const dialogdrag = {
  name: "dialogdrag",
  directive: {
    bind(el, binding, vnode, oldVnode) {
      const dialogHeaderEl = el.querySelector('.el-dialog__header');
      const dragDom = el.querySelector('.el-dialog');

      dialogHeaderEl.style.cssText += ';cursor:move;'
      dragDom.style.cssText += ';top:0px;'

      // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
      const sty = (() => {
        if (window.document.currentStyle) {
          return (dom, attr) => dom.currentStyle[attr];
        } else {
          return (dom, attr) => getComputedStyle(dom, false)[attr];
        }
      })()

      dialogHeaderEl.onmousedown = (e) => {
        // 鼠标按下，计算当前元素距离可视区的距离
        const disX = e.clientX - dialogHeaderEl.offsetLeft;
        const disY = e.clientY - dialogHeaderEl.offsetTop;
        const screenWidth = document.body.clientWidth; // body当前宽度
        const screenHeight = document.documentElement.clientHeight; // 可见区域高度(应为body高度，可某些环境下无法获取)

        const dragDomWidth = dragDom.offsetWidth; // 对话框宽度
        const dragDomheight = dragDom.offsetHeight; // 对话框高度
        const marginWidth = 8 //边距
        const minDragDomLeft = dragDom.offsetLeft - marginWidth;
        const maxDragDomLeft = screenWidth - dragDom.offsetLeft - dragDomWidth - marginWidth;

        const minDragDomTop = dragDom.offsetTop - marginWidth;
        const maxDragDomTop = screenHeight - dragDom.offsetTop - dragDomheight - marginWidth;

        // 获取到的值带px 正则匹配替换
        let styL = sty(dragDom, 'left');
        let styT = sty(dragDom, 'top');

        // 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 (styL.includes('%')) {
          styL = +document.body.clientWidth * (+styL.replace(/\%/g, '') / 100);
          styT = +document.body.clientHeight * (+styT.replace(/\%/g, '') / 100);
        } else {
          styL = +styL.replace(/\px/g, '');
          styT = +styT.replace(/\px/g, '');
        };

        document.onmousemove = function (e) {
          // 通过事件委托，计算移动的距离
          let left = e.clientX - disX;
          let top = e.clientY - disY;

          // 边界处理
          if (-(left) > minDragDomLeft) {
            left = -(minDragDomLeft);
          } else if (left > maxDragDomLeft) {
            left = maxDragDomLeft;
          }

          if (-(top) > minDragDomTop) {
            top = -(minDragDomTop);
          } else if (top > maxDragDomTop) {
            top = maxDragDomTop;
          }

          // 移动当前元素 
          dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`;
        };

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

export default dialogdrag;
