'use client'

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

type Theme = 'light' | 'dark'

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

const ThemeContext = createContext<ThemeContextValue>({
  theme: 'light',
  toggle: () => {},
})

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

  useEffect(() => {
    const saved = localStorage.getItem('mp-theme') as Theme | null
    const initial = saved ?? 'light'
    setTheme(initial)
    applyTheme(initial)
  }, [])

  function applyTheme(t: Theme) {
    const root = document.documentElement
    if (t === 'dark') {
      root.classList.add('dark')
    } else {
      root.classList.remove('dark')
    }
  }

  function toggle() {
    setTheme((prev) => {
      const next: Theme = prev === 'light' ? 'dark' : 'light'
      localStorage.setItem('mp-theme', next)
      applyTheme(next)
      return next
    })
  }

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

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