modrinth-code/apps/app-frontend/src/components/ui/NavTabs.vue

<template>
  <nav
    class="card-shadow experimental-styles-within relative flex w-fit overflow-clip rounded-full bg-bg-raised p-1 text-sm font-bold"
  >
    <RouterLink
      v-for="(link, index) in filteredLinks"
      v-show="link.shown === undefined ? true : link.shown"
      :key="index"
      ref="tabLinkElements"
      :to="query ? (link.href ? `?${query}=${link.href}` : '?') : link.href"
      :class="`button-animation z-[1] flex flex-row items-center gap-2 px-4 py-2 focus:rounded-full ${activeIndex === index && !subpageSelected ? 'text-button-textSelected' : activeIndex === index && subpageSelected ? 'text-contrast' : 'text-primary'}`"
    >
      <component :is="link.icon" v-if="link.icon" class="size-5" />
      <span class="text-nowrap">{{ link.label }}</span>
    </RouterLink>
    <div
      :class="`navtabs-transition pointer-events-none absolute h-[calc(100%-0.5rem)] overflow-hidden rounded-full p-1 ${subpageSelected ? 'bg-button-bg' : 'bg-button-bgSelected'}`"
      :style="{
        left: sliderLeftPx,
        top: sliderTopPx,
        right: sliderRightPx,
        bottom: sliderBottomPx,
        opacity: sliderLeft === 4 && sliderLeft === sliderRight ? 0 : activeIndex === -1 ? 0 : 1,
      }"
      aria-hidden="true"
    ></div>
  </nav>
</template>

<script setup lang="ts">
import { computed, onMounted, onUnmounted, ref, watch } from 'vue'
import type { RouteLocationRaw } from 'vue-router'
import { useRoute, RouterLink } from 'vue-router'

const route = useRoute()

interface Tab {
  label: string
  href: string | RouteLocationRaw
  shown?: boolean
  icon?: unknown
  subpages?: string[]
}

const props = defineProps<{
  links: Tab[]
  query?: string
}>()

const sliderLeft = ref(4)
const sliderTop = ref(4)
const sliderRight = ref(4)
const sliderBottom = ref(4)
const activeIndex = ref(-1)
const oldIndex = ref(-1)
const subpageSelected = ref(false)

const filteredLinks = computed(() =>
  props.links.filter((x) => (x.shown === undefined ? true : x.shown)),
)
const sliderLeftPx = computed(() => `${sliderLeft.value}px`)
const sliderTopPx = computed(() => `${sliderTop.value}px`)
const sliderRightPx = computed(() => `${sliderRight.value}px`)
const sliderBottomPx = computed(() => `${sliderBottom.value}px`)

function pickLink() {
  let index = -1
  subpageSelected.value = false
  for (let i = filteredLinks.value.length - 1; i >= 0; i--) {
    const link = filteredLinks.value[i]

    if (route.path === (typeof link.href === 'string' ? link.href : link.href.path)) {
      index = i
      break
    } else if (link.subpages && link.subpages.some((subpage) => route.path.includes(subpage))) {
      index = i
      subpageSelected.value = true
      break
    }
  }
  activeIndex.value = index

  if (activeIndex.value !== -1) {
    startAnimation()
  } else {
    oldIndex.value = -1
    sliderLeft.value = 0
    sliderRight.value = 0
  }
}

const tabLinkElements = ref()

function startAnimation() {
  const el = tabLinkElements.value[activeIndex.value].$el

  if (!el || !el.offsetParent) return

  const newValues = {
    left: el.offsetLeft,
    top: el.offsetTop,
    right: el.offsetParent.offsetWidth - el.offsetLeft - el.offsetWidth,
    bottom: el.offsetParent.offsetHeight - el.offsetTop - el.offsetHeight,
  }

  if (sliderLeft.value === 4 && sliderRight.value === 4) {
    sliderLeft.value = newValues.left
    sliderRight.value = newValues.right
    sliderTop.value = newValues.top
    sliderBottom.value = newValues.bottom
  } else {
    const delay = 200

    if (newValues.left < sliderLeft.value) {
      sliderLeft.value = newValues.left
      setTimeout(() => {
        sliderRight.value = newValues.right
      }, delay)
    } else {
      sliderRight.value = newValues.right
      setTimeout(() => {
        sliderLeft.value = newValues.left
      }, delay)
    }

    if (newValues.top < sliderTop.value) {
      sliderTop.value = newValues.top
      setTimeout(() => {
        sliderBottom.value = newValues.bottom
      }, delay)
    } else {
      sliderBottom.value = newValues.bottom
      setTimeout(() => {
        sliderTop.value = newValues.top
      }, delay)
    }
  }
}

onMounted(() => {
  window.addEventListener('resize', pickLink)
  pickLink()
})

onUnmounted(() => {
  window.removeEventListener('resize', pickLink)
})

watch(route, () => {
  pickLink()
})
</script>
<style scoped>
.navtabs-transition {
  /* Delay on opacity is to hide any jankiness as the page loads */
  transition:
    all 150ms cubic-bezier(0.4, 0, 0.2, 1) 0s,
    opacity 250ms cubic-bezier(0.5, 0, 0.2, 1) 50ms;
}

.card-shadow {
  box-shadow: var(--shadow-card);
}
</style>