/**
* @author mrdoob / http://mrdoob.com/
* @author WestLangley / http://github.com/WestLangley
*/
export class VertexNormalsHelper {
   // THREE.VertexNormalsHelper = function(object, size, hex, linewidth) {
   //    this.object = object;
   //    this.size = (size !== undefined) ? size : 1;
   //    var color = (hex !== undefined) ? hex : 0xff0000;
   //    var width = (linewidth !== undefined) ? linewidth : 1;
   //    //
   //    var nNormals = 0;
   //    var objGeometry = this.object.geometry;
   //    if (objGeometry instanceof THREE.Geometry) {
   //       nNormals = objGeometry.faces.length * 3;
   //    } else if (objGeometry instanceof THREE.BufferGeometry) {
   //       nNormals = objGeometry.attributes.normal.count
   //    }
   //    //
   //    var geometry = new THREE.BufferGeometry();
   //    var positions = new THREE.Float32Attribute(nNormals * 2 * 3, 3);
   //    geometry.addAttribute('position', positions);
   //    THREE.LineSegments.call(this, geometry, new THREE.LineBasicMaterial({ color: color, linewidth: width }));
   //    //
   //    this.matrixAutoUpdate = false;
   //    this.update();
   // };
   // THREE.VertexNormalsHelper.prototype = Object.create(THREE.LineSegments.prototype);
   // THREE.VertexNormalsHelper.prototype.constructor = THREE.VertexNormalsHelper;
   // THREE.VertexNormalsHelper.prototype.update = (function() {
   //    var v1 = new THREE.Vector3();
   //    var v2 = new THREE.Vector3();
   //    var normalMatrix = new THREE.Matrix3();
   //    return function update() {
   //       var keys = ['a', 'b', 'c'];
   //       this.object.updateMatrixWorld(true);
   //       normalMatrix.getNormalMatrix(this.object.matrixWorld);
   //       var matrixWorld = this.object.matrixWorld;
   //       var position = this.geometry.attributes.position;
   //       //
   //       var objGeometry = this.object.geometry;
   //       if (objGeometry instanceof THREE.Geometry) {
   //          var vertices = objGeometry.vertices;
   //          var faces = objGeometry.faces;
   //          var idx = 0;
   //          for (var i = 0, l = faces.length; i < l; i++) {
   //             var face = faces[i];
   //             for (var j = 0, jl = face.vertexNormals.length; j < jl; j++) {
   //                var vertex = vertices[face[keys[j]]];
   //                var normal = face.vertexNormals[j];
   //                v1.copy(vertex).applyMatrix4(matrixWorld);
   //                v2.copy(normal).applyMatrix3(normalMatrix).normalize().multiplyScalar(this.size).add(v1);
   //                position.setXYZ(idx, v1.x, v1.y, v1.z);
   //                idx = idx + 1;
   //                position.setXYZ(idx, v2.x, v2.y, v2.z);
   //                idx = idx + 1;
   //             }
   //          }
   //       } else if (objGeometry instanceof THREE.BufferGeometry) {
   //          var objPos = objGeometry.attributes.position;
   //          var objNorm = objGeometry.attributes.normal;
   //          var idx = 0;
   //          // for simplicity, ignore index and drawcalls, and render every normal
   //          for (var j = 0, jl = objPos.count; j < jl; j++) {
   //             v1.set(objPos.getX(j), objPos.getY(j), objPos.getZ(j)).applyMatrix4(matrixWorld);
   //             v2.set(objNorm.getX(j), objNorm.getY(j), objNorm.getZ(j));
   //             v2.applyMatrix3(normalMatrix).normalize().multiplyScalar(this.size).add(v1);
   //             position.setXYZ(idx, v1.x, v1.y, v1.z);
   //             idx = idx + 1;
   //             position.setXYZ(idx, v2.x, v2.y, v2.z);
   //             idx = idx + 1;
   //          }
   //       }
   //       position.needsUpdate = true;
   //       return this;
   //    }
   // } ());
}