    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.License
    -- Copyright   :  Isaac Jones 2003-2005
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- The License datatype.  For more information about these and other
    -- open-source licenses, you may visit <http://www.opensource.org/>.
    --
    -- The @.cabal@ file allows you to specify a license file. Of course you can
    -- use any license you like but people often pick common open source licenses
    -- and it's useful if we can automatically recognise that (eg so we can display
    -- it on the hackage web pages). So you can also specify the license itself in
    -- the @.cabal@ file from a short enumeration defined in this module. It
    -- includes 'GPL', 'LGPL' and 'BSD3' licenses.

    {- 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.License (
            License(..)
      ) where

    import Distribution.Version (Version)

    import Distribution.Text (Text(..), display)
    import qualified Distribution.Compat.ReadP as Parse
    import qualified Text.PrettyPrint as Disp
    import qualified Data.Char as Char (isAlphaNum)

    -- |This datatype indicates the license under which your package is
    -- released.  It is also wise to add your license to each source file
    -- using the license-file field.  The 'AllRightsReserved' constructor
    -- is not actually a license, but states that you are not giving
    -- anyone else a license to use or distribute your work.  The comments
    -- below are general guidelines.  Please read the licenses themselves
    -- and consult a lawyer if you are unsure of your rights to release
    -- the software.
    --
    data License =

    --TODO: * deprecate BSD4
    --      * add optional gpl versions
    --      * add MIT license

        -- | GNU Public License. Source code must accompany alterations.
        GPL --(Maybe Version)

        -- | Lesser GPL, Less restrictive than GPL, useful for libraries.
      | LGPL --(Maybe Version)

        -- | 3-clause BSD license, newer, no advertising clause. Very free license.
      | BSD3

        -- | 4-clause BSD license, older, with advertising clause.
      | BSD4

    --    -- | The MIT license, similar to the BSD3. Very free license.
    --  | MIT

        -- | Holder makes no claim to ownership, least restrictive license.
      | PublicDomain

        -- | No rights are granted to others. Undistributable. Most restrictive.
      | AllRightsReserved

        -- | Some other license.
      | OtherLicense

        -- | Not a recognised license.
        -- Allows us to deal with future extensions more gracefully.
      | UnknownLicense String
      deriving (Read, Show, Eq)

    --TODO: use knownLicenses to give a better parse error message
    --knownLicenses :: [License]
    --knownLicenses = [GPL Nothing, LGPL Nothing, BSD3, BSD4, MIT
    --                ,PublicDomain, AllRightsReserved, OtherLicense]

    instance Text License where
    --disp (GPL  version)         = "GPL"  <> showOptionalVersion version
    --disp (LGPL version)         = "LGPL" <> showOptionalVersion version
      disp (UnknownLicense other) = Disp.text other
      disp other                  = Disp.text (show other)

      parse = do
        name    <- Parse.munch1 Char.isAlphaNum
        version <- Parse.option Nothing (Parse.char '-' >> fmap Just parse)
        -- We parse an optional version but do not yet allow it on any known
        -- license. However parsing the version will allow forwards compatibility
        -- for when we do introduce optional (L)GPL license versions.
        return $ case (name, version :: Maybe Version) of
          ("GPL",               Nothing) -> GPL
          ("LGPL",              Nothing) -> LGPL
      --  ("GPL",               version) -> GPL  version
      --  ("LGPL",              version) -> LGPL version
          ("BSD3",              Nothing) -> BSD3
          ("BSD4",              Nothing) -> BSD4
      --  ("MIT",               Nothing) -> MIT
          ("PublicDomain",      Nothing) -> PublicDomain
          ("AllRightsReserved", Nothing) -> AllRightsReserved
          ("OtherLicense",      Nothing) -> OtherLicense
          _                              -> UnknownLicense $ name
                                         ++ maybe "" (('-':) . display) version