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"use client";
import styles from "./switch.module.css";
import { memo, useEffect, useState } from "react";
declare global {
var updateDOM: () => void;
}
type ColorSchemePreference = "system" | "dark" | "light";
const STORAGE_KEY = "nextjs-blog-starter-theme";
const modes: ColorSchemePreference[] = ["system", "dark", "light"];
/** to reuse updateDOM function defined inside injected script */
/** function to be injected in script tag for avoiding FOUC (Flash of Unstyled Content) */
export const NoFOUCScript = (storageKey: string) => {
/* can not use outside constants or function as this script will be injected in a different context */
const [SYSTEM, DARK, LIGHT] = ["system", "dark", "light"];
/** Modify transition globally to avoid patched transitions */
const modifyTransition = () => {
const css = document.createElement("style");
css.textContent = "*,*:after,*:before{transition:none !important;}";
document.head.appendChild(css);
return () => {
/* Force restyle */
getComputedStyle(document.body);
/* Wait for next tick before removing */
setTimeout(() => document.head.removeChild(css), 1);
};
};
const media = matchMedia(`(prefers-color-scheme: ${DARK})`);
/** function to add remove dark class */
window.updateDOM = () => {
const restoreTransitions = modifyTransition();
const mode = localStorage.getItem(storageKey) ?? SYSTEM;
const systemMode = media.matches ? DARK : LIGHT;
const resolvedMode = mode === SYSTEM ? systemMode : mode;
const classList = document.documentElement.classList;
if (resolvedMode === DARK) classList.add(DARK);
else classList.remove(DARK);
document.documentElement.setAttribute("data-mode", mode);
restoreTransitions();
};
window.updateDOM();
media.addEventListener("change", window.updateDOM);
};
let updateDOM: () => void;
/**
* Switch button to quickly toggle user preference.
*/
const Switch = () => {
const [mode, setMode] = useState<ColorSchemePreference>(
() =>
((typeof localStorage !== "undefined" &&
localStorage.getItem(STORAGE_KEY)) ??
"system") as ColorSchemePreference,
);
useEffect(() => {
// store global functions to local variables to avoid any interference
updateDOM = window.updateDOM;
/** Sync the tabs */
addEventListener("storage", (e: StorageEvent): void => {
e.key === STORAGE_KEY && setMode(e.newValue as ColorSchemePreference);
});
}, []);
useEffect(() => {
localStorage.setItem(STORAGE_KEY, mode);
updateDOM();
}, [mode]);
/** toggle mode */
const handleModeSwitch = () => {
const index = modes.indexOf(mode);
setMode(modes[(index + 1) % modes.length]);
};
return (
<button
suppressHydrationWarning
className={styles.switch}
onClick={handleModeSwitch}
/>
);
};
const Script = memo(() => (
<script
dangerouslySetInnerHTML={{
__html: `(${NoFOUCScript.toString()})('${STORAGE_KEY}')`,
}}
/>
));
/**
* This component wich applies classes and transitions.
*/
export const ThemeSwitcher = () => {
return (
);
};
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