    {-# OPTIONS -cpp #-}
    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.Compiler
    -- Copyright   :  Isaac Jones 2003-2004
    --
    -- Maintainer  :  Isaac Jones <ijones@syntaxpolice.org>
    -- Stability   :  alpha
    -- Portability :  portable
    --
    -- Haskell implementations.

    {- 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.Compiler (
            -- * Haskell implementations
    	module Distribution.Compiler,
    	Compiler(..),
            showCompilerId, compilerVersion,

            -- * Support for package databases
            PackageDB(..),

            -- * Support for language extensions
            Flag,
            extensionsToFlags,
            unsupportedExtensions
    #ifdef DEBUG
            ,hunitTests
    #endif
      ) where

    import Distribution.Compiler
    import Distribution.Version (Version(..))
    import Distribution.Package (PackageIdentifier(..), showPackageId)
    import Language.Haskell.Extension (Extension(..))

    import Data.List (nub)
    import Data.Maybe (catMaybes, isNothing)

    #ifdef DEBUG
    import Test.HUnit (Test)
    #endif

    data Compiler = Compiler {
            compilerFlavor          :: CompilerFlavor,
            compilerId              :: PackageIdentifier,
    	compilerExtensions      :: [(Extension, Flag)]
        }
        deriving (Show, Read)

    showCompilerId :: Compiler -> String
    showCompilerId = showPackageId . compilerId

    compilerVersion :: Compiler -> Version
    compilerVersion = pkgVersion . compilerId

    -- ------------------------------------------------------------
    -- * Package databases
    -- ------------------------------------------------------------

    -- |Some compilers have a notion of a database of available packages.
    -- For some there is just one global db of packages, other compilers
    -- support a per-user or an arbitrary db specified at some location in
    -- the file system. This can be used to build isloated environments of
    -- packages, for example to build a collection of related packages
    -- without installing them globally.
    data PackageDB = GlobalPackageDB
                   | UserPackageDB
                   | SpecificPackageDB FilePath
        deriving (Show, Read)

    -- ------------------------------------------------------------
    -- * Extensions
    -- ------------------------------------------------------------

    -- |For the given compiler, return the flags for the supported extensions.
    unsupportedExtensions :: Compiler -> [Extension] -> [Extension]
    unsupportedExtensions comp exts =
      [ ext | ext <- exts
            , isNothing $ lookup ext (compilerExtensions comp) ]

    type Flag = String

    -- |For the given compiler, return the flags for the supported extensions.
    extensionsToFlags :: Compiler -> [Extension] -> [Flag]
    extensionsToFlags comp exts =
      nub $ filter (not . null) $ catMaybes
      [ lookup ext (compilerExtensions comp)
      | ext <- exts ]

    -- ------------------------------------------------------------
    -- * Testing
    -- ------------------------------------------------------------

    #ifdef DEBUG
    hunitTests :: [Test]
    hunitTests = []
    #endif