'use client';

import { useState, useEffect, useCallback } from 'react';
import { Menu, X } from 'lucide-react';
import { motion, AnimatePresence } from 'framer-motion';
import { Button } from '@/components/ui/button';
import { COMPANY_INFO, NAVIGATION } from '@/lib/constants';

export function Header() {
  const [isOpen, setIsOpen] = useState(false);
  const [activeSection, setActiveSection] = useState('home');
  const [isScrolled, setIsScrolled] = useState(false);

  const handleNavClick = useCallback((e: React.MouseEvent<HTMLAnchorElement>, href: string) => {
    e.preventDefault();
    const targetId = href.replace('#', '');
    const element = document.getElementById(targetId);
    
    if (element) {
      const headerOffset = 64;
      const elementPosition = element.getBoundingClientRect().top;
      const offsetPosition = elementPosition + window.pageYOffset - headerOffset;

      window.scrollTo({
        top: offsetPosition,
        behavior: 'smooth'
      });
      
      setActiveSection(targetId);
      setIsOpen(false);
    }
  }, []);

  useEffect(() => {
    const handleScroll = () => {
      setIsScrolled(window.scrollY > 20);

      const sections = NAVIGATION.map(item => item.href.replace('#', ''));
      const scrollPosition = window.scrollY + 100;

      for (let i = sections.length - 1; i >= 0; i--) {
        const section = document.getElementById(sections[i]);
        if (section) {
          const sectionTop = section.offsetTop;
          if (scrollPosition >= sectionTop) {
            setActiveSection(sections[i]);
            break;
          }
        }
      }
    };

    window.addEventListener('scroll', handleScroll, { passive: true });
    handleScroll();

    return () => window.removeEventListener('scroll', handleScroll);
  }, []);

  return (
    <>
      <header 
        className={`
          fixed top-0 left-0 right-0 z-50
          transition-all duration-300 ease-out
          ${isScrolled 
            ? 'bg-white/95 backdrop-blur-xl border-b border-[#E2E8F0] shadow-sm' 
            : 'bg-transparent'
          }
        `}
      >
        <div className="container-wide">
          <div className="flex items-center justify-between h-16">
            <a 
              href="#home" 
              onClick={(e) => handleNavClick(e, '#home')}
              className="flex items-center group"
            >
              <img 
                src="/logo.svg" 
                alt={COMPANY_INFO.name}
                className="h-8 w-auto transition-transform duration-200 group-hover:scale-105"
              />
            </a>

            <nav className="hidden md:flex items-center gap-1">
              {NAVIGATION.map((item) => (
                <a
                  key={item.id}
                  href={item.href}
                  onClick={(e) => handleNavClick(e, item.href)}
                  className={`
                    relative px-3 py-1.5 text-sm font-medium
                    transition-all duration-300
                    ${activeSection === item.id.replace('#', '')
                      ? 'text-[#005EB8]'
                      : 'text-[#4A5568] hover:text-[#005EB8]'
                    }
                  `}
                >
                  {item.label}
                  {activeSection === item.id.replace('#', '') && (
                    <motion.span 
                      layoutId="activeNav"
                      className="absolute bottom-0 left-1/2 -translate-x-1/2 w-6 h-0.5 bg-[#005EB8] rounded-full"
                      transition={{ type: "spring", stiffness: 380, damping: 30 }}
                    />
                  )}
                </a>
              ))}
            </nav>

            <div className="hidden md:flex items-center gap-3">
              <Button 
                variant="ghost"
                size="sm"
                onClick={(e) => {
                  const element = document.getElementById('contact');
                  if (element) {
                    element.scrollIntoView({ behavior: 'smooth' });
                  }
                }}
              >
                联系我们
              </Button>
              <Button 
                size="sm"
                onClick={(e) => {
                  const element = document.getElementById('about');
                  if (element) {
                    element.scrollIntoView({ behavior: 'smooth' });
                  }
                }}
              >
                了解更多
              </Button>
            </div>

            <button
              className="md:hidden p-2 -mr-2 text-[#4A5568] hover:text-[#005EB8] transition-colors"
              onClick={() => setIsOpen(!isOpen)}
            >
              {isOpen ? <X className="w-5 h-5" /> : <Menu className="w-5 h-5" />}
            </button>
          </div>
        </div>
      </header>

      <AnimatePresence>
        {isOpen && (
          <motion.div 
            initial={{ opacity: 0 }}
            animate={{ opacity: 1 }}
            exit={{ opacity: 0 }}
            className="fixed inset-0 z-40 md:hidden"
          >
            <div 
              className="absolute inset-0 bg-black/20 backdrop-blur-sm"
              onClick={() => setIsOpen(false)}
            />
            <motion.div 
              initial={{ y: -20, opacity: 0 }}
              animate={{ y: 0, opacity: 1 }}
              exit={{ y: -20, opacity: 0 }}
              transition={{ type: "spring", stiffness: 300, damping: 30 }}
              className="absolute top-16 left-0 right-0 bg-white/95 backdrop-blur-xl border-b border-[#E2E8F0] shadow-lg"
            >
              <nav className="container-wide py-4">
                {NAVIGATION.map((item, index) => (
                  <motion.a
                    key={item.id}
                    href={item.href}
                    onClick={(e) => handleNavClick(e, item.href)}
                    initial={{ x: -20, opacity: 0 }}
                    animate={{ x: 0, opacity: 1 }}
                    transition={{ delay: index * 0.05 }}
                    className={`
                      block px-4 py-3 text-base font-medium
                      transition-all duration-300
                      border-l-2
                      ${activeSection === item.id.replace('#', '')
                        ? 'text-[#005EB8] border-[#005EB8] bg-[#E8F4FD]'
                        : 'text-[#4A5568] border-transparent hover:text-[#005EB8] hover:bg-[#F5F7FA]'
                      }
                    `}
                  >
                    {item.label}
                  </motion.a>
                ))}
                <div className="mt-4 px-4 pt-4 border-t border-[#E2E8F0] space-y-3">
                  <Button 
                    className="w-full"
                    onClick={() => {
                      const element = document.getElementById('contact');
                      if (element) {
                        element.scrollIntoView({ behavior: 'smooth' });
                      }
                      setIsOpen(false);
                    }}
                  >
                    联系我们
                  </Button>
                </div>
              </nav>
            </motion.div>
          </motion.div>
        )}
      </AnimatePresence>
    </>
  );
}
