bpmn-optimizer/src/v1/optimizer/steps/EdgeRoutingStep.ts

import AlgorithmStep from "../AlgorithmStep.js";
import {SiguiyamaContext} from "../siguiyama/SiguiyamaContext.js";
import EdgeRoutingStepError from "../../errors/optimizer/EdgeRoutingStepError.js";
import Node from "../../graph/node/Node.js";
import Edge from "../../graph/edge/Edge.js";
import DummyNode from "../../graph/node/DummyNode.js";
import DummyEdge from "../../graph/edge/DummyEdge.js";

export default class EdgeRoutingStep extends AlgorithmStep<SiguiyamaContext> {
	public constructor() {
		super(EdgeRoutingStep.name);
	}

	public run(context: SiguiyamaContext) : void {
		const { layering, graph } = context;

		if(!layering)
			throw new EdgeRoutingStepError("Layering is null or undefined");
		if(!graph)
			throw new EdgeRoutingStepError("Graph is null or undefined");

		this.routeEdges(graph.getEdges(), layering, graph);
	}

	private routeEdges(edges: Edge<Node>[], layering: NonNullable<SiguiyamaContext["layering"]>, graph: NonNullable<SiguiyamaContext["graph"]>): void {
		const layers = layering.getLayers();

		for(const edge of edges) {
			const from = edge.getFrom();
			const to = edge.getTo();

			const fromLayerIndex = layering.getNodeLayerIndex(from);
			const toLayerIndex = layering.getNodeLayerIndex(to);

			if(fromLayerIndex < 0 || toLayerIndex < 0)
				continue;

			const fromRowIndex = layers[fromLayerIndex]?.getNodes().findIndex(node => node === from) ?? -1;
			const toRowIndex = layers[toLayerIndex]?.getNodes().findIndex(node => node === to) ?? -1;

			if(fromRowIndex < 0 || toRowIndex < 0 || fromRowIndex === toRowIndex)
				continue;

			const rightLayer = layers[fromLayerIndex - 1];
			if(!rightLayer)
				continue;

			const rightLayerNodes = rightLayer.getNodes();
			if(rightLayerNodes.length === 0)
				continue;

			const anchorNode = rightLayerNodes[0]!;
			const routedNode = new DummyNode(
				anchorNode.getX() + anchorNode.getWidth() / 2,
				from.getY() + from.getHeight() / 2,
				edge.getId()
			);

			layering.addToLayer(fromLayerIndex - 1, routedNode);
			graph.addNode(routedNode);

			const firstSegment = new DummyEdge(from, routedNode, []);
			const secondSegment = new DummyEdge(routedNode, to, []);

			graph.addEdge(firstSegment);
			graph.addEdge(secondSegment);
			graph.removeEdge(edge.getId());
		}

	}
}