/**
 * 贝塞尔曲线
 */
function bezier(points, times) {
  // 0、以3个控制点为例，点A,B,C,AB上设置点D,BC上设置点E,DE连线上设置点F,则最终的贝塞尔曲线是点F的坐标轨迹。
  // 1、计算相邻控制点间距。
  // 2、根据完成时间,计算每次执行时D在AB方向上移动的距离，E在BC方向上移动的距离。
  // 3、时间每递增100ms，则D,E在指定方向上发生位移, F在DE上的位移则可通过AD/AB = DF/DE得出。
  // 4、根据DE的正余弦值和DE的值计算出F的坐标。
  // 邻控制AB点间距
  var bezier_points = [];
  var points_D = [];
  var points_E = [];
  const DIST_AB = Math.sqrt(Math.pow(points[1]['x'] - points[0]['x'], 2) + Math.pow(points[1]['y'] - points[0]['y'], 2));
  // 邻控制BC点间距
  const DIST_BC = Math.sqrt(Math.pow(points[2]['x'] - points[1]['x'], 2) + Math.pow(points[2]['y'] - points[1]['y'], 2));
  // D每次在AB方向上移动的距离
  const EACH_MOVE_AD = DIST_AB / times;
  // E每次在BC方向上移动的距离 
  const EACH_MOVE_BE = DIST_BC / times;
  // 点AB的正切
  const TAN_AB = (points[1]['y'] - points[0]['y']) / (points[1]['x'] - points[0]['x']);
  // 点BC的正切
  const TAN_BC = (points[2]['y'] - points[1]['y']) / (points[2]['x'] - points[1]['x']);
  // 点AB的弧度值
  const RADIUS_AB = Math.atan(TAN_AB);
  // 点BC的弧度值
  const RADIUS_BC = Math.atan(TAN_BC);
  // 每次执行
  for (var i = 1; i <= times; i++) {
    // AD的距离
    var dist_AD = EACH_MOVE_AD * i;
    // BE的距离
    var dist_BE = EACH_MOVE_BE * i;
    // D点的坐标
    var point_D = {};
    point_D['x'] = dist_AD * Math.cos(RADIUS_AB) + points[0]['x'];
    point_D['y'] = dist_AD * Math.sin(RADIUS_AB) + points[0]['y'];
    points_D.push(point_D);
    // E点的坐标
    var point_E = {};
    point_E['x'] = dist_BE * Math.cos(RADIUS_BC) + points[1]['x'];
    point_E['y'] = dist_BE * Math.sin(RADIUS_BC) + points[1]['y'];
    points_E.push(point_E);
    // 此时线段DE的正切值
    var tan_DE = (point_E['y'] - point_D['y']) / (point_E['x'] - point_D['x']);
    // tan_DE的弧度值
    var radius_DE = Math.atan(tan_DE);
    // 地市DE的间距
    var dist_DE = Math.sqrt(Math.pow((point_E['x'] - point_D['x']), 2) + Math.pow((point_E['y'] - point_D['y']), 2));
    // 此时DF的距离
    var dist_DF = (dist_AD / DIST_AB) * dist_DE;
    // 此时DF点的坐标
    var point_F = {};
    point_F['x'] = dist_DF * Math.cos(radius_DE) + point_D['x'];
    point_F['y'] = dist_DF * Math.sin(radius_DE) + point_D['y'];
    bezier_points.push(point_F);
  }
  return {
    'bezier_points': bezier_points
  };
}


/**
 * 播放加入购物车动画
 */
function playAnimation(param, callBack) {
  console.log("playAnimation");

  //页面对象
  var page = param.page;
  //点击事件
  var event = param.event;


  if (!page.data.hide_good_box) return;
  page.finger = {};
  var topPoint = {};
  page.finger['y'] = event.touches["0"].clientY;
  page.finger['x'] = event.touches["0"].clientX;

  if (page.finger['x'] > page.busPos['x']) {
    page.isFingerXQtBusX = true;
  } else {
    page.isFingerXQtBusX = false;
  }
  if (page.finger['y'] < page.busPos['y']) {
    topPoint['y'] = page.finger['y'] - 150;
  } else {
    topPoint['y'] = page.busPos['y'] - 150;
  }
  topPoint['x'] = Math.abs(page.finger['x'] - page.busPos['x']) / 2;
  if (page.finger['x'] > page.busPos['x']) {
    topPoint['x'] = (page.finger['x'] - page.busPos['x']) / 2 + page.busPos['x'];
  } else {
    topPoint['x'] = (page.busPos['x'] - page.finger['x']) / 2 + page.finger['x'];
  }


  if (page.isFingerXQtBusX) {
    page.linePos = bezier([page.busPos, topPoint, page.finger], 30);
    //启动动画
    startAnimation(page,callBack);

  } else {
    page.linePos = bezier([page.finger, topPoint, page.busPos], 30);
    //启动动画
    startAnimationTow(page,callBack);
  }



}

function startAnimation(page, callBack) {
  var index = 29,
    bezier_points = page.linePos['bezier_points'];
  page.setData({
    hide_good_box: false,
    bus_x: page.finger['x'],
    bus_y: page.finger['y']
  })
  page.timer = setInterval(function () {

    page.setData({
      bus_x: bezier_points[index]['x'],
      bus_y: bezier_points[index]['y']
    })
    index--;
    if (index < 0) {
      clearInterval(page.timer);
      page.setData({
        hide_good_box: true,
        hideCount: false,
        count: page.data.count += 1
      })
      callBack();
    }
  }, 20);
}



function startAnimationTow(page, callBack) {
  var index = 0,
    bezier_points = page.linePos['bezier_points'];

  page.setData({
    hide_good_box: false,
    bus_x: page.finger['x'],
    bus_y: page.finger['y']
  })
  page.timer = setInterval(function () {

    page.setData({
      bus_x: bezier_points[index]['x'],
      bus_y: bezier_points[index]['y']
    })
    index++;
    if (index > 28) {
      clearInterval(page.timer);
      page.setData({
        hide_good_box: true,
        hideCount: false,
        count: page.data.count += 1
      })

      callBack();
    }
  }, 20);

}


module.exports = {

  bezier: bezier,
  playAnimation: playAnimation,

}