    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Package
    -- Copyright   :  Isaac Jones 2003-2004
    --
    -- Maintainer  :  Isaac Jones <ijones@syntaxpolice.org>
    -- Stability   :  alpha
    -- Portability :  portable
    --
    -- Packages are fundamentally just a name and a version.

    {- 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.Package (
    	PackageIdentifier(..),
    	showPackageId, parsePackageId, parsePackageName,
      ) where

    import Distribution.Version
    import Distribution.Compat.ReadP as ReadP
    import Data.Char ( isDigit, isAlphaNum )
    import Data.List ( intersperse )

    -- | The name and version of a package.
    data PackageIdentifier
        = PackageIdentifier {
    	pkgName    :: String, -- ^The name of this package, eg. foo
    	pkgVersion :: Version -- ^the version of this package, eg 1.2
         }
         deriving (Read, Show, Eq, Ord)

    -- |Creates a string like foo-1.2
    showPackageId :: PackageIdentifier -> String
    showPackageId (PackageIdentifier n (Version [] _)) = n -- if no version, don't show version.
    showPackageId pkgid =
      pkgName pkgid ++ '-': showVersion (pkgVersion pkgid)

    parsePackageName :: ReadP r String
    parsePackageName = do ns <- sepBy1 component (char '-')
                          return (concat (intersperse "-" ns))
      where component = do
    	   cs <- munch1 isAlphaNum
    	   if all isDigit cs then pfail else return cs
    	-- each component must contain an alphabetic character, to avoid
    	-- ambiguity in identifiers like foo-1 (the 1 is the version number).

    -- |A package ID looks like foo-1.2.
    parsePackageId :: ReadP r PackageIdentifier
    parsePackageId = do
      n <- parsePackageName
      v <- (ReadP.char '-' >> parseVersion) <++ return (Version [] [])
      return PackageIdentifier{pkgName=n,pkgVersion=v}