class Draggable {
  /**
   * 
   * @param {*} elem  -拖拽的元素
   * @param {*} dragHandle -拖拽的手柄
   * @param {*} resizeHandle -缩放的手柄
   * @param {*} resizeHandle  -是否按照像素定位(不是则为百分比)
   * @param {*} dragFn - 拖拽完成后的回调
   * @param {*} resizeFn - 缩放完成后的回调
   */
  constructor(container, elem, dragHandle, resizeHandle, isPixel, dragFn, resizeFn) {
    this.container = container;
    this.elem = elem;
    this.dragHandle = dragHandle;
    this.resizeHandle = resizeHandle;
    this.isPixel = isPixel;
    this.dragFn = dragFn;
    this.resizeFn = resizeFn;
    this.dragMinWidth = 5; //最小宽度
    this.dragMinHeight = 5; //最大宽度
    this.init();
    this.drag();
    this.resize();
  }
  init() {
    if (getStyle(this.container, "position") === "") {
      this.container.style.position = "relative";
    }
    if (getStyle(this.elem, "position") === "") {
      this.elem.style.position = "absolute";
    }
  }
  drag() {

    if(this.dragHandle === null || this.dragHandle === undefined)
      return;

    let disX = 0;
    let disY = 0;
    let realL = "";
    let realT = "";
    this.dragHandle = this.dragHandle || this.elem;
    this.dragHandle.style.cursor = "move";
    this.dragHandle.onmousedown = event => {
      var event = event || window.event;
      disX = event.clientX - this.elem.offsetLeft;
      disY = event.clientY - this.elem.offsetTop;

      document.onmousemove = event => {
        var event = event || window.event;
        let iL = event.clientX - disX;
        let iT = event.clientY - disY;
        let maxL = this.elem.parentNode.clientWidth - this.elem.offsetWidth;
        let maxT = this.elem.parentNode.clientHeight - this.elem.offsetHeight;

        iL <= 0 && (iL = 0);
        iT <= 0 && (iT = 0);
        iL >= maxL && (iL = maxL);
        iT >= maxT && (iT = maxT);
        // this.elem.style.left = iL + "px";
        // this.elem.style.top = iT + "px";
        if (this.isPixel) {
          //按像素
          realL = iL + "px";
          realT = iT + "px";
        } else {
          //按百分比
          realL = (iL / this.elem.parentNode.clientWidth) * 100 + "%";
          realT = (iT / this.elem.parentNode.clientHeight) * 100 + "%";
        }

        this.elem.style.left = realL;
        this.elem.style.top = realT;

        return false
      };

      document.onmouseup = () => {
        document.onmousemove = null;
        document.onmouseup = null;
        this.releaseCapture && this.releaseCapture()
        if (this.dragFn) {
          this.dragFn({
            left: realL,
            top: realT
          });
        }
      };
      this.setCapture && this.setCapture();
      return false
    };

  }
  resize() {

    if(this.resizeHandle === null || this.resizeHandle === undefined)
      return;

    this.resizeHandle.onmousedown = event => {
      var event = event || window.event;
      let disX = event.clientX - this.resizeHandle.offsetLeft;
      let disY = event.clientY - this.resizeHandle.offsetTop;
      let iW = 0;
      let iH = 0;
      let realW = "";
      let realH = "";
      document.onmousemove = event => {
        var event = event || window.event;

        let iL = event.clientX - disX;
        let iT = event.clientY - disY;
        let maxW = this.elem.parentNode.clientWidth - this.elem.offsetLeft;
        let maxH = this.elem.parentNode.clientHeight - this.elem.offsetTop;
        iW = this.resizeHandle.offsetWidth + iL;
        iH = this.resizeHandle.offsetHeight + iT;

        // 宽
        iW < this.dragMinWidth && (iW = this.dragMinWidth);
        iW > maxW && (iW = maxW);
        // lockX || (this.elem.style.width = iW + "px");
        if (this.isPixel) {
          realW = iW + "px";
        } else {
          realW = (iW / this.elem.parentNode.clientWidth) * 100 + "%";
        }
        this.elem.style.width = realW;

        // 高
        iH < this.dragMinHeight && (iH = this.dragMinHeight);
        iH > maxH && (iH = maxH);
        // lockY || (this.elem.style.height = iH + "px");
        if (this.isPixel) {
          realH = iH + "px"
        } else {
          realH = (iH / this.elem.parentNode.clientHeight) * 100 + "%"
        }
        this.elem.style.height = realH;
        if ((iW == this.dragMinWidth) || (iH == this.dragMinHeight)) document.onmousemove = null;
        return false;
      };
      document.onmouseup = () => {
        document.onmousemove = null;
        document.onmouseup = null;
        if (this.resizeFn) {
          this.resizeFn({
            width: realW,
            height: realH
          });
        }
      };
      return false;
    }
  }

}

function getStyle(obj, attr) {
  const style = obj.currentStyle ? obj.currentStyle[attr] : getComputedStyle(obj, false)[attr];
  if (!style || style === "static") {
    return "";
  }
  return style;
}