'use client'

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

type Theme = 'light' | 'dark'

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

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

export function ThemeProvider({ children }: { children: ReactNode }) {
  const [theme, setTheme] = useState<Theme>('light')
  const [ready, setReady] = useState(false)

  useEffect(() => {
    const stored = (localStorage.getItem('theme') as Theme) || 'light'
    setTheme(stored)
    setReady(true)
  }, [])

  useEffect(() => {
    if (!ready) return
    document.documentElement.classList.toggle('dark', theme === 'dark')
    localStorage.setItem('theme', theme)
  }, [theme, ready])

  const toggleTheme = () => setTheme((t) => (t === 'light' ? 'dark' : 'light'))

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

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