-----------------------------------------------------------------------------
-- |
-- Module      :  System.IO
-- Copyright   :  (c) The University of Glasgow 2001
-- License     :  BSD-style (see the file libraries/base/LICENSE)
-- 
-- Maintainer  :  libraries@haskell.org
-- Stability   :  provisional
-- Portability :  portable
--
-- The standard IO library.
--
-----------------------------------------------------------------------------

module System.IO (
    -- * The IO monad

    IO,                        -- instance MonadFix
    fixIO,                     -- :: (a -> IO a) -> IO a

    -- * Files and handles

    FilePath,                  -- :: String

    Handle,             -- abstract, instance of: Eq, Show.

    -- ** Standard handles

    -- | Three handles are allocated during program initialisation,
    -- and are initially open.

    stdin, stdout, stderr,   -- :: Handle

    -- * Opening and closing files

    -- ** Opening files

    openFile,                  -- :: FilePath -> IOMode -> IO Handle
    IOMode(ReadMode,WriteMode,AppendMode,ReadWriteMode),

    -- ** Closing files

    hClose,                    -- :: Handle -> IO ()

    -- ** Special cases

    -- | These functions are also exported by the "Prelude".

    readFile,                  -- :: FilePath -> IO String
    writeFile,                 -- :: FilePath -> String -> IO ()
    appendFile,                -- :: FilePath -> String -> IO ()

    -- ** File locking

    -- $locking

    -- * Operations on handles

    -- ** Determining the size of a file

    hFileSize,                 -- :: Handle -> IO Integer

    -- ** Detecting the end of input

    hIsEOF,                    -- :: Handle -> IO Bool
    isEOF,                     -- :: IO Bool

    -- ** Buffering operations

    BufferMode(NoBuffering,LineBuffering,BlockBuffering),
    hSetBuffering,             -- :: Handle -> BufferMode -> IO ()
    hGetBuffering,             -- :: Handle -> IO BufferMode
    hFlush,                    -- :: Handle -> IO ()

    -- ** Repositioning handles

    hGetPosn,                  -- :: Handle -> IO HandlePosn
    hSetPosn,                  -- :: HandlePosn -> IO ()
    HandlePosn,                -- abstract, instance of: Eq, Show.

    hSeek,                     -- :: Handle -> SeekMode -> Integer -> IO ()
    SeekMode(AbsoluteSeek,RelativeSeek,SeekFromEnd),

    hTell,                     -- :: Handle -> IO Integer

    -- ** Handle properties

    hIsOpen, hIsClosed,        -- :: Handle -> IO Bool
    hIsReadable, hIsWritable,  -- :: Handle -> IO Bool
    hIsSeekable,               -- :: Handle -> IO Bool

    -- ** Terminal operations

    -- ** Showing handle state

    -- * Text input and output

    -- ** Text input

    hWaitForInput,             -- :: Handle -> Int -> IO Bool
    hReady,                    -- :: Handle -> IO Bool
    hGetChar,                  -- :: Handle -> IO Char
    hGetLine,                  -- :: Handle -> IO [Char]
    hLookAhead,                -- :: Handle -> IO Char
    hGetContents,              -- :: Handle -> IO [Char]

    -- ** Text output

    hPutChar,                  -- :: Handle -> Char -> IO ()
    hPutStr,                   -- :: Handle -> [Char] -> IO ()
    hPutStrLn,                 -- :: Handle -> [Char] -> IO ()
    hPrint,                    -- :: Show a => Handle -> a -> IO ()

    -- ** Special cases for standard input and output

    -- | These functions are also exported by the "Prelude".

    interact,                  -- :: (String -> String) -> IO ()
    putChar,                   -- :: Char   -> IO ()
    putStr,                    -- :: String -> IO () 
    putStrLn,                  -- :: String -> IO ()
    print,                     -- :: Show a => a -> IO ()
    getChar,                   -- :: IO Char
    getLine,                   -- :: IO String
    getContents,               -- :: IO String
    readIO,                    -- :: Read a => String -> IO a
    readLn,                    -- :: Read a => IO a

    -- * Binary input and output

    openBinaryFile,            -- :: FilePath -> IOMode -> IO Handle

    module System.IO.Error,
  ) where

import Hugs.IO
import Hugs.IOExts

import System.IO.Error (
    isAlreadyExistsError, isDoesNotExistError,  -- :: IOError -> Bool
    isAlreadyInUseError, isFullError,
    isEOFError, isIllegalOperation,
    isPermissionError, isUserError,

    ioeGetErrorString,         -- :: IOError -> String
    ioeGetHandle,              -- :: IOError -> Maybe Handle
    ioeGetFileName,            -- :: IOError -> Maybe FilePath

    try,                       -- :: IO a -> IO (Either IOError a)

    -- re-exports of Prelude names
    IOError,
    ioError,                   -- :: IOError -> IO a
    userError,                 -- :: String  -> IOError
    catch                      -- :: IO a    -> (IOError -> IO a) -> IO a
  )

-- -----------------------------------------------------------------------------
-- Standard IO

-- | Computation 'hReady' @hdl@ indicates whether at least one item is
-- available for input from handle @hdl@.
-- 
-- This operation may fail with:
--
--  * 'isEOFError' if the end of file has been reached.

hReady          :: Handle -> IO Bool
hReady h        =  hWaitForInput h 0

-- | The same as 'hPutStr', but adds a newline character.

hPutStrLn       :: Handle -> String -> IO ()
hPutStrLn hndl str = do
 hPutStr  hndl str
 hPutChar hndl '\n'

-- | Computation 'hPrint' @hdl t@ writes the string representation of @t@
-- given by the 'shows' function to the file or channel managed by @hdl@
-- and appends a newline.
--
-- This operation may fail with:
--
--  * 'isFullError' if the device is full; or
--
--  * 'isPermissionError' if another system resource limit would be exceeded.

hPrint          :: Show a => Handle -> a -> IO ()
hPrint hdl      =  hPutStrLn hdl . show

-- ---------------------------------------------------------------------------
-- fixIO

-- $locking
-- Implementations should enforce as far as possible, at least locally to the
-- Haskell process, multiple-reader single-writer locking on files.
-- That is, /there may either be many handles on the same file which manage
-- input, or just one handle on the file which manages output/.  If any
-- open or semi-closed handle is managing a file for output, no new
-- handle can be allocated for that file.  If any open or semi-closed
-- handle is managing a file for input, new handles can only be allocated
-- if they do not manage output.  Whether two files are the same is
-- implementation-dependent, but they should normally be the same if they
-- have the same absolute path name and neither has been renamed, for
-- example.
--
-- /Warning/: the 'readFile' operation holds a semi-closed handle on
-- the file until the entire contents of the file have been consumed.
-- It follows that an attempt to write to a file (using 'writeFile', for
-- example) that was earlier opened by 'readFile' will usually result in
-- failure with 'isAlreadyInUseError'.