/**
 * 生成随机字符串
 * @param len 生成个数
 */
export const randomString = (len?: number) => {
  len = len || 10;
  const str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
  const maxPos = str.length;
  let random_str = '';
  for (let i = 0; i < len; i++) {
    random_str += str.charAt(Math.floor(Math.random() * maxPos));
  }
  return random_str;
};

// 通过泛型定义通用类型保护函数
export const isOfType = <T>(target: unknown, prop: keyof T): target is T => {
  return (target as T)[prop] !== undefined;
};
/**
 * 获取坐标偏移量
 * @param length 真实宽/高
 * @param scale 缩放倍数
 * @returns 坐标偏移量
 */
export const getCoordinateOffset = (length: number, scale: number) => {
  return (length / 2) * (scale - 1);
};
// 角度转弧度
// Math.PI = 180 度
export const angleToRadian = (angle: number) => {
  return (angle * Math.PI) / 180;
};
/**
 * 计算根据圆心旋转后的点的坐标
 * @param   {Object}  point  旋转前的点坐标
 * @param   {Object}  center 旋转中心
 * @param   {Number}  rotate 旋转的角度
 * @return  {Object}         旋转后的坐标
 * https://www.zhihu.com/question/67425734/answer/252724399 旋转矩阵公式
 */
export const calculateRotatedPointCoordinate = (
  point: { x: number; y: number },
  center: { x: number; y: number },
  rotate: number
) => {
  /**
   * 旋转公式：
   *  点a(x, y)
   *  旋转中心c(x, y)
   *  旋转后点n(x, y)
   *  旋转角度θ                tan ??
   * nx = cosθ * (ax - cx) - sinθ * (ay - cy) + cx
   * ny = sinθ * (ax - cx) + cosθ * (ay - cy) + cy
   */

  return {
    x:
      (point.x - center.x) * Math.cos(angleToRadian(rotate)) -
      (point.y - center.y) * Math.sin(angleToRadian(rotate)) +
      center.x,
    y:
      (point.x - center.x) * Math.sin(angleToRadian(rotate)) +
      (point.y - center.y) * Math.cos(angleToRadian(rotate)) +
      center.y
  };
};
// 求两点之间的中点坐标
export const getCenterPoint = (p1: { x: number; y: number }, p2: { x: number; y: number }) => {
  return {
    x: p1.x + (p2.x - p1.x) / 2,
    y: p1.y + (p2.y - p1.y) / 2
  };
};