{-# LANGUAGE CPP #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE BangPatterns #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Distribution.Simple.Utils
-- Copyright   :  Isaac Jones, Simon Marlow 2003-2004
-- License     :  BSD3
--                portions Copyright (c) 2007, Galois Inc.
--
-- Maintainer  :  [email protected]
-- Portability :  portable
--
-- A large and somewhat miscellaneous collection of utility functions used
-- throughout the rest of the Cabal lib and in other tools that use the Cabal
-- lib like @[email protected] It has a very simple set of logging actions. It
-- has low level functions for running programs, a bunch of wrappers for
-- various directory and file functions that do extra logging.

module Distribution.Simple.Utils (
        cabalVersion,

        -- * logging and errors
        -- Old style
        die, dieWithLocation,
        -- New style
        dieNoVerbosity,
        die', dieWithLocation',
        dieNoWrap,
        topHandler, topHandlerWith,
        warn,
        notice, noticeNoWrap, noticeDoc,
        setupMessage,
        info, infoNoWrap,
        debug, debugNoWrap,
        chattyTry,
        annotateIO,
        printRawCommandAndArgs, printRawCommandAndArgsAndEnv,

        -- * exceptions
        handleDoesNotExist,

        -- * running programs
        rawSystemExit,
        rawSystemExitCode,
        rawSystemExitWithEnv,
        rawSystemStdout,
        rawSystemStdInOut,
        rawSystemIOWithEnv,
        createProcessWithEnv,
        maybeExit,
        xargs,
        findProgramLocation,
        findProgramVersion,

        -- * copying files
        smartCopySources,
        createDirectoryIfMissingVerbose,
        copyFileVerbose,
        copyDirectoryRecursiveVerbose,
        copyFiles,
        copyFileTo,

        -- * installing files
        installOrdinaryFile,
        installExecutableFile,
        installMaybeExecutableFile,
        installOrdinaryFiles,
        installExecutableFiles,
        installMaybeExecutableFiles,
        installDirectoryContents,
        copyDirectoryRecursive,

        -- * File permissions
        doesExecutableExist,
        setFileOrdinary,
        setFileExecutable,

        -- * file names
        currentDir,
        shortRelativePath,
        dropExeExtension,
        exeExtensions,

        -- * finding files
        findFile,
        findFirstFile,
        findFileWithExtension,
        findFileWithExtension',
        findAllFilesWithExtension,
        findModuleFile,
        findModuleFiles,
        getDirectoryContentsRecursive,

        -- * environment variables
        isInSearchPath,
        addLibraryPath,

        -- * simple file globbing
        matchFileGlob,
        matchDirFileGlob,
        parseFileGlob,
        FileGlob(..),

        -- * modification time
        moreRecentFile,
        existsAndIsMoreRecentThan,

        -- * temp files and dirs
        TempFileOptions(..), defaultTempFileOptions,
        withTempFile, withTempFileEx,
        withTempDirectory, withTempDirectoryEx,

        -- * .cabal and .buildinfo files
        defaultPackageDesc,
        findPackageDesc,
        tryFindPackageDesc,
        defaultHookedPackageDesc,
        findHookedPackageDesc,

        -- * reading and writing files safely
        withFileContents,
        writeFileAtomic,
        rewriteFile,
        rewriteFileEx,

        -- * Unicode
        fromUTF8,
        fromUTF8BS,
        fromUTF8LBS,
        toUTF8,
        readUTF8File,
        withUTF8FileContents,
        writeUTF8File,
        normaliseLineEndings,

        -- * BOM
        startsWithBOM,
        fileHasBOM,
        ignoreBOM,

        -- * generic utils
        dropWhileEndLE,
        takeWhileEndLE,
        equating,
        comparing,
        isInfixOf,
        intercalate,
        lowercase,
        listUnion,
        listUnionRight,
        ordNub,
        ordNubBy,
        ordNubRight,
        safeTail,
        unintersperse,
        wrapText,
        wrapLine,

        -- * FilePath stuff
        isAbsoluteOnAnyPlatform,
        isRelativeOnAnyPlatform,
  ) where

import Prelude ()
import Distribution.Compat.Prelude

import Distribution.Text
import Distribution.Utils.Generic
import Distribution.ModuleName as ModuleName
import Distribution.System
import Distribution.Version
import Distribution.Compat.CopyFile
import Distribution.Compat.Internal.TempFile
import Distribution.Compat.Exception
import Distribution.Compat.Stack
import Distribution.Verbosity
import Distribution.Types.PackageId

#if __GLASGOW_HASKELL__ < 711
#ifdef VERSION_base
#define BOOTSTRAPPED_CABAL 1
#endif
#else
#ifdef CURRENT_PACKAGE_KEY
#define BOOTSTRAPPED_CABAL 1
#endif
#endif

#ifdef BOOTSTRAPPED_CABAL
import qualified Paths_Cabal (version)
#endif

import Control.Concurrent.MVar
    ( newEmptyMVar, putMVar, takeMVar )
import Data.Typeable
    ( cast )
import qualified Data.ByteString.Lazy.Char8 as BS.Char8

import System.Directory
    ( Permissions(executable), getDirectoryContents, getPermissions
    , doesDirectoryExist, doesFileExist, removeFile, findExecutable
    , getModificationTime )
import System.Environment
    ( getProgName )
import System.Exit
    ( exitWith, ExitCode(..) )
import System.FilePath
    ( normalise, (</>), (<.>)
    , getSearchPath, joinPath, takeDirectory, splitFileName
    , splitExtension, splitExtensions, splitDirectories
    , searchPathSeparator )
import System.Directory
    ( createDirectory, removeDirectoryRecursive )
import System.IO
    ( Handle, hSetBinaryMode, hGetContents, stderr, stdout, hPutStr, hFlush
    , hClose, hSetBuffering, BufferMode(..) )
import System.IO.Error
import System.IO.Unsafe
    ( unsafeInterleaveIO )
import qualified Control.Exception as Exception

import Control.Exception (IOException, evaluate, throwIO)
import Control.Concurrent (forkIO)
import qualified System.Process as Process
         ( CreateProcess(..), StdStream(..), proc)
import System.Process
         ( ProcessHandle, createProcess, rawSystem, runInteractiveProcess
         , showCommandForUser, waitForProcess)

import qualified Text.PrettyPrint as Disp

-- We only get our own version number when we're building with ourselves
cabalVersion :: Version
#if defined(BOOTSTRAPPED_CABAL)
cabalVersion = mkVersion' Paths_Cabal.version
#elif defined(CABAL_VERSION)
cabalVersion = mkVersion [CABAL_VERSION]
#else
cabalVersion = mkVersion [1,9999]  --used when bootstrapping
#endif

-- ----------------------------------------------------------------------------
-- Exception and logging utils

-- Cabal's logging infrastructure has a few constraints:
--
--  * We must make all logging formatting and emissions decisions based
--    on the 'Verbosity' parameter, which is the only parameter that is
--    plumbed to enough call-sites to actually be used for this matter.
--    (One of Cabal's "big mistakes" is to have never have defined a
--    monad of its own.)
--
--  * When we 'die', we must raise an IOError.  This a backwards
--    compatibility consideration, because that's what we've raised
--    previously, and if we change to any other exception type,
--    exception handlers which match on IOError will no longer work.
--    One case where it is known we rely on IOError being catchable
--    is 'readPkgConfigDb' in cabal-install; there may be other
--    user code that also assumes this.
--
--  * The 'topHandler' does not know what 'Verbosity' is, because
--    it gets called before we've done command line parsing (where
--    the 'Verbosity' parameter would come from).
--
-- This leads to two big architectural choices:
--
--  * Although naively we might imagine 'Verbosity' to be a simple
--    enumeration type, actually it is a full-on abstract data type
--    that may contain arbitrarily complex information.  At the
--    moment, it is fully representable as a string, but we might
--    eventually also use verbosity to let users register their
--    own logging handler.
--
--  * When we call 'die', we perform all the formatting and addition
--    of extra information we need, and then ship this in the IOError
--    to the top-level handler.  Here are alternate designs that
--    don't work:
--
--      a) Ship the unformatted info to the handler.  This doesn't
--      work because at the point the handler gets the message,
--      we've lost call stacks, and even if we did, we don't have access
--      to 'Verbosity' to decide whether or not to render it.
--
--      b) Print the information at the 'die' site, then raise an
--      error.  This means that if the exception is subsequently
--      caught by a handler, we will still have emitted the output,
--      which is not the correct behavior.
--
--    For the top-level handler to "know" that an error message
--    contains one of these fully formatted packets, we set a sentinel
--    in one of IOError's extra fields.  This is handled by
--    'ioeSetVerbatim' and 'ioeGetVerbatim'.
--

{-# DEPRECATED dieWithLocation "Messages thrown with dieWithLocation can't be controlled with Verbosity; use dieWithLocation' instead" #-}
dieWithLocation :: FilePath -> Maybe Int -> String -> IO a
dieWithLocation filename lineno msg =
  ioError . setLocation lineno
          . flip ioeSetFileName (normalise filename)
          $ userError msg
  where
    setLocation Nothing  err = err
    setLocation (Just n) err = ioeSetLocation err (show n)
    _ = callStack -- TODO: Attach CallStack to exception

{-# DEPRECATED die "Messages thrown with die can't be controlled with Verbosity; use die' instead, or dieNoVerbosity if Verbosity truly is not available" #-}
die :: String -> IO a
die = dieNoVerbosity

dieNoVerbosity :: String -> IO a
dieNoVerbosity msg
    = ioError (userError msg)
  where
    _ = callStack -- TODO: Attach CallStack to exception

-- | Tag an 'IOError' whose error string should be output to the screen
-- verbatim.
ioeSetVerbatim :: IOError -> IOError
ioeSetVerbatim e = ioeSetLocation e "dieVerbatim"

-- | Check if an 'IOError' should be output verbatim to screen.
ioeGetVerbatim :: IOError -> Bool
ioeGetVerbatim e = ioeGetLocation e == "dieVerbatim"

-- | Create a 'userError' whose error text will be output verbatim
verbatimUserError :: String -> IOError
verbatimUserError = ioeSetVerbatim . userError

dieWithLocation' :: Verbosity -> FilePath -> Maybe Int -> String -> IO a
dieWithLocation' verbosity filename mb_lineno msg = withFrozenCallStack $ do
    pname <- getProgName
    ioError . verbatimUserError
            . withMetadata AlwaysMark VerboseTrace verbosity
            . wrapTextVerbosity verbosity
            $ pname ++ ": " ++
              filename ++ (case mb_lineno of
                            Just lineno -> ":" ++ show lineno
                            Nothing -> "") ++
              ": " ++ msg

die' :: Verbosity -> String -> IO a
die' verbosity msg = withFrozenCallStack $ do
    pname <- getProgName
    ioError . verbatimUserError
            . withMetadata AlwaysMark VerboseTrace verbosity
            . wrapTextVerbosity verbosity
            $ pname ++ ": " ++ msg

dieNoWrap :: Verbosity -> String -> IO a
dieNoWrap verbosity msg = withFrozenCallStack $ do
    -- TODO: should this have program name or not?
    ioError . verbatimUserError
            . withMetadata AlwaysMark VerboseTrace verbosity
            $ msg

-- | Given a block of IO code that may raise an exception, annotate
-- it with the metadata from the current scope.  Use this as close
-- to external code that raises IO exceptions as possible, since
-- this function unconditionally wraps the error message with a trace
-- (so it is NOT idempotent.)
annotateIO :: Verbosity -> IO a -> IO a
annotateIO verbosity = modifyIOError f
  where
    f ioe = ioeSetErrorString ioe
          . withMetadata NeverMark VerboseTrace verbosity
          $ ioeGetErrorString ioe

topHandlerWith :: forall a. (Exception.SomeException -> IO a) -> IO a -> IO a
topHandlerWith cont prog = do
    -- By default, stderr to a terminal device is NoBuffering. But this
    -- is *really slow*
    hSetBuffering stderr LineBuffering
    Exception.catches prog [
        Exception.Handler rethrowAsyncExceptions
      , Exception.Handler rethrowExitStatus
      , Exception.Handler handle
      ]
  where
    -- Let async exceptions rise to the top for the default top-handler
    rethrowAsyncExceptions :: Exception.AsyncException -> NoCallStackIO a
    rethrowAsyncExceptions a = throwIO a

    -- ExitCode gets thrown asynchronously too, and we don't want to print it
    rethrowExitStatus :: ExitCode -> NoCallStackIO a
    rethrowExitStatus = throwIO

    -- Print all other exceptions
    handle :: Exception.SomeException -> NoCallStackIO a
    handle se = do
      hFlush stdout
      pname <- getProgName
      hPutStr stderr (message pname se)
      cont se

    message :: String -> Exception.SomeException -> String
    message pname (Exception.SomeException se) =
      case cast se :: Maybe Exception.IOException of
        Just ioe
         | ioeGetVerbatim ioe ->
            -- Use the message verbatim
            ioeGetErrorString ioe
         | isUserError ioe ->
          let file         = case ioeGetFileName ioe of
                               Nothing   -> ""
                               Just path -> path ++ location ++ ": "
              location     = case ioeGetLocation ioe of
                               l@(n:_) | isDigit n -> ':' : l
                               _                        -> ""
              detail       = ioeGetErrorString ioe
          in wrapText (pname ++ ": " ++ file ++ detail)
        _ ->
          displaySomeException se

-- | BC wrapper around 'Exception.displayException'.
displaySomeException :: Exception.Exception e => e -> String
displaySomeException se =
#if __GLASGOW_HASKELL__ < 710
    show se
#else
    Exception.displayException se
#endif

topHandler :: IO a -> IO a
topHandler prog = topHandlerWith (const $ exitWith (ExitFailure 1)) prog

-- | Non fatal conditions that may be indicative of an error or problem.
--
-- We display these at the 'normal' verbosity level.
--
warn :: Verbosity -> String -> IO ()
warn verbosity msg = withFrozenCallStack $ do
  when (verbosity >= normal) $ do
    hFlush stdout
    hPutStr stderr . withMetadata NormalMark FlagTrace verbosity
                   . wrapTextVerbosity verbosity
                   $ "Warning: " ++ msg

-- | Useful status messages.
--
-- We display these at the 'normal' verbosity level.
--
-- This is for the ordinary helpful status messages that users see. Just
-- enough information to know that things are working but not floods of detail.
--
notice :: Verbosity -> String -> IO ()
notice verbosity msg = withFrozenCallStack $ do
  when (verbosity >= normal) $ do
    hPutStr stdout . withMetadata NormalMark FlagTrace verbosity
                   . wrapTextVerbosity verbosity
                   $ msg

-- | Display a message at 'normal' verbosity level, but without
-- wrapping.
--
noticeNoWrap :: Verbosity -> String -> IO ()
noticeNoWrap verbosity msg = withFrozenCallStack $ do
  when (verbosity >= normal) $ do
    hPutStr stdout . withMetadata NormalMark FlagTrace verbosity $ msg

-- | Pretty-print a 'Disp.Doc' status message at 'normal' verbosity
-- level.  Use this if you need fancy formatting.
--
noticeDoc :: Verbosity -> Disp.Doc -> IO ()
noticeDoc verbosity msg = withFrozenCallStack $ do
  when (verbosity >= normal) $ do
    hPutStr stdout . withMetadata NormalMark FlagTrace verbosity
                   . Disp.renderStyle defaultStyle $ msg

-- | Display a "setup status message".  Prefer using setupMessage'
-- if possible.
--
setupMessage :: Verbosity -> String -> PackageIdentifier -> IO ()
setupMessage verbosity msg pkgid = withFrozenCallStack $ do
    noticeNoWrap verbosity (msg ++ ' ': display pkgid ++ "...")

-- | More detail on the operation of some action.
--
-- We display these messages when the verbosity level is 'verbose'
--
info :: Verbosity -> String -> IO ()
info verbosity msg = withFrozenCallStack $
  when (verbosity >= verbose) $ do
    hPutStr stdout . withMetadata NeverMark FlagTrace verbosity
                   . wrapTextVerbosity verbosity
                   $ msg

infoNoWrap :: Verbosity -> String -> IO ()
infoNoWrap verbosity msg = withFrozenCallStack $
  when (verbosity >= verbose) $ do
    hPutStr stdout . withMetadata NeverMark FlagTrace verbosity
                   $ msg

-- | Detailed internal debugging information
--
-- We display these messages when the verbosity level is 'deafening'
--
debug :: Verbosity -> String -> IO ()
debug verbosity msg = withFrozenCallStack $
  when (verbosity >= deafening) $ do
    hPutStr stdout . withMetadata NeverMark FlagTrace verbosity
                   . wrapTextVerbosity verbosity
                   $ msg
    -- ensure that we don't lose output if we segfault/infinite loop
    hFlush stdout

-- | A variant of 'debug' that doesn't perform the automatic line
-- wrapping. Produces better output in some cases.
debugNoWrap :: Verbosity -> String -> IO ()
debugNoWrap verbosity msg = withFrozenCallStack $
  when (verbosity >= deafening) $ do
    hPutStr stdout . withMetadata NeverMark FlagTrace verbosity
                   $ msg
    -- ensure that we don't lose output if we segfault/infinite loop
    hFlush stdout

-- | Perform an IO action, catching any IO exceptions and printing an error
--   if one occurs.
chattyTry :: String  -- ^ a description of the action we were attempting
          -> IO ()   -- ^ the action itself
          -> IO ()
chattyTry desc action =
  catchIO action $ \exception ->
    putStrLn $ "Error while " ++ desc ++ ": " ++ show exception

-- | Run an IO computation, returning @[email protected] if it raises a "file
-- does not exist" error.
handleDoesNotExist :: a -> NoCallStackIO a -> NoCallStackIO a
handleDoesNotExist e =
    Exception.handleJust
      (\ioe -> if isDoesNotExistError ioe then Just ioe else Nothing)
      (\_ -> return e)

-- -----------------------------------------------------------------------------
-- Helper functions

-- | Wraps text unless the @[email protected] verbosity flag is active
wrapTextVerbosity :: Verbosity -> String -> String
wrapTextVerbosity verb
  | isVerboseNoWrap verb = withTrailingNewline
  | otherwise            = wrapText

-- | Wrap output with a marker if @[email protected] verbosity flag is set.
--
-- NB: Why is markoutput done with start/end markers, and not prefixes?
-- Markers are more convenient to add (if we want to add prefixes,
-- we have to 'lines' and then 'map'; here's it's just some
-- concatenates).  Note that even in the prefix case, we can't
-- guarantee that the markers are unambiguous, because some of
-- Cabal's output comes straight from external programs, where
-- we don't have the ability to interpose on the output.
--
withOutputMarker :: Verbosity -> String -> String
withOutputMarker v xs | not (isVerboseMarkOutput v) = xs
withOutputMarker _ "" = "" -- Minor optimization, don't mark uselessly
withOutputMarker _ xs =
    "-----BEGIN CABAL OUTPUT-----\n" ++
    withTrailingNewline xs ++
    "-----END CABAL OUTPUT-----\n"

-- | Append a trailing newline to a string if it does not
-- already have a trailing newline.
--
withTrailingNewline :: String -> String
withTrailingNewline "" = ""
withTrailingNewline (x:xs) = x : go x xs
  where
    go   _ (c:cs) = c : go c cs
    go '\n' "" = ""
    go   _  "" = "\n"

-- | Prepend a call-site and/or call-stack based on Verbosity
--
withCallStackPrefix :: WithCallStack (TraceWhen -> Verbosity -> String -> String)
withCallStackPrefix tracer verbosity s = withFrozenCallStack $
    (if isVerboseCallSite verbosity
        then parentSrcLocPrefix ++
             -- Hack: need a newline before starting output marker :(
             if isVerboseMarkOutput verbosity
                then "\n"
                else ""
        else "") ++
    (case traceWhen verbosity tracer of
        Just pre -> pre ++ prettyCallStack callStack ++ "\n"
        Nothing  -> "") ++
    s

-- | When should we emit the call stack?  We always emit
-- for internal errors, emit the trace for errors when we
-- are in verbose mode, and otherwise only emit it if
-- explicitly asked for using the @[email protected] verbosity
-- flag.  (At the moment, 'AlwaysTrace' is not used.
--
data TraceWhen
    = AlwaysTrace
    | VerboseTrace
    | FlagTrace
    deriving (Eq)

-- | Determine if we should emit a call stack.
-- If we trace, it also emits any prefix we should append.
traceWhen :: Verbosity -> TraceWhen -> Maybe String
traceWhen _ AlwaysTrace = Just ""
traceWhen v VerboseTrace | v >= verbose         = Just ""
traceWhen v FlagTrace    | isVerboseCallStack v = Just "----\n"
traceWhen _ _ = Nothing

-- | When should we output the marker?  Things like 'die'
-- always get marked, but a 'NormalMark' will only be
-- output if we're not a quiet verbosity.
--
data MarkWhen = AlwaysMark | NormalMark | NeverMark

-- | Add all necessary metadata to a logging message
--
withMetadata :: WithCallStack (MarkWhen -> TraceWhen -> Verbosity -> String -> String)
withMetadata marker tracer verbosity x = withFrozenCallStack $
    -- NB: order matters.  Output marker first because we
    -- don't want to capture call stacks.
      withTrailingNewline
    . withCallStackPrefix tracer verbosity
    . (case marker of
        AlwaysMark -> withOutputMarker verbosity
        NormalMark | not (isVerboseQuiet verbosity)
                   -> withOutputMarker verbosity
                   | otherwise
                   -> id
        NeverMark  -> id)
    -- Clear out any existing markers
    . clearMarkers
    $ x

clearMarkers :: String -> String
clearMarkers s = unlines . filter isMarker $ lines s
  where
    isMarker "-----BEGIN CABAL OUTPUT-----" = False
    isMarker "-----END CABAL OUTPUT-----"   = False
    isMarker _ = True

-- -----------------------------------------------------------------------------
-- rawSystem variants
maybeExit :: IO ExitCode -> IO ()
maybeExit cmd = do
  res <- cmd
  unless (res == ExitSuccess) $ exitWith res

printRawCommandAndArgs :: Verbosity -> FilePath -> [String] -> IO ()
printRawCommandAndArgs verbosity path args = withFrozenCallStack $
    printRawCommandAndArgsAndEnv verbosity path args Nothing Nothing

printRawCommandAndArgsAndEnv :: Verbosity
                             -> FilePath
                             -> [String]
                             -> Maybe FilePath
                             -> Maybe [(String, String)]
                             -> IO ()
printRawCommandAndArgsAndEnv verbosity path args mcwd menv = do
    case menv of
        Just env -> debugNoWrap verbosity ("Environment: " ++ show env)
        Nothing -> return ()
    case mcwd of
        Just cwd -> debugNoWrap verbosity ("Working directory: " ++ show cwd)
        Nothing -> return ()
    infoNoWrap verbosity (showCommandForUser path args)

-- Exit with the same exit code if the subcommand fails
rawSystemExit :: Verbosity -> FilePath -> [String] -> IO ()
rawSystemExit verbosity path args = withFrozenCallStack $ do
  printRawCommandAndArgs verbosity path args
  hFlush stdout
  exitcode <- rawSystem path args
  unless (exitcode == ExitSuccess) $ do
    debug verbosity $ path ++ " returned " ++ show exitcode
    exitWith exitcode

rawSystemExitCode :: Verbosity -> FilePath -> [String] -> IO ExitCode
rawSystemExitCode verbosity path args = withFrozenCallStack $ do
  printRawCommandAndArgs verbosity path args
  hFlush stdout
  exitcode <- rawSystem path args
  unless (exitcode == ExitSuccess) $ do
    debug verbosity $ path ++ " returned " ++ show exitcode
  return exitcode

rawSystemExitWithEnv :: Verbosity
                     -> FilePath
                     -> [String]
                     -> [(String, String)]
                     -> IO ()
rawSystemExitWithEnv verbosity path args env = withFrozenCallStack $ do
    printRawCommandAndArgsAndEnv verbosity path args Nothing (Just env)
    hFlush stdout
    (_,_,_,ph) <- createProcess $
                  (Process.proc path args) { Process.env = (Just env)
#ifdef MIN_VERSION_process
#if MIN_VERSION_process(1,2,0)
-- delegate_ctlc has been added in process 1.2, and we still want to be able to
-- bootstrap GHC on systems not having that version
                                           , Process.delegate_ctlc = True
#endif
#endif
                                           }
    exitcode <- waitForProcess ph
    unless (exitcode == ExitSuccess) $ do
        debug verbosity $ path ++ " returned " ++ show exitcode
        exitWith exitcode

-- Closes the passed in handles before returning.
rawSystemIOWithEnv :: Verbosity
                   -> FilePath
                   -> [String]
                   -> Maybe FilePath           -- ^ New working dir or inherit
                   -> Maybe [(String, String)] -- ^ New environment or inherit
                   -> Maybe Handle  -- ^ stdin
                   -> Maybe Handle  -- ^ stdout
                   -> Maybe Handle  -- ^ stderr
                   -> IO ExitCode
rawSystemIOWithEnv verbosity path args mcwd menv inp out err = withFrozenCallStack $ do
    (_,_,_,ph) <- createProcessWithEnv verbosity path args mcwd menv
                                       (mbToStd inp) (mbToStd out) (mbToStd err)
    exitcode <- waitForProcess ph
    unless (exitcode == ExitSuccess) $ do
      debug verbosity $ path ++ " returned " ++ show exitcode
    return exitcode
  where
    mbToStd :: Maybe Handle -> Process.StdStream
    mbToStd = maybe Process.Inherit Process.UseHandle

createProcessWithEnv ::
     Verbosity
  -> FilePath
  -> [String]
  -> Maybe FilePath           -- ^ New working dir or inherit
  -> Maybe [(String, String)] -- ^ New environment or inherit
  -> Process.StdStream  -- ^ stdin
  -> Process.StdStream  -- ^ stdout
  -> Process.StdStream  -- ^ stderr
  -> IO (Maybe Handle, Maybe Handle, Maybe Handle,ProcessHandle)
  -- ^ Any handles created for stdin, stdout, or stderr
  -- with 'CreateProcess', and a handle to the process.
createProcessWithEnv verbosity path args mcwd menv inp out err = withFrozenCallStack $ do
    printRawCommandAndArgsAndEnv verbosity path args mcwd menv
    hFlush stdout
    (inp', out', err', ph) <- createProcess $
                                (Process.proc path args) {
                                    Process.cwd           = mcwd
                                  , Process.env           = menv
                                  , Process.std_in        = inp
                                  , Process.std_out       = out
                                  , Process.std_err       = err
#ifdef MIN_VERSION_process
#if MIN_VERSION_process(1,2,0)
-- delegate_ctlc has been added in process 1.2, and we still want to be able to
-- bootstrap GHC on systems not having that version
                                  , Process.delegate_ctlc = True
#endif
#endif
                                  }
    return (inp', out', err', ph)

-- | Run a command and return its output.
--
-- The output is assumed to be text in the locale encoding.
--
rawSystemStdout :: Verbosity -> FilePath -> [String] -> IO String
rawSystemStdout verbosity path args = withFrozenCallStack $ do
  (output, errors, exitCode) <- rawSystemStdInOut verbosity path args
                                                  Nothing Nothing
                                                  Nothing False
  when (exitCode /= ExitSuccess) $
    die errors
  return output

-- | Run a command and return its output, errors and exit status. Optionally
-- also supply some input. Also provides control over whether the binary/text
-- mode of the input and output.
--
rawSystemStdInOut :: Verbosity
                  -> FilePath                 -- ^ Program location
                  -> [String]                 -- ^ Arguments
                  -> Maybe FilePath           -- ^ New working dir or inherit
                  -> Maybe [(String, String)] -- ^ New environment or inherit
                  -> Maybe (String, Bool)     -- ^ input text and binary mode
                  -> Bool                     -- ^ output in binary mode
                  -> IO (String, String, ExitCode) -- ^ output, errors, exit
rawSystemStdInOut verbosity path args mcwd menv input outputBinary = withFrozenCallStack $ do
  printRawCommandAndArgs verbosity path args

  Exception.bracket
     (runInteractiveProcess path args mcwd menv)
     (\(inh,outh,errh,_) -> hClose inh >> hClose outh >> hClose errh)
    $ \(inh,outh,errh,pid) -> do

      -- output mode depends on what the caller wants
      hSetBinaryMode outh outputBinary
      -- but the errors are always assumed to be text (in the current locale)
      hSetBinaryMode errh False

      -- fork off a couple threads to pull on the stderr and stdout
      -- so if the process writes to stderr we do not block.

      err <- hGetContents errh
      out <- hGetContents outh

      mv <- newEmptyMVar
      let force str = do
            mberr <- Exception.try (evaluate (length str) >> return ())
            putMVar mv (mberr :: Either IOError ())
      _ <- forkIO $ force out
      _ <- forkIO $ force err

      -- push all the input, if any
      case input of
        Nothing -> return ()
        Just (inputStr, inputBinary) -> do
                -- input mode depends on what the caller wants
          hSetBinaryMode inh inputBinary
          hPutStr inh inputStr
          hClose inh
          --TODO: this probably fails if the process refuses to consume
          -- or if it closes stdin (eg if it exits)

      -- wait for both to finish, in either order
      mberr1 <- takeMVar mv
      mberr2 <- takeMVar mv

      -- wait for the program to terminate
      exitcode <- waitForProcess pid
      unless (exitcode == ExitSuccess) $
        debug verbosity $ path ++ " returned " ++ show exitcode
                       ++ if null err then "" else
                          " with error message:\n" ++ err
                       ++ case input of
                            Nothing       -> ""
                            Just ("",  _) -> ""
                            Just (inp, _) -> "\nstdin input:\n" ++ inp

      -- Check if we we hit an exception while consuming the output
      -- (e.g. a text decoding error)
      reportOutputIOError mberr1
      reportOutputIOError mberr2

      return (out, err, exitcode)
  where
    reportOutputIOError :: Either IOError () -> NoCallStackIO ()
    reportOutputIOError =
      either (\e -> throwIO (ioeSetFileName e ("output of " ++ path)))
             return


{-# DEPRECATED findProgramLocation
    "No longer used within Cabal, try findProgramOnSearchPath" #-}
-- | Look for a program on the path.
findProgramLocation :: Verbosity -> FilePath -> IO (Maybe FilePath)
findProgramLocation verbosity prog = withFrozenCallStack $ do
  debug verbosity $ "searching for " ++ prog ++ " in path."
  res <- findExecutable prog
  case res of
      Nothing   -> debug verbosity ("Cannot find " ++ prog ++ " on the path")
      Just path -> debug verbosity ("found " ++ prog ++ " at "++ path)
  return res


-- | Look for a program and try to find it's version number. It can accept
-- either an absolute path or the name of a program binary, in which case we
-- will look for the program on the path.
--
findProgramVersion :: String             -- ^ version args
                   -> (String -> String) -- ^ function to select version
                                         --   number from program output
                   -> Verbosity
                   -> FilePath           -- ^ location
                   -> IO (Maybe Version)
findProgramVersion versionArg selectVersion verbosity path = withFrozenCallStack $ do
  str <- rawSystemStdout verbosity path [versionArg]
         `catchIO`   (\_ -> return "")
         `catchExit` (\_ -> return "")
  let version :: Maybe Version
      version = simpleParse (selectVersion str)
  case version of
      Nothing -> warn verbosity $ "cannot determine version of " ++ path
                               ++ " :\n" ++ show str
      Just v  -> debug verbosity $ path ++ " is version " ++ display v
  return version


-- | Like the Unix xargs program. Useful for when we've got very long command
-- lines that might overflow an OS limit on command line length and so you
-- need to invoke a command multiple times to get all the args in.
--
-- Use it with either of the rawSystem variants above. For example:
--
-- > xargs (32*1024) (rawSystemExit verbosity) prog fixedArgs bigArgs
--
xargs :: Int -> ([String] -> IO ())
      -> [String] -> [String] -> IO ()
xargs maxSize rawSystemFun fixedArgs bigArgs =
  let fixedArgSize = sum (map length fixedArgs) + length fixedArgs
      chunkSize = maxSize - fixedArgSize
   in traverse_ (rawSystemFun . (fixedArgs ++)) (chunks chunkSize bigArgs)

  where chunks len = unfoldr $ \s ->
          if null s then Nothing
                    else Just (chunk [] len s)

        chunk acc _   []     = (reverse acc,[])
        chunk acc len (s:ss)
          | len' < len = chunk (s:acc) (len-len'-1) ss
          | otherwise  = (reverse acc, s:ss)
          where len' = length s

-- ------------------------------------------------------------
-- * File Utilities
-- ------------------------------------------------------------

----------------
-- Finding files

-- | Find a file by looking in a search path. The file path must match exactly.
--
findFile :: [FilePath]    -- ^search locations
         -> FilePath      -- ^File Name
         -> IO FilePath
findFile searchPath fileName =
  findFirstFile id
    [ path </> fileName
    | path <- nub searchPath]
  >>= maybe (die $ fileName ++ " doesn't exist") return

-- | Find a file by looking in a search path with one of a list of possible
-- file extensions. The file base name should be given and it will be tried
-- with each of the extensions in each element of the search path.
--
findFileWithExtension :: [String]
                      -> [FilePath]
                      -> FilePath
                      -> NoCallStackIO (Maybe FilePath)
findFileWithExtension extensions searchPath baseName =
  findFirstFile id
    [ path </> baseName <.> ext
    | path <- nub searchPath
    , ext <- nub extensions ]

findAllFilesWithExtension :: [String]
                          -> [FilePath]
                          -> FilePath
                          -> NoCallStackIO [FilePath]
findAllFilesWithExtension extensions searchPath basename =
  findAllFiles id
    [ path </> basename <.> ext
    | path <- nub searchPath
    , ext <- nub extensions ]

-- | Like 'findFileWithExtension' but returns which element of the search path
-- the file was found in, and the file path relative to that base directory.
--
findFileWithExtension' :: [String]
                       -> [FilePath]
                       -> FilePath
                       -> NoCallStackIO (Maybe (FilePath, FilePath))
findFileWithExtension' extensions searchPath baseName =
  findFirstFile (uncurry (</>))
    [ (path, baseName <.> ext)
    | path <- nub searchPath
    , ext <- nub extensions ]

findFirstFile :: (a -> FilePath) -> [a] -> NoCallStackIO (Maybe a)
findFirstFile file = findFirst
  where findFirst []     = return Nothing
        findFirst (x:xs) = do exists <- doesFileExist (file x)
                              if exists
                                then return (Just x)
                                else findFirst xs

findAllFiles :: (a -> FilePath) -> [a] -> NoCallStackIO [a]
findAllFiles file = filterM (doesFileExist . file)

-- | Finds the files corresponding to a list of Haskell module names.
--
-- As 'findModuleFile' but for a list of module names.
--
findModuleFiles :: [FilePath]   -- ^ build prefix (location of objects)
                -> [String]     -- ^ search suffixes
                -> [ModuleName] -- ^ modules
                -> IO [(FilePath, FilePath)]
findModuleFiles searchPath extensions moduleNames =
  traverse (findModuleFile searchPath extensions) moduleNames

-- | Find the file corresponding to a Haskell module name.
--
-- This is similar to 'findFileWithExtension'' but specialised to a module
-- name. The function fails if the file corresponding to the module is missing.
--
findModuleFile :: [FilePath]  -- ^ build prefix (location of objects)
               -> [String]    -- ^ search suffixes
               -> ModuleName  -- ^ module
               -> IO (FilePath, FilePath)
findModuleFile searchPath extensions mod_name =
      maybe notFound return
  =<< findFileWithExtension' extensions searchPath
                             (ModuleName.toFilePath mod_name)
  where
    notFound = die $ "Error: Could not find module: " ++ display mod_name
                  ++ " with any suffix: " ++ show extensions
                  ++ " in the search path: " ++ show searchPath

-- | List all the files in a directory and all subdirectories.
--
-- The order places files in sub-directories after all the files in their
-- parent directories. The list is generated lazily so is not well defined if
-- the source directory structure changes before the list is used.
--
getDirectoryContentsRecursive :: FilePath -> IO [FilePath]
getDirectoryContentsRecursive topdir = recurseDirectories [""]
  where
    recurseDirectories :: [FilePath] -> IO [FilePath]
    recurseDirectories []         = return []
    recurseDirectories (dir:dirs) = unsafeInterleaveIO $ do
      (files, dirs') <- collect [] [] =<< getDirectoryContents (topdir </> dir)
      files' <- recurseDirectories (dirs' ++ dirs)
      return (files ++ files')

      where
        collect files dirs' []              = return (reverse files
                                                     ,reverse dirs')
        collect files dirs' (entry:entries) | ignore entry
                                            = collect files dirs' entries
        collect files dirs' (entry:entries) = do
          let dirEntry = dir </> entry
          isDirectory <- doesDirectoryExist (topdir </> dirEntry)
          if isDirectory
            then collect files (dirEntry:dirs') entries
            else collect (dirEntry:files) dirs' entries

        ignore ['.']      = True
        ignore ['.', '.'] = True
        ignore _          = False

------------------------
-- Environment variables

-- | Is this directory in the system search path?
isInSearchPath :: FilePath -> NoCallStackIO Bool
isInSearchPath path = fmap (elem path) getSearchPath

addLibraryPath :: OS
               -> [FilePath]
               -> [(String,String)]
               -> [(String,String)]
addLibraryPath os paths = addEnv
  where
    pathsString = intercalate [searchPathSeparator] paths
    ldPath = case os of
               OSX -> "DYLD_LIBRARY_PATH"
               _   -> "LD_LIBRARY_PATH"

    addEnv [] = [(ldPath,pathsString)]
    addEnv ((key,value):xs)
      | key == ldPath =
          if null value
             then (key,pathsString):xs
             else (key,value ++ (searchPathSeparator:pathsString)):xs
      | otherwise     = (key,value):addEnv xs

----------------
-- File globbing

data FileGlob
   -- | No glob at all, just an ordinary file
   = NoGlob FilePath

   -- | dir prefix and extension, like @\"foo\/bar\/\*.baz\"@ corresponds to
   --    @FileGlob \"foo\/bar\" \".baz\"@
   | FileGlob FilePath String

parseFileGlob :: FilePath -> Maybe FileGlob
parseFileGlob filepath = case splitExtensions filepath of
  (filepath', ext) -> case splitFileName filepath' of
    (dir, "*") | '*' `elem` dir
              || '*' `elem` ext
              || null ext            -> Nothing
               | null dir            -> Just (FileGlob "." ext)
               | otherwise           -> Just (FileGlob dir ext)
    _          | '*' `elem` filepath -> Nothing
               | otherwise           -> Just (NoGlob filepath)

matchFileGlob :: FilePath -> IO [FilePath]
matchFileGlob = matchDirFileGlob "."

matchDirFileGlob :: FilePath -> FilePath -> IO [FilePath]
matchDirFileGlob dir filepath = case parseFileGlob filepath of
  Nothing -> die $ "invalid file glob '" ++ filepath
                ++ "'. Wildcards '*' are only allowed in place of the file"
                ++ " name, not in the directory name or file extension."
                ++ " If a wildcard is used it must be with an file extension."
  Just (NoGlob filepath') -> return [filepath']
  Just (FileGlob dir' ext) -> do
    files <- getDirectoryContents (dir </> dir')
    case   [ dir' </> file
           | file <- files
           , let (name, ext') = splitExtensions file
           , not (null name) && ext' == ext ] of
      []      -> die $ "filepath wildcard '" ++ filepath
                    ++ "' does not match any files."
      matches -> return matches

--------------------
-- Modification time

-- | Compare the modification times of two files to see if the first is newer
-- than the second. The first file must exist but the second need not.
-- The expected use case is when the second file is generated using the first.
-- In this use case, if the result is True then the second file is out of date.
--
moreRecentFile :: FilePath -> FilePath -> NoCallStackIO Bool
moreRecentFile a b = do
  exists <- doesFileExist b
  if not exists
    then return True
    else do tb <- getModificationTime b
            ta <- getModificationTime a
            return (ta > tb)

-- | Like 'moreRecentFile', but also checks that the first file exists.
existsAndIsMoreRecentThan :: FilePath -> FilePath -> NoCallStackIO Bool
existsAndIsMoreRecentThan a b = do
  exists <- doesFileExist a
  if not exists
    then return False
    else a `moreRecentFile` b

----------------------------------------
-- Copying and installing files and dirs

-- | Same as 'createDirectoryIfMissing' but logs at higher verbosity levels.
--
createDirectoryIfMissingVerbose :: Verbosity
                                -> Bool     -- ^ Create its parents too?
                                -> FilePath
                                -> IO ()
createDirectoryIfMissingVerbose verbosity create_parents path0
  | create_parents = withFrozenCallStack $ createDirs (parents path0)
  | otherwise      = withFrozenCallStack $ createDirs (take 1 (parents path0))
  where
    parents = reverse . scanl1 (</>) . splitDirectories . normalise

    createDirs []         = return ()
    createDirs (dir:[])   = createDir dir throwIO
    createDirs (dir:dirs) =
      createDir dir $ \_ -> do
        createDirs dirs
        createDir dir throwIO

    createDir :: FilePath -> (IOException -> IO ()) -> IO ()
    createDir dir notExistHandler = do
      r <- tryIO $ createDirectoryVerbose verbosity dir
      case (r :: Either IOException ()) of
        Right ()                   -> return ()
        Left  e
          | isDoesNotExistError  e -> notExistHandler e
          -- createDirectory (and indeed POSIX mkdir) does not distinguish
          -- between a dir already existing and a file already existing. So we
          -- check for it here. Unfortunately there is a slight race condition
          -- here, but we think it is benign. It could report an exception in
          -- the case that the dir did exist but another process deletes the
          -- directory and creates a file in its place before we can check
          -- that the directory did indeed exist.
          | isAlreadyExistsError e -> (do
              isDir <- doesDirectoryExist dir
              if isDir then return ()
                       else throwIO e
              ) `catchIO` ((\_ -> return ()) :: IOException -> IO ())
          | otherwise              -> throwIO e

createDirectoryVerbose :: Verbosity -> FilePath -> IO ()
createDirectoryVerbose verbosity dir = withFrozenCallStack $ do
  info verbosity $ "creating " ++ dir
  createDirectory dir
  setDirOrdinary dir

-- | Copies a file without copying file permissions. The target file is created
-- with default permissions. Any existing target file is replaced.
--
-- At higher verbosity levels it logs an info message.
--
copyFileVerbose :: Verbosity -> FilePath -> FilePath -> IO ()
copyFileVerbose verbosity src dest = withFrozenCallStack $ do
  info verbosity ("copy " ++ src ++ " to " ++ dest)
  copyFile src dest

-- | Install an ordinary file. This is like a file copy but the permissions
-- are set appropriately for an installed file. On Unix it is \"-rw-r--r--\"
-- while on Windows it uses the default permissions for the target directory.
--
installOrdinaryFile :: Verbosity -> FilePath -> FilePath -> IO ()
installOrdinaryFile verbosity src dest = withFrozenCallStack $ do
  info verbosity ("Installing " ++ src ++ " to " ++ dest)
  copyOrdinaryFile src dest

-- | Install an executable file. This is like a file copy but the permissions
-- are set appropriately for an installed file. On Unix it is \"-rwxr-xr-x\"
-- while on Windows it uses the default permissions for the target directory.
--
installExecutableFile :: Verbosity -> FilePath -> FilePath -> IO ()
installExecutableFile verbosity src dest = withFrozenCallStack $ do
  info verbosity ("Installing executable " ++ src ++ " to " ++ dest)
  copyExecutableFile src dest

-- | Install a file that may or not be executable, preserving permissions.
installMaybeExecutableFile :: Verbosity -> FilePath -> FilePath -> IO ()
installMaybeExecutableFile verbosity src dest = withFrozenCallStack $ do
  perms <- getPermissions src
  if (executable perms) --only checks user x bit
    then installExecutableFile verbosity src dest
    else installOrdinaryFile   verbosity src dest

-- | Given a relative path to a file, copy it to the given directory, preserving
-- the relative path and creating the parent directories if needed.
copyFileTo :: Verbosity -> FilePath -> FilePath -> IO ()
copyFileTo verbosity dir file = withFrozenCallStack $ do
  let targetFile = dir </> file
  createDirectoryIfMissingVerbose verbosity True (takeDirectory targetFile)
  installOrdinaryFile verbosity file targetFile

-- | Common implementation of 'copyFiles', 'installOrdinaryFiles',
-- 'installExecutableFiles' and 'installMaybeExecutableFiles'.
copyFilesWith :: (Verbosity -> FilePath -> FilePath -> IO ())
              -> Verbosity -> FilePath -> [(FilePath, FilePath)] -> IO ()
copyFilesWith doCopy verbosity targetDir srcFiles = withFrozenCallStack $ do

  -- Create parent directories for everything
  let dirs = map (targetDir </>) . nub . map (takeDirectory . snd) $ srcFiles
  traverse_ (createDirectoryIfMissingVerbose verbosity True) dirs

  -- Copy all the files
  sequence_ [ let src  = srcBase   </> srcFile
                  dest = targetDir </> srcFile
               in doCopy verbosity src dest
            | (srcBase, srcFile) <- srcFiles ]

-- | Copies a bunch of files to a target directory, preserving the directory
-- structure in the target location. The target directories are created if they
-- do not exist.
--
-- The files are identified by a pair of base directory and a path relative to
-- that base. It is only the relative part that is preserved in the
-- destination.
--
-- For example:
--
-- > copyFiles normal "dist/src"
-- >    [("", "src/Foo.hs"), ("dist/build/", "src/Bar.hs")]
--
-- This would copy \"src\/Foo.hs\" to \"dist\/src\/src\/Foo.hs\" and
-- copy \"dist\/build\/src\/Bar.hs\" to \"dist\/src\/src\/Bar.hs\".
--
-- This operation is not atomic. Any IO failure during the copy (including any
-- missing source files) leaves the target in an unknown state so it is best to
-- use it with a freshly created directory so that it can be simply deleted if
-- anything goes wrong.
--
copyFiles :: Verbosity -> FilePath -> [(FilePath, FilePath)] -> IO ()
copyFiles v fp fs = withFrozenCallStack (copyFilesWith copyFileVerbose v fp fs)

-- | This is like 'copyFiles' but uses 'installOrdinaryFile'.
--
installOrdinaryFiles :: Verbosity -> FilePath -> [(FilePath, FilePath)] -> IO ()
installOrdinaryFiles v fp fs = withFrozenCallStack (copyFilesWith installOrdinaryFile v fp fs)

-- | This is like 'copyFiles' but uses 'installExecutableFile'.
--
installExecutableFiles :: Verbosity -> FilePath -> [(FilePath, FilePath)]
                          -> IO ()
installExecutableFiles v fp fs = withFrozenCallStack (copyFilesWith installExecutableFile v fp fs)

-- | This is like 'copyFiles' but uses 'installMaybeExecutableFile'.
--
installMaybeExecutableFiles :: Verbosity -> FilePath -> [(FilePath, FilePath)]
                               -> IO ()
installMaybeExecutableFiles v fp fs = withFrozenCallStack (copyFilesWith installMaybeExecutableFile v fp fs)

-- | This installs all the files in a directory to a target location,
-- preserving the directory layout. All the files are assumed to be ordinary
-- rather than executable files.
--
installDirectoryContents :: Verbosity -> FilePath -> FilePath -> IO ()
installDirectoryContents verbosity srcDir destDir = withFrozenCallStack $ do
  info verbosity ("copy directory '" ++ srcDir ++ "' to '" ++ destDir ++ "'.")
  srcFiles <- getDirectoryContentsRecursive srcDir
  installOrdinaryFiles verbosity destDir [ (srcDir, f) | f <- srcFiles ]

-- | Recursively copy the contents of one directory to another path.
copyDirectoryRecursive :: Verbosity -> FilePath -> FilePath -> IO ()
copyDirectoryRecursive verbosity srcDir destDir = withFrozenCallStack $ do
  info verbosity ("copy directory '" ++ srcDir ++ "' to '" ++ destDir ++ "'.")
  srcFiles <- getDirectoryContentsRecursive srcDir
  copyFilesWith (const copyFile) verbosity destDir [ (srcDir, f)
                                                   | f <- srcFiles ]

-------------------
-- File permissions

-- | Like 'doesFileExist', but also checks that the file is executable.
doesExecutableExist :: FilePath -> NoCallStackIO Bool
doesExecutableExist f = do
  exists <- doesFileExist f
  if exists
    then do perms <- getPermissions f
            return (executable perms)
    else return False

---------------------------------
-- Deprecated file copy functions

{-# DEPRECATED smartCopySources
      "Use findModuleFiles and copyFiles or installOrdinaryFiles" #-}
smartCopySources :: Verbosity -> [FilePath] -> FilePath
                 -> [ModuleName] -> [String] -> IO ()
smartCopySources verbosity searchPath targetDir moduleNames extensions = withFrozenCallStack $
      findModuleFiles searchPath extensions moduleNames
  >>= copyFiles verbosity targetDir

{-# DEPRECATED copyDirectoryRecursiveVerbose
      "You probably want installDirectoryContents instead" #-}
copyDirectoryRecursiveVerbose :: Verbosity -> FilePath -> FilePath -> IO ()
copyDirectoryRecursiveVerbose verbosity srcDir destDir = withFrozenCallStack $ do
  info verbosity ("copy directory '" ++ srcDir ++ "' to '" ++ destDir ++ "'.")
  srcFiles <- getDirectoryContentsRecursive srcDir
  copyFiles verbosity destDir [ (srcDir, f) | f <- srcFiles ]

---------------------------
-- Temporary files and dirs

-- | Advanced options for 'withTempFile' and 'withTempDirectory'.
data TempFileOptions = TempFileOptions {
  optKeepTempFiles :: Bool  -- ^ Keep temporary files?
  }

defaultTempFileOptions :: TempFileOptions
defaultTempFileOptions = TempFileOptions { optKeepTempFiles = False }

-- | Use a temporary filename that doesn't already exist.
--
withTempFile :: FilePath    -- ^ Temp dir to create the file in
                -> String   -- ^ File name template. See 'openTempFile'.
                -> (FilePath -> Handle -> IO a) -> IO a
withTempFile tmpDir template action =
  withTempFileEx defaultTempFileOptions tmpDir template action

-- | A version of 'withTempFile' that additionally takes a 'TempFileOptions'
-- argument.
withTempFileEx :: TempFileOptions
                 -> FilePath -- ^ Temp dir to create the file in
                 -> String   -- ^ File name template. See 'openTempFile'.
                 -> (FilePath -> Handle -> IO a) -> IO a
withTempFileEx opts tmpDir template action =
  Exception.bracket
    (openTempFile tmpDir template)
    (\(name, handle) -> do hClose handle
                           unless (optKeepTempFiles opts) $
                             handleDoesNotExist () . removeFile $ name)
    (withLexicalCallStack (uncurry action))

-- | Create and use a temporary directory.
--
-- Creates a new temporary directory inside the given directory, making use
-- of the template. The temp directory is deleted after use. For example:
--
-- > withTempDirectory verbosity "src" "sdist." $ \tmpDir -> do ...
--
-- The @[email protected] will be a new subdirectory of the given directory, e.g.
-- @src/[email protected]
--
withTempDirectory :: Verbosity -> FilePath -> String -> (FilePath -> IO a) -> IO a
withTempDirectory verbosity targetDir template f = withFrozenCallStack $
  withTempDirectoryEx verbosity defaultTempFileOptions targetDir template
    (withLexicalCallStack f)

-- | A version of 'withTempDirectory' that additionally takes a
-- 'TempFileOptions' argument.
withTempDirectoryEx :: Verbosity -> TempFileOptions
                       -> FilePath -> String -> (FilePath -> IO a) -> IO a
withTempDirectoryEx _verbosity opts targetDir template f = withFrozenCallStack $
  Exception.bracket
    (createTempDirectory targetDir template)
    (unless (optKeepTempFiles opts)
     . handleDoesNotExist () . removeDirectoryRecursive)
    (withLexicalCallStack f)

-----------------------------------
-- Safely reading and writing files

-- | See 'rewriteFileEx'
--
-- This function is provided for backwards-compatibility
rewriteFile :: FilePath -> String -> IO ()
rewriteFile = rewriteFileEx normal

-- | Write a file but only if it would have new content. If we would be writing
-- the same as the existing content then leave the file as is so that we do not
-- update the file's modification time.
--
-- NB: the file is assumed to be ASCII-encoded.
rewriteFileEx :: Verbosity -> FilePath -> String -> IO ()
rewriteFileEx verbosity path newContent =
  flip catchIO mightNotExist $ do
    existingContent <- annotateIO verbosity $ readFile path
    _ <- evaluate (length existingContent)
    unless (existingContent == newContent) $
      annotateIO verbosity $
        writeFileAtomic path (BS.Char8.pack newContent)
  where
    mightNotExist e | isDoesNotExistError e
                    = annotateIO verbosity $ writeFileAtomic path
                        (BS.Char8.pack newContent)
                    | otherwise
                    = ioError e

-- | The path name that represents the current directory.
-- In Unix, it's @\".\"@, but this is system-specific.
-- (E.g. AmigaOS uses the empty string @\"\"@ for the current directory.)
currentDir :: FilePath
currentDir = "."

shortRelativePath :: FilePath -> FilePath -> FilePath
shortRelativePath from to =
    case dropCommonPrefix (splitDirectories from) (splitDirectories to) of
        (stuff, path) -> joinPath (map (const "..") stuff ++ path)
  where
    dropCommonPrefix :: Eq a => [a] -> [a] -> ([a],[a])
    dropCommonPrefix (x:xs) (y:ys)
        | x == y    = dropCommonPrefix xs ys
    dropCommonPrefix xs ys = (xs,ys)

-- | Drop the extension if it's one of 'exeExtensions', or return the path
-- unchanged.
dropExeExtension :: FilePath -> FilePath
dropExeExtension filepath =
  case splitExtension filepath of
    (filepath', extension) | extension `elem` exeExtensions -> filepath'
                           | otherwise                      -> filepath

-- | List of possible executable file extensions on the current platform.
exeExtensions :: [String]
exeExtensions = case buildOS of
  -- Possible improvement: on Windows, read the list of extensions from the
  -- PATHEXT environment variable. By default PATHEXT is ".com; .exe; .bat;
  -- .cmd".
  Windows -> ["", "exe"]
  Ghcjs   -> ["", "exe"]
  _       -> [""]

-- ------------------------------------------------------------
-- * Finding the description file
-- ------------------------------------------------------------

-- |Package description file (/pkgname/@[email protected])
defaultPackageDesc :: Verbosity -> IO FilePath
defaultPackageDesc _verbosity = tryFindPackageDesc currentDir

-- |Find a package description file in the given directory.  Looks for
-- @[email protected] files.
findPackageDesc :: FilePath                    -- ^Where to look
                -> NoCallStackIO (Either String FilePath) -- ^<pkgname>.cabal
findPackageDesc dir
 = do files <- getDirectoryContents dir
      -- to make sure we do not mistake a ~/.cabal/ dir for a <pkgname>.cabal
      -- file we filter to exclude dirs and null base file names:
      cabalFiles <- filterM doesFileExist
                       [ dir </> file
                       | file <- files
                       , let (name, ext) = splitExtension file
                       , not (null name) && ext == ".cabal" ]
      case cabalFiles of
        []          -> return (Left  noDesc)
        [cabalFile] -> return (Right cabalFile)
        multiple    -> return (Left  $ multiDesc multiple)

  where
    noDesc :: String
    noDesc = "No cabal file found.\n"
             ++ "Please create a package description file <pkgname>.cabal"

    multiDesc :: [String] -> String
    multiDesc l = "Multiple cabal files found.\n"
                  ++ "Please use only one of: "
                  ++ intercalate ", " l

-- |Like 'findPackageDesc', but calls 'die' in case of error.
tryFindPackageDesc :: FilePath -> IO FilePath
tryFindPackageDesc dir = either die return =<< findPackageDesc dir

-- |Optional auxiliary package information file (/pkgname/@[email protected])
defaultHookedPackageDesc :: IO (Maybe FilePath)
defaultHookedPackageDesc = findHookedPackageDesc currentDir

-- |Find auxiliary package information in the given directory.
-- Looks for @[email protected] files.
findHookedPackageDesc
    :: FilePath                 -- ^Directory to search
    -> IO (Maybe FilePath)      -- ^/dir/@\/@/pkgname/@[email protected], if present
findHookedPackageDesc dir = do
    files <- getDirectoryContents dir
    buildInfoFiles <- filterM doesFileExist
                        [ dir </> file
                        | file <- files
                        , let (name, ext) = splitExtension file
                        , not (null name) && ext == buildInfoExt ]
    case buildInfoFiles of
        [] -> return Nothing
        [f] -> return (Just f)
        _ -> die ("Multiple files with extension " ++ buildInfoExt)

buildInfoExt  :: String
buildInfoExt = ".buildinfo"