{-# LANGUAGE
  EmptyDataDecls,
  FlexibleContexts,
  FlexibleInstances,
  MultiParamTypeClasses,
  TypeFamilies
  #-}
module Data.HList.Graph
    ( HNodeSet
    , HNodeIDSet
    , HNode(..)
    , HGraph(..)

    , HNodeIDA
    )
    where

import Data.HList.Prelude

-- HNodeSet
class    HNodeSet ns
instance HNodeSet HNil
instance HNodeSet ns => HNodeSet (HCons n ns)

-- HNodeIDSet
class    HNoDuplicates nids => HNodeIDSet nids
instance HNodeIDSet HNil
instance (HOccursNot nid nids, HNodeIDSet nids) => HNodeIDSet (HCons nid nids)

-- HNode
class HNodeIDSet (HLinksFrom n) => HNode n
    where
      type HNodeID n
      type HLinksFrom n

-- HNodeIDA
data HNodeIDA
instance ApplyT HNodeIDA n where
    type Apply HNodeIDA n = HNodeID n

-- HGraph
class ( HNodeSet (HNodes g)
      , HNoDuplicates (HMap HNodeIDA g)
      )
    => HGraph g
    where
      type HNodes g

--type family HGetNode g n