'use client';

import { createContext, useCallback, useContext, useEffect, useMemo, useState, type ReactNode } from 'react';
import type { ThemeMode } from '@nextcraft/types';

interface ThemeContextValue {
  mode: ThemeMode;
  toggle: () => void;
  setMode: (mode: ThemeMode) => void;
}

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

export function ThemeProvider({ children }: { children: ReactNode }) {
  const [mode, setModeState] = useState<ThemeMode>('light');

  useEffect(() => {
    const stored = typeof window !== 'undefined' ? window.localStorage.getItem('nextcraft-theme') : null;
    const prefersDark =
      typeof window !== 'undefined' && window.matchMedia('(prefers-color-scheme: dark)').matches;
    const initial: ThemeMode = stored === 'dark' || stored === 'light' ? stored : prefersDark ? 'dark' : 'light';
    setModeState(initial);
  }, []);

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

  const setMode = useCallback((m: ThemeMode) => setModeState(m), []);
  const toggle = useCallback(() => setModeState((m) => (m === 'dark' ? 'light' : 'dark')), []);

  const value = useMemo(() => ({ mode, toggle, setMode }), [mode, toggle, setMode]);
  return <ThemeContext.Provider value={value}>{children}</ThemeContext.Provider>;
}

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