'use client';

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

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

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

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

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [theme, setTheme] = useState<Theme>(() => {
    if (typeof window !== 'undefined') {
      const savedTheme = localStorage.getItem('theme') as Theme | null;
      if (savedTheme) return savedTheme;
    }
    return 'system';
  });
  const [resolvedTheme, setResolvedTheme] = useState<'light' | 'dark'>(() => {
    if (typeof window !== 'undefined') {
      const savedTheme = localStorage.getItem('theme') as Theme | null;
      if (savedTheme === 'dark') return 'dark';
      if (savedTheme === 'light') return 'light';
      return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
    }
    return 'light';
  });
  const [mounted, setMounted] = useState(false);

  useEffect(() => {
    setMounted(true);
  }, []);

  useEffect(() => {
    if (!mounted) return;
    
    const root = window.document.documentElement;
    
    // Remove previous theme classes
    root.classList.remove('light', 'dark');

    let effectiveTheme: 'light' | 'dark';

    if (theme === 'system') {
      // Use system preference
      const systemTheme = window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
      effectiveTheme = systemTheme;
    } else {
      effectiveTheme = theme;
    }

    // Apply theme
    root.classList.add(effectiveTheme);
    setResolvedTheme(effectiveTheme);

    // Save to localStorage
    localStorage.setItem('theme', theme);
  }, [theme, mounted]);

  // Listen for system theme changes
  useEffect(() => {
    if (theme !== 'system') return;

    const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
    const handleChange = (e: MediaQueryListEvent) => {
      const root = window.document.documentElement;
      root.classList.remove('light', 'dark');
      const newTheme = e.matches ? 'dark' : 'light';
      root.classList.add(newTheme);
      setResolvedTheme(newTheme);
    };

    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 === undefined) {
    throw new Error('useTheme must be used within a ThemeProvider');
  }
  return context;
}