{-# LANGUAGE Safe #-}
{-# LANGUAGE CPP #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  System.Environment
-- Copyright   :  (c) The University of Glasgow 2001
-- License     :  BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer  :  libraries@haskell.org
-- Stability   :  provisional
-- Portability :  portable
--
-- Miscellaneous information about the system environment.
--
-----------------------------------------------------------------------------

module System.Environment
    (
      getArgs,
      getProgName,
      getExecutablePath,
      getEnv,
      lookupEnv,
      setEnv,
      unsetEnv,
      withArgs,
      withProgName,
      getEnvironment,
  ) where

import Foreign
import Foreign.C
import System.IO.Error (mkIOError)
import Control.Exception.Base (bracket_, throwIO)
#ifdef mingw32_HOST_OS
import Control.Exception.Base (bracket)
#endif
-- import GHC.IO
import GHC.IO.Exception
import GHC.IO.Encoding (getFileSystemEncoding)
import qualified GHC.Foreign as GHC
import Control.Monad
#ifdef mingw32_HOST_OS
import GHC.Environment
import GHC.Windows
#else
import System.Posix.Internals (withFilePath)
#endif

import System.Environment.ExecutablePath

#ifdef mingw32_HOST_OS
# if defined(i386_HOST_ARCH)
#  define WINDOWS_CCONV stdcall
# elif defined(x86_64_HOST_ARCH)
#  define WINDOWS_CCONV ccall
# else
#  error Unknown mingw32 arch
# endif
#endif

#include "HsBaseConfig.h"

-- ---------------------------------------------------------------------------
-- getArgs, getProgName, getEnv

#ifdef mingw32_HOST_OS

{-
Note [Ignore hs_init argv]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Ignore the arguments to hs_init on Windows for the sake of Unicode compat

Instead on Windows we get the list of arguments from getCommandLineW and
filter out arguments which the RTS would not have passed along.

This is done to ensure we get the arguments in proper Unicode Encoding which
the RTS at this moment does not seem provide. The filtering has to match the
one done by the RTS to avoid inconsistencies like #13287.
-}

getWin32ProgArgv_certainly :: IO [String]
getWin32ProgArgv_certainly = do
        mb_argv <- getWin32ProgArgv
        case mb_argv of
          -- see Note [Ignore hs_init argv]
          Nothing   -> fmap dropRTSArgs getFullArgs
          Just argv -> return argv

withWin32ProgArgv :: [String] -> IO a -> IO a
withWin32ProgArgv argv act = bracket begin setWin32ProgArgv (\_ -> act)
  where
    begin = do
          mb_old_argv <- getWin32ProgArgv
          setWin32ProgArgv (Just argv)
          return mb_old_argv

getWin32ProgArgv :: IO (Maybe [String])
getWin32ProgArgv = alloca $ \p_argc -> alloca $ \p_argv -> do
        c_getWin32ProgArgv p_argc p_argv
        argc <- peek p_argc
        argv_p <- peek p_argv
        if argv_p == nullPtr
         then return Nothing
         else do
          argv_ps <- peekArray (fromIntegral argc) argv_p
          fmap Just $ mapM peekCWString argv_ps

setWin32ProgArgv :: Maybe [String] -> IO ()
setWin32ProgArgv Nothing = c_setWin32ProgArgv 0 nullPtr
setWin32ProgArgv (Just argv) = withMany withCWString argv $ \argv_ps -> withArrayLen argv_ps $ \argc argv_p -> do
        c_setWin32ProgArgv (fromIntegral argc) argv_p

foreign import ccall unsafe "getWin32ProgArgv"
  c_getWin32ProgArgv :: Ptr CInt -> Ptr (Ptr CWString) -> IO ()

foreign import ccall unsafe "setWin32ProgArgv"
  c_setWin32ProgArgv :: CInt -> Ptr CWString -> IO ()

-- See Note [Ignore hs_init argv]
dropRTSArgs :: [String] -> [String]
dropRTSArgs []             = []
dropRTSArgs rest@("--":_)  = rest
dropRTSArgs ("+RTS":rest)  = dropRTSArgs (dropWhile (/= "-RTS") rest)
dropRTSArgs ("--RTS":rest) = rest
dropRTSArgs ("-RTS":rest)  = dropRTSArgs rest
dropRTSArgs (arg:rest)     = arg : dropRTSArgs rest

#endif

-- | Computation 'getArgs' returns a list of the program's command
-- line arguments (not including the program name).
getArgs :: IO [String]

#ifdef mingw32_HOST_OS
getArgs =  fmap tail getWin32ProgArgv_certainly
#else
getArgs =
  alloca $ \ p_argc ->
  alloca $ \ p_argv -> do
   getProgArgv p_argc p_argv
   p    <- fromIntegral `liftM` peek p_argc
   argv <- peek p_argv
   enc <- getFileSystemEncoding
   peekArray (p - 1) (advancePtr argv 1) >>= mapM (GHC.peekCString enc)

foreign import ccall unsafe "getProgArgv"
  getProgArgv :: Ptr CInt -> Ptr (Ptr CString) -> IO ()
#endif

{-|
Computation 'getProgName' returns the name of the program as it was
invoked.

However, this is hard-to-impossible to implement on some non-Unix
OSes, so instead, for maximum portability, we just return the leafname
of the program as invoked. Even then there are some differences
between platforms: on Windows, for example, a program invoked as foo
is probably really @FOO.EXE@, and that is what 'getProgName' will return.
-}
getProgName :: IO String
#ifdef mingw32_HOST_OS
-- Ignore the arguments to hs_init on Windows for the sake of Unicode compat
getProgName = fmap (basename . head) getWin32ProgArgv_certainly
#else
getProgName =
  alloca $ \ p_argc ->
  alloca $ \ p_argv -> do
     getProgArgv p_argc p_argv
     argv <- peek p_argv
     unpackProgName argv

unpackProgName  :: Ptr (Ptr CChar) -> IO String   -- argv[0]
unpackProgName argv = do
  enc <- getFileSystemEncoding
  s <- peekElemOff argv 0 >>= GHC.peekCString enc
  return (basename s)
#endif

basename :: FilePath -> FilePath
basename f = go f f
 where
  go acc [] = acc
  go acc (x:xs)
    | isPathSeparator x = go xs xs
    | otherwise         = go acc xs

  isPathSeparator :: Char -> Bool
  isPathSeparator '/'  = True
#ifdef mingw32_HOST_OS
  isPathSeparator '\\' = True
#endif
  isPathSeparator _    = False


-- | Computation 'getEnv' @var@ returns the value
-- of the environment variable @var@. For the inverse, POSIX users
-- can use 'System.Posix.Env.putEnv'.
--
-- This computation may fail with:
--
--  * 'System.IO.Error.isDoesNotExistError' if the environment variable
--    does not exist.

getEnv :: String -> IO String
getEnv name = lookupEnv name >>= maybe handleError return
  where
#ifdef mingw32_HOST_OS
    handleError = do
        err <- c_GetLastError
        if err == eRROR_ENVVAR_NOT_FOUND
            then ioe_missingEnvVar name
            else throwGetLastError "getEnv"

eRROR_ENVVAR_NOT_FOUND :: DWORD
eRROR_ENVVAR_NOT_FOUND = 203

foreign import WINDOWS_CCONV unsafe "windows.h GetLastError"
  c_GetLastError:: IO DWORD

#else
    handleError = ioe_missingEnvVar name
#endif

-- | Return the value of the environment variable @var@, or @Nothing@ if
-- there is no such value.
--
-- For POSIX users, this is equivalent to 'System.Posix.Env.getEnv'.
--
-- @since 4.6.0.0
lookupEnv :: String -> IO (Maybe String)
#ifdef mingw32_HOST_OS
lookupEnv name = withCWString name $ \s -> try_size s 256
  where
    try_size s size = allocaArray (fromIntegral size) $ \p_value -> do
      res <- c_GetEnvironmentVariable s p_value size
      case res of
        0 -> return Nothing
        _ | res > size -> try_size s res -- Rare: size increased between calls to GetEnvironmentVariable
          | otherwise  -> peekCWString p_value >>= return . Just

foreign import WINDOWS_CCONV unsafe "windows.h GetEnvironmentVariableW"
  c_GetEnvironmentVariable :: LPWSTR -> LPWSTR -> DWORD -> IO DWORD
#else
lookupEnv name =
    withCString name $ \s -> do
      litstring <- c_getenv s
      if litstring /= nullPtr
        then do enc <- getFileSystemEncoding
                result <- GHC.peekCString enc litstring
                return $ Just result
        else return Nothing

foreign import ccall unsafe "getenv"
   c_getenv :: CString -> IO (Ptr CChar)
#endif

ioe_missingEnvVar :: String -> IO a
ioe_missingEnvVar name = ioException (IOError Nothing NoSuchThing "getEnv"
    "no environment variable" Nothing (Just name))

-- | @setEnv name value@ sets the specified environment variable to @value@.
--
-- On Windows setting an environment variable to the /empty string/ removes
-- that environment variable from the environment.  For the sake of
-- compatibility we adopt that behavior.  In particular
--
-- @
-- setEnv name \"\"
-- @
--
-- has the same effect as
--
-- @
-- `unsetEnv` name
-- @
--
-- If you don't care about Windows support and want to set an environment
-- variable to the empty string use @System.Posix.Env.setEnv@ from the @unix@
-- package instead.
--
-- Throws `Control.Exception.IOException` if @name@ is the empty string or
-- contains an equals sign.
--
-- @since 4.7.0.0
setEnv :: String -> String -> IO ()
setEnv key_ value_
  | null key       = throwIO (mkIOError InvalidArgument "setEnv" Nothing Nothing)
  | '=' `elem` key = throwIO (mkIOError InvalidArgument "setEnv" Nothing Nothing)
  | null value     = unsetEnv key
  | otherwise      = setEnv_ key value
  where
    key   = takeWhile (/= '\NUL') key_
    value = takeWhile (/= '\NUL') value_

setEnv_ :: String -> String -> IO ()
#ifdef mingw32_HOST_OS
setEnv_ key value = withCWString key $ \k -> withCWString value $ \v -> do
  success <- c_SetEnvironmentVariable k v
  unless success (throwGetLastError "setEnv")

foreign import WINDOWS_CCONV unsafe "windows.h SetEnvironmentVariableW"
  c_SetEnvironmentVariable :: LPTSTR -> LPTSTR -> IO Bool
#else

-- NOTE: The 'setenv()' function is not available on all systems, hence we use
-- 'putenv()'.  This leaks memory, but so do common implementations of
-- 'setenv()' (AFAIK).
setEnv_ k v = putEnv (k ++ "=" ++ v)

putEnv :: String -> IO ()
putEnv keyvalue = do
  s <- getFileSystemEncoding >>= (`GHC.newCString` keyvalue)
  -- IMPORTANT: Do not free `s` after calling putenv!
  --
  -- According to SUSv2, the string passed to putenv becomes part of the
  -- environment.
  throwErrnoIf_ (/= 0) "putenv" (c_putenv s)

foreign import ccall unsafe "putenv" c_putenv :: CString -> IO CInt
#endif

-- | @unsetEnv name@ removes the specified environment variable from the
-- environment of the current process.
--
-- Throws `Control.Exception.IOException` if @name@ is the empty string or
-- contains an equals sign.
--
-- @since 4.7.0.0
unsetEnv :: String -> IO ()
#ifdef mingw32_HOST_OS
unsetEnv key = withCWString key $ \k -> do
  success <- c_SetEnvironmentVariable k nullPtr
  unless success $ do
    -- We consider unsetting an environment variable that does not exist not as
    -- an error, hence we ignore eRROR_ENVVAR_NOT_FOUND.
    err <- c_GetLastError
    unless (err == eRROR_ENVVAR_NOT_FOUND) $ do
      throwGetLastError "unsetEnv"
#else

#ifdef HAVE_UNSETENV
unsetEnv key = withFilePath key (throwErrnoIf_ (/= 0) "unsetEnv" . c_unsetenv)
foreign import ccall unsafe "__hsbase_unsetenv" c_unsetenv :: CString -> IO CInt
#else
unsetEnv key = setEnv_ key ""
#endif

#endif

{-|
'withArgs' @args act@ - while executing action @act@, have 'getArgs'
return @args@.
-}
withArgs :: [String] -> IO a -> IO a
withArgs xs act = do
   p <- System.Environment.getProgName
   withArgv (p:xs) act

{-|
'withProgName' @name act@ - while executing action @act@,
have 'getProgName' return @name@.
-}
withProgName :: String -> IO a -> IO a
withProgName nm act = do
   xs <- System.Environment.getArgs
   withArgv (nm:xs) act

-- Worker routine which marshals and replaces an argv vector for
-- the duration of an action.

withArgv :: [String] -> IO a -> IO a

#ifdef mingw32_HOST_OS
-- We have to reflect the updated arguments in the RTS-side variables as
-- well, because the RTS still consults them for error messages and the like.
-- If we don't do this then ghc-e005 fails.
withArgv new_args act = withWin32ProgArgv new_args $ withProgArgv new_args act
#else
withArgv = withProgArgv
#endif

withProgArgv :: [String] -> IO a -> IO a
withProgArgv new_args act = do
  pName <- System.Environment.getProgName
  existing_args <- System.Environment.getArgs
  bracket_ (setProgArgv new_args)
           (setProgArgv (pName:existing_args))
           act

setProgArgv :: [String] -> IO ()
setProgArgv argv = do
  enc <- getFileSystemEncoding
  GHC.withCStringsLen enc argv $ \len css ->
    c_setProgArgv (fromIntegral len) css

-- setProgArgv copies the arguments
foreign import ccall unsafe "setProgArgv"
  c_setProgArgv  :: CInt -> Ptr CString -> IO ()

-- |'getEnvironment' retrieves the entire environment as a
-- list of @(key,value)@ pairs.
--
-- If an environment entry does not contain an @\'=\'@ character,
-- the @key@ is the whole entry and the @value@ is the empty string.
getEnvironment :: IO [(String, String)]

#ifdef mingw32_HOST_OS
getEnvironment = bracket c_GetEnvironmentStrings c_FreeEnvironmentStrings $ \pBlock ->
    if pBlock == nullPtr then return []
     else go pBlock
  where
    go pBlock = do
        -- The block is terminated by a null byte where there
        -- should be an environment variable of the form X=Y
        c <- peek pBlock
        if c == 0 then return []
         else do
          -- Seek the next pair (or terminating null):
          pBlock' <- seekNull pBlock False
          -- We now know the length in bytes, but ignore it when
          -- getting the actual String:
          str <- peekCWString pBlock
          fmap (divvy str :) $ go pBlock'

    -- Returns pointer to the byte *after* the next null
    seekNull pBlock done = do
        let pBlock' = pBlock `plusPtr` sizeOf (undefined :: CWchar)
        if done then return pBlock'
         else do
           c <- peek pBlock'
           seekNull pBlock' (c == (0 :: Word8 ))

foreign import WINDOWS_CCONV unsafe "windows.h GetEnvironmentStringsW"
  c_GetEnvironmentStrings :: IO (Ptr CWchar)

foreign import WINDOWS_CCONV unsafe "windows.h FreeEnvironmentStringsW"
  c_FreeEnvironmentStrings :: Ptr CWchar -> IO Bool
#else
getEnvironment = do
   pBlock <- getEnvBlock
   if pBlock == nullPtr then return []
    else do
      enc <- getFileSystemEncoding
      stuff <- peekArray0 nullPtr pBlock >>= mapM (GHC.peekCString enc)
      return (map divvy stuff)

foreign import ccall unsafe "__hscore_environ"
  getEnvBlock :: IO (Ptr CString)
#endif

divvy :: String -> (String, String)
divvy str =
  case break (=='=') str of
    (xs,[])        -> (xs,[]) -- don't barf (like Posix.getEnvironment)
    (name,_:value) -> (name,value)
