From 56c5b906294f425e9f06e79d2d95a62672ec06e3 Mon Sep 17 00:00:00 2001
From: Elijah Duffy <elijah@thatoneguy.ca>
Date: Fri, 11 Jul 2025 13:50:06 -0700
Subject: [PATCH] add tabs component

---
 src/lib/Tabs.svelte     | 133 ++++++++++++++++++++++++++++++++++++++++
 src/lib/index.ts        |   1 +
 src/routes/+page.svelte |  71 +++++++++++++++++++++
 3 files changed, 205 insertions(+)
 create mode 100644 src/lib/Tabs.svelte

diff --git a/src/lib/Tabs.svelte b/src/lib/Tabs.svelte
new file mode 100644
index 0000000..fa7d8e4
--- /dev/null
+++ b/src/lib/Tabs.svelte
@@ -0,0 +1,133 @@
+<script lang="ts" module>
+	export type TabPage = {
+		title: string;
+		onMount?: () => void;
+		onUnmount?: () => void;
+		content: Snippet<[tab: TabPage]>;
+	};
+</script>
+
+<script lang="ts">
+	import { onMount, tick, type Snippet } from 'svelte';
+	import type { ClassValue } from 'svelte/elements';
+	import { fly, type FlyParams } from 'svelte/transition';
+
+	interface Props {
+		pages: TabPage[];
+		activeIndex?: number;
+		onchange?: (event: { index: number; tab: TabPage }) => void;
+		class?: ClassValue | null;
+	}
+
+	let { pages, activeIndex = 0, onchange, class: classValue }: Props = $props();
+
+	let primaryContainerEl: HTMLDivElement;
+	let tabContainerEl: HTMLDivElement;
+	let indicatorEl: HTMLDivElement;
+	let prevIndex = $state(activeIndex);
+	const activePage = $derived(pages[activeIndex]);
+	const refs = $state<HTMLButtonElement[]>([]);
+
+	const changePage = (index: number) => {
+		if (activeIndex === index) return;
+		pages[activeIndex].onUnmount?.(); // run cleanup
+		prevIndex = activeIndex; // store previous index
+		activeIndex = index; // update active index
+		onchange?.({ index, tab: pages[index] }); // run on change
+		updateIndicator(); // update selected tab indicator
+		// run on mount after tick
+		tick().then(() => {
+			pages[index].onMount?.();
+		});
+	};
+
+	const updateIndicator = () => {
+		if (!indicatorEl || !refs[activeIndex]) return;
+		const parentRect = tabContainerEl.getBoundingClientRect();
+		const rect = refs[activeIndex].getBoundingClientRect();
+
+		const width = rect.width;
+		const mul = 0.75;
+
+		indicatorEl.style.left = `${rect.left - parentRect.left + (width / 2) * (1 - mul)}px`;
+		indicatorEl.style.width = `${rect.width * mul}px`;
+	};
+
+	const flyX = (
+		node: HTMLElement,
+		{ direction = 1, ...opts }: { direction: number } & FlyParams
+	) => {
+		return fly(node, {
+			...opts,
+			x: direction * 100, // fly left or right
+			y: 0
+		});
+	};
+
+	const lockHeight = () => {
+		if (!primaryContainerEl) return;
+		const height = primaryContainerEl.getBoundingClientRect().height;
+		primaryContainerEl.style.height = `${height}px`;
+		primaryContainerEl.style.overflow = 'hidden';
+	};
+
+	const unlockHeight = () => {
+		if (!primaryContainerEl) return;
+		primaryContainerEl.style.height = '';
+		primaryContainerEl.style.overflow = '';
+	};
+
+	onMount(() => {
+		updateIndicator();
+		setTimeout(() => {
+			indicatorEl.style.opacity = '1';
+		}, 100);
+	});
+</script>
+
+<div bind:this={primaryContainerEl} class={[classValue]}>
+	<div
+		bind:this={tabContainerEl}
+		class={['border-sui-text/15 relative mb-4 flex items-center gap-5 border-b-2']}
+	>
+		{#each pages as page, i (page.title)}
+			{@const active = activeIndex === i}
+			<button
+				bind:this={refs[i]}
+				class={['-mb-[2px] cursor-pointer px-2']}
+				onclick={() => {
+					changePage(i);
+				}}
+			>
+				<div
+					class={[
+						'hover:text-sui-text border-b-0 py-1.5 text-lg font-medium transition-colors duration-100',
+						active ? 'border-sui-text-900 text-sui-text' : 'text-sui-text/75 border-transparent'
+					]}
+				>
+					{page.title}
+				</div>
+			</button>
+		{/each}
+
+		<div
+			bind:this={indicatorEl}
+			class={[
+				'border-sui-text-900 pointer-events-none absolute top-0 -bottom-[2px] w-16 border-b-2',
+				'opacity-0 transition-[left,width,opacity]'
+			]}
+		></div>
+	</div>
+
+	{#key activeIndex}
+		<div
+			class={[]}
+			in:flyX={{ direction: activeIndex > prevIndex ? 1 : -1, duration: 180, delay: 181 }}
+			out:flyX={{ direction: activeIndex > prevIndex ? -1 : 1, duration: 180 }}
+			onoutrostart={lockHeight}
+			onintroend={unlockHeight}
+		>
+			{@render activePage.content(activePage)}
+		</div>
+	{/key}
+</div>
diff --git a/src/lib/index.ts b/src/lib/index.ts
index c81c47c..81eebe7 100644
--- a/src/lib/index.ts
+++ b/src/lib/index.ts
@@ -18,6 +18,7 @@ export { default as RadioGroup } from './RadioGroup.svelte';
 export { default as Spinner } from './Spinner.svelte';
 export { default as StateMachine, type StateMachinePage } from './StateMachine.svelte';
 export { default as StyledRawInput } from './StyledRawInput.svelte';
+export { default as Tabs, type TabPage } from './Tabs.svelte';
 export { default as TextInput } from './TextInput.svelte';
 export { default as TimeInput } from './TimeInput.svelte';
 export { default as TimezoneInput } from './TimezoneInput.svelte';
diff --git a/src/routes/+page.svelte b/src/routes/+page.svelte
index 3036561..6fa9e1d 100644
--- a/src/routes/+page.svelte
+++ b/src/routes/+page.svelte
@@ -29,6 +29,7 @@
 		TextUnderline
 	} from 'phosphor-svelte';
 	import type { Option } from '$lib';
+	import Tabs from '$lib/Tabs.svelte';
 
 	let dateInputValue = $state<CalendarDate | undefined>(undefined);
 	let checkboxValue = $state<CheckboxState>('indeterminate');
@@ -276,6 +277,76 @@
 	</div>
 </div>
 
+<div class="component">
+	<p class="title">Tabs</p>
+
+	<Tabs
+		pages={[
+			{
+				title: 'Dashboard',
+				content: tab1
+			},
+			{
+				title: 'Activity',
+				content: tab2
+			},
+			{
+				title: 'Settings',
+				content: tab3
+			}
+		]}
+	/>
+
+	{#snippet tab1()}
+		<h3 class="mb-4 text-2xl font-bold">Dashboard Overview</h3>
+		<div class="grid grid-cols-2 gap-4">
+			<div class="rounded bg-blue-100 p-4">
+				<h4 class="font-semibold">Total Users</h4>
+				<p class="text-3xl font-bold text-blue-600">1,247</p>
+			</div>
+			<div class="rounded bg-green-100 p-4">
+				<h4 class="font-semibold">Revenue</h4>
+				<p class="text-3xl font-bold text-green-600">$12,450</p>
+			</div>
+		</div>
+	{/snippet}
+
+	{#snippet tab2()}
+		<h3 class="mb-3 text-xl font-semibold">Recent Activity</h3>
+		<ul class="space-y-2">
+			<li class="flex items-center gap-2">
+				<span class="h-2 w-2 rounded-full bg-green-500"></span>
+				<span>User John Doe logged in</span>
+			</li>
+			<li class="flex items-center gap-2">
+				<span class="h-2 w-2 rounded-full bg-blue-500"></span>
+				<span>New order #1234 received</span>
+			</li>
+			<li class="flex items-center gap-2">
+				<span class="h-2 w-2 rounded-full bg-yellow-500"></span>
+				<span>System backup completed</span>
+			</li>
+		</ul>
+	{/snippet}
+
+	{#snippet tab3()}
+		<h3 class="mb-3 text-xl font-semibold">Settings</h3>
+		<form class="space-y-3">
+			<div class="flex items-center gap-2">
+				<input type="checkbox" id="notifications" checked />
+				<label for="notifications">Enable notifications</label>
+			</div>
+			<div class="flex items-center gap-2">
+				<input type="checkbox" id="darkmode" />
+				<label for="darkmode">Dark mode</label>
+			</div>
+			<button class="rounded bg-blue-500 px-4 py-2 text-white hover:bg-blue-600">
+				Save Changes
+			</button>
+		</form>
+	{/snippet}
+</div>
+
 <Dialog
 	bind:open={dialogOpen}
 	title="Dialog Title"