import React, { forwardRef, useState, useEffect, useCallback } from 'react';
import { clsx } from 'clsx';
import { Link } from 'react-router-dom';
import { useTranslation } from 'react-i18next';
import { Button, ThemeToggle } from '../../ui';
import { CompactLanguageSelector } from '../../ui/LanguageSelector';
import { getRegisterUrl, getLoginUrl } from '../../../utils/navigation';
import { X } from 'lucide-react';

export interface PublicHeaderProps {
  className?: string;
  /**
   * Custom logo component
   */
  logo?: React.ReactNode;
  /**
   * Show theme toggle
   */
  showThemeToggle?: boolean;
  /**
   * Show authentication buttons (login/register)
   */
  showAuthButtons?: boolean;
  /**
   * Show language selector
   */
  showLanguageSelector?: boolean;
  /**
   * Custom navigation items
   */
  navigationItems?: Array<{
    id: string;
    label: string;
    href: string;
    external?: boolean;
  }>;
  /**
   * Header variant
   */
  variant?: 'default' | 'transparent' | 'minimal';
}

export interface PublicHeaderRef {
  scrollIntoView: () => void;
}

/**
 * PublicHeader - Header component for public pages (landing, login, register)
 * 
 * Features:
 * - Clean, minimal design suitable for public pages
 * - Integrated theme toggle for consistent theming
 * - Authentication buttons (login/register)
 * - Optional custom navigation items
 * - Multiple visual variants
 * - Responsive design with mobile optimization
 * - Accessible navigation structure
 */
export const PublicHeader = forwardRef<PublicHeaderRef, PublicHeaderProps>(({
  className,
  logo,
  showThemeToggle = true,
  showAuthButtons = true,
  showLanguageSelector = true,
  navigationItems = [],
  variant = 'default',
}, ref) => {
  const { t } = useTranslation();
  const headerRef = React.useRef<HTMLDivElement>(null);

  // State for mobile menu
  const [isMobileMenuOpen, setIsMobileMenuOpen] = useState(false);

  // State for sticky header
  const [isScrolled, setIsScrolled] = useState(false);

  // State for active section
  const [activeSection, setActiveSection] = useState<string>('');

  // Default navigation items
  const defaultNavItems: Array<{id: string; label: string; href: string; external?: boolean}> = [
    { id: 'home', label: t('common:nav.home', 'Inicio'), href: '/' },
    { id: 'features', label: t('common:nav.features', 'Funcionalidades'), href: '/features' },
    { id: 'about', label: t('common:nav.about', 'Nosotros'), href: '/about' },
    { id: 'contact', label: t('common:nav.contact', 'Contacto'), href: '/help/support' }
  ];

  const navItems = navigationItems.length > 0 ? navigationItems : defaultNavItems;

  // Smooth scroll to section
  const scrollToSection = useCallback((href: string) => {
    if (href.startsWith('#')) {
      const element = document.querySelector(href);
      if (element) {
        const headerHeight = headerRef.current?.offsetHeight || 0;
        const elementPosition = element.getBoundingClientRect().top + window.pageYOffset;
        const offsetPosition = elementPosition - headerHeight - 20; // 20px additional offset

        window.scrollTo({
          top: offsetPosition,
          behavior: 'smooth'
        });

        // Update URL hash
        window.history.pushState(null, '', href);

        // Close mobile menu
        setIsMobileMenuOpen(false);
      }
    }
  }, []);

  // Handle scroll for sticky header
  useEffect(() => {
    const handleScroll = () => {
      setIsScrolled(window.scrollY > 20);
    };

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

  // Active section detection with Intersection Observer
  useEffect(() => {
    const observerOptions = {
      rootMargin: '-100px 0px -66%',
      threshold: 0
    };

    const observerCallback = (entries: IntersectionObserverEntry[]) => {
      entries.forEach((entry) => {
        if (entry.isIntersecting) {
          const id = entry.target.getAttribute('id');
          if (id) {
            setActiveSection(id);
          }
        }
      });
    };

    const observer = new IntersectionObserver(observerCallback, observerOptions);

    // Observe all sections that are navigation targets
    navItems.forEach(item => {
      if (item.href.startsWith('#')) {
        const element = document.querySelector(item.href);
        if (element) {
          observer.observe(element);
        }
      }
    });

    return () => observer.disconnect();
  }, [navItems]);

  // Close mobile menu on ESC key
  useEffect(() => {
    const handleEscape = (e: KeyboardEvent) => {
      if (e.key === 'Escape' && isMobileMenuOpen) {
        setIsMobileMenuOpen(false);
      }
    };

    document.addEventListener('keydown', handleEscape);
    return () => document.removeEventListener('keydown', handleEscape);
  }, [isMobileMenuOpen]);

  // Prevent body scroll when mobile menu is open
  useEffect(() => {
    if (isMobileMenuOpen) {
      document.body.style.overflow = 'hidden';
    } else {
      document.body.style.overflow = '';
    }

    return () => {
      document.body.style.overflow = '';
    };
  }, [isMobileMenuOpen]);

  // Scroll into view
  const scrollIntoView = useCallback(() => {
    headerRef.current?.scrollIntoView({ behavior: 'smooth', block: 'start' });
  }, []);

  // Expose ref methods
  React.useImperativeHandle(ref, () => ({
    scrollIntoView,
  }), [scrollIntoView]);

  // Render navigation link with improved styles and active state
  const renderNavLink = (item: typeof navItems[0], isMobile = false) => {
    const isActive = activeSection === item.id || (item.href.startsWith('#') && item.href === `#${activeSection}`);

    const linkContent = (
      <span className={clsx(
        "relative text-sm font-medium transition-all duration-200",
        isMobile ? "text-base py-1" : "",
        isActive
          ? "text-[var(--color-primary)]"
          : "text-[var(--text-secondary)] hover:text-[var(--text-primary)]",
        // Animated underline on hover
        !isMobile && "after:content-[''] after:absolute after:bottom-[-4px] after:left-0 after:w-0 after:h-[2px] after:bg-[var(--color-primary)] after:transition-all after:duration-300 hover:after:w-full",
        // Active state indicator
        isActive && !isMobile && "after:w-full"
      )}>
        {item.label}
      </span>
    );

    if (item.href.startsWith('#')) {
      return (
        <a
          key={item.id}
          href={item.href}
          onClick={(e) => {
            e.preventDefault();
            scrollToSection(item.href);
          }}
          className={clsx(
            "focus:outline-none focus:ring-2 focus:ring-[var(--color-primary)] focus:ring-offset-2 rounded-sm",
            isMobile && "block w-full py-3 px-4 hover:bg-[var(--bg-secondary)] transition-colors"
          )}
          aria-current={isActive ? 'page' : undefined}
        >
          {linkContent}
        </a>
      );
    }

    if (item.external || item.href.startsWith('http')) {
      return (
        <a
          key={item.id}
          href={item.href}
          target={item.external ? '_blank' : undefined}
          rel={item.external ? 'noopener noreferrer' : undefined}
          className={clsx(
            "focus:outline-none focus:ring-2 focus:ring-[var(--color-primary)] focus:ring-offset-2 rounded-sm",
            isMobile && "block w-full py-3 px-4 hover:bg-[var(--bg-secondary)] transition-colors"
          )}
        >
          {linkContent}
        </a>
      );
    }

    return (
      <Link
        key={item.id}
        to={item.href}
        className={clsx(
          "focus:outline-none focus:ring-2 focus:ring-[var(--color-primary)] focus:ring-offset-2 rounded-sm",
          isMobile && "block w-full py-3 px-4 hover:bg-[var(--bg-secondary)] transition-colors"
        )}
      >
        {linkContent}
      </Link>
    );
  };

  return (
    <>
      {/* Skip to main content link for accessibility */}
      <a
        href="#main-content"
        className="sr-only focus:not-sr-only focus:absolute focus:z-50 focus:top-4 focus:left-4 focus:px-4 focus:py-2 focus:bg-[var(--color-primary)] focus:text-white focus:rounded-md"
      >
        {t('common:header.skip_to_content', 'Saltar al contenido principal')}
      </a>

      <header
        ref={headerRef}
        className={clsx(
          'w-full transition-all duration-300',
          // Sticky header
          'fixed top-0 left-0 right-0 z-40',
          // Base styles with scroll effect
          variant === 'default' && [
            isScrolled
              ? 'bg-[var(--bg-primary)]/95 backdrop-blur-md border-b border-[var(--border-primary)] shadow-lg'
              : 'bg-[var(--bg-primary)] border-b border-[var(--border-primary)] shadow-sm'
          ],
          variant === 'transparent' && [
            isScrolled
              ? 'bg-[var(--bg-primary)]/95 backdrop-blur-md shadow-lg'
              : 'bg-transparent'
          ],
          variant === 'minimal' && 'bg-[var(--bg-primary)]',
          className
        )}
        role="banner"
        aria-label="Navegación principal"
      >
        <div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8">
          <div className={clsx(
            "flex justify-between items-center transition-all duration-300",
            isScrolled ? "py-3 lg:py-4" : "py-4 lg:py-6"
          )}>
          {/* Logo and brand */}
          <div className="flex items-center gap-3 min-w-0">
            <Link to="/" className="flex items-center gap-3 hover:opacity-80 transition-opacity">
              {logo || (
                <>
                  <div className="w-8 h-8 bg-gradient-to-br from-[var(--color-primary)] to-[var(--color-primary-dark)] rounded-lg flex items-center justify-center text-white font-bold text-sm">
                    PI
                  </div>
                  <h1 className="text-xl lg:text-2xl font-bold text-[var(--text-primary)]">
                    Panadería IA
                  </h1>
                </>
              )}
            </Link>
          </div>

          {/* Desktop navigation */}
          <nav className="hidden md:flex items-center space-x-8" role="navigation">
            {navItems.map((item) => renderNavLink(item, false))}
          </nav>

          {/* Right side actions */}
          <div className="flex items-center gap-2 lg:gap-3">
            {/* Language selector - More compact */}
            {showLanguageSelector && (
              <div className="hidden sm:flex">
                <CompactLanguageSelector className="w-[70px]" />
              </div>
            )}

            {/* Theme toggle */}
            {showThemeToggle && (
              <ThemeToggle
                variant="button"
                size="md"
                className="hidden sm:flex"
              />
            )}

            {/* Authentication buttons - Enhanced */}
            {showAuthButtons && (
              <div className="flex items-center gap-2 lg:gap-3">
                <Link to={getLoginUrl()}>
                  <Button
                    variant="ghost"
                    size="md"
                    className="hidden sm:inline-flex font-medium hover:bg-[var(--bg-secondary)] transition-all duration-200"
                  >
                    {t('common:header.login')}
                  </Button>
                </Link>
                <Link to={getRegisterUrl()}>
                  <Button
                    size="md"
                    className="bg-gradient-to-r from-[var(--color-primary)] to-[var(--color-primary-dark)] hover:opacity-90 text-white font-semibold shadow-lg hover:shadow-xl transition-all duration-200 px-6"
                  >
                    <span className="hidden sm:inline">{t('common:header.start_free')}</span>
                    <span className="sm:hidden">{t('common:header.register')}</span>
                  </Button>
                </Link>
              </div>
            )}

            {/* Mobile theme toggle */}
            {showThemeToggle && (
              <ThemeToggle
                variant="button"
                size="sm"
                className="sm:hidden"
              />
            )}

            {/* Mobile menu button */}
            <div className="md:hidden">
              <Button
                variant="ghost"
                size="sm"
                className="p-2 min-h-[44px] min-w-[44px]"
                aria-label={isMobileMenuOpen ? t('common:header.close_menu', 'Cerrar menú') : t('common:header.open_menu', 'Abrir menú')}
                aria-expanded={isMobileMenuOpen}
                aria-controls="mobile-menu"
                onClick={() => setIsMobileMenuOpen(!isMobileMenuOpen)}
              >
                <svg
                  className={clsx("w-6 h-6 transition-transform duration-300", isMobileMenuOpen && "rotate-90")}
                  fill="none"
                  stroke="currentColor"
                  viewBox="0 0 24 24"
                >
                  {isMobileMenuOpen ? (
                    <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M6 18L18 6M6 6l12 12" />
                  ) : (
                    <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M4 6h16M4 12h16M4 18h16" />
                  )}
                </svg>
              </Button>
            </div>
          </div>
          </div>
        </div>
      </header>

      {/* Spacer to prevent content from hiding under fixed header */}
      <div className={clsx(
        "transition-all duration-300",
        isScrolled ? "h-[72px] lg:h-[80px]" : "h-[80px] lg:h-[96px]"
      )} aria-hidden="true" />

      {/* Mobile menu drawer */}
      {isMobileMenuOpen && (
        <>
          {/* Backdrop */}
          <div
            className="fixed inset-0 bg-black/50 backdrop-blur-sm z-50 md:hidden animate-in fade-in duration-200"
            onClick={() => setIsMobileMenuOpen(false)}
            aria-hidden="true"
          />

          {/* Drawer */}
          <div
            id="mobile-menu"
            className={clsx(
              "fixed top-0 right-0 bottom-0 w-[85%] max-w-sm bg-[var(--bg-primary)] shadow-2xl z-50 md:hidden",
              "animate-in slide-in-from-right duration-300",
              "flex flex-col"
            )}
            role="dialog"
            aria-modal="true"
            aria-label={t('common:header.mobile_menu', 'Menú de navegación móvil')}
          >
            {/* Drawer header */}
            <div className="flex items-center justify-between p-4 border-b border-[var(--border-primary)]">
              <div className="flex items-center gap-2">
                <div className="w-8 h-8 bg-gradient-to-br from-[var(--color-primary)] to-[var(--color-primary-dark)] rounded-lg flex items-center justify-center text-white font-bold text-sm">
                  PI
                </div>
                <h2 className="text-lg font-bold text-[var(--text-primary)]">
                  Panadería IA
                </h2>
              </div>
              <Button
                variant="ghost"
                size="sm"
                className="p-2 min-h-[44px] min-w-[44px]"
                onClick={() => setIsMobileMenuOpen(false)}
                aria-label={t('common:header.close_menu', 'Cerrar menú')}
              >
                <X className="w-6 h-6" />
              </Button>
            </div>

            {/* Drawer content */}
            <div className="flex-1 overflow-y-auto">
              {/* Navigation items */}
              <nav className="py-4" role="navigation">
                <div className="flex flex-col">
                  {navItems.map((item) => (
                    <div key={item.id}>
                      {renderNavLink(item, true)}
                    </div>
                  ))}
                </div>
              </nav>

              {/* Mobile language selector */}
              {showLanguageSelector && (
                <div className="px-4 py-4 border-t border-[var(--border-primary)]">
                  <div className="text-sm font-medium text-[var(--text-secondary)] mb-3">
                    {t('common:header.language', 'Idioma')}
                  </div>
                  <CompactLanguageSelector className="w-full" />
                </div>
              )}

              {/* Theme toggle for mobile */}
              {showThemeToggle && (
                <div className="px-4 py-4 border-t border-[var(--border-primary)]">
                  <div className="text-sm font-medium text-[var(--text-secondary)] mb-3">
                    {t('common:header.theme', 'Tema')}
                  </div>
                  <ThemeToggle variant="button" size="md" className="w-full" />
                </div>
              )}
            </div>

            {/* Drawer footer with auth buttons */}
            {showAuthButtons && (
              <div className="p-4 border-t border-[var(--border-primary)] bg-[var(--bg-secondary)]">
                <div className="flex flex-col gap-3">
                  <Link to={getLoginUrl()} onClick={() => setIsMobileMenuOpen(false)}>
                    <Button
                      variant="outline"
                      size="lg"
                      className="w-full font-medium min-h-[48px]"
                    >
                      {t('common:header.login', 'Iniciar Sesión')}
                    </Button>
                  </Link>
                  <Link to={getRegisterUrl()} onClick={() => setIsMobileMenuOpen(false)}>
                    <Button
                      size="lg"
                      className="w-full bg-gradient-to-r from-[var(--color-primary)] to-[var(--color-primary-dark)] hover:opacity-90 text-white font-semibold shadow-lg min-h-[48px]"
                    >
                      {t('common:header.start_free', 'Comenzar Gratis')}
                    </Button>
                  </Link>
                </div>
              </div>
            )}
          </div>
        </>
      )}
    </>
  );
});

PublicHeader.displayName = 'PublicHeader';