111 lines
3.5 KiB
TypeScript
111 lines
3.5 KiB
TypeScript
import { createContext, useContext, useEffect, useState, type ReactNode } from 'react';
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/**
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* Themes: 'light' | 'dark' | 'system'
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* Persisted to localStorage under key 'bt-theme'.
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*
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* 'system' follows the device's `prefers-color-scheme` and updates live when the
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* OS flips. `resolvedTheme` is always the concrete 'light' | 'dark' actually
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* applied — consume it for anything that needs a real value (e.g. Sonner).
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*
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* Class mapping on document.documentElement:
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* light → (no classes) dark → 'dark'
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*/
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type Theme = 'light' | 'dark' | 'system';
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type ResolvedTheme = 'light' | 'dark';
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const STORAGE_KEY = 'bt-theme';
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const VALID_THEMES: Theme[] = ['light', 'dark', 'system'];
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const DEFAULT_THEME: Theme = 'dark';
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// Keep in sync with the inline pre-bundle script in index.html.
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const THEME_COLORS: Record<ResolvedTheme, string> = { light: '#ffffff', dark: '#18181b' };
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function systemPrefersDark(): boolean {
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return typeof window !== 'undefined' && !!window.matchMedia?.('(prefers-color-scheme: dark)').matches;
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}
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function resolveTheme(theme: Theme): ResolvedTheme {
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if (theme === 'system') return systemPrefersDark() ? 'dark' : 'light';
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return theme;
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}
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function applyTheme(theme: Theme): ResolvedTheme {
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const resolved = resolveTheme(theme);
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const root = document.documentElement;
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root.classList.toggle('dark', resolved === 'dark');
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const meta = document.querySelector('meta[name="theme-color"]');
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if (meta) meta.setAttribute('content', THEME_COLORS[resolved]);
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return resolved;
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}
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function loadStoredTheme(): Theme {
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try {
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const stored = localStorage.getItem(STORAGE_KEY);
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if (stored === 'dark-purple') return 'dark';
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if (stored && (VALID_THEMES as string[]).includes(stored)) return stored as Theme;
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} catch {
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// localStorage unavailable
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}
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return DEFAULT_THEME;
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}
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interface ThemeContextValue {
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theme: Theme;
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resolvedTheme: ResolvedTheme;
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setTheme: (theme: string) => void;
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}
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const ThemeContext = createContext<ThemeContextValue | null>(null);
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export function ThemeProvider({ children }: { children: ReactNode }) {
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const [theme, setThemeState] = useState<Theme>(() => {
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const stored = loadStoredTheme();
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// Apply immediately (before first paint) to avoid flash.
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applyTheme(stored);
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return stored;
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});
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const [resolvedTheme, setResolvedTheme] = useState<ResolvedTheme>(() => resolveTheme(loadStoredTheme()));
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const setTheme = (newTheme: string) => {
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if (!(VALID_THEMES as string[]).includes(newTheme)) return;
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const next = newTheme as Theme;
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setResolvedTheme(applyTheme(next));
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setThemeState(next);
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try {
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localStorage.setItem(STORAGE_KEY, next);
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} catch {
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// localStorage unavailable
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}
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};
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// Keep DOM in sync if theme state ever changes externally.
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useEffect(() => {
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setResolvedTheme(applyTheme(theme));
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}, [theme]);
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// While on 'system', re-apply live when the OS light/dark preference flips.
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useEffect(() => {
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if (theme !== 'system' || typeof window === 'undefined' || !window.matchMedia) return;
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const mq = window.matchMedia('(prefers-color-scheme: dark)');
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const onChange = () => setResolvedTheme(applyTheme('system'));
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mq.addEventListener('change', onChange);
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return () => mq.removeEventListener('change', onChange);
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}, [theme]);
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return (
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<ThemeContext.Provider value={{ theme, resolvedTheme, setTheme }}>
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{children}
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</ThemeContext.Provider>
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);
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}
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export function useTheme() {
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const ctx = useContext(ThemeContext);
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if (!ctx) {
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throw new Error('useTheme must be used within a ThemeProvider');
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}
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return ctx;
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}
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