83 lines
2.0 KiB
TypeScript
83 lines
2.0 KiB
TypeScript
import { createContext, useContext, useEffect, useState, type ReactNode } from 'react';
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/**
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* Themes: 'light' | 'dark'
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* Persisted to localStorage under key 'bt-theme'.
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*
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* Class mapping on document.documentElement:
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* light → (no classes)
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* dark → 'dark'
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*/
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type Theme = 'light' | 'dark';
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const STORAGE_KEY = 'bt-theme';
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const VALID_THEMES: Theme[] = ['light', 'dark'];
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const DEFAULT_THEME: Theme = 'dark';
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function applyTheme(theme: Theme) {
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const root = document.documentElement;
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root.classList.remove('dark');
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if (theme === 'dark') {
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root.classList.add('dark');
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}
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// 'light' → no classes
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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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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 setTheme = (newTheme: string) => {
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if (!(VALID_THEMES as string[]).includes(newTheme)) return;
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applyTheme(newTheme as Theme);
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setThemeState(newTheme as Theme);
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try {
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localStorage.setItem(STORAGE_KEY, newTheme);
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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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applyTheme(theme);
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}, [theme]);
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return (
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<ThemeContext.Provider value={{ theme, 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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