    {-# LANGUAGE ScopedTypeVariables #-}
    {- Shell Equivalents
    Copyright (C) 2004-2009 John Goerzen <jgoerzen@complete.org>
    Please see the COPYRIGHT file
    -}

    {- |
       Module     : HSH.ShellEquivs
       Copyright  : Copyright (C) 2009 John Goerzen
       License    : GNU LGPL, version 2.1 or above

       Maintainer : John Goerzen <jgoerzen@complete.org>
       Stability  : provisional
       Portability: portable

    Copyright (c) 2006-2009 John Goerzen, jgoerzen\@complete.org

    This module provides shell-like commands.  Most, but not all, are designed
    to be used directly as part of a HSH pipeline.  All may be used outside
    HSH entirely as well.

    -}

    {-# LANGUAGE ScopedTypeVariables #-}

    #if !(defined(mingw32_HOST_OS) || defined(mingw32_TARGET_OS) || defined(__MINGW32__))
    #define __HSH_POSIX__
    #else
    #define __HSH_WINDOWS__
    #endif

    module HSH.ShellEquivs(
                           abspath,
                           appendTo,
                           basename,
                           bracketCD,
                           catFrom,
                           catBytes,
                           catBytesFrom,
                           catTo,
    #ifdef __HSH_POSIX__
                           catToFIFO,
    #endif
                           cd,
                           cut,
                           cutR,
                           dirname,
                           discard,
                           echo,
                           exit,
                           glob,
                           grep,
                           grepV,
                           egrep,
                           egrepV,
                           joinLines,
                           lower,
                           upper,
                           mkdir,
                           numberLines,
                           pwd,
    #ifdef __HSH_POSIX__
                           readlink,
                           readlinkabs,
    #endif
                           rev,
                           revW,
                           HSH.Command.setenv,
                           space,
                           unspace,
                           tac,
                           tee,
    #ifdef __HSH_POSIX__
                           teeFIFO,
    #endif
                           tr,
                           trd,
                           wcW,
                           wcL,
                           HSH.Command.unsetenv,
                           uniq,
                          ) where

    import Data.List (genericLength, intersperse, isInfixOf, nub)
    import Data.Char (toLower, toUpper)
    import Text.Regex (matchRegex, mkRegex)
    import Text.Printf (printf)
    import Control.Monad (foldM)
    import System.Directory hiding (createDirectory, isSymbolicLink)
    import qualified Control.Exception as E
    -- import System.FilePath (splitPath)

    #ifdef __HSH_POSIX__
    import System.Posix.Files (getFileStatus, isSymbolicLink, readSymbolicLink)
    import System.Posix.User (getEffectiveUserName, getUserEntryForName, homeDirectory)
    import System.Posix.Directory (createDirectory)
    import System.Posix.Types (FileMode())
    import System.Posix.IO
    import System.Posix.Error
    #endif

    import System.Path (absNormPath, bracketCWD)
    import System.Exit
    import System.IO
    import System.Process
    import qualified System.Directory as SD
    import qualified System.Path.Glob as Glob (glob)
    import qualified Data.ByteString.Lazy as BSL
    import qualified Data.ByteString as BS
    import System.IO.Unsafe(unsafeInterleaveIO)
    import HSH.Channel
    import HSH.Command(setenv, unsetenv)

    {- | Return the absolute path of the arg.  Raises an error if the
    computation is impossible. This is a thin wrapper around
    System.Path.absNormPath.  Unix/Linux users note:
    System.Path.absNormPath is known to produce odd results when
    a tilde expansion is requested; you might prefer 'glob' to this
    function if you know your input is free of wildcards. See
    https://github.com/jgoerzen/hsh/issues/7 for details. -}
    abspath :: FilePath -> IO FilePath
    abspath inp =
        do p <- pwd
           case absNormPath p inp of
             Nothing -> fail $ "Cannot make " ++ show inp ++ " absolute within " ++
                        show p
             Just x -> return x

    {- | The filename part of a path -}
    basename :: FilePath -> FilePath
    basename =  snd . splitpath

    {- | The directory part of a path -}
    dirname :: FilePath -> FilePath
    dirname = fst . splitpath

    {- | Changes the current working directory to the given path, executes
    the given I\/O action, then changes back to the original directory,
    even if the I\/O action raised an exception.

    This is an alias for the MissingH function System.Path.bracketCWD. -}
    bracketCD :: FilePath -> IO a -> IO a
    bracketCD = bracketCWD

    {- | Load the specified files and display them, one at a time.

    The special file @-@ means to display the input.  If it is not given,
    no input is processed at all.

    @-@ may be given a maximum of one time.

    See also 'catBytes' . -}
    catFrom :: [FilePath] -> Channel -> IO Channel
    catFrom fplist ichan =
        do r <- foldM foldfunc BSL.empty fplist
           return (toChannel r)
        where foldfunc accum fp =
                      case fp of
                        "-" -> do c <- chanAsBSL ichan
                                  return (BSL.append accum c)
                        fn -> do c <- BSL.readFile fn
                                 return (BSL.append accum c)

    {- | Copy data from input to output, optionally with a fixed
    maximum size, in bytes.  Processes data using ByteStrings internally,
    so be aware of any possible UTF-8 conversions.

    You may wish to use @hSetBuffering h (BlockBuffering Nothing)@ prior to calling
    this function for optimal performance.

    See also 'catFrom', 'catBytesFrom' -}
    catBytes :: (Maybe Integer)    -- ^ Maximum amount of data to transfer
              -> Channel             -- ^ Handle for input
              -> IO Channel
    catBytes count hr = catBytesFrom hr count hr

    {- | Generic version of 'catBytes'; reads data from specified Channel, and
    ignores stdin.
    -}

    catBytesFrom :: Channel          -- ^ Handle to read from
                 -> (Maybe Integer)  -- ^ Maximum amount of data to transfer
                 -> Channel          -- ^ Handle for input (ignored)
                 -> IO Channel
    catBytesFrom (ChanHandle hr) count cignore =
        case count of
             Nothing -> return (ChanHandle hr)
             Just m -> do c <- BSL.hGet hr (fromIntegral m)
                          return (ChanBSL c)
    catBytesFrom cinput count cignore =
        case count of
          Nothing -> return cinput
          Just m -> do r <- chanAsBSL cinput
                       return (ChanBSL (BSL.take (fromIntegral m) r))

    {- | Takes input, writes it to the specified file, and does not pass it on.
         The return value is the empty string.  See also 'catToBS',
         'catToFIFO' -}
    catTo :: FilePath -> Channel -> IO Channel
    catTo fp ichan =
        do ofile <- openFile fp WriteMode
           chanToHandle True ichan ofile
           return (ChanString "")

    #ifdef __HSH_POSIX__

    {- | Like 'catTo', but opens the destination in ReadWriteMode instead of
    ReadOnlyMode.  Due to an oddity of the Haskell IO system, this is required
    when writing to a named pipe (FIFO) even if you will never read from it.

    This call will BLOCK all threads on open until a reader connects.

    This is provided in addition to 'catTo' because you may want to cat to
    something that you do not have permission to read from.

    This function is only available on POSIX platforms.

    See also 'catTo' -}
    catToFIFO :: FilePath -> Channel -> IO Channel
    catToFIFO fp ichan =
        do h <- fifoOpen fp
           chanToHandle True ichan h
           return (ChanString "")

    fifoOpen :: FilePath -> IO Handle
    fifoOpen fp =
        do fd <- throwErrnoPathIf (< 0) "HSH fifoOpen" fp $
                 openFd fp WriteOnly Nothing defaultFileFlags
           fdToHandle fd

    #endif

    {- | Like 'catTo', but appends to the file. -}
    appendTo :: FilePath -> String -> IO String
    appendTo fp inp =
        do appendFile fp inp
           return ""

    {- | An alias for System.Directory.setCurrentDirectory.

    Want to change to a user\'s home directory?  Try this:

    > glob "~jgoerzen" >>= cd . head

    See also 'bracketCD'.
    -}
    cd :: FilePath -> IO ()
    cd = setCurrentDirectory

    {- | Split a list by a given character and select the nth list.

    > cut ' ' 2 "foo bar baz quux" -> "bar"
    -}
    cut :: Integer -> Char -> String -> String
    cut pos = cutR [pos]

    {- | Read all input and produce no output.  Discards input completely. -}
    discard :: Channel -> IO Channel
    discard inh =
        do c <- chanAsBSL inh
           E.evaluate (BSL.length c)
           return (ChanString "")

    {- | Split a list by a given character and select ranges of the resultant lists.

    > cutR [2..4] ' ' "foo bar baz quux foobar" -> "baz quux foobar"
    > cutR [1..1000] ' ' "foo bar baz quux foobar" -> "bar baz quux foobar"
    > cutR [-1000..1000] ' ' "foo bar baz quux foobar" -> "foo bar baz quux foobar"

       Note that too large and too small indices are essentially ignored.
    -}
    cutR :: [Integer] -> Char -> String -> String
    cutR nums delim z = drop 1 $ concat [delim:x | (x, y) <- zip string [0..], elem y nums]
         where string = split delim z

    {- | Takes a string and sends it on as standard output.

    The input to this function is never read.

    You can pass this thing a String, a ByteString, or even a Handle.

    See also 'echoBS'. -}
    echo :: Channelizable a => a -> Channel -> IO Channel
    echo inp _ = return . toChannel $ inp

    {- | Search for the regexp in the lines.  Return those that match. -}
    egrep :: String -> [String] -> [String]
    egrep pat = filter (ismatch regex)
        where regex = mkRegex pat
              ismatch r inp = case matchRegex r inp of
                                Nothing -> False
                                Just _ -> True

    {- | Search for the regexp in the lines.  Return those that do NOT match. -}
    egrepV :: String -> [String] -> [String]
    egrepV pat = filter (not . ismatch regex)
        where regex = mkRegex pat
              ismatch r inp = case matchRegex r inp of
                                Nothing -> False
                                Just _ -> True

    {- | Exits with the specified error code. 0 indicates no error. -}
    exit :: Int -> IO a
    exit code
        | code == 0 = exitWith ExitSuccess
        | otherwise = exitWith (ExitFailure code)

    {- | Takes a pattern.  Returns a list of names that match that pattern.
    Handles:

    >~username at beginning of file to expand to user's home dir
    >? matches exactly one character
    >* matches zero or more characters
    >[list] matches any character in list
    >[!list] matches any character not in list

    The result of a tilde expansion on a nonexistant username is to do no
    tilde expansion.

    The tilde with no username equates to the current user.

    Non-tilde expansion is done by the MissingH module System.Path.Glob. -}
    glob :: FilePath -> IO [FilePath]
    glob inp@('~':remainder) =
        E.catch expanduser (\(e::E.SomeException) -> Glob.glob rest)
        where (username, rest) = span (/= '/') remainder
    #ifdef __HSH_POSIX__
              expanduser =
                  do lookupuser <-
                         if username /= ""
                            then return username
                            else getEffectiveUserName
                     ue <- getUserEntryForName lookupuser
                     Glob.glob (homeDirectory ue ++ rest)
    #else
              expanduser = fail "non-posix; will be caught above"
    #endif
    glob x = Glob.glob x

    {- | Search for the string in the lines.  Return those that match.
    Same as:

    > grep needle = filter (isInfixOf needle)
    -}
    grep :: String -> [String] -> [String]
    grep = filter . isInfixOf

    {- | Search for the string in the lines.  Return those that do NOT match. -}
    grepV :: String -> [String] -> [String]
    grepV needle = filter (not . isInfixOf needle)

    -- | Join lines of a file
    joinLines :: [String] -> [String]
    joinLines = return . concat

    #ifdef __HSH_POSIX__
    {- | Creates the given directory.  A value of 0o755 for mode would be typical.

    An alias for System.Posix.Directory.createDirectory.

    The second argument will be ignored on non-POSIX systems. -}
    mkdir :: FilePath -> FileMode -> IO ()
    mkdir = createDirectory
    #else
    mkdir :: FilePath -> a -> IO ()
    mkdir fp _ = SD.createDirectory fp
    #endif

    {- | Number each line of a file -}
    numberLines :: [String] -> [String]
    numberLines = zipWith (printf "%3d %s") [(1::Int)..]

    {- | An alias for System.Directory.getCurrentDirectory. -}
    pwd :: IO FilePath
    pwd = getCurrentDirectory

    #ifdef __HSH_POSIX__
    {- | Return the destination that the given symlink points to.

    An alias for System.Posix.Files.readSymbolicLink

    This function is only available on POSIX platforms. -}
    readlink :: FilePath -> IO FilePath
    readlink fp =
        do issym <- (getFileStatus fp >>= return . isSymbolicLink)
           if issym
               then readSymbolicLink fp
               else return fp

    {- | As 'readlink', but turns the result into an absolute path.

    This function is only available on POSIX platforms. -}
    readlinkabs :: FilePath -> IO FilePath
    readlinkabs inp =
           do issym <- (getFileStatus inp >>= return . isSymbolicLink)
              if issym
                 then do rl <- readlink inp
                         case absNormPath (dirname inp) rl of
                           Nothing -> fail $ "Cannot make " ++ show rl ++ " absolute within " ++
                                      show (dirname inp)
                           Just x -> return x
                 else abspath inp
    #endif

    {- | Reverse characters on each line (rev) -}
    rev, revW :: [String] -> [String]
    rev = map reverse

    {- | Reverse words on each line -}
    revW = map (unwords . reverse . words)

    {- | Reverse lines in a String (like Unix tac).

    Implemented as:

    > tac = reverse

    See 'uniq'. -}
    tac :: [String] -> [String]
    tac = reverse

    {- | Takes input, writes it to all the specified files, and passes it on.
    This function does /NOT/ buffer input.

    See also 'catFrom'. -}
    tee :: [FilePath] -> Channel -> IO Channel
    tee fplist inp = teeBSGeneric (\fp -> openFile fp WriteMode) fplist inp

    #ifdef __HSH_POSIX__
    {- | FIFO-safe version of 'tee'.

    This call will BLOCK all threads on open until a reader connects.

    This function is only available on POSIX platforms. -}
    teeFIFO :: [FilePath] -> Channel -> IO Channel
    teeFIFO fplist inp = teeBSGeneric fifoOpen fplist inp
    #endif

    teeBSGeneric :: (FilePath -> IO Handle)
                 -> [FilePath]
                 -> Channel -> IO Channel
    teeBSGeneric openfunc fplist ichan =
        do handles <- mapM openfunc fplist
           inp <- chanAsBSL ichan
           resultChunks <- hProcChunks handles (BSL.toChunks inp)
           return (ChanBSL $ BSL.fromChunks resultChunks)
        where hProcChunks :: [Handle] -> [BS.ByteString] -> IO [BS.ByteString]
              hProcChunks handles chunks = unsafeInterleaveIO $
                  case chunks of
                    [] -> do mapM_ hClose handles
                             return [BS.empty]
                    (x:xs) -> do mapM_ (\h -> BS.hPutStr h x) handles
                                 remainder <- hProcChunks handles xs
                                 return (x : remainder)

    {- | Translate a character x to y, like:

    >tr 'e' 'f'

    Or, in sed,

    >y//
     -}
    tr :: Char -> Char -> String -> String
    tr a b = map (\x -> if x == a then b else x)

    {- | Delete specified character in a string. -}
    trd :: Char -> String -> String
    trd = filter . (/=)

    {- | Remove duplicate lines from a file (like Unix uniq).

    Takes a String representing a file or output and plugs it through lines and then nub to uniqify on a line basis. -}
    uniq :: String -> String
    uniq = unlines . nub . lines

    {- | Double space a file; add an empty line between each line. -}
    space :: [String] -> [String]
    space = intersperse ""

    {- | Inverse of double 'space'; drop all empty lines. -}
    unspace :: [String] -> [String]
    unspace = filter (not . null)

    {- | Convert a string to all lower case -}
    lower :: String -> String
    lower = map toLower

    {- | Convert a string to all upper case -}
    upper :: String -> String
    upper = map toUpper

    {- | Count number of lines.  Like wc -l -}
    wcL :: [String] -> [String]
    wcL inp = [show (genericLength inp :: Integer)]

    {- | Count number of words in a file (like wc -w) -}
    wcW :: [String] -> [String]
    wcW inp = [show ((genericLength $ words $ unlines inp) :: Integer)]

    {- Utility function.
    > split ' ' "foo bar baz" -> ["foo","bar","baz"] -}
    split :: Char -> String -> [String]
    split c s = case rest of
                  []     -> [chunk]
                  _:rst -> chunk : split c rst
        where (chunk, rest) = break (==c) s

    -- TODO: Perhaps simplify to make use of split
    splitpath :: String -> (String, String)
    splitpath "" = (".", ".")
    splitpath "/" = ("/", "/")
    splitpath p
        | last p == '/' = splitpath (init p)
        | not ('/' `elem` p) = (".", p)
        | head p == '/' && length (filter (== '/') p) == 1 = ("/", tail p)
        | otherwise = (\(base, dir) -> (reverse (tail dir), reverse base))
            (break (== '/') (reverse p))