    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.Hugs
    -- Copyright   :  Isaac Jones 2003-2006
    --                Duncan Coutts 2009
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This module contains most of the NHC-specific code for configuring, building
    -- and installing packages.

    {- Copyright (c) 2003-2005, Isaac Jones
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are
    met:

        * Redistributions of source code must retain the above copyright
          notice, this list of conditions and the following disclaimer.

        * Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials provided
          with the distribution.

        * Neither the name of Isaac Jones nor the names of other
          contributors may be used to endorse or promote products derived
          from this software without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -}

    module Distribution.Simple.Hugs (
        configure,
        getInstalledPackages,
        buildLib,
        buildExe,
        install,
        registerPackage,
      ) where

    import Distribution.Package
             ( PackageName, PackageIdentifier(..), InstalledPackageId(..)
             , packageName )
    import Distribution.InstalledPackageInfo
             ( InstalledPackageInfo, emptyInstalledPackageInfo
             , InstalledPackageInfo_( InstalledPackageInfo, installedPackageId
                                    , sourcePackageId )
             , parseInstalledPackageInfo, showInstalledPackageInfo )
    import Distribution.PackageDescription
             ( PackageDescription(..), BuildInfo(..), hcOptions, allExtensions
             , Executable(..), withExe, Library(..), withLib, libModules )
    import Distribution.ModuleName (ModuleName)
    import qualified Distribution.ModuleName as ModuleName
    import Distribution.Simple.Compiler
             ( CompilerFlavor(..), CompilerId(..)
             , Compiler(..), Flag, languageToFlags, extensionsToFlags
             , PackageDB(..), PackageDBStack )
    import qualified Distribution.Simple.PackageIndex as PackageIndex
    import Distribution.Simple.PackageIndex (PackageIndex)
    import Distribution.Simple.Program
             ( Program(programFindVersion)
             , ProgramConfiguration, userMaybeSpecifyPath
             , requireProgram, requireProgramVersion
             , rawSystemProgramConf, programPath
             , ffihugsProgram, hugsProgram )
    import Distribution.Version
             ( Version(..), orLaterVersion )
    import Distribution.Simple.PreProcess   ( ppCpp, runSimplePreProcessor )
    import Distribution.Simple.PreProcess.Unlit
                                    ( unlit )
    import Distribution.Simple.LocalBuildInfo
             ( LocalBuildInfo(..), ComponentLocalBuildInfo(..)
             , InstallDirs(..), absoluteInstallDirs )
    import Distribution.Simple.BuildPaths
                                    ( autogenModuleName, autogenModulesDir,
                                      dllExtension )
    import Distribution.Simple.Setup
             ( CopyDest(..) )
    import Distribution.Simple.Utils
             ( createDirectoryIfMissingVerbose, installOrdinaryFiles
             , withUTF8FileContents, writeFileAtomic, writeUTF8File
             , copyFileVerbose, findFile, findFileWithExtension, findModuleFiles
             , rawSystemStdInOut
             , die, info, notice )
    import Language.Haskell.Extension
             ( Language(Haskell98), Extension(..) )
    import System.FilePath          ( (</>), takeExtension, (<.>),
                                      searchPathSeparator, normalise, takeDirectory )
    import Distribution.System
             ( OS(..), buildOS )
    import Distribution.Text
             ( display, simpleParse )
    import Distribution.ParseUtils
             ( ParseResult(..) )
    import Distribution.Verbosity

    import Data.Char                ( isSpace )
    import Data.Maybe               ( mapMaybe, catMaybes )
    import Data.Monoid              ( Monoid(..) )
    import Control.Monad            ( unless, when, filterM )
    import Data.List                ( nub, sort, isSuffixOf )
    import System.Directory
             ( doesFileExist, doesDirectoryExist, getDirectoryContents
             , removeDirectoryRecursive, getHomeDirectory )
    import System.Exit
             ( ExitCode(ExitSuccess) )
    import Distribution.Compat.CopyFile
             ( setFileExecutable )
    import Distribution.Compat.Exception

    -- -----------------------------------------------------------------------------
    -- Configuring

    configure :: Verbosity -> Maybe FilePath -> Maybe FilePath
              -> ProgramConfiguration -> IO (Compiler, ProgramConfiguration)
    configure verbosity hcPath _hcPkgPath conf = do

      (_ffihugsProg, conf') <- requireProgram verbosity ffihugsProgram
                                (userMaybeSpecifyPath "ffihugs" hcPath conf)
      (_hugsProg, version, conf'')
                            <- requireProgramVersion verbosity hugsProgram'
                                (orLaterVersion (Version [2006] [])) conf'

      let comp = Compiler {
            compilerId             = CompilerId Hugs version,
            compilerLanguages      = hugsLanguages,
            compilerExtensions     = hugsLanguageExtensions
          }
      return (comp, conf'')

      where
        hugsProgram' = hugsProgram { programFindVersion = getVersion }

    getVersion :: Verbosity -> FilePath -> IO (Maybe Version)
    getVersion verbosity hugsPath = do
      (output, _err, exit) <- rawSystemStdInOut verbosity hugsPath []
                                  (Just (":quit", False)) False
      if exit == ExitSuccess
        then return $! findVersion output
        else return Nothing

      where
        findVersion output = do
          (monthStr, yearStr) <- selectWords output
          year  <- convertYear yearStr
          month <- convertMonth monthStr
          return (Version [year, month] [])

        selectWords output =
          case [ (month, year)
               | [_,_,"Version:", month, year,_] <- map words (lines output) ] of
            [(month, year)] -> Just (month, year)
            _               -> Nothing
        convertYear year = case reads year of
          [(y, [])] | y >= 1999 && y < 2020 -> Just y
          _                                 -> Nothing
        convertMonth month = lookup month (zip months [1..])
        months = [ "January", "February", "March", "April", "May", "June", "July"
                 , "August", "September", "October", "November", "December" ]

    hugsLanguages :: [(Language, Flag)]
    hugsLanguages = [(Haskell98, "")] --default is 98 mode

    -- | The flags for the supported extensions
    hugsLanguageExtensions :: [(Extension, Flag)]
    hugsLanguageExtensions =
        [(OverlappingInstances       , "+o")
        ,(IncoherentInstances        , "+oO")
        ,(HereDocuments              , "+H")
        ,(TypeSynonymInstances       , "-98")
        ,(RecursiveDo                , "-98")
        ,(ParallelListComp           , "-98")
        ,(MultiParamTypeClasses      , "-98")
        ,(FunctionalDependencies     , "-98")
        ,(Rank2Types                 , "-98")
        ,(PolymorphicComponents      , "-98")
        ,(ExistentialQuantification  , "-98")
        ,(ScopedTypeVariables        , "-98")
        ,(ImplicitParams             , "-98")
        ,(ExtensibleRecords          , "-98")
        ,(RestrictedTypeSynonyms     , "-98")
        ,(FlexibleContexts           , "-98")
        ,(FlexibleInstances          , "-98")
        ,(ForeignFunctionInterface   , "")
        ,(EmptyDataDecls             , "")
        ,(CPP                        , "")
        ]

    getInstalledPackages :: Verbosity -> PackageDBStack -> ProgramConfiguration
                         -> IO PackageIndex
    getInstalledPackages verbosity packagedbs conf = do
      homedir       <- getHomeDirectory
      (hugsProg, _) <- requireProgram verbosity hugsProgram conf
      let hugsbindir = takeDirectory (programPath hugsProg)
          hugslibdir = takeDirectory hugsbindir </> "lib" </> "hugs"
          dbdirs = nub (concatMap (packageDbPaths homedir hugslibdir) packagedbs)
      indexes  <- mapM getIndividualDBPackages dbdirs
      return $! mconcat indexes

      where
        getIndividualDBPackages :: FilePath -> IO PackageIndex
        getIndividualDBPackages dbdir = do
          pkgdirs <- getPackageDbDirs dbdir
          pkgs    <- sequence [ getInstalledPackage pkgname pkgdir
                              | (pkgname, pkgdir) <- pkgdirs ]
          let pkgs' = map setInstalledPackageId (catMaybes pkgs)
          return (PackageIndex.fromList pkgs')

    packageDbPaths :: FilePath -> FilePath -> PackageDB -> [FilePath]
    packageDbPaths home hugslibdir db = case db of
      GlobalPackageDB        -> [ hugslibdir </> "packages"
                                , "/usr/local/lib/hugs/packages" ]
      UserPackageDB          -> [ home </> "lib/hugs/packages" ]
      SpecificPackageDB path -> [ path ]

    getPackageDbDirs :: FilePath -> IO [(PackageName, FilePath)]
    getPackageDbDirs dbdir = do
      dbexists <- doesDirectoryExist dbdir
      if not dbexists
        then return []
        else do
          entries  <- getDirectoryContents dbdir
          pkgdirs  <- sequence
            [ do pkgdirExists <- doesDirectoryExist pkgdir
                 return (pkgname, pkgdir, pkgdirExists)
            | (entry, Just pkgname) <- [ (entry, simpleParse entry)
                                       | entry <- entries ]
            , let pkgdir = dbdir </> entry ]
          return [ (pkgname, pkgdir) | (pkgname, pkgdir, True) <- pkgdirs ]

    getInstalledPackage :: PackageName -> FilePath -> IO (Maybe InstalledPackageInfo)
    getInstalledPackage pkgname pkgdir = do
      let pkgconfFile = pkgdir </> "package.conf"
      pkgconfExists <- doesFileExist pkgconfFile

      let pathsModule = pkgdir </> ("Paths_" ++ display pkgname)  <.> "hs"
      pathsModuleExists <- doesFileExist pathsModule

      case () of
        _ | pkgconfExists     -> getFullInstalledPackageInfo pkgname pkgconfFile
          | pathsModuleExists -> getPhonyInstalledPackageInfo pkgname pathsModule
          | otherwise         -> return Nothing

    getFullInstalledPackageInfo :: PackageName -> FilePath
                                -> IO (Maybe InstalledPackageInfo)
    getFullInstalledPackageInfo pkgname pkgconfFile =
      withUTF8FileContents pkgconfFile $ \contents ->
        case parseInstalledPackageInfo contents of
          ParseOk _ pkginfo | packageName pkginfo == pkgname
                            -> return (Just pkginfo)
          _                 -> return Nothing

    -- | This is a backup option for existing versions of Hugs which do not supply
    -- proper installed package info files for the bundled libs. Instead we look
    -- for the Paths_pkgname.hs file and extract the package version from that.
    -- We don't know any other details for such packages, in particular we pretend
    -- that they have no dependencies.
    --
    getPhonyInstalledPackageInfo :: PackageName -> FilePath
                                 -> IO (Maybe InstalledPackageInfo)
    getPhonyInstalledPackageInfo pkgname pathsModule = do
      content <- readFile pathsModule
      case extractVersion content of
        Nothing      -> return Nothing
        Just version -> return (Just pkginfo)
          where
            pkgid   = PackageIdentifier pkgname version
            pkginfo = emptyInstalledPackageInfo { sourcePackageId = pkgid }
      where
        -- search through the Paths_pkgname.hs file, looking for a line like:
        --
        -- > version = Version {versionBranch = [2,0], versionTags = []}
        --
        -- and parse it using 'Read'. Yes we are that evil.
        --
        extractVersion content =
          case [ version
               | ("version":"=":rest) <- map words (lines content)
               , (version, []) <- reads (concat rest) ] of
            [version] -> Just version
            _         -> Nothing

    -- Older installed package info files did not have the installedPackageId
    -- field, so if it is missing then we fill it as the source package ID.
    setInstalledPackageId :: InstalledPackageInfo -> InstalledPackageInfo
    setInstalledPackageId pkginfo@InstalledPackageInfo {
                            installedPackageId = InstalledPackageId "",
                            sourcePackageId    = pkgid
                          }
                        = pkginfo {
                            --TODO use a proper named function for the conversion
                            -- from source package id to installed package id
                            installedPackageId = InstalledPackageId (display pkgid)
                          }
    setInstalledPackageId pkginfo = pkginfo

    -- -----------------------------------------------------------------------------
    -- Building

    -- |Building a package for Hugs.
    buildLib :: Verbosity -> PackageDescription -> LocalBuildInfo
                          -> Library            -> ComponentLocalBuildInfo -> IO ()
    buildLib verbosity pkg_descr lbi lib _clbi = do
        let pref = scratchDir lbi
        createDirectoryIfMissingVerbose verbosity True pref
        copyFileVerbose verbosity (autogenModulesDir lbi </> paths_modulename)
                                  (pref </> paths_modulename)
        compileBuildInfo verbosity pref [] (libModules lib) (libBuildInfo lib) lbi
      where
        paths_modulename = ModuleName.toFilePath (autogenModuleName pkg_descr)
                             <.> ".hs"
        --TODO: switch to using autogenModulesDir as a search dir, rather than
        --      always copying the file over.

    -- |Building an executable for Hugs.
    buildExe :: Verbosity -> PackageDescription -> LocalBuildInfo
                          -> Executable         -> ComponentLocalBuildInfo -> IO ()
    buildExe verbosity pkg_descr lbi
      exe@Executable {modulePath=mainPath, buildInfo=bi} _clbi = do
        let pref = scratchDir lbi
        createDirectoryIfMissingVerbose verbosity True pref

        let destDir = pref </> "programs"
        let exeMods = otherModules bi
        srcMainFile <- findFile (hsSourceDirs bi) mainPath
        let exeDir = destDir </> exeName exe
        let destMainFile = exeDir </> hugsMainFilename exe
        copyModule verbosity (CPP `elem` allExtensions bi) bi lbi srcMainFile destMainFile
        let destPathsFile = exeDir </> paths_modulename
        copyFileVerbose verbosity (autogenModulesDir lbi </> paths_modulename)
                                  destPathsFile
        compileBuildInfo verbosity exeDir
          (maybe [] (hsSourceDirs . libBuildInfo) (library pkg_descr)) exeMods bi lbi
        compileFiles verbosity bi lbi exeDir [destMainFile, destPathsFile]

      where
        paths_modulename = ModuleName.toFilePath (autogenModuleName pkg_descr)
                             <.> ".hs"

    compileBuildInfo :: Verbosity
                     -> FilePath -- ^output directory
                     -> [FilePath] -- ^library source dirs, if building exes
                     -> [ModuleName] -- ^Modules
                     -> BuildInfo
                     -> LocalBuildInfo
                     -> IO ()
    --TODO: should not be using mLibSrcDirs at all
    compileBuildInfo verbosity destDir mLibSrcDirs mods bi lbi = do
        -- Pass 1: copy or cpp files from build directory to scratch directory
        let useCpp = CPP `elem` allExtensions bi
        let srcDir = buildDir lbi
            srcDirs = nub $ srcDir : hsSourceDirs bi ++ mLibSrcDirs
        info verbosity $ "Source directories: " ++ show srcDirs
        flip mapM_ mods $ \ m -> do
            fs <- findFileWithExtension suffixes srcDirs (ModuleName.toFilePath m)
            case fs of
              Nothing ->
                die ("can't find source for module " ++ display m)
              Just srcFile -> do
                let ext = takeExtension srcFile
                copyModule verbosity useCpp bi lbi srcFile
                    (destDir </> ModuleName.toFilePath m <.> ext)
        -- Pass 2: compile foreign stubs in scratch directory
        stubsFileLists <- fmap catMaybes $ sequence
          [ findFileWithExtension suffixes [destDir] (ModuleName.toFilePath modu)
          | modu <- mods]
        compileFiles verbosity bi lbi destDir stubsFileLists

    suffixes :: [String]
    suffixes = ["hs", "lhs"]

    -- Copy or cpp a file from the source directory to the build directory.
    copyModule :: Verbosity -> Bool -> BuildInfo -> LocalBuildInfo -> FilePath -> FilePath -> IO ()
    copyModule verbosity cppAll bi lbi srcFile destFile = do
        createDirectoryIfMissingVerbose verbosity True (takeDirectory destFile)
        (exts, opts, _) <- getOptionsFromSource srcFile
        let ghcOpts = [ op | (GHC, ops) <- opts, op <- ops ]
        if cppAll || CPP `elem` exts || "-cpp" `elem` ghcOpts then do
            runSimplePreProcessor (ppCpp bi lbi) srcFile destFile verbosity
            return ()
          else
            copyFileVerbose verbosity srcFile destFile

    compileFiles :: Verbosity -> BuildInfo -> LocalBuildInfo -> FilePath -> [FilePath] -> IO ()
    compileFiles verbosity bi lbi modDir fileList = do
        ffiFileList <- filterM testFFI fileList
        unless (null ffiFileList) $ do
            notice verbosity "Compiling FFI stubs"
            mapM_ (compileFFI verbosity bi lbi modDir) ffiFileList

    -- Only compile FFI stubs for a file if it contains some FFI stuff
    testFFI :: FilePath -> IO Bool
    testFFI file =
      withHaskellFile file $ \inp ->
        return $! "foreign" `elem` symbols (stripComments False inp)

    compileFFI :: Verbosity -> BuildInfo -> LocalBuildInfo -> FilePath -> FilePath -> IO ()
    compileFFI verbosity bi lbi modDir file = do
        (_, opts, file_incs) <- getOptionsFromSource file
        let ghcOpts = [ op | (GHC, ops) <- opts, op <- ops ]
        let pkg_incs = ["\"" ++ inc ++ "\"" | inc <- includes bi]
        let incs = nub (sort (file_incs ++ includeOpts ghcOpts ++ pkg_incs))
        let pathFlag = "-P" ++ modDir ++ [searchPathSeparator]
        let hugsArgs = "-98" : pathFlag : map ("-i" ++) incs
        cfiles <- getCFiles file
        let cArgs =
                ["-I" ++ dir | dir <- includeDirs bi] ++
                ccOptions bi ++
                cfiles ++
                ["-L" ++ dir | dir <- extraLibDirs bi] ++
                ldOptions bi ++
                ["-l" ++ lib | lib <- extraLibs bi] ++
                concat [["-framework", f] | f <- frameworks bi]
        rawSystemProgramConf verbosity ffihugsProgram (withPrograms lbi)
          (hugsArgs ++ file : cArgs)

    includeOpts :: [String] -> [String]
    includeOpts [] = []
    includeOpts ("-#include" : arg : opts) = arg : includeOpts opts
    includeOpts (_ : opts) = includeOpts opts

    -- get C file names from CFILES pragmas throughout the source file
    getCFiles :: FilePath -> IO [String]
    getCFiles file =
      withHaskellFile file $ \inp ->
        let cfiles =
              [ normalise cfile
              | "{-#" : "CFILES" : rest <- map words
                                         $ lines
                                         $ stripComments True inp
              , last rest == "#-}"
              , cfile <- init rest]
         in seq (length cfiles) (return cfiles)

    -- List of terminal symbols in a source file.
    symbols :: String -> [String]
    symbols cs = case lex cs of
        (sym, cs'):_ | not (null sym) -> sym : symbols cs'
        _ -> []

    -- Get the non-literate source of a Haskell module.
    withHaskellFile :: FilePath -> (String -> IO a) -> IO a
    withHaskellFile file action =
        withUTF8FileContents file $ \text ->
            if ".lhs" `isSuffixOf` file
              then either action die (unlit file text)
              else action text

    -- ------------------------------------------------------------
    -- * options in source files
    -- ------------------------------------------------------------

    -- |Read the initial part of a source file, before any Haskell code,
    -- and return the contents of any LANGUAGE, OPTIONS and INCLUDE pragmas.
    getOptionsFromSource
        :: FilePath
        -> IO ([Extension],                 -- LANGUAGE pragma, if any
               [(CompilerFlavor,[String])], -- OPTIONS_FOO pragmas
               [String]                     -- INCLUDE pragmas
              )
    getOptionsFromSource file =
        withHaskellFile file $
            (return $!)
          . foldr appendOptions ([],[],[]) . map getOptions
          . takeWhileJust . map getPragma
          . filter textLine . map (dropWhile isSpace) . lines
          . stripComments True

      where textLine [] = False
            textLine ('#':_) = False
            textLine _ = True

            getPragma :: String -> Maybe [String]
            getPragma line = case words line of
                ("{-#" : rest) | last rest == "#-}" -> Just (init rest)
                _ -> Nothing

            getOptions ("OPTIONS":opts) = ([], [(GHC, opts)], [])
            getOptions ("OPTIONS_GHC":opts) = ([], [(GHC, opts)], [])
            getOptions ("OPTIONS_NHC98":opts) = ([], [(NHC, opts)], [])
            getOptions ("OPTIONS_HUGS":opts) = ([], [(Hugs, opts)], [])
            getOptions ("LANGUAGE":ws) = (mapMaybe readExtension ws, [], [])
              where readExtension :: String -> Maybe Extension
                    readExtension w = case reads w of
                        [(ext, "")] -> Just ext
                        [(ext, ",")] -> Just ext
                        _ -> Nothing
            getOptions ("INCLUDE":ws) = ([], [], ws)
            getOptions _ = ([], [], [])

            appendOptions (exts, opts, incs) (exts', opts', incs')
              = (exts++exts', opts++opts', incs++incs')

    -- takeWhileJust f = map fromJust . takeWhile isJust
    takeWhileJust :: [Maybe a] -> [a]
    takeWhileJust (Just x:xs) = x : takeWhileJust xs
    takeWhileJust _ = []

    -- |Strip comments from Haskell source.
    stripComments
        :: Bool     -- ^ preserve pragmas?
        -> String   -- ^ input source text
        -> String
    stripComments keepPragmas = stripCommentsLevel 0
      where stripCommentsLevel :: Int -> String -> String
            stripCommentsLevel 0 ('"':cs) = '"':copyString cs
            stripCommentsLevel 0 ('-':'-':cs) =     -- FIX: symbols like -->
                stripCommentsLevel 0 (dropWhile (/= '\n') cs)
            stripCommentsLevel 0 ('{':'-':'#':cs)
              | keepPragmas = '{' : '-' : '#' : copyPragma cs
            stripCommentsLevel n ('{':'-':cs) = stripCommentsLevel (n+1) cs
            stripCommentsLevel 0 (c:cs) = c : stripCommentsLevel 0 cs
            stripCommentsLevel n ('-':'}':cs) = stripCommentsLevel (n-1) cs
            stripCommentsLevel n (_:cs) = stripCommentsLevel n cs
            stripCommentsLevel _ [] = []

            copyString ('\\':c:cs) = '\\' : c : copyString cs
            copyString ('"':cs) = '"' : stripCommentsLevel 0 cs
            copyString (c:cs) = c : copyString cs
            copyString [] = []

            copyPragma ('#':'-':'}':cs) = '#' : '-' : '}' : stripCommentsLevel 0 cs
            copyPragma (c:cs) = c : copyPragma cs
            copyPragma [] = []

    -- -----------------------------------------------------------------------------
    -- |Install for Hugs.
    -- For install, copy-prefix = prefix, but for copy they're different.
    -- The library goes in \<copy-prefix>\/lib\/hugs\/packages\/\<pkgname>
    -- (i.e. \<prefix>\/lib\/hugs\/packages\/\<pkgname> on the target system).
    -- Each executable goes in \<copy-prefix>\/lib\/hugs\/programs\/\<exename>
    -- (i.e. \<prefix>\/lib\/hugs\/programs\/\<exename> on the target system)
    -- with a script \<copy-prefix>\/bin\/\<exename> pointing at
    -- \<prefix>\/lib\/hugs\/programs\/\<exename>.
    install
        :: Verbosity -- ^verbosity
        -> LocalBuildInfo
        -> FilePath  -- ^Library install location
        -> FilePath  -- ^Program install location
        -> FilePath  -- ^Executable install location
        -> FilePath  -- ^Program location on target system
        -> FilePath  -- ^Build location
        -> (FilePath,FilePath)  -- ^Executable (prefix,suffix)
        -> PackageDescription
        -> IO ()
    --FIXME: this script should be generated at build time, just installed at this stage
    install verbosity lbi libDir installProgDir binDir targetProgDir buildPref (progprefix,progsuffix) pkg_descr = do
        removeDirectoryRecursive libDir `catchIO` \_ -> return ()
        withLib pkg_descr $ \ lib ->
          findModuleFiles [buildPref] hugsInstallSuffixes (libModules lib)
            >>= installOrdinaryFiles verbosity libDir
        let buildProgDir = buildPref </> "programs"
        when (any (buildable . buildInfo) (executables pkg_descr)) $
            createDirectoryIfMissingVerbose verbosity True binDir
        withExe pkg_descr $ \ exe -> do
            let bi = buildInfo exe
            let theBuildDir = buildProgDir </> exeName exe
            let installDir = installProgDir </> exeName exe
            let targetDir = targetProgDir </> exeName exe
            removeDirectoryRecursive installDir `catchIO` \_ -> return ()
            findModuleFiles [theBuildDir] hugsInstallSuffixes
                            (ModuleName.main : autogenModuleName pkg_descr
                                             : otherModules (buildInfo exe))
              >>= installOrdinaryFiles verbosity installDir
            let targetName = "\"" ++ (targetDir </> hugsMainFilename exe) ++ "\""
            let hugsOptions = hcOptions Hugs (buildInfo exe)
                           ++ languageToFlags (compiler lbi) (defaultLanguage bi)
                           ++ extensionsToFlags (compiler lbi) (allExtensions bi)
            let baseExeFile = progprefix ++ (exeName exe) ++ progsuffix
            let exeFile = case buildOS of
                              Windows -> binDir </> baseExeFile <.> ".bat"
                              _       -> binDir </> baseExeFile
            let script = case buildOS of
                             Windows ->
                                 let args = hugsOptions ++ [targetName, "%*"]
                                 in unlines ["@echo off",
                                             unwords ("runhugs" : args)]
                             _ ->
                                 let args = hugsOptions ++ [targetName, "\"$@\""]
                                 in unlines ["#! /bin/sh",
                                             unwords ("runhugs" : args)]
            writeFileAtomic exeFile script
            setFileExecutable exeFile

    hugsInstallSuffixes :: [String]
    hugsInstallSuffixes = [".hs", ".lhs", dllExtension]

    -- |Filename used by Hugs for the main module of an executable.
    -- This is a simple filename, so that Hugs will look for any auxiliary
    -- modules it uses relative to the directory it's in.
    hugsMainFilename :: Executable -> FilePath
    hugsMainFilename exe = "Main" <.> ext
      where ext = takeExtension (modulePath exe)

    -- -----------------------------------------------------------------------------
    -- Registering

    registerPackage
      :: Verbosity
      -> InstalledPackageInfo
      -> PackageDescription
      -> LocalBuildInfo
      -> Bool
      -> PackageDBStack
      -> IO ()
    registerPackage verbosity installedPkgInfo pkg lbi inplace _packageDbs = do
      --TODO: prefer to have it based on the packageDbs, but how do we know
      -- the package subdir based on the name? the user can set crazy libsubdir
      let installDirs = absoluteInstallDirs pkg lbi NoCopyDest
          pkgdir  | inplace   = buildDir lbi
                  | otherwise = libdir installDirs
      createDirectoryIfMissingVerbose verbosity True pkgdir
      writeUTF8File (pkgdir </> "package.conf")
                    (showInstalledPackageInfo installedPkgInfo)