    {-# LANGUAGE CPP #-}
    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.CCompiler
    -- Copyright   :  2011, Dan Knapp
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This simple package provides types and functions for interacting with
    -- C compilers.  Currently it's just a type enumerating extant C-like
    -- languages, which we call dialects.

    {-
    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.CCompiler (
       CDialect(..),
       cSourceExtensions,
       cDialectFilenameExtension,
       filenameCDialect
      ) where

    #if __GLASGOW_HASKELL__ < 710
    import Data.Monoid
         ( Monoid(..) )
    #endif
    import System.FilePath
         ( takeExtension )

    -- | Represents a dialect of C.  The Monoid instance expresses backward
    --   compatibility, in the sense that 'mappend a b' is the least inclusive
    --   dialect which both 'a' and 'b' can be correctly interpreted as.
    data CDialect = C
                  | ObjectiveC
                  | CPlusPlus
                  | ObjectiveCPlusPlus
                  deriving (Eq, Show)

    instance Monoid CDialect where
      mempty = C

      mappend C                  anything           = anything
      mappend ObjectiveC         CPlusPlus          = ObjectiveCPlusPlus
      mappend CPlusPlus          ObjectiveC         = ObjectiveCPlusPlus
      mappend _                  ObjectiveCPlusPlus = ObjectiveCPlusPlus
      mappend ObjectiveC         _                  = ObjectiveC
      mappend CPlusPlus          _                  = CPlusPlus
      mappend ObjectiveCPlusPlus _                  = ObjectiveCPlusPlus

    -- | A list of all file extensions which are recognized as possibly containing
    --   some dialect of C code.  Note that this list is only for source files,
    --   not for header files.
    cSourceExtensions :: [String]
    cSourceExtensions = ["c", "i", "ii", "m", "mi", "mm", "M", "mii", "cc", "cp",
                         "cxx", "cpp", "CPP", "c++", "C"]

    -- | Takes a dialect of C and whether code is intended to be passed through
    --   the preprocessor, and returns a filename extension for containing that
    --   code.
    cDialectFilenameExtension :: CDialect -> Bool -> String
    cDialectFilenameExtension C True  = "c"
    cDialectFilenameExtension C False = "i"
    cDialectFilenameExtension ObjectiveC True  = "m"
    cDialectFilenameExtension ObjectiveC False = "mi"
    cDialectFilenameExtension CPlusPlus True   = "cpp"
    cDialectFilenameExtension CPlusPlus False  = "ii"
    cDialectFilenameExtension ObjectiveCPlusPlus True  = "mm"
    cDialectFilenameExtension ObjectiveCPlusPlus False = "mii"

    -- | Infers from a filename's extension the dialect of C which it contains,
    --   and whether it is intended to be passed through the preprocessor.
    filenameCDialect :: String -> Maybe (CDialect, Bool)
    filenameCDialect filename = do
      extension <- case takeExtension filename of
                     '.':ext -> Just ext
                     _       -> Nothing
      case extension of
        "c"   -> return (C, True)
        "i"   -> return (C, False)
        "ii"  -> return (CPlusPlus, False)
        "m"   -> return (ObjectiveC, True)
        "mi"  -> return (ObjectiveC, False)
        "mm"  -> return (ObjectiveCPlusPlus, True)
        "M"   -> return (ObjectiveCPlusPlus, True)
        "mii" -> return (ObjectiveCPlusPlus, False)
        "cc"  -> return (CPlusPlus, True)
        "cp"  -> return (CPlusPlus, True)
        "cxx" -> return (CPlusPlus, True)
        "cpp" -> return (CPlusPlus, True)
        "CPP" -> return (CPlusPlus, True)
        "c++" -> return (CPlusPlus, True)
        "C"   -> return (CPlusPlus, True)
        _     -> Nothing