text: import * as dataUtil from '../../utils/data_structure_util';
  import Line from './Line';
  import {mathSin,mathCos} from '../../utils/constants';
  
  /**
   * @class fishTopo.graphic.shape.Trochold
   * Trochold.
   * 
   *  
   * 内外旋轮曲线。
   * @docauthor 大漠穷秋 <damoqiongqiu@126.com>
   */
  export default class Trochold extends Line{
      /**
       * @method constructor Trochold
       * @param {Object} options 
       */
      constructor(options){
          super(dataUtil.merge({
              shape: {
                  cx: 0,
                  cy: 0,
                  r: 0,
                  r0: 0,
                  d: 0,
                  location: 'out'
              },
              style: {
                  stroke: '#000',
                  fill: null
              }
          },options,true));
  
          /**
           * @property {String} type
           */
          this.type='trochoid';
      }
  
      /**
       * @method buildPath
       * Build the path of current line, the data structure is like the path attribute in SVG.
       * 
       * 
       * 构建当前线条的路径，数据结构类似 SVG 中的 path 属性。
       * @param {Object} ctx 
       * @param {String} shape 
       */
      buildPath(ctx, shape) {
          let x1;
          let y1;
          let x2;
          let y2;
          let R = shape.r;
          let r = shape.r0;
          let d = shape.d;
          let offsetX = shape.cx;
          let offsetY = shape.cy;
          let delta = shape.location === 'out' ? 1 : -1;
  
          if (shape.location && R <= r) {
              return;
          }
  
          let num = 0;
          let i = 1;
          let theta;
  
          x1 = (R + delta * r) * mathCos(0)
              - delta * d * mathCos(0) + offsetX;
          y1 = (R + delta * r) * mathSin(0)
              - d * mathSin(0) + offsetY;
  
          ctx.moveTo(x1, y1);
  
          // 计算结束时的i
          do {
              num++;
          }
          while ((r * num) % (R + delta * r) !== 0);
  
          do {
              theta = Math.PI / 180 * i;
              x2 = (R + delta * r) * mathCos(theta)
                      - delta * d * mathCos((R / r + delta) * theta)
                      + offsetX;
              y2 = (R + delta * r) * mathSin(theta)
                      - d * mathSin((R / r + delta) * theta)
                      + offsetY;
              ctx.lineTo(x2, y2);
              i++;
          }
          while (i <= (r * num) / (R + delta * r) * 360);
  
      }
  }