{- Linux library copier and binary shimmer
 -
 - Copyright 2013 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Main where

import Control.Applicative
import System.Environment
import Data.Maybe
import System.FilePath
import System.Directory
import Control.Monad
import Data.List
import Data.List.Utils
import System.Posix.Files
import Data.Char
import Control.Monad.IfElse

import Utility.PartialPrelude
import Utility.Directory
import Utility.Process
import Utility.Monad
import Utility.Path
import Utility.FileMode
import Utility.CopyFile

main :: IO ()
main = getArgs >>= go
  where
	go [] = error "specify LINUXSTANDALONE_DIST"
	go (top:_) = mklibs top

mklibs :: FilePath -> IO ()
mklibs top = do
	fs <- dirContentsRecursive top
	mapM_ symToHardLink fs
	exes <- filterM checkExe fs
	libs <- parseLdd <$> readProcess "ldd" exes
	glibclibs <- glibcLibs
	let libs' = nub $ libs ++ glibclibs
	libdirs <- nub . catMaybes <$> mapM (installLib top) libs'

	-- Various files used by runshell to set up env vars used by the
	-- linker shims.
	writeFile (top </> "libdirs") (unlines libdirs)
	writeFile (top </> "linker")
		(Prelude.head $ filter ("ld-linux" `isInfixOf`) libs')
	writeFile (top </> "gconvdir")
		(parentDir $ Prelude.head $ filter ("/gconv/" `isInfixOf`) glibclibs)
	
	mapM_ (installLinkerShim top) exes

{- Installs a library. If the library is a symlink to another file,
 - install the file it links to, and update the symlink to be relative. -}
installLib :: FilePath -> FilePath -> IO (Maybe FilePath)
installLib top lib = ifM (doesFileExist lib)
	( do
		installFile top lib
		checksymlink lib
		return $ Just $ parentDir lib
	, return Nothing
	)
  where
	checksymlink f = whenM (isSymbolicLink <$> getSymbolicLinkStatus (inTop top f)) $ do
		l <- readSymbolicLink (inTop top f)
		let absl = absPathFrom (parentDir f) l
		let target = relPathDirToFile (parentDir f) absl
		installFile top absl
		nukeFile (top ++ f)
		createSymbolicLink target (inTop top f)
		checksymlink absl

{- Installs a linker shim script around a binary.
 -
 - Note that each binary is put into its own separate directory,
 - to avoid eg git looking for binaries in its directory rather
 - than in PATH.-}
installLinkerShim :: FilePath -> FilePath -> IO ()
installLinkerShim top exe = do
	createDirectoryIfMissing True shimdir
	renameFile exe exedest
	writeFile exe $ unlines
		[ "#!/bin/sh"
		, "exec \"$GIT_ANNEX_LINKER\" --library-path \"$GIT_ANNEX_LD_LIBRARY_PATH\" \"$GIT_ANNEX_SHIMMED/" ++ base ++ "/" ++ base ++ "\" \"$@\""
		]
	modifyFileMode exe $ addModes executeModes
  where
	base = takeFileName exe
	shimdir = top </> "shimmed" </> base
	exedest = shimdir </> base

{- Converting symlinks to hard links simplifies the binary shimming
 - process. -}
symToHardLink :: FilePath -> IO ()
symToHardLink f = whenM (isSymbolicLink <$> getSymbolicLinkStatus f) $ do
	l <- readSymbolicLink f
	let absl = absPathFrom (parentDir f) l
	nukeFile f
	createLink absl f

installFile :: FilePath -> FilePath -> IO ()
installFile top f = do
	createDirectoryIfMissing True destdir
	void $ copyFileExternal f destdir
  where
	destdir = inTop top $ parentDir f

-- Note that f is not relative, so cannot use </>
inTop :: FilePath -> FilePath -> FilePath
inTop top f = top ++ f -- 

checkExe :: FilePath -> IO Bool
checkExe f
	| ".so" `isSuffixOf` f = return False
	| otherwise = ifM (isExecutable . fileMode <$> getFileStatus f)
		( checkFileExe <$> readProcess "file" [f]
		, return False
		)

{- Check that file(1) thinks it's a Linux ELF executable, or possibly
 - a shared library (a few executables like ssh appear as shared libraries). -}
checkFileExe :: String -> Bool
checkFileExe s = and
	[ "ELF" `isInfixOf` s
	, "executable" `isInfixOf` s || "shared object" `isInfixOf` s
	]

{- Parse ldd output, getting all the libraries that the input files
 - link to. Note that some of the libraries may not exist 
 - (eg, linux-vdso.so) -}
parseLdd :: String -> [FilePath]
parseLdd = catMaybes . map (getlib . dropWhile isSpace) . lines
  where
	getlib l = headMaybe . words =<< lastMaybe (split " => " l)

{- Get all glibc libs and other support files, including gconv files
 -
 - XXX Debian specific. -}
glibcLibs :: IO [FilePath]
glibcLibs = lines <$> readProcess "sh"
	["-c", "dpkg -L libc6 libgcc1 | egrep '\\.so|gconv'"]