-- | Most of the functions for graph scrutinisation ('GraphRewriting.Graph.Read') and modification ('GraphRewriting.Graph.Write') are defined monadically. This module defines functions for extracting these monadic values and a few non-monadic graph scrutinisation/modification functions.
module GraphRewriting.Graph (module GraphRewriting.Graph, module GraphRewriting.Graph.Types) where

import GraphRewriting.Graph.Types
import GraphRewriting.Graph.Internal
import Control.Monad.State
import qualified Data.IntMap as Map
import qualified Data.IntSet as Set
import Data.Maybe (fromJust)

emptyGraph  Graph n
emptyGraph = Graph {nodeMap = Map.empty, edgeMap = Map.empty, nextKey = 0}

nodes  Graph n  [n]
nodes = Map.elems . nodeMap

-- | Each edge corresponds to the set of nodes it connects
edges  Graph n  [(Edge, [n])]
edges g = map lookupNodes $ Map.assocs (edgeMap g) where
	lookupNodes (e,ns) = (Edge e, map (\n  fromJust $ Map.lookup n $ nodeMap g) $ Set.elems ns)

-- | unsafe, as no check for changed edge references is performed
unsafeMapNodes  (n  n')  Graph n  Graph n'
unsafeMapNodes f g = g {nodeMap = Map.map f $ nodeMap g}

-- | unsafe map that supplies an additional unique key to the mapping function
unsafeMapNodesUnique  (Int  n  n')  Graph n  Graph n'
unsafeMapNodesUnique f g = g {nodeMap = Map.mapWithKey f $ nodeMap g}

-- | apply a monadic graph modification to a graph
runGraph  Rewrite n a  Graph n  (a, Graph n)
runGraph = runState

evalGraph  Rewrite n a  Graph n  a
evalGraph = evalState

execGraph  Rewrite n a  Graph n  Graph n
execGraph = execState