marketing-app/client/src/contexts/ThemeContext.jsx

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

const ThemeContext = createContext()

export function ThemeProvider({ children }) {
  const [darkMode, setDarkMode] = useState(() => {
    // Check localStorage or system preference
    const stored = localStorage.getItem('darkMode')
    if (stored !== null) return stored === 'true'
    return window.matchMedia('(prefers-color-scheme: dark)').matches
  })

  useEffect(() => {
    // Apply dark mode class to document
    if (darkMode) {
      document.documentElement.classList.add('dark')
    } else {
      document.documentElement.classList.remove('dark')
    }
    localStorage.setItem('darkMode', String(darkMode))
  }, [darkMode])

  const toggleDarkMode = () => setDarkMode(prev => !prev)

  return (
    <ThemeContext.Provider value={{ darkMode, toggleDarkMode }}>
      {children}
    </ThemeContext.Provider>
  )
}

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