    {-
    Copyright (C) 2015 Martin Linnemann <theCodingMarlin@googlemail.com>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    -}

    {- |
       Module      : Text.Pandoc.Readers.Odt.Generic.SetMap
       Copyright   : Copyright (C) 2015 Martin Linnemann
       License     : GNU GPL, version 2 or above

       Maintainer  : Martin Linnemann <theCodingMarlin@googlemail.com>
       Stability   : alpha
       Portability : portable

    A map of values to sets of values.
    -}

    module Text.Pandoc.Readers.Odt.Generic.SetMap where

    import qualified Data.Map as M
    import qualified Data.Set as S

    type SetMap k v = M.Map k (S.Set v)

    empty :: SetMap k v
    empty = M.empty

    fromList :: (Ord k, Ord v) => [(k,v)] -> SetMap k v
    fromList = foldr (uncurry insert) empty

    insert :: (Ord k, Ord v) => k -> v -> SetMap k v -> SetMap k v
    insert key value setMap = M.insertWith S.union key (S.singleton value) setMap

    union3 :: (Ord k) => SetMap k v -> SetMap k v -> SetMap k v -> SetMap k v
    union3 sm1 sm2 sm3 = sm1 `M.union` sm2 `M.union` sm3