'use client';

import { useState, useEffect } from 'react';
import { motion, AnimatePresence } from 'framer-motion';

export default function ScrollToTop() {
  const [showScrollTop, setShowScrollTop] = useState(false);

  useEffect(() => {
    let ticking = false;
    
    const handleScroll = () => {
      if (!ticking) {
        window.requestAnimationFrame(() => {
          const currentScrollY = window.scrollY;
          // 显示返回顶部按钮（滚动超过300px）
          setShowScrollTop(currentScrollY > 300);
          ticking = false;
        });
        ticking = true;
      }
    };

    window.addEventListener('scroll', handleScroll, { passive: true });
    return () => window.removeEventListener('scroll', handleScroll);
  }, []);

  const scrollToTop = () => {
    window.scrollTo({
      top: 0,
      behavior: 'smooth'
    });
  };

  return (
    <AnimatePresence>
      {showScrollTop && (
        <motion.button
          initial={{ opacity: 0, scale: 0.8, y: 20 }}
          animate={{ opacity: 1, scale: 1, y: 0 }}
          exit={{ opacity: 0, scale: 0.8, y: 20 }}
          transition={{ duration: 0.2, ease: 'easeOut' }}
          onClick={scrollToTop}
          className="fixed bottom-6 right-6 w-12 h-12 bg-gradient-to-br from-orange-500 to-orange-600 hover:from-orange-600 hover:to-orange-700 text-white rounded-full shadow-lg hover:shadow-xl transition-all duration-200 flex items-center justify-center z-40 group"
          whileHover={{ scale: 1.1, y: -2 }}
          whileTap={{ scale: 0.9 }}
        >
          <svg 
            className="w-5 h-5 transition-transform duration-200 group-hover:-translate-y-0.5" 
            fill="none" 
            stroke="currentColor" 
            viewBox="0 0 24 24"
          >
            <path 
              strokeLinecap="round" 
              strokeLinejoin="round" 
              strokeWidth={2} 
              d="M5 10l7-7m0 0l7 7m-7-7v18" 
            />
          </svg>
        </motion.button>
      )}
    </AnimatePresence>
  );
}