'use client';

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

type Theme = 'light' | 'dark' | 'system';

interface ThemeContextValue {
    theme: Theme;
    setTheme: (theme: Theme) => void;
    resolvedTheme: 'light' | 'dark';
}

const ThemeContext = createContext<ThemeContextValue | undefined>(undefined);

export function ThemeProvider({ children }: { children: ReactNode }) {
    const [theme, setTheme] = useState<Theme>('system');
    const [resolvedTheme, setResolvedTheme] = useState<'light' | 'dark'>('light');

    useEffect(() => {
        // Load theme from localStorage
        const stored = localStorage.getItem('gcx-fshs-theme') as Theme;
        if (stored) {
            setTheme(stored);
        }
    }, []);

    useEffect(() => {
        // Determine resolved theme
        let resolved: 'light' | 'dark' = 'light';

        if (theme === 'system') {
            resolved = window.matchMedia('(prefers-color-scheme: dark)').matches
                ? 'dark'
                : 'light';
        } else {
            resolved = theme;
        }

        setResolvedTheme(resolved);

        // Apply to document
        const root = document.documentElement;
        root.classList.remove('light', 'dark');
        root.classList.add(resolved);

        // Save to localStorage
        localStorage.setItem('gcx-fshs-theme', theme);
    }, [theme]);

    // Listen for system theme changes
    useEffect(() => {
        const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
        const handleChange = () => {
            if (theme === 'system') {
                setResolvedTheme(mediaQuery.matches ? 'dark' : 'light');
            }
        };

        mediaQuery.addEventListener('change', handleChange);
        return () => mediaQuery.removeEventListener('change', handleChange);
    }, [theme]);

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

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