.esl-popup-arrow-init(
  @arrowClassName: esl-popup-arrow,
  @popupArrowSize: 20px,
  @popupBackgroundColor: #FFF,
  @popupBorderColor: #DBDBDB,
  @popupBorderWidth: 1px
) {
  @popupArrowHalf: (@popupArrowSize / 2);
  @popupArrowShift: (
    @popupArrowSize * 0.2071 - @popupBorderWidth
  ); /* 0.2071 = (sqrt(2) - 1) / 2  (Don't ask why, it's an axiom)*/

  .@{arrowClassName} {
    position: absolute;
    top: (-@popupArrowHalf - @popupBorderWidth);
    bottom: 100%;
    z-index: -1;
    transform: rotate(45deg);
    width: @popupArrowSize;
    height: @popupArrowSize;
    margin-left: @popupArrowShift;
    border-left: @popupBorderWidth solid @popupBorderColor;
    border-top: @popupBorderWidth solid @popupBorderColor;
    background: @popupBackgroundColor;
  }

  &:is([placed-at='top'], [placed-at='bottom-inner']) {
    .@{arrowClassName} {
      top: auto;
      bottom: (-@popupArrowHalf - @popupBorderWidth);
      transform: rotate(225deg);
    }
  }

  &:is([placed-at='left'], [placed-at='right-inner']) {
    .@{arrowClassName} {
      right: (-@popupArrowHalf - @popupBorderWidth);
      left: auto;
      transform: rotate(135deg);
      margin-top: @popupArrowShift;
    }
  }

  &:is([placed-at='right'], [placed-at='left-inner']) {
    .@{arrowClassName} {
      left: (-@popupArrowHalf - @popupBorderWidth - @popupArrowShift);
      right: auto;
      transform: rotate(315deg);
      margin-top: @popupArrowShift;
    }
  }

  &.disable-arrow {
    .@{arrowClassName} {
      display: none;
    }
  }
}

.esl-popup-init(
  @className: esl-popup,
  @arrowClassName: esl-popup-arrow,
  @arrowSize: 20px,
  @backgroundColor: #FFF,
  @borderColor: #DBDBDB,
  @borderWidth: 1px,
  @zIndex: 999
) {
  .@{className} {
    position: absolute;
    left: 0;
    top: 0;
    display: block;
    opacity: 0;
    visibility: hidden;
    transition: visibility 0.5s 0.2s;
    box-sizing: border-box;
    box-shadow: 1px 1px 5px rgba(0, 0, 0, 0.2);
    border: @borderWidth solid @borderColor;
    background: @backgroundColor;
    cursor: default;
    will-change: auto;

    &[open] {
      z-index: @zIndex;
      opacity: 1;
      visibility: visible;
      transition:
        opacity 0.15s,
        transform 0.2s;
    }

    &:not([open]) {
      display: none;
    }

    .esl-popup-arrow-init(@arrowClassName, @arrowSize, @backgroundColor, @borderColor, @borderWidth);
  }
}