content: {-# 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.
  
  -}
  
  #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 $ 
  #if MIN_VERSION_unix(2,8,0)
               openFd fp WriteOnly defaultFileFlags
  #else
               openFd fp WriteOnly Nothing defaultFileFlags
  #endif
         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))
  