"use client";

import { useState, useEffect } from 'react'
import { useTheme } from 'next-themes'

const themes = ['system', 'light', 'dark'] as const

const ThemeSwitch = () => {
  const [mounted, setMounted] = useState(false)
  const { theme, setTheme } = useTheme()

  useEffect(() => {
    setMounted(true)
  }, [])

  if (!mounted) return null

  const nextTheme = themes[(themes.indexOf(theme as (typeof themes)[number]) + 1) % themes.length]
  const next = () => setTheme(nextTheme)
  const label = `Theme: ${theme}. Click to switch to ${nextTheme}.`

  return (
    <button
      onClick={next}
      aria-label={label}
      title={label}
      style={{
        position: 'fixed',
        top: 'var(--space-4)',
        right: 'var(--space-4)',
        zIndex: 9999,
        background: 'var(--surface)',
        border: '1px solid var(--border)',
        borderRadius: 'var(--radius-md)',
        color: 'var(--fg-secondary)',
        cursor: 'pointer',
        padding: '8px',
        display: 'grid',
        placeItems: 'center',
        transition: `background var(--duration-fast) var(--ease-out),
                     border-color var(--duration-fast) var(--ease-out),
                     color var(--duration-fast) var(--ease-out)`,
      }}
      onMouseEnter={e => {
        e.currentTarget.style.background = 'var(--surface-hover)'
        e.currentTarget.style.borderColor = 'var(--border-strong)'
        e.currentTarget.style.color = 'var(--fg)'
      }}
      onMouseLeave={e => {
        e.currentTarget.style.background = 'var(--surface)'
        e.currentTarget.style.borderColor = 'var(--border)'
        e.currentTarget.style.color = 'var(--fg-secondary)'
      }}
    >
      <svg
        width="18"
        height="18"
        viewBox="0 0 24 24"
        fill="none"
        stroke="currentColor"
        strokeWidth="1.75"
        strokeLinecap="round"
        strokeLinejoin="round"
      >
        {theme === 'dark' ? (
          // Moon
          <path d="M21 12.79A9 9 0 1 1 11.21 3a7 7 0 0 0 9.79 9.79z" />
        ) : theme === 'light' ? (
          // Sun
          <>
            <circle cx="12" cy="12" r="5" />
            <line x1="12" y1="1" x2="12" y2="3" />
            <line x1="12" y1="21" x2="12" y2="23" />
            <line x1="4.22" y1="4.22" x2="5.64" y2="5.64" />
            <line x1="18.36" y1="18.36" x2="19.78" y2="19.78" />
            <line x1="1" y1="12" x2="3" y2="12" />
            <line x1="21" y1="12" x2="23" y2="12" />
            <line x1="4.22" y1="19.78" x2="5.64" y2="18.36" />
            <line x1="18.36" y1="5.64" x2="19.78" y2="4.22" />
          </>
        ) : (
          // Monitor (system)
          <>
            <rect x="2" y="3" width="20" height="14" rx="2" ry="2" />
            <line x1="8" y1="21" x2="16" y2="21" />
            <line x1="12" y1="17" x2="12" y2="21" />
          </>
        )}
      </svg>
    </button>
  )
}

export default ThemeSwitch