/**
* v-dialogDrag 弹窗拖拽
* Copyright (c) 2019 iufc
*/

export default {
  bind(el, binding, vnode, oldVnode) {
    const value = binding.value
    if (value == false) return
    // 获取拖拽内容头部
    const dialogHeaderEl = el.querySelector('.el-dialog__header');
    const dragDom = el.querySelector('.el-dialog');
    dialogHeaderEl.style.cursor = 'move';
    // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
    const sty = dragDom.currentStyle || window.getComputedStyle(dragDom, null);
    dragDom.style.position = 'absolute';
    dragDom.style.marginTop = 0;
    let width = dragDom.style.width;
    if (width.includes('%')) {
      width = +document.body.clientWidth * (+width.replace(/\%/g, '') / 100);
    } else {
      width = +width.replace(/\px/g, '');
    }
    dragDom.style.left = `${(document.body.clientWidth - width) / 2}px`;
    // 鼠标按下事件
    dialogHeaderEl.onmousedown = (e) => {
      // 鼠标按下，计算当前元素距离可视区的距离 (鼠标点击位置距离可视窗口的距离)
      const disX = e.clientX - dialogHeaderEl.offsetLeft;
      const disY = e.clientY - dialogHeaderEl.offsetTop;

      // 获取到的值带px 正则匹配替换
      let styL, styT;

      // 注意在ie中 第一次获取到的值为组件自带50% 移动之后赋值为px
      if (sty.left.includes('%')) {
        styL = +document.body.clientWidth * (+sty.left.replace(/\%/g, '') / 100);
        styT = +document.body.clientHeight * (+sty.top.replace(/\%/g, '') / 100);
      } else {
        styL = +sty.left.replace(/\px/g, '');
        styT = +sty.top.replace(/\px/g, '');
      };

      // 鼠标拖拽事件
      document.onmousemove = function (e) {
        // 通过事件委托，计算移动的距离 （开始拖拽至结束拖拽的距离）
        const l = e.clientX - disX;
        const t = e.clientY - disY;

        let finallyL = l + styL
        let finallyT = t + styT

        // 移动当前元素
        dragDom.style.left = `${finallyL}px`;
        dragDom.style.top = `${finallyT}px`;

      };

      document.onmouseup = function (e) {
        document.onmousemove = null;
        document.onmouseup = null;
      };
    }
  }
};
