{-# LANGUAGE CPP, TypeFamilies, FlexibleContexts #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Data.Graph.Class.VertexEnumerable
-- Copyright   :  (C) 2011 Edward Kmett
-- License     :  BSD-style (see the file LICENSE)
--
-- Maintainer  :  Edward Kmett <ekmett@gmail.com>
-- Stability   :  experimental
-- Portability :  type families
--
----------------------------------------------------------------------------

module Data.Graph.Class.VertexEnumerable
  ( VertexEnumerableGraph(..)
  , module Data.Graph.Class
  ) where

import qualified Control.Monad.Trans.State.Strict as Strict
import qualified Control.Monad.Trans.State.Lazy as Lazy
import qualified Control.Monad.Trans.Writer.Strict as Strict
import qualified Control.Monad.Trans.Writer.Lazy as Lazy
import qualified Control.Monad.Trans.RWS.Strict as Strict
import qualified Control.Monad.Trans.RWS.Lazy as Lazy
import Control.Monad.Trans.Identity
import Control.Monad.Trans.Maybe
#if !(MIN_VERSION_transformers(0,6,0))
import Control.Monad.Trans.Error
#endif
import Control.Monad.Trans.Class
import Control.Monad.Trans.Reader
#if __GLASGOW_HASKELL__ < 710
import Data.Monoid
#endif
import Data.Graph.Class
import Data.Functor.Identity

class Graph g => VertexEnumerableGraph g where
  -- | /O(v)/
  vertices :: g [Vertex g]

instance VertexEnumerableGraph g => VertexEnumerableGraph (Strict.StateT s g) where
  vertices = lift vertices

instance VertexEnumerableGraph g => VertexEnumerableGraph (Lazy.StateT s g) where
  vertices = lift vertices

instance (VertexEnumerableGraph g, Monoid m) => VertexEnumerableGraph (Strict.WriterT m g) where
  vertices = lift vertices

instance (VertexEnumerableGraph g, Monoid m) => VertexEnumerableGraph (Lazy.WriterT m g) where
  vertices = lift vertices

instance (VertexEnumerableGraph g, Monoid m) => VertexEnumerableGraph (Strict.RWST r m s g) where
  vertices = lift vertices

instance (VertexEnumerableGraph g, Monoid m) => VertexEnumerableGraph (Lazy.RWST r m s g) where
  vertices = lift vertices

instance VertexEnumerableGraph g => VertexEnumerableGraph (MaybeT g) where
  vertices = lift vertices

instance VertexEnumerableGraph g => VertexEnumerableGraph (IdentityT g) where
  vertices = lift vertices

#if !(MIN_VERSION_transformers(0,6,0))
instance (VertexEnumerableGraph g, Error e) => VertexEnumerableGraph (ErrorT e g) where
  vertices = lift vertices
#endif

instance VertexEnumerableGraph g => VertexEnumerableGraph (ReaderT m g) where
  vertices = lift vertices

instance VertexEnumerableGraph Identity where
  vertices = Identity []