/*
 *  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/BalloonLink.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 {@link go.Shape} to surround the comment node (the from node).
 * If the Shape is filled, it will obscure the comment itself unless the Link is behind the comment node.
 * Thus the default layer for BalloonLinks is "Background".
 *
 * The "corner" property controls the radius of the curves at the corners of the rectangular area surrounding the comment node,
 * rather than the curve at corners along the route, which is always straight.
 * The default value is 10.
 *
 * If you want to experiment with this extension, try the <a href="../../samples/BalloonLink.html">Balloon Links</a> sample.
 * @category Part Extension
 */
export class BalloonLink extends go.Link {
  private _base: number;

  /**
   * Constructs a BalloonLink and sets the {@link go.Part.layerName} property to "Background".
   */
  constructor(init?: Partial<BalloonLink>) {
    super();
    this._base = 15;
    this.layerName = 'Background';
    this.corner = 10;
    this.defaultToPoint = new go.Point(0, 0);
    if (init) Object.assign(this, init);
  }

  /**
   * Copies properties to a cloned BalloonLink.
   */
  override cloneProtected(copy: this): void {
    super.cloneProtected(copy);
    copy._base = this._base;
  }

  /**
   * Gets or sets width of the base of the triangle at the center point of the {@link go.Link.fromNode}.
   *
   * The default value is 15.
   */
  get base(): number {
    return this._base;
  }
  set base(value: number) {
    const old = this._base;
    if (old !== value) {
      if (typeof value !== 'number') throw new Error('BalloonLink.base must be a number');
      this._base = value;
      this.raiseChangedEvent(go.ChangeType.Property, 'base', this, old, value);
    }
  }

  /**
   * Produce a Geometry from the Link's route that draws a "balloon" shape around the {@link go.Link.fromNode}
   * and has a triangular shape with the base at the fromNode and the top at the toNode.
   */
  override makeGeometry(): go.Geometry {
    if (this.fromNode === null) return new go.Geometry();
    // assume the fromNode is the comment and the toNode is the commented-upon node
    const bb = this.fromNode.actualBounds.copy().addMargin(this.fromNode.margin as go.Margin);

    let pn = this.pointsCount === 0 ? bb.center : this.getPoint(this.pointsCount - 1);
    if (this.toNode !== null && bb.intersectsRect(this.toNode.actualBounds)) {
      pn = this.toNode.actualBounds.center;
    } else if (this.toNode === null && this.pointsCount === 0) {
      pn = new go.Point(bb.centerX, bb.bottom + 50);
    }

    const base = Math.max(0, this.base);
    const corner = Math.min(Math.max(0, this.corner), Math.min(bb.width / 2, bb.height / 2));
    const cornerext = Math.min(base, corner + base / 2);

    const fig = new go.PathFigure();
    let prevx = 0;
    let prevy = 0;

    // helper functions
    function start(x: number, y: number) {
      fig.startX = prevx = x;
      fig.startY = prevy = y;
    }
    function point(x: number, y: number, v: number, w: number) {
      fig.add(new go.PathSegment(go.SegmentType.Line, x, y));
      fig.add(new go.PathSegment(go.SegmentType.Line, v, w));
      prevx = v;
      prevy = w;
    }
    function turn(x: number, y: number) {
      if (prevx === x && prevy > y) {
        // top left
        fig.add(new go.PathSegment(go.SegmentType.Line, x, y + corner));
        fig.add(
          new go.PathSegment(go.SegmentType.Arc, 180, 90, x + corner, y + corner, corner, corner)
        );
      } else if (prevx < x && prevy === y) {
        // top right
        fig.add(new go.PathSegment(go.SegmentType.Line, x - corner, y));
        fig.add(
          new go.PathSegment(go.SegmentType.Arc, 270, 90, x - corner, y + corner, corner, corner)
        );
      } else if (prevx === x && prevy < y) {
        // bottom right
        fig.add(new go.PathSegment(go.SegmentType.Line, x, y - corner));
        fig.add(
          new go.PathSegment(go.SegmentType.Arc, 0, 90, x - corner, y - corner, corner, corner)
        );
      } else if (prevx > x && prevy === y) {
        // bottom left
        fig.add(new go.PathSegment(go.SegmentType.Line, x + corner, y));
        fig.add(
          new go.PathSegment(go.SegmentType.Arc, 90, 90, x + corner, y - corner, corner, corner)
        );
      } // else if prevx === x && prevy === y, no-op
      prevx = x;
      prevy = y;
    }

    if (pn.x < bb.left) {
      if (pn.y < bb.top) {
        start(bb.left, Math.min(bb.top + cornerext, bb.bottom - corner));
        point(pn.x, pn.y, Math.min(bb.left + cornerext, bb.right - corner), bb.top);
        turn(bb.right, bb.top);
        turn(bb.right, bb.bottom);
        turn(bb.left, bb.bottom);
      } else if (pn.y > bb.bottom) {
        start(Math.min(bb.left + cornerext, bb.right - corner), bb.bottom);
        point(pn.x, pn.y, bb.left, Math.max(bb.bottom - cornerext, bb.top + corner));
        turn(bb.left, bb.top);
        turn(bb.right, bb.top);
        turn(bb.right, bb.bottom);
      } else {
        // pn.y >= bb.top && pn.y <= bb.bottom
        const y = Math.min(Math.max(pn.y + base / 3, bb.top + corner + base), bb.bottom - corner);
        start(bb.left, y);
        point(pn.x, pn.y, bb.left, Math.max(y - base, bb.top + corner));
        turn(bb.left, bb.top);
        turn(bb.right, bb.top);
        turn(bb.right, bb.bottom);
        turn(bb.left, bb.bottom);
      }
    } else if (pn.x > bb.right) {
      if (pn.y < bb.top) {
        start(Math.max(bb.right - cornerext, bb.left + corner), bb.top);
        point(pn.x, pn.y, bb.right, Math.min(bb.top + cornerext, bb.bottom - corner));
        turn(bb.right, bb.bottom);
        turn(bb.left, bb.bottom);
        turn(bb.left, bb.top);
      } else if (pn.y > bb.bottom) {
        start(bb.right, Math.max(bb.bottom - cornerext, bb.top + corner));
        point(pn.x, pn.y, Math.max(bb.right - cornerext, bb.left + corner), bb.bottom);
        turn(bb.left, bb.bottom);
        turn(bb.left, bb.top);
        turn(bb.right, bb.top);
      } else {
        // pn.y >= bb.top && pn.y <= bb.bottom
        const y = Math.min(Math.max(pn.y + base / 3, bb.top + corner + base), bb.bottom - corner);
        start(bb.right, Math.max(y - base, bb.top + corner));
        point(pn.x, pn.y, bb.right, y);
        turn(bb.right, bb.bottom);
        turn(bb.left, bb.bottom);
        turn(bb.left, bb.top);
        turn(bb.right, bb.top);
      }
    } else {
      // pn.x >= bb.left && pn.x <= bb.right
      const x = Math.min(Math.max(pn.x + base / 3, bb.left + corner + base), bb.right - corner);
      if (pn.y < bb.top) {
        start(Math.max(x - base, bb.left + corner), bb.top);
        point(pn.x, pn.y, x, bb.top);
        turn(bb.right, bb.top);
        turn(bb.right, bb.bottom);
        turn(bb.left, bb.bottom);
        turn(bb.left, bb.top);
      } else if (pn.y > bb.bottom) {
        start(x, bb.bottom);
        point(pn.x, pn.y, Math.max(x - base, bb.left + corner), bb.bottom);
        turn(bb.left, bb.bottom);
        turn(bb.left, bb.top);
        turn(bb.right, bb.top);
        turn(bb.right, bb.bottom);
      } else {
        // inside
        start(bb.left, bb.top + bb.height / 2);
        // no "point", just corners
        turn(bb.left, bb.top);
        turn(bb.right, bb.top);
        turn(bb.right, bb.bottom);
        turn(bb.left, bb.bottom);
      }
    }

    const geo = new go.Geometry();
    (fig.segments.last() as go.PathSegment).close();
    geo.add(fig);
    geo.offset(-this.routeBounds.x, -this.routeBounds.y);
    return geo;
  }
}