{-# LANGUAGE
  EmptyDataDecls,
  TypeFamilies
  #-}
module Data.HList.Graph
    ( Context
    , Graph

    , Empty
    , IsEmpty
--    , Match
    )
    where

import Data.HList.Prelude
import Types.Data.Bool

-- Graph is a map from node ID to context
data Context preNodes node sucNodes
data Graph nodeMap

-- Empty
type Empty = Graph Nil

-- IsEmpty
type family   IsEmpty g
type instance IsEmpty (Graph Nil)         = True
type instance IsEmpty (Graph (Cons x xs)) = False

-- Match
--type Match n g
--    = 

{-
-- NodeSet
class    NodeSet ns
instance NodeSet Nil
instance NodeSet ns => NodeSet (Cons n ns)

-- NodeIDSet
class    NoDuplicates ids => NodeIDSet ids
instance NodeIDSet Nil
instance (OccursNot id ids, NodeIDSet ids) => NodeIDSet (Cons id ids)

-- LPath (list of labeled node IDs)
class    LPath p
instance LPath Nil
instance LPath p => LPath (Cons (Cons l id) p)

-- Node
class NodeIDSet (LinksFrom n) => Node n
    where
      type NodeID n
      type LinksFrom n

-- NodeIDA
data NodeIDA
instance ApplyT NodeIDA n where
    type Apply NodeIDA n = NodeID n

-- Graph
class ( NodeSet (Nodes g)
      , NoDuplicates (Map NodeIDA g)
      )
    => Graph g
    where
      type Empty g
      type Nodes g

-- IsEmpty
type family IsEmpty g
-}