module GraphRewriting.Layout.SpringEmbedder where

import GraphRewriting.Graph
import GraphRewriting.Graph.Read
import GraphRewriting.Layout.Position
import GraphRewriting.Layout.PortSpec
import GraphRewriting.Layout.Rotation
import GraphRewriting.Layout.RotPortSpec
import GraphRewriting.Layout.Force
import Control.Monad
import Data.Vector.Class


springForce ∷ (View [Port] n, View Position n, View Rotation n, PortSpec n) ⇒ Double → Node → WithGraph n Force
springForce springLength n = liftM fsum $ mapM edgeForce =<< attachedEdges n where
	
	edgeForce e = do
		ns ← adverseNodes n e
		nTs ← springTargets e n
		nsTs ← liftM concat $ mapM (springTargets e) ns
		return $ fsum [attraction nsT nT | nsT ← nsTs, nT ← nTs]
	
	springTargets e node = do
		ps ← liftM (propOfPort absRotPortSpec e) (readNode node)
		return $ map (\(p,dir) → p + vnormalise dir |* springLength) ps