/**
 * @fileOverview quadTree
 * @author shiwu.wyy@antfin.com
 */
export default class QuadTree {
    // each quadtree represents a quadrant and an aggregate body
    // that represents all bodies inside the quadrant
    constructor(param) {
        /**
         * (aggregated) body in this quad
         * @type  {object}
         */
        this.body = null;
        /**
         * tree representing the northwest quadrant
         * @type  {object}
         */
        this.quad = null;
        this.NW = null;
        this.NE = null;
        this.SW = null;
        this.SE = null;
        /**
         * threshold
         * @type  {number}
         */
        this.theta = 0.5;
        if (param != null)
            this.quad = param;
    }
    // insert a body(node) into the tree
    insert(bo) {
        // if this node does not contain a body, put the new body bo here
        if (this.body == null) {
            this.body = bo;
            return;
        }
        // internal node
        if (!this._isExternal()) {
            // update mass info
            this.body = this.body.add(bo);
            // insert body into quadrant
            this._putBody(bo);
        }
        else {
            // external node
            // divide this region into four children
            if (this.quad) {
                this.NW = new QuadTree(this.quad.NW());
                this.NE = new QuadTree(this.quad.NE());
                this.SW = new QuadTree(this.quad.SW());
                this.SE = new QuadTree(this.quad.SE());
            }
            // insert this body and bo
            this._putBody(this.body);
            this._putBody(bo);
            // update the mass info
            this.body = this.body.add(bo);
        }
    }
    // inserts bo into a quad
    // tslint:disable-next-line
    _putBody(bo) {
        if (!this.quad)
            return;
        if (bo.in(this.quad.NW()) && this.NW)
            this.NW.insert(bo);
        else if (bo.in(this.quad.NE()) && this.NE)
            this.NE.insert(bo);
        else if (bo.in(this.quad.SW()) && this.SW)
            this.SW.insert(bo);
        else if (bo.in(this.quad.SE()) && this.SE)
            this.SE.insert(bo);
    }
    // tslint:disable-next-line
    _isExternal() {
        // four children are null
        return (this.NW == null && this.NE == null && this.SW == null && this.SE == null);
    }
    // update the forces
    updateForce(bo) {
        if (this.body == null || bo === this.body) {
            return;
        }
        // if the current node is external
        if (this._isExternal())
            bo.addForce(this.body);
        // internal nodes
        else {
            const s = this.quad ? this.quad.getLength() : 0;
            const d = this.body.distanceTo(bo);
            // b is far enough
            if (s / d < this.theta)
                bo.addForce(this.body);
            else {
                this.NW && this.NW.updateForce(bo);
                this.NE && this.NE.updateForce(bo);
                this.SW && this.SW.updateForce(bo);
                this.SE && this.SE.updateForce(bo);
            }
        }
    }
}
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