{- directory manipulation
 -
 - Copyright 2011-2014 Joey Hess <joey@kitenet.net>
 -
 - License: BSD-2-clause
 -}

{-# LANGUAGE CPP #-}

module Utility.Directory where

import System.IO.Error
import System.Directory
import Control.Exception (throw)
import Control.Monad
import Control.Monad.IfElse
import System.FilePath
import Control.Applicative
import System.IO.Unsafe (unsafeInterleaveIO)

#ifdef mingw32_HOST_OS
import qualified System.Win32 as Win32
#else
import qualified System.Posix as Posix
#endif

import Utility.PosixFiles
import Utility.SafeCommand
import Utility.Tmp
import Utility.Exception
import Utility.Monad
import Utility.Applicative

{- Unlike getDirectoryContents, this can be used in arbitrarily
 - large directories without using much memory; the list steams lazily.
 -
 - However, any errors that may be encountered while reading the directory
 - contents are *ignored*, rather than throw them in the context of
 - whatever code consumes the lazy list.
 -
 - See https://ghc.haskell.org/trac/ghc/ticket/9266
 -}
getDirectoryContents' :: FilePath -> IO [FilePath]
getDirectoryContents' path = loop =<< opendir
  where
#ifndef mingw32_HOST_OS
	opendir = Posix.openDirStream path
	loop dirp = do
		v <- tryNonAsync $ Posix.readDirStream dirp
		case v of
			(Right ent) | not (null ent) -> do
				rest <- unsafeInterleaveIO (loop dirp)
				return (ent:rest)
			_ -> do
				void $ tryNonAsync $ Posix.closeDirStream dirp
				return []
#else
	opendir = Win32.findFirstFile (path </> "*")
	loop (h, fdat) = do
		-- there is always at least 1 file ("." and "..")
		ent <- Win32.getFindDataFileName fdat
		v <- tryNonAsync $ Win32.findNextFile h fdat
		case v of
			Right True -> 
				rest <- unsafeInterleaveIO loop (h, fdat)
				return (ent:rest)
			_ -> 
				void $ tryNonAsync $ Win32.findClose h
				return [ent]
#endif

dirCruft :: FilePath -> Bool
dirCruft "." = True
dirCruft ".." = True
dirCruft _ = False

{- Lists the contents of a directory.
 - Unlike getDirectoryContents, paths are not relative to the directory. -}
dirContents :: FilePath -> IO [FilePath]
dirContents d = map (d </>) . filter (not . dirCruft) <$> getDirectoryContents d

{- Gets files in a directory, and then its subdirectories, recursively,
 - and lazily.
 -
 - Does not follow symlinks to other subdirectories.
 -
 - When the directory does not exist, no exception is thrown,
 - instead, [] is returned. -}
dirContentsRecursive :: FilePath -> IO [FilePath]
dirContentsRecursive = dirContentsRecursiveSkipping (const False) True

{- Skips directories whose basenames match the skipdir. -}
dirContentsRecursiveSkipping :: (FilePath -> Bool) -> Bool -> FilePath -> IO [FilePath]
dirContentsRecursiveSkipping skipdir followsubdirsymlinks topdir = go [topdir]
  where
  	go [] = return []
	go (dir:dirs)
		| skipdir (takeFileName dir) = go dirs
		| otherwise = unsafeInterleaveIO $ do
			(files, dirs') <- collect [] []
				=<< catchDefaultIO [] (dirContents dir)
			files' <- go (dirs' ++ dirs)
			return (files ++ files')
	collect files dirs' [] = return (reverse files, reverse dirs')
	collect files dirs' (entry:entries)
		| dirCruft entry = collect files dirs' entries
		| otherwise = do
			let skip = collect (entry:files) dirs' entries
			let recurse = collect files (entry:dirs') entries
			ms <- catchMaybeIO $ getSymbolicLinkStatus entry
			case ms of
				(Just s) 
					| isDirectory s -> recurse
					| isSymbolicLink s && followsubdirsymlinks ->
						ifM (doesDirectoryExist entry)
							( recurse
							, skip
							)
				_ -> skip

{- Gets the directory tree from a point, recursively and lazily,
 - with leaf directories **first**, skipping any whose basenames
 - match the skipdir. Does not follow symlinks. -}
dirTreeRecursiveSkipping :: (FilePath -> Bool) -> FilePath -> IO [FilePath]
dirTreeRecursiveSkipping skipdir topdir = go [] [topdir]
  where
  	go c [] = return c
	go c (dir:dirs)
		| skipdir (takeFileName dir) = go c dirs
		| otherwise = unsafeInterleaveIO $ do
			subdirs <- go c
				=<< filterM (isDirectory <$$> getSymbolicLinkStatus)
				=<< catchDefaultIO [] (dirContents dir)
			go (subdirs++[dir]) dirs

{- Moves one filename to another.
 - First tries a rename, but falls back to moving across devices if needed. -}
moveFile :: FilePath -> FilePath -> IO ()
moveFile src dest = tryIO (rename src dest) >>= onrename
  where
	onrename (Right _) = noop
	onrename (Left e)
		| isPermissionError e = rethrow
		| isDoesNotExistError e = rethrow
		| otherwise = do
			-- copyFile is likely not as optimised as
			-- the mv command, so we'll use the latter.
			-- But, mv will move into a directory if
			-- dest is one, which is not desired.
			whenM (isdir dest) rethrow
			viaTmp mv dest undefined
	  where
		rethrow = throw e
		mv tmp _ = do
			ok <- boolSystem "mv" [Param "-f", Param src, Param tmp]
			unless ok $ do
				-- delete any partial
				_ <- tryIO $ removeFile tmp
				rethrow

	isdir f = do
		r <- tryIO $ getFileStatus f
		case r of
			(Left _) -> return False
			(Right s) -> return $ isDirectory s

{- Removes a file, which may or may not exist, and does not have to
 - be a regular file.
 -
 - Note that an exception is thrown if the file exists but
 - cannot be removed. -}
nukeFile :: FilePath -> IO ()
nukeFile file = void $ tryWhenExists go
  where
#ifndef mingw32_HOST_OS
	go = removeLink file
#else
	go = removeFile file
#endif