/*
 *  Copyright 1998-2025 by Northwoods Software Corporation. All Rights Reserved.
 */

/*
 * This is an extension and not part of the main GoJS library.
 * The source code for this is at extensionsJSM/ParallelRouteLink.ts.
 * Note that the API for this class may change with any version, even point releases.
 * If you intend to use an extension in production, you should copy the code to your own source directory.
 * Extensions can be found in the GoJS kit under the extensions or extensionsJSM folders.
 * See the Extensions intro page (https://gojs.net/latest/intro/extensions.html) for more information.
 */

import * as go from 'gojs';

/**
 * This custom {@link go.Link} class customizes its route to go parallel to other links connecting the same ports,
 * if the link is not orthogonal and is not Bezier curved.
 *
 * If you want to experiment with this extension, try the <a href="../../samples/ParallelRoute.html">Parallel Route Links</a> sample.
 * @category Part Extension
 */
export class ParallelRouteLink extends go.Link {
  constructor(init?: Partial<ParallelRouteLink>) {
    super();
    if (init) Object.assign(this, init);
  }

  /**
   * Constructs the link's route by modifying {@link points}.
   * @returns true if it computed a route of points
   */
  override computePoints(): boolean {
    const result = super.computePoints();
    if (!this.isOrthogonal && this.curve !== go.Curve.Bezier && this.hasCurviness()) {
      const curv = this.computeCurviness();
      if (curv !== 0) {
        const num = this.pointsCount;
        let pidx = 0;
        let qidx = num - 1;
        if (num >= 4) {
          pidx++;
          qidx--;
        }

        const frompt = this.getPoint(pidx);
        const topt = this.getPoint(qidx);
        const dx = topt.x - frompt.x;
        const dy = topt.y - frompt.y;

        let mx = frompt.x + (dx * 1) / 8;
        let my = frompt.y + (dy * 1) / 8;
        let px = mx;
        let py = my;
        if (-0.01 < dy && dy < 0.01) {
          if (dx > 0) py -= curv;
          else py += curv;
        } else {
          const slope = -dx / dy;
          let e = Math.sqrt((curv * curv) / (slope * slope + 1));
          if (curv < 0) e = -e;
          px = (dy < 0 ? -1 : 1) * e + mx;
          py = slope * (px - mx) + my;
        }

        mx = frompt.x + (dx * 7) / 8;
        my = frompt.y + (dy * 7) / 8;
        let qx = mx;
        let qy = my;
        if (-0.01 < dy && dy < 0.01) {
          if (dx > 0) qy -= curv;
          else qy += curv;
        } else {
          const slope = -dx / dy;
          let e = Math.sqrt((curv * curv) / (slope * slope + 1));
          if (curv < 0) e = -e;
          qx = (dy < 0 ? -1 : 1) * e + mx;
          qy = slope * (qx - mx) + my;
        }

        this.insertPointAt(pidx + 1, px, py);
        this.insertPointAt(qidx + 1, qx, qy);
      }
    }
    return result;
  }
}