// 鼠标移动滚动位置类
class Drag {
  constructor(vm) {
    this.dragWrap = vm;// 要挂载的容器
    this._dom = {};
    this._x = 0;
    this._y = 0;
    this._top = 0;
    this._left = 0;
    this.move = false;
    this.down = false;
    this.init.apply(this, arguments);
  }

  // 绑定事件
  init() {
    this.bindEvent();
  }

  // 给要素增加鼠标事件mousedown，mouseup，mousemove
  bindEvent() {
    var t = this;
    this.dragWrap.addEventListener('mousedown', function (e) {
      e && e.preventDefault();
      if (!t.move) {
        t.move = false;
        t.down = true;
        t._x = e.clientX;
        t._y = e.clientY;
        t._top = t.dragWrap.scrollTop;
        t._left = t.dragWrap.scrollLeft;
      }
    });
    this.dragWrap.addEventListener('mouseup', function (e) {
      e && e.preventDefault();
      t.move = false;
      t.down = false;
    });
    this.dragWrap.addEventListener('mousemove', function (e) {
      if (t.down) {
        e && e.preventDefault();
        t.move = true;
        let x = t._x - e.clientX;
        let y = t._y - e.clientY;
        t.dragWrap.scrollLeft = t._left + x;
        t.dragWrap.scrollTop = t._top + y;
      }
    });
  }
}
export default Drag;