-- This source file is part of HGamer3D
-- (A project to enable 3D game development in Haskell)
-- For the latest info, see http://www.hgamer3d.org
--
-- (c) 2011-2013 Peter Althainz
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.

-- UniqueName.hs

-- | Utility to provide a unique name, carries internal state in a IORef
module HGamer3D.Common.UniqueName
(
  
  UniqueName,
  createUniqueName,
  nextUniqueName
  
) where

import Data.IORef

data UniqueName = UniqueName String (IORef [Int])

-- | creates a unique name holder
createUniqueName :: String -> IO UniqueName
createUniqueName baseName = do
  ref <- newIORef [0..]
  return $ UniqueName baseName ref
  
-- | delivers the next unique name from the name holder
nextUniqueName :: UniqueName -> IO String
nextUniqueName (UniqueName baseName ref) = do
  name <- atomicModifyIORef ref (\ilist -> (tail ilist, baseName ++ (show (head ilist))))
  return name