healthy-fit/frontend/src/context/ThemeContext.tsx

import React, { createContext, useContext, useEffect, useState, ReactNode } from 'react';

type Theme = 'light' | 'dark';

interface ThemeContextType {
    theme: Theme;
    toggleTheme: () => void;
}

// eslint-disable-next-line @typescript-eslint/no-explicit-any
const ThemeContext = createContext<ThemeContextType | undefined>(undefined);

export const ThemeProvider = ({ children }: { children: ReactNode }) => {
    const [theme, setTheme] = useState<Theme>(() => {
        // Check local storage or system preference
        const saved = localStorage.getItem('theme');
        if (saved === 'light' || saved === 'dark') {
            return saved;
        }
        return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
    });

    useEffect(() => {
        const root = window.document.documentElement;
        root.classList.remove('light', 'dark');
        root.classList.add(theme);
        localStorage.setItem('theme', theme);
    }, [theme]);

    const toggleTheme = () => {
        setTheme((prev) => (prev === 'light' ? 'dark' : 'light'));
    };

    return (
        <ThemeContext.Provider value={{ theme, toggleTheme }}>
            {children}
        </ThemeContext.Provider>
    );
};

export const useTheme = () => {
    const context = useContext(ThemeContext);
    if (!context) {
        throw new Error('useTheme must be used within a ThemeProvider');
    }
    return context;
};