From 4ba8df44257f963231cfc264669256457abd9d34 Mon Sep 17 00:00:00 2001
From: Eric Liu <ericyl.us@gmail.com>
Date: Sun, 22 Dec 2019 05:50:12 -0800
Subject: [PATCH] feat(components): add Tabs

Closes #32
---
 README.md                               |   4 +
 src/components/Tabs/Tab.svelte          |  69 ++++++++++++++
 src/components/Tabs/TabContent.svelte   |  20 +++++
 src/components/Tabs/Tabs.Story.svelte   |  43 +++++++++
 src/components/Tabs/Tabs.stories.js     |  45 ++++++++++
 src/components/Tabs/Tabs.svelte         | 114 ++++++++++++++++++++++++
 src/components/Tabs/TabsSkeleton.svelte |  25 ++++++
 src/components/Tabs/index.js            |   6 ++
 src/index.js                            |   5 ++
 9 files changed, 331 insertions(+)
 create mode 100644 src/components/Tabs/Tab.svelte
 create mode 100644 src/components/Tabs/TabContent.svelte
 create mode 100644 src/components/Tabs/Tabs.Story.svelte
 create mode 100644 src/components/Tabs/Tabs.stories.js
 create mode 100644 src/components/Tabs/Tabs.svelte
 create mode 100644 src/components/Tabs/TabsSkeleton.svelte
 create mode 100644 src/components/Tabs/index.js

diff --git a/README.md b/README.md
index d6990025..f84ff158 100644
--- a/README.md
+++ b/README.md
@@ -38,6 +38,10 @@ Currently, the following components are supported:
   - SearchSkeleton
 - SkeletonPlaceholder
 - SkeletonText
+- Tabs
+  - Tab
+  - TabContent
+  - TabsSkeleton
 - Tag
   - TagSkeleton
 - TextArea
diff --git a/src/components/Tabs/Tab.svelte b/src/components/Tabs/Tab.svelte
new file mode 100644
index 00000000..38480380
--- /dev/null
+++ b/src/components/Tabs/Tab.svelte
@@ -0,0 +1,69 @@
+<script>
+  // TODO: fix space not selecting
+  let className = undefined;
+  export { className as class };
+  export let role = 'presentation';
+  export let label = '';
+  export let tabindex = '0';
+  export let href = '#';
+  export let disabled = false;
+  export let style = undefined;
+
+  import { getContext } from 'svelte';
+  import { cx } from '../../lib';
+
+  const id = Math.random();
+  const { selectedTab, add, update, change } = getContext('Tabs');
+
+  let anchorRef = undefined;
+
+  add({ id, label, disabled });
+
+  $: selected = $selectedTab === id;
+  $: if (selected && anchorRef) {
+    anchorRef.focus();
+  }
+  $: _class = cx(
+    '--tabs__nav-item',
+    disabled && '--tabs__nav-item--disabled',
+    selected && '--tabs__nav-item--selected',
+    className
+  );
+</script>
+
+<li
+  tabindex="-1"
+  class={_class}
+  on:click|preventDefault={() => {
+    if (!disabled) {
+      update(id);
+    }
+  }}
+  on:mouseover
+  on:mouseenter
+  on:mouseleave
+  on:keydown={event => {
+    if (disabled) {
+      return;
+    }
+    if (event.key === 'ArrowRight') {
+      change(1);
+    } else if (event.key === 'ArrowLeft') {
+      change(-1);
+    } else if (event.key === ' ' || event.key === 'Enter') {
+      update(id);
+    }
+  }}
+  {role}
+  {style}>
+  <a
+    bind:this={anchorRef}
+    role="tab"
+    class={cx('--tabs__nav-link')}
+    tabindex={disabled ? '-1' : tabindex}
+    aria-selected={selected}
+    aria-disabled={disabled}
+    {href}>
+    {label}
+  </a>
+</li>
diff --git a/src/components/Tabs/TabContent.svelte b/src/components/Tabs/TabContent.svelte
new file mode 100644
index 00000000..7ed20da9
--- /dev/null
+++ b/src/components/Tabs/TabContent.svelte
@@ -0,0 +1,20 @@
+<script>
+  let className = undefined;
+  export { className as class };
+  export let style = undefined;
+
+  import { getContext } from 'svelte';
+  import { cx } from '../../lib';
+
+  const _class = cx('--tab-content', className);
+  const id = Math.random();
+  const { selectedContent, addContent } = getContext('Tabs');
+
+  addContent({ id });
+
+  $: selected = $selectedContent === id;
+</script>
+
+<div class={_class} aria-hidden={!selected} hidden={!selected} {style}>
+  <slot />
+</div>
diff --git a/src/components/Tabs/Tabs.Story.svelte b/src/components/Tabs/Tabs.Story.svelte
new file mode 100644
index 00000000..a171e3c7
--- /dev/null
+++ b/src/components/Tabs/Tabs.Story.svelte
@@ -0,0 +1,43 @@
+<script>
+  export let story = undefined;
+
+  import Layout from '../../internal/ui/Layout.svelte';
+  import Tabs from './Tabs.svelte';
+  import Tab from './Tab.svelte';
+  import TabContent from './TabContent.svelte';
+  import TabsSkeleton from './TabsSkeleton.svelte';
+
+  const { tabProps, ...tabsProps } = $$props;
+
+  let selected = 0;
+</script>
+
+<Layout>
+  {#if story === 'skeleton'}
+    <TabsSkeleton />
+  {:else if story === 'container'}
+    <Tabs {...tabsProps} type="container" bind:selected>
+      <Tab {...tabProps} label="Tab label 1" />
+      <Tab {...tabProps} label="Tab label 2" />
+      <Tab {...tabProps} label="Tab label 3" />
+      <div slot="content">
+        <TabContent>Content 1</TabContent>
+        <TabContent>Content 2</TabContent>
+        <TabContent>Content 3</TabContent>
+      </div>
+    </Tabs>
+  {:else}
+    <Tabs {...tabsProps} bind:selected>
+      <Tab {...tabProps} label="Tab label 1" />
+      <Tab {...tabProps} label="Tab label 2" />
+      <Tab {...tabProps} label="Tab label 3" disabled />
+      <Tab {...tabProps} label="Tab label 4" />
+      <div slot="content">
+        <TabContent>Content 1</TabContent>
+        <TabContent>Content 2</TabContent>
+        <TabContent>Content 3</TabContent>
+        <TabContent>Content 4</TabContent>
+      </div>
+    </Tabs>
+  {/if}
+</Layout>
diff --git a/src/components/Tabs/Tabs.stories.js b/src/components/Tabs/Tabs.stories.js
new file mode 100644
index 00000000..1bf413c9
--- /dev/null
+++ b/src/components/Tabs/Tabs.stories.js
@@ -0,0 +1,45 @@
+import { withKnobs, boolean, number, text } from '@storybook/addon-knobs';
+import Component from './Tabs.Story.svelte';
+
+export default { title: 'Tabs', decorators: [withKnobs] };
+
+export const Default = () => ({
+  Component,
+  props: {
+    tabProps: {
+      disabled: boolean('Disabled (disabled in <Tab>)', false),
+      href: text('The href for tab (href in <Tab>)', '#'),
+      role: text('ARIA role (role in <Tab>)', 'presentation'),
+      tabindex: number('Tab index (tabindex in <Tab>)', 0)
+    },
+    tabsProps: {
+      className: 'some-class',
+      selected: number('The index of the selected tab (selected in <Tabs>)', 1),
+      triggerHref: text('The href of trigger button for narrow mode (triggerHref in <Tabs>)', '#'),
+      role: text('ARIA role (role in <Tabs>)', 'navigation'),
+      iconDescription: text(
+        'The description of the trigger icon for narrow mode (iconDescription in <Tabs>)',
+        'show menu options'
+      ),
+      tabContentClassName: text(
+        'The className for the child `<TabContent>` components',
+        'tab-content'
+      )
+    }
+  }
+});
+
+export const Container = () => ({
+  Component,
+  props: {
+    story: 'container',
+    tabProps: {
+      disabled: boolean('Disabled (disabled in <Tab>)', false),
+      href: text('The href for tab (href in <Tab>)', '#'),
+      role: text('ARIA role (role in <Tab>)', 'presentation'),
+      tabindex: number('Tab index (tabindex in <Tab>)', 0)
+    }
+  }
+});
+
+export const Skeleton = () => ({ Component, props: { story: 'skeleton' } });
diff --git a/src/components/Tabs/Tabs.svelte b/src/components/Tabs/Tabs.svelte
new file mode 100644
index 00000000..b25e0396
--- /dev/null
+++ b/src/components/Tabs/Tabs.svelte
@@ -0,0 +1,114 @@
+<script>
+  let className = undefined;
+  export { className as class };
+  export let selected = 0;
+  export let iconDescription = 'Show menu options';
+  export let role = 'navigation';
+  export let type = 'default';
+  export let triggerHref = '#';
+  export let style = undefined;
+
+  import { createEventDispatcher, setContext } from 'svelte';
+  import { writable, derived } from 'svelte/store';
+  import ChevronDownGlyph from 'carbon-icons-svelte/lib/ChevronDownGlyph';
+  import { cx } from '../../lib';
+
+  const dispatch = createEventDispatcher();
+  const _class = cx('--tabs', type === 'container' && '--tabs--container', className);
+  let dropdownHidden = true;
+  let tabs = writable([]);
+  let tabsById = derived(tabs, _ => _.reduce((a, c) => ({ ...a, [c.id]: c }), {}));
+  let currentIndex = selected;
+  let selectedTab = writable(undefined);
+  let content = writable([]);
+  let selectedContent = writable(undefined);
+
+  setContext('Tabs', {
+    selectedTab,
+    selectedContent,
+    add: data => {
+      tabs.update(_ => [..._, { ...data, index: _.length }]);
+    },
+    addContent: data => {
+      content.update(_ => [..._, { ...data, index: _.length }]);
+    },
+    update: id => {
+      currentIndex = $tabsById[id].index;
+    },
+    change: direction => {
+      let index = currentIndex + direction;
+
+      if (index < 0) {
+        index = $tabs.length - 1;
+      } else if (index >= $tabs.length) {
+        index = 0;
+      }
+
+      let disabled = $tabs[index].disabled;
+
+      while (disabled) {
+        index = index + direction;
+
+        if (index < 0) {
+          index = $tabs.length - 1;
+        } else if (index >= $tabs.length) {
+          index = 0;
+        }
+
+        disabled = $tabs[index].disabled;
+      }
+
+      currentIndex = index;
+    }
+  });
+
+  $: currentTab = $tabs[currentIndex] || undefined;
+  $: currentContent = $content[currentIndex] || undefined;
+  $: {
+    selected = currentIndex;
+    dispatch('change', currentIndex);
+
+    if (currentTab) {
+      selectedTab.set(currentTab.id);
+    }
+
+    if (currentContent) {
+      selectedContent.set(currentContent.id);
+    }
+  }
+  $: if ($selectedTab) {
+    dropdownHidden = true;
+  }
+  $: _listClass = cx('--tabs__nav', dropdownHidden && '--tabs__nav--hidden');
+</script>
+
+<div class={_class} {style} {role}>
+  <div
+    role="listbox"
+    tabindex="0"
+    class={cx('--tabs-trigger')}
+    aria-label={$$props['aria-label'] || 'listbox'}
+    on:click={() => {
+      dropdownHidden = !dropdownHidden;
+    }}
+    on:keypress
+    on:keypress={() => {
+      dropdownHidden = !dropdownHidden;
+    }}>
+    <a
+      tabindex="-1"
+      class={cx('--tabs-trigger-text')}
+      href={triggerHref}
+      on:click
+      on:click={() => {
+        dropdownHidden = !dropdownHidden;
+      }}>
+      {#if currentTab}{currentTab.label}{/if}
+    </a>
+    <ChevronDownGlyph aria-hidden="true" title={iconDescription} />
+  </div>
+  <ul role="tablist" class={_listClass}>
+    <slot />
+  </ul>
+</div>
+<slot name="content" />
diff --git a/src/components/Tabs/TabsSkeleton.svelte b/src/components/Tabs/TabsSkeleton.svelte
new file mode 100644
index 00000000..b2b02af9
--- /dev/null
+++ b/src/components/Tabs/TabsSkeleton.svelte
@@ -0,0 +1,25 @@
+<script>
+  let className = undefined;
+  export { className as class };
+  export let style = undefined;
+
+  import { cx } from '../../lib';
+
+  const _class = cx('--tabs', '--skeleton', className);
+</script>
+
+<div on:click on:mouseover on:mouseenter on:mouseleave class={_class} {style}>
+  <div class={cx('--tabs-trigger')}>
+    <div class={cx('--tabs-trigger-text')}>&nbsp;</div>
+    <svg width="10" height="5" viewBox="0 0 10 5" fillRule="evenodd">
+      <path d="M10 0L5 5 0 0z" />
+    </svg>
+  </div>
+  <ul class={cx('--tabs__nav', '--tabs__nav--hidden')}>
+    {#each [0, 1, 2, 3] as item, i (item)}
+      <li class={cx('--tabs__nav-item')}>
+        <div class={cx('--tabs__nav-link')}>&nbsp;</div>
+      </li>
+    {/each}
+  </ul>
+</div>
diff --git a/src/components/Tabs/index.js b/src/components/Tabs/index.js
new file mode 100644
index 00000000..9ff5322a
--- /dev/null
+++ b/src/components/Tabs/index.js
@@ -0,0 +1,6 @@
+import Tabs from './Tabs.svelte';
+
+export default Tabs;
+export { default as Tab } from './Tab.svelte';
+export { default as TabContent } from './TabContent.svelte';
+export { default as TabsSkeleton } from './TabsSkeleton.svelte';
diff --git a/src/index.js b/src/index.js
index 3fa2aa64..04968613 100644
--- a/src/index.js
+++ b/src/index.js
@@ -16,6 +16,7 @@ import RadioButton, { RadioButtonSkeleton } from './components/RadioButton';
 import Search, { SearchSkeleton } from './components/Search';
 import SkeletonPlaceholder from './components/SkeletonPlaceholder';
 import SkeletonText from './components/SkeletonText';
+import Tabs, { Tab, TabContent, TabsSkeleton } from './components/Tabs';
 import Tag, { TagSkeleton } from './components/Tag';
 import TextArea, { TextAreaSkeleton } from './components/TextArea';
 import TextInput, { TextInputSkeleton, PasswordInput } from './components/TextInput';
@@ -66,6 +67,10 @@ export {
   SkeletonPlaceholder,
   SkeletonText,
   Switch,
+  Tabs,
+  Tab,
+  TabContent,
+  TabsSkeleton,
   Tag,
   TagSkeleton,
   TextArea,