String
configParse s = Map.fromList $ map pair $ lines s
	where
		pair l = (key l, val l)
		key l = (keyval l) !! 0
		val l = join sep $ drop 1 $ keyval l
		keyval l = split sep l :: [String]
		sep = "="

{- Returns a single git config setting, or a default value if not set. -}
configGet :: Repo -> String -> String -> String
configGet repo key defaultValue = 
	Map.findWithDefault defaultValue key (config repo)

{- Access to raw config Map -}
configMap :: Repo -> Map.Map String String
configMap repo = config repo

{- Looks up a gitattributes value for each file in a list. -}
checkAttr :: Repo -> String -> [FilePath] -> IO [(FilePath, String)]
checkAttr repo attr files = do
	(_, s) <- pipeBoth "git" params files0
	return $ map topair $ lines s
	-- XXX handle is left open, this is ok for git-annex, but may need
	-- to be cleaned up for other uses.
	where
		params = gitCommandLine repo ["check-attr", attr, "-z", "--stdin"]
		files0 = join "\0" files
		topair l = (file, value)
			where 
				file = decodeGitFile $ join sep $ take end bits
				value = bits !! end
				end = length bits - 1
				bits = split sep l
				sep = ": " ++ attr ++ ": "

{- Some git commands output encoded filenames. Decode that (annoyingly
 - complex) encoding. -}
decodeGitFile :: String -> FilePath
decodeGitFile [] = []
decodeGitFile f@(c:s)
	-- encoded strings will be inside double quotes
	| c == '"' = unescape ("", middle)
	| otherwise = f
	where
		e = '\\'
		middle = take (length s - 1) s
		unescape (b, []) = b
		-- look for escapes starting with '\'
		unescape (b, v) = b ++ beginning ++ unescape (decode rest)
			where
				pair = span (/= e) v
				beginning = fst pair
				rest = snd pair
		isescape x = x == e
		-- \NNN is an octal encoded character
		decode (x:n1:n2:n3:rest)
			| isescape x && alloctal = (fromoctal, rest)
				where
					alloctal = isOctDigit n1 &&
						isOctDigit n2 &&
						isOctDigit n3
					fromoctal = [chr $ readoctal (n1:n2:n3:[])]
					readoctal o = read $ "0o" ++ o :: Int
		-- \C is used for a few special characters
		decode (x:nc:rest)
			| isescape x = ([echar nc], rest)
			where
				echar 'a' = '\a'
				echar 'b' = '\b'
				echar 'f' = '\f'
				echar 'n' = '\n'
				echar 'r' = '\r'
				echar 't' = '\t'
				echar 'v' = '\v'
				echar a = a
		decode n = ("", n)

{- Should not need to use this, except for testing decodeGitFile. -}
encodeGitFile :: FilePath -> String
encodeGitFile s = (foldl (++) "\"" (map echar s)) ++ "\""
	where
		e c = "\\" ++ [c]
		echar '\a' = e 'a'
		echar '\b' = e 'b'
		echar '\f' = e 'f'
		echar '\n' = e 'n'
		echar '\r' = e 'r'
		echar '\t' = e 't'
		echar '\v' = e 'v'
		echar '\\' = e '\\'
		echar '"'  = e '"'
		echar x
			| ord x < 0x20 = e_num x -- low ascii
			| ord x >= 256 = e_utf x
			| ord x > 0x7E = e_num x -- high ascii
			| otherwise = [x]        -- printable ascii
			where 
				showoctal i = "\\" ++ (printf "%03o" i)
				e_num c = showoctal $ ord c
				-- unicode character is decomposed to
				-- Word8s and each is shown in octal
				e_utf c = foldl (++) "" $ map showoctal $
						(encode [c] :: [Word8])


{- for quickcheck -}
prop_idempotent_deencode :: String -> Bool
prop_idempotent_deencode s = s == (decodeGitFile $ encodeGitFile s)

{- Finds the current git repository, which may be in a parent directory. -}
repoFromCwd :: IO Repo
repoFromCwd = do
	cwd <- getCurrentDirectory
	top <- seekUp cwd isRepoTop
	case top of
		(Just dir) -> return $ repoFromPath dir
		Nothing -> error "Not in a git repository."

seekUp :: String -> (String -> IO Bool) -> IO (Maybe String)
seekUp dir want = do
	ok <- want dir
	if ok
		then return (Just dir)
		else case (parentDir dir) of
			"" -> return Nothing
			d -> seekUp d want

isRepoTop :: FilePath -> IO Bool
isRepoTop dir = do
	r <- isRepo
	b <- isBareRepo
	return (r || b)
	where
		isRepo = gitSignature ".git" ".git/config"
		isBareRepo = gitSignature "objects" "config"
		gitSignature subdir file = do
			s <- (doesDirectoryExist (dir ++ "/" ++ subdir))
			f <- (doesFileExist (dir ++ "/" ++ file))
			return (s && f)