core/themes/olivero/css/components/tabs.pcss.css
@import "../base/media-queries.pcss.css";

/* Breakpoint where tabs switch between vertical and horizontal layouts. */
@custom-media --tabs-layout-switch (--md);

.tabs {
  --tabs-height: var(--sp3);
  --tabs-padding-inline: var(--sp1-5);
  --tabs-active-border-size: 6px;
  --tabs-highlight-color: var(--color--primary-50); /* Minimum 3:1 contrast ratio against --tabs-background-color and --tabs-background-color-hover. */
  --tabs-text-color: var(--color-text-neutral-soft); /* Minimum 4.5:1 contrast ratio against --tabs-background-color and --tabs-background-color-hover. */
  --tabs-text-color-active: var(--color--gray-5); /* Minimum 4.5:1 contrast ratio against --tabs-background-color and --tabs-background-color-hover. */
  --tabs-letter-spacing: 1px;
  --tabs-font-size: var(--font-size-s);
  --tabs-background-color: var(--color--gray-100);
  --tabs-background-color-hover: var(--color--gray-95);
  --tabs-border-width: 1px;
  --tabs-border-color: var(--color--gray-95);
  --tabs-transition-duration: 0.2s;

  display: flex;
  flex-direction: column;
  width: 100%;
  margin: 0;
  margin-inline-start: 0; /* Override [dir] attribute in base <ul> in compiled CSS. */
  padding: 0;
  list-style: none;

  @media (--tabs-layout-switch) {
    flex-direction: row;
    flex-wrap: wrap;
  }
}

.tabs__tab {
  display: none;
  margin: 0;
  margin-block-end: calc(-1 * var(--tabs-border-width));

  &.is-active {
    display: flex;
  }

  /* Show tabs when JavaScript disabled. */
  html:not(.js) & {
    display: flex;
  }

  /* Show tabs when tabs-expanded class is present. */
  .tabs.is-expanded & {
    display: flex;
  }

  /* Secondary tabs will always be expanded. */
  .tabs--secondary & {
    display: block;

    @media (--tabs-layout-switch) {
      display: flex;
    }
  }

  @media (--tabs-layout-switch) {
    display: flex;
    margin-block-end: 0;
    margin-inline-start: calc(-1 * var(--tabs-border-width));
  }
}

.tabs__link {
  display: flex;
  flex-grow: 1;
  align-items: center;
  height: var(--tabs-height);
  padding-block: 0;
  padding-inline: var(--tabs-padding-inline);
  transition: background-color var(--tabs-transition-duration);
  text-decoration: none;
  letter-spacing: var(--tabs-letter-spacing);
  color: var(--tabs-text-color);
  border: var(--tabs-border-width) solid var(--tabs-border-color);
  background-color: var(--tabs-background-color);
  font-size: var(--tabs-font-size);

  &:hover {
    color: var(--tabs-text-color-active);
    background-color: var(--tabs-background-color-hover);
  }

  &:focus {
    position: relative;
    outline: solid 3px var(--tabs-highlight-color);
    outline-offset: -3px;
  }

  &.is-active {
    position: relative; /* Anchor ::after pseudo-element. */
    color: var(--tabs-text-color-active);
    font-weight: 600;

    /*
     * We use ::after pseudo-element in place of border so edges do not appear
     * diagonally cut off due to other edges with transparent borders.
     */
    &::after {
      position: absolute;
      inset-block-start: calc(-1 * var(--tabs-border-width));
      inset-inline-start: calc(-1 * var(--tabs-border-width));
      height: calc(100% + var(--tabs-border-width) * 2);
      content: "";
      border-inline-start: var(--tabs-active-border-size) solid var(--tabs-highlight-color);

      @media (--tabs-layout-switch) {
        inset-block: auto calc(-1 * var(--tabs-border-width));
        width: calc(100% + 2 * var(--tabs-border-width));
        height: 0;
        border-block-start: var(--tabs-active-border-size) solid var(--tabs-highlight-color);
        border-inline-start: 0;
      }
    }
  }

  /* No regular borders or background color for secondary tab links. */
  .tabs--secondary & {
    @media (--tabs-layout-switch) {
      border-color: transparent;
      background-color: transparent;
    }
  }
}

/* Button that opens and closes primary tabs at narrow viewports. */
.tabs__trigger {
  display: flex;
  align-items: center;
  justify-content: center;
  width: var(--tabs-height);
  margin-block: 0;
  margin-inline: calc(-1 * var(--tabs-border-width)) 0;
  cursor: pointer;
  border: solid var(--tabs-border-width) var(--tabs-border-color);
  background-color: var(--tabs-background-color);

  &:hover {
    background-color: var(--tabs-background-color-hover);
  }

  &:focus {
    position: relative;
    border-color: var(--tabs-highlight-color);
    outline: none;
  }

  /* Button will not work when JavaScript is disabled, so we hide it. */
  html:not(.js) & {
    display: none;
  }

  @media (--tabs-layout-switch) {
    display: none;
  }
}

.tabs__trigger-icon {
  position: relative;
  display: block;
  width: var(--sp);
  height: 10px;
  margin-block-start: calc(-2 * var(--tabs-border-width));

  & > span {
    position: absolute;
    inset-inline-start: 0;
    display: block;
    width: 100%;
    transition:
      transform var(--tabs-transition-duration),
      opacity var(--tabs-transition-duration),
      top var(--tabs-transition-duration);
    border-block-start: solid 2px var(--tabs-highlight-color);

    &:nth-child(1) {
      inset-block-start: 0;

      .tabs__trigger[aria-expanded="true"] & {
        inset-block-start: calc(50% + 1px);
        transform: rotate(45deg);
      }
    }

    &:nth-child(2) {
      inset-block-start: calc(50% + 1px);

      .tabs__trigger[aria-expanded="true"] & {
        opacity: 0;
      }
    }

    &:nth-child(3) {
      inset-block-start: calc(100% + 2px);

      .tabs__trigger[aria-expanded="true"] & {
        inset-block-start: calc(50% + 1px);
        transform: rotate(-45deg);
      }
    }
  }
}
