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

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

interface ThemeContextType {
  theme: Theme
  setTheme: (t: Theme) => void
  resolvedTheme: 'light' | 'dark'
}

const ThemeContext = createContext<ThemeContextType>({
  theme: 'system',
  setTheme: () => {},
  resolvedTheme: 'light',
})

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [theme, setThemeState] = useState<Theme>('system')
  const [resolvedTheme, setResolvedTheme] = useState<'light' | 'dark'>('light')

  useEffect(() => {
    const stored = localStorage.getItem('theme') as Theme | null
    if (stored) setThemeState(stored)
  }, [])

  useEffect(() => {
    const root = document.documentElement
    const mq = window.matchMedia('(prefers-color-scheme: dark)')

    const apply = () => {
      const resolved = theme === 'system' ? (mq.matches ? 'dark' : 'light') : theme
      setResolvedTheme(resolved)
      root.classList.toggle('dark', resolved === 'dark')
    }

    apply()
    mq.addEventListener('change', apply)
    return () => mq.removeEventListener('change', apply)
  }, [theme])

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

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

export const useTheme = () => useContext(ThemeContext)