'use client';

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

type Theme = 'dark' | 'light';

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

const ThemeContext = createContext<ThemeContextType>({
  theme: 'dark',
  setTheme: () => {},
  toggleTheme: () => {},
});

export function ThemeProvider({ children }: { children: ReactNode }) {
  const [theme, setThemeState] = useState<Theme>('dark');

  useEffect(() => {
    const saved = localStorage.getItem('once-theme') as Theme | null;
    if (saved && ['dark', 'light'].includes(saved)) {
      setThemeState(saved);
      return;
    }
    // Auto-detect from system preference
    if (window.matchMedia('(prefers-color-scheme: light)').matches) {
      setThemeState('light');
    }
  }, []);

  const setTheme = (t: Theme) => {
    setThemeState(t);
    localStorage.setItem('once-theme', t);
  };

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

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

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

export function useTheme() {
  return useContext(ThemeContext);
}