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pulsenode/components/layout/ThemeToggle.tsx
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"use client";
import { useEffect, useState } from "react";
const STORAGE_KEY = "pulsenode-theme";
export function ThemeToggle() {
const [theme, setTheme] = useState<"dark" | "light" | null>(null);
useEffect(() => {
// One-time read of browser-only state (DOM attribute set by the anti-FOUC
// inline script, or the OS color-scheme preference) to resolve the theme
// React couldn't know during SSR. Not a case of syncing to external state
// that changes over time, so a single setState here is the right call.
const attr = document.documentElement.dataset.theme;
if (attr === "light" || attr === "dark") {
// eslint-disable-next-line react-hooks/set-state-in-effect
setTheme(attr);
return;
}
const prefersLight = window.matchMedia("(prefers-color-scheme: light)").matches;
setTheme(prefersLight ? "light" : "dark");
}, []);
function toggle() {
const next = theme === "light" ? "dark" : "light";
setTheme(next);
document.documentElement.dataset.theme = next;
try {
localStorage.setItem(STORAGE_KEY, next);
} catch {
// private browsing or storage disabled; toggle still works for this session
}
}
if (theme === null) {
return <div className="h-7 w-16 rounded-[var(--radius-widget)] border border-border bg-surface" />;
}
return (
<button
type="button"
onClick={toggle}
className="rounded-[var(--radius-widget)] border border-border bg-surface px-3 py-1.5 text-xs text-fg-muted transition-colors hover:text-fg"
aria-label="Toggle color theme"
>
{theme === "light" ? "Light" : "Dark"}
</button>
);
}