    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.ModuleName
    -- Copyright   :  Duncan Coutts 2008
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- Data type for Haskell module names.

    {- 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,
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    LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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    module Distribution.ModuleName (
            ModuleName,
            fromString,
            components,
            toFilePath,
            main,
            simple,
      ) where

    import Distribution.Text
             ( Text(..) )

    import qualified Distribution.Compat.ReadP as Parse
    import qualified Text.PrettyPrint as Disp
    import qualified Data.Char as Char
             ( isAlphaNum, isUpper )
    import System.FilePath
             ( pathSeparator )
    import Data.List
             ( intersperse )

    -- | A valid Haskell module name.
    --
    newtype ModuleName = ModuleName [String]
      deriving (Eq, Ord, Read, Show)

    instance Text ModuleName where
      disp (ModuleName ms) =
        Disp.hcat (intersperse (Disp.char '.') (map Disp.text ms))

      parse = do
        ms <- Parse.sepBy1 component (Parse.char '.')
        return (ModuleName ms)

        where
          component = do
            c  <- Parse.satisfy Char.isUpper
            cs <- Parse.munch validModuleChar
            return (c:cs)

    validModuleChar :: Char -> Bool
    validModuleChar c = Char.isAlphaNum c || c == '_' || c == '\''

    validModuleComponent :: String -> Bool
    validModuleComponent []     = False
    validModuleComponent (c:cs) = Char.isUpper c
                               && all validModuleChar cs

    {-# DEPRECATED simple "use ModuleName.fromString instead" #-}
    simple :: String -> ModuleName
    simple str = ModuleName [str]

    -- | Construct a 'ModuleName' from a valid module name 'String'.
    --
    -- This is just a convenience function intended for valid module strings. It is
    -- an error if it is used with a string that is not a valid module name. If you
    -- are parsing user input then use 'Distribution.Text.simpleParse' instead.
    --
    fromString :: String -> ModuleName
    fromString string
      | all validModuleComponent components' = ModuleName components'
      | otherwise                            = error badName

      where
        components' = split string
        badName     = "ModuleName.fromString: invalid module name " ++ show string

        split cs = case break (=='.') cs of
          (chunk,[])     -> chunk : []
          (chunk,_:rest) -> chunk : split rest

    -- | The module name @Main@.
    --
    main :: ModuleName
    main = ModuleName ["Main"]

    -- | The individual components of a hierarchical module name. For example
    --
    -- > components (fromString "A.B.C") = ["A", "B", "C"]
    --
    components :: ModuleName -> [String]
    components (ModuleName ms) = ms

    -- | Convert a module name to a file path, but without any file extension.
    -- For example:
    --
    -- > toFilePath (fromString "A.B.C") = "A/B/C"
    --
    toFilePath :: ModuleName -> FilePath
    toFilePath = concat . intersperse [pathSeparator] . components