/**
 * iOS 虚拟键盘处理 Hook
 *
 * iOS Safari 键盘弹起时 window.innerHeight 不变，
 * 需用 visualViewport.height 来检测实际可用高度。
 * Android 键盘弹起会直接 resize viewport，CSS 自动处理。
 */
import { useState, useEffect } from 'react';

export function useVirtualKeyboard() {
  const [keyboardHeight, setKeyboardHeight] = useState(0);

  useEffect(() => {
    const viewport = window.visualViewport;
    if (!viewport) return;

    const handler = () => {
      const kh = Math.max(0, window.innerHeight - viewport.height - viewport.offsetTop);
      setKeyboardHeight(kh);
    };

    viewport.addEventListener('resize', handler);
    viewport.addEventListener('scroll', handler);

    return () => {
      viewport.removeEventListener('resize', handler);
      viewport.removeEventListener('scroll', handler);
    };
  }, []);

  return { keyboardHeight };
}