'use client'

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

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

interface ThemeContextType {
  theme: Theme
  resolvedTheme: 'light' | 'dark'
  setTheme: (theme: Theme) => void
  toggleTheme: () => void
}

const ThemeContext = createContext<ThemeContextType | undefined>(undefined)

export function useTheme() {
  const context = useContext(ThemeContext)
  if (!context) {
    // Return default values when not in provider (SSR/prerendering)
    return {
      theme: 'system' as const,
      resolvedTheme: 'light' as const,
      setTheme: () => {},
      toggleTheme: () => {},
    }
  }
  return context
}

interface ThemeProviderProps {
  children: ReactNode
  defaultTheme?: Theme
}

export function ThemeProvider({ children, defaultTheme = 'system' }: ThemeProviderProps) {
  const [theme, setThemeState] = useState<Theme>(defaultTheme)
  const [resolvedTheme, setResolvedTheme] = useState<'light' | 'dark'>('light')
  const [mounted, setMounted] = useState(false)

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

  useEffect(() => {
    if (!mounted) return

    const root = document.documentElement
    let resolved: 'light' | 'dark'

    if (theme === 'system') {
      resolved = window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light'
      root.removeAttribute('data-theme')
    } else {
      resolved = theme
      root.setAttribute('data-theme', theme)
    }

    setResolvedTheme(resolved)
  }, [theme, mounted])

  useEffect(() => {
    if (!mounted) return

    const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)')
    const handleChange = (e: MediaQueryListEvent) => {
      if (theme === 'system') {
        setResolvedTheme(e.matches ? 'dark' : 'light')
      }
    }

    mediaQuery.addEventListener('change', handleChange)
    return () => mediaQuery.removeEventListener('change', handleChange)
  }, [theme, mounted])

  const setTheme = (newTheme: Theme) => {
    setThemeState(newTheme)
    localStorage.setItem('theme', newTheme)
  }

  const toggleTheme = () => {
    const newTheme = resolvedTheme === 'light' ? 'dark' : 'light'
    setTheme(newTheme)
  }

  // Prevent hydration mismatch - render children without context until mounted
  if (!mounted) {
    return <>{children}</>
  }

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

// Theme toggle button component
export function ThemeToggle() {
  const { resolvedTheme, toggleTheme } = useTheme()

  return (
    <button
      onClick={toggleTheme}
      className="relative p-2 rounded-lg bg-gray-100 dark:bg-gray-800 hover:bg-gray-200 dark:hover:bg-gray-700 transition-all duration-200 group"
      style={{
        background: resolvedTheme === 'dark' ? 'var(--color-background-tertiary)' : 'var(--color-background-tertiary)',
      }}
      aria-label={resolvedTheme === 'dark' ? 'Switch to light mode' : 'Switch to dark mode'}
    >
      {/* Sun icon */}
      <svg
        className={`w-5 h-5 transition-all duration-300 ${
          resolvedTheme === 'dark' 
            ? 'opacity-0 rotate-90 scale-0' 
            : 'opacity-100 rotate-0 scale-100'
        }`}
        style={{ color: 'var(--color-foreground)', position: resolvedTheme === 'dark' ? 'absolute' : 'relative' }}
        fill="none"
        stroke="currentColor"
        viewBox="0 0 24 24"
      >
        <path
          strokeLinecap="round"
          strokeLinejoin="round"
          strokeWidth={2}
          d="M12 3v1m0 16v1m9-9h-1M4 12H3m15.364 6.364l-.707-.707M6.343 6.343l-.707-.707m12.728 0l-.707.707M6.343 17.657l-.707.707M16 12a4 4 0 11-8 0 4 4 0 018 0z"
        />
      </svg>
      {/* Moon icon */}
      <svg
        className={`w-5 h-5 transition-all duration-300 ${
          resolvedTheme === 'dark' 
            ? 'opacity-100 rotate-0 scale-100' 
            : 'opacity-0 -rotate-90 scale-0'
        }`}
        style={{ color: 'var(--color-foreground)', position: resolvedTheme === 'light' ? 'absolute' : 'relative' }}
        fill="none"
        stroke="currentColor"
        viewBox="0 0 24 24"
      >
        <path
          strokeLinecap="round"
          strokeLinejoin="round"
          strokeWidth={2}
          d="M20.354 15.354A9 9 0 018.646 3.646 9.003 9.003 0 0012 21a9.003 9.003 0 008.354-5.646z"
        />
      </svg>
    </button>
  )
}