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refactor(web): conventional class-based dark mode + decoupled theme module #97

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84 changes: 49 additions & 35 deletions web/src/app.css
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Original file line number Diff line number Diff line change
@@ -1,26 +1,34 @@
@import 'tailwindcss';

/*
* Bind the `dark:` utility variant to a `.dark` class on <html> instead of the
* OS media query. This is the universal Tailwind v4 convention and keeps the
* variant in lockstep with the CSS-variable swap below (both react to the same
* class), so manual light/dark toggling never desyncs from `dark:` utilities.
*/
@custom-variant dark (&:is(.dark *));

@theme inline {
/* Dark mode (default) */
--color-background: oklch(0.145 0.015 265);
--color-foreground: oklch(0.985 0 0);
--color-card: oklch(0.18 0.015 265);
--color-card-foreground: oklch(0.985 0 0);
--color-popover: oklch(0.18 0.015 265);
--color-popover-foreground: oklch(0.985 0 0);
--color-primary: oklch(0.55 0.2 250);
/* Light mode = default token values */
--color-background: oklch(0.985 0 0);
--color-foreground: oklch(0.145 0.015 265);
--color-card: oklch(0.985 0 0);
--color-card-foreground: oklch(0.145 0.015 265);
--color-popover: oklch(0.985 0 0);
--color-popover-foreground: oklch(0.145 0.015 265);
--color-primary: oklch(0.5 0.2 250);
--color-primary-foreground: oklch(0.985 0 0);
--color-secondary: oklch(0.27 0.015 265);
--color-secondary-foreground: oklch(0.985 0 0);
--color-muted: oklch(0.27 0.015 265);
--color-muted-foreground: oklch(0.7 0.015 265);
--color-accent: oklch(0.27 0.015 265);
--color-accent-foreground: oklch(0.985 0 0);
--color-secondary: oklch(0.96 0.005 265);
--color-secondary-foreground: oklch(0.25 0.015 265);
--color-muted: oklch(0.96 0.005 265);
--color-muted-foreground: oklch(0.55 0.015 265);
--color-accent: oklch(0.96 0.005 265);
--color-accent-foreground: oklch(0.25 0.015 265);
--color-destructive: oklch(0.55 0.22 25);
--color-destructive-foreground: oklch(0.985 0 0);
--color-border: oklch(0.35 0.015 265);
--color-input: oklch(0.35 0.015 265);
--color-ring: oklch(0.6 0.15 250);
--color-border: oklch(0.87 0.005 265);
--color-input: oklch(0.87 0.005 265);
--color-ring: oklch(0.45 0.15 250);
--radius-sm: 0.25rem;
--radius-md: 0.375rem;
--radius-lg: 0.5rem;
Expand All @@ -38,26 +46,32 @@
font-family: system-ui, -apple-system, sans-serif;
}

/* Light mode — applied via .light class on <html> */
:root.light {
--color-background: oklch(0.985 0 0);
--color-foreground: oklch(0.145 0.015 265);
--color-card: oklch(0.985 0 0);
--color-card-foreground: oklch(0.145 0.015 265);
--color-popover: oklch(0.985 0 0);
--color-popover-foreground: oklch(0.145 0.015 265);
--color-primary: oklch(0.5 0.2 250);
/* Native UI (scrollbars, <select>, autofill, form controls) follows the theme. */
:root {
color-scheme: light;
}

/* Dark mode — applied via .dark class on <html> */
.dark {
color-scheme: dark;
--color-background: oklch(0.145 0.015 265);
--color-foreground: oklch(0.985 0 0);
--color-card: oklch(0.18 0.015 265);
--color-card-foreground: oklch(0.985 0 0);
--color-popover: oklch(0.18 0.015 265);
--color-popover-foreground: oklch(0.985 0 0);
--color-primary: oklch(0.55 0.2 250);
--color-primary-foreground: oklch(0.985 0 0);
--color-secondary: oklch(0.96 0.005 265);
--color-secondary-foreground: oklch(0.25 0.015 265);
--color-muted: oklch(0.96 0.005 265);
--color-muted-foreground: oklch(0.55 0.015 265);
--color-accent: oklch(0.96 0.005 265);
--color-accent-foreground: oklch(0.25 0.015 265);
--color-secondary: oklch(0.27 0.015 265);
--color-secondary-foreground: oklch(0.985 0 0);
--color-muted: oklch(0.27 0.015 265);
--color-muted-foreground: oklch(0.7 0.015 265);
--color-accent: oklch(0.27 0.015 265);
--color-accent-foreground: oklch(0.985 0 0);
--color-destructive: oklch(0.55 0.22 25);
--color-destructive-foreground: oklch(0.985 0 0);
--color-border: oklch(0.87 0.005 265);
--color-input: oklch(0.87 0.005 265);
--color-ring: oklch(0.45 0.15 250);
--color-border: oklch(0.35 0.015 265);
--color-input: oklch(0.35 0.015 265);
--color-ring: oklch(0.6 0.15 250);
}
}
18 changes: 12 additions & 6 deletions web/src/app.html
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Expand Up @@ -5,17 +5,23 @@
<meta name="viewport" content="width=device-width, initial-scale=1" />
<link rel="icon" href="data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'%3E%3Ctext y='.9em' font-size='90'%3E🛡️%3C/text%3E%3C/svg%3E" />
<script>
// Prevent flash of wrong theme — runs before page render
// Prevent flash of wrong theme — runs before page render.
// Mirrors the logic in src/lib/theme.ts: 'system' resolves via the
// OS preference, so we must NOT treat a stored 'system' value as a
// concrete dark choice (that caused a dark→light flash for
// system + light-OS users).
(function () {
try {
var stored = localStorage.getItem('rungu-theme');
var prefersLight = window.matchMedia('(prefers-color-scheme: light)').matches;
var isLight = stored ? stored === 'light' : prefersLight;
if (isLight) {
document.documentElement.classList.add('light');
var prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
var isDark =
stored === 'dark' ||
((!stored || stored === 'system') && prefersDark);
if (isDark) {
document.documentElement.classList.add('dark');
}
} catch (e) {
// localStorage unavailable (incognito, disabled) — default to dark
// localStorage unavailable (incognito, disabled) — follow OS only.
}
})();
</script>
Expand Down
59 changes: 22 additions & 37 deletions web/src/lib/components/ThemeToggle.svelte
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@@ -1,49 +1,34 @@
<script lang="ts">
import { Button } from '$lib/components/ui/button';
import { browser } from '$app/environment';

let {
theme = $bindable(
browser
? (() => {
try {
const saved = localStorage.getItem('rungu-theme');
if (saved === 'light' || saved === 'dark' || saved === 'system') return saved;
} catch {}
return 'system' as const;
})()
: 'system'
),
}: { theme?: 'light' | 'dark' | 'system' } = $props();
import {
getStoredTheme,
applyTheme,
setTheme,
cycleTheme,
watchSystemTheme,
type Theme,
} from '$lib/theme';

// Read the persisted theme once on the client; 'system' during SSR so the
// server-rendered markup matches the pre-hydration FOUC script output.
let theme = $state<Theme>(browser ? getStoredTheme() : 'system');

function cycle() {
const order: Array<'light' | 'dark' | 'system'> = ['light', 'dark', 'system'];
const idx = order.indexOf(theme);
theme = order[(idx + 1) % order.length];
applyTheme();
theme = cycleTheme(theme);
setTheme(theme);
}

function applyTheme() {
const root = document.documentElement;
const prefersLight = window.matchMedia('(prefers-color-scheme: light)').matches;

const isLight = theme === 'light' || (theme === 'system' && prefersLight);

if (isLight) {
root.classList.add('light');
} else {
root.classList.remove('light');
}

try {
localStorage.setItem('rungu-theme', theme);
} catch {
// localStorage unavailable
}
}
// Apply on mount and whenever the user changes modes.
$effect(() => {
applyTheme(theme);
});

// When following the OS, react to live changes without a reload.
$effect(() => {
applyTheme();
if (theme !== 'system') return;
const stop = watchSystemTheme(() => applyTheme('system'));
return stop;
});
</script>

Expand Down
192 changes: 192 additions & 0 deletions web/src/lib/theme.test.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,192 @@
import { describe, it, expect, beforeEach, vi, afterEach } from 'vitest';
import {
getStoredTheme,
resolveTheme,
cycleTheme,
applyTheme,
setTheme,
persistTheme,
watchSystemTheme,
THEME_STORAGE_KEY,
DARK_CLASS,
type Theme,
} from '$lib/theme';

// ── jsdom does not implement matchMedia; provide a controllable mock ──

let prefersDark = false;

function installMatchMedia() {
const listeners = new Set<(e: MediaQueryListEvent) => void>();
const mql = {
get matches() {
return prefersDark;
},
media: '(prefers-color-scheme: dark)',
onchange: null,
addEventListener: (_ev: string, cb: (e: MediaQueryListEvent) => void) =>
listeners.add(cb),
removeEventListener: (_ev: string, cb: (e: MediaQueryListEvent) => void) =>
listeners.delete(cb),
addListener: (cb: (e: MediaQueryListEvent) => void) => listeners.add(cb),
removeListener: (cb: (e: MediaQueryListEvent) => void) => listeners.delete(cb),
dispatchEvent: () => false,
};
vi.stubGlobal('matchMedia', () => mql);
return {
mql,
setPrefersDark(v: boolean) {
prefersDark = v;
},
emit() {
for (const cb of listeners) {
cb({ matches: prefersDark } as MediaQueryListEvent);
}
},
clear() {
listeners.clear();
},
};
}

describe('getStoredTheme', () => {
beforeEach(() => {
localStorage.clear();
prefersDark = false;
installMatchMedia();
});

it('defaults to system when nothing is stored', () => {
expect(getStoredTheme()).toBe('system');
});

it('returns a valid stored value', () => {
localStorage.setItem(THEME_STORAGE_KEY, 'dark');
expect(getStoredTheme()).toBe('dark');
});

it('falls back to system for an invalid value', () => {
localStorage.setItem(THEME_STORAGE_KEY, 'hot-pink');
expect(getStoredTheme()).toBe('system');
});
});

describe('resolveTheme', () => {
beforeEach(() => {
prefersDark = false;
installMatchMedia();
});

it('resolves explicit modes directly', () => {
expect(resolveTheme('light')).toBe('light');
expect(resolveTheme('dark')).toBe('dark');
});

it('resolves system via the OS preference (light)', () => {
prefersDark = false;
expect(resolveTheme('system')).toBe('light');
});

it('resolves system via the OS preference (dark)', () => {
prefersDark = true;
expect(resolveTheme('system')).toBe('dark');
});
});

describe('cycleTheme', () => {
it('cycles light → dark → system → light', () => {
expect(cycleTheme('light')).toBe('dark');
expect(cycleTheme('dark')).toBe('system');
expect(cycleTheme('system')).toBe('light');
});
});

describe('applyTheme / setTheme', () => {
beforeEach(() => {
document.documentElement.classList.remove(DARK_CLASS);
localStorage.clear();
prefersDark = false;
installMatchMedia();
});

it('adds the dark class for dark', () => {
applyTheme('dark');
expect(document.documentElement.classList.contains(DARK_CLASS)).toBe(true);
});

it('removes the dark class for light', () => {
document.documentElement.classList.add(DARK_CLASS);
applyTheme('light');
expect(document.documentElement.classList.contains(DARK_CLASS)).toBe(false);
});

it('resolves system against the OS preference', () => {
prefersDark = true;
applyTheme('system');
expect(document.documentElement.classList.contains(DARK_CLASS)).toBe(true);

prefersDark = false;
applyTheme('system');
expect(document.documentElement.classList.contains(DARK_CLASS)).toBe(false);
});

it('setTheme applies and persists', () => {
setTheme('dark');
expect(document.documentElement.classList.contains(DARK_CLASS)).toBe(true);
expect(localStorage.getItem(THEME_STORAGE_KEY)).toBe('dark');
});

it('persistTheme writes to localStorage', () => {
persistTheme('light');
expect(localStorage.getItem(THEME_STORAGE_KEY)).toBe('light');
});
});

describe('watchSystemTheme', () => {
let mock: ReturnType<typeof installMatchMedia>;

beforeEach(() => {
prefersDark = false;
mock = installMatchMedia();
});

afterEach(() => {
mock.clear();
vi.unstubAllGlobals();
});

it('invokes the callback with the resolved theme on OS change', () => {
const cb = vi.fn();
const stop = watchSystemTheme(cb);

prefersDark = true;
mock.emit();
expect(cb).toHaveBeenCalledWith('dark');

prefersDark = false;
mock.emit();
expect(cb).toHaveBeenCalledWith('light');

stop();
});

it('unsubscribe stops further callbacks', () => {
const cb = vi.fn();
const stop = watchSystemTheme(cb);
stop();
mock.emit();
expect(cb).not.toHaveBeenCalled();
});
});

describe('Theme type contract', () => {
it('exposes the expected storage key and class name', () => {
expect(THEME_STORAGE_KEY).toBe('rungu-theme');
expect(DARK_CLASS).toBe('dark');
});

it('Theme covers exactly the three modes', () => {
const themes: Theme[] = ['light', 'dark', 'system'];
expect(themes).toHaveLength(3);
});
});
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