    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Compiler
    -- Copyright   :  Isaac Jones 2003-2004
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This has an enumeration of the various compilers that Cabal knows about. It
    -- also specifies the default compiler. Sadly you'll often see code that does
    -- case analysis on this compiler flavour enumeration like:
    --
    -- > case compilerFlavor comp of
    -- >   GHC -> GHC.getInstalledPackages verbosity packageDb progconf
    -- >   JHC -> JHC.getInstalledPackages verbosity packageDb progconf
    --
    -- Obviously it would be better to use the proper 'Compiler' abstraction
    -- because that would keep all the compiler-specific code together.
    -- Unfortunately we cannot make this change yet without breaking the
    -- 'UserHooks' api, which would break all custom @Setup.hs@ files, so for the
    -- moment we just have to live with this deficiency. If you're interested, see
    -- ticket #50.

    {- 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,
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    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -}

    module Distribution.Compiler (
      -- * Compiler flavor
      CompilerFlavor(..),
      buildCompilerFlavor,
      defaultCompilerFlavor,
      parseCompilerFlavorCompat,

      -- * Compiler id
      CompilerId(..),
      ) where

    import Distribution.Version (Version(..))

    import qualified System.Info (compilerName)
    import Distribution.Text (Text(..), display)
    import qualified Distribution.Compat.ReadP as Parse
    import qualified Text.PrettyPrint as Disp
    import Text.PrettyPrint ((<>))

    import qualified Data.Char as Char (toLower, isDigit, isAlphaNum)
    import Control.Monad (when)

    data CompilerFlavor = GHC | NHC | YHC | Hugs | HBC | Helium | JHC | LHC | UHC
                        | OtherCompiler String
      deriving (Show, Read, Eq, Ord)

    knownCompilerFlavors :: [CompilerFlavor]
    knownCompilerFlavors = [GHC, NHC, YHC, Hugs, HBC, Helium, JHC, LHC, UHC]

    instance Text CompilerFlavor where
      disp (OtherCompiler name) = Disp.text name
      disp NHC                  = Disp.text "nhc98"
      disp other                = Disp.text (lowercase (show other))

      parse = do
        comp <- Parse.munch1 Char.isAlphaNum
        when (all Char.isDigit comp) Parse.pfail
        return (classifyCompilerFlavor comp)

    classifyCompilerFlavor :: String -> CompilerFlavor
    classifyCompilerFlavor s =
      case lookup (lowercase s) compilerMap of
        Just compiler -> compiler
        Nothing       -> OtherCompiler s
      where
        compilerMap = [ (display compiler, compiler)
                      | compiler <- knownCompilerFlavors ]

    --TODO: In some future release, remove 'parseCompilerFlavorCompat' and use
    -- ordinary 'parse'. Also add ("nhc", NHC) to the above 'compilerMap'.

    -- | Like 'classifyCompilerFlavor' but compatible with the old ReadS parser.
    --
    -- It is compatible in the sense that it accepts only the same strings,
    -- eg "GHC" but not "ghc". However other strings get mapped to 'OtherCompiler'.
    -- The point of this is that we do not allow extra valid values that would
    -- upset older Cabal versions that had a stricter parser however we cope with
    -- new values more gracefully so that we'll be able to introduce new value in
    -- future without breaking things so much.
    --
    parseCompilerFlavorCompat :: Parse.ReadP r CompilerFlavor
    parseCompilerFlavorCompat = do
      comp <- Parse.munch1 Char.isAlphaNum
      when (all Char.isDigit comp) Parse.pfail
      case lookup comp compilerMap of
        Just compiler -> return compiler
        Nothing       -> return (OtherCompiler comp)
      where
        compilerMap = [ (show compiler, compiler)
                      | compiler <- knownCompilerFlavors
                      , compiler /= YHC ]

    buildCompilerFlavor :: CompilerFlavor
    buildCompilerFlavor = classifyCompilerFlavor System.Info.compilerName

    -- | The default compiler flavour to pick when compiling stuff. This defaults
    -- to the compiler used to build the Cabal lib.
    --
    -- However if it's not a recognised compiler then it's 'Nothing' and the user
    -- will have to specify which compiler they want.
    --
    defaultCompilerFlavor :: Maybe CompilerFlavor
    defaultCompilerFlavor = case buildCompilerFlavor of
      OtherCompiler _ -> Nothing
      _               -> Just buildCompilerFlavor

    -- ------------------------------------------------------------
    -- * Compiler Id
    -- ------------------------------------------------------------

    data CompilerId = CompilerId CompilerFlavor Version
      deriving (Eq, Ord, Read, Show)

    instance Text CompilerId where
      disp (CompilerId f (Version [] _)) = disp f
      disp (CompilerId f v) = disp f <> Disp.char '-' <> disp v

      parse = do
        flavour <- parse
        version <- (Parse.char '-' >> parse) Parse.<++ return (Version [] [])
        return (CompilerId flavour version)

    lowercase :: String -> String
    lowercase = map Char.toLower