/**
 * 全局Header导航样式
 * 应用原则：DRY、响应式设计、WCAG可访问性
 */

:root {
  --header-height: 60px;
  --header-bg: #ffffff;
  --header-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  --header-z-index: 1000;
}

/* Header容器 */
.site-header {
  position: sticky;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background-color: var(--header-bg);
  box-shadow: var(--header-shadow);
  z-index: var(--header-z-index);
  transition: transform 0.3s ease;
}

.site-header.hidden {
  transform: translateY(-100%);
}

/* Header内容容器 */
.header-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
  height: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

/* Logo */
.site-logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  text-decoration: none;
  color: var(--color-text-dark);
  font-size: 1.25rem;
  font-weight: bold;
  transition: opacity 0.3s;
}

.site-logo:hover {
  opacity: 0.8;
}

.site-logo:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 4px;
  border-radius: 4px;
}

.logo-icon {
  font-size: 1.5rem;
}

/* 导航菜单 */
.nav-menu {
  display: flex;
  align-items: center;
  gap: var(--spacing-lg);
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-item {
  margin: 0;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: var(--spacing-sm) var(--spacing-md);
  text-decoration: none;
  color: var(--color-text-dark);
  font-size: 1rem;
  font-weight: 500;
  border-radius: 6px;
  transition: all 0.3s;
}

.nav-link:hover {
  background-color: rgba(91, 155, 213, 0.1);
  color: var(--color-primary);
}

.nav-link:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
}

.nav-link.active {
  background-color: var(--color-primary);
  color: white;
}

/* 汉堡菜单按钮（移动端） */
.hamburger-btn {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: var(--spacing-sm);
  background: none;
  border: none;
  cursor: pointer;
  transition: opacity 0.3s;
}

.hamburger-btn:hover {
  opacity: 0.7;
}

.hamburger-btn:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 4px;
}

.hamburger-line {
  width: 25px;
  height: 3px;
  background-color: var(--color-text-dark);
  border-radius: 2px;
  transition: all 0.3s;
}

/* 汉堡菜单动画 */
.hamburger-btn.active .hamburger-line:nth-child(1) {
  transform: translateY(8px) rotate(45deg);
}

.hamburger-btn.active .hamburger-line:nth-child(2) {
  opacity: 0;
}

.hamburger-btn.active .hamburger-line:nth-child(3) {
  transform: translateY(-8px) rotate(-45deg);
}

/* 搜索框 */
.header-search {
  position: relative;
  display: flex;
  align-items: center;
}

.search-input {
  padding: var(--spacing-sm) var(--spacing-md);
  padding-left: 36px;
  border: 2px solid var(--color-border);
  border-radius: 20px;
  font-size: 0.9rem;
  width: 200px;
  transition: all 0.3s;
}

.search-input:focus {
  outline: none;
  border-color: var(--color-primary);
  width: 250px;
}

.search-icon {
  position: absolute;
  left: 12px;
  color: var(--color-text-muted);
  pointer-events: none;
}

/* 移动端响应式 */
@media (max-width: 768px) {
  .hamburger-btn {
    display: flex;
  }

  .nav-menu {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background-color: var(--header-bg);
    box-shadow: var(--header-shadow);
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
  }

  .nav-menu.active {
    max-height: 400px;
    border-top: 1px solid var(--color-border);
  }

  .nav-item {
    border-bottom: 1px solid var(--color-border);
  }

  .nav-link {
    padding: var(--spacing-md);
    border-radius: 0;
  }

  .header-search {
    padding: var(--spacing-md);
    border-bottom: 1px solid var(--color-border);
  }

  .search-input {
    width: 100%;
  }

  .search-input:focus {
    width: 100%;
  }
}

@media (max-width: 576px) {
  .site-logo .logo-text {
    display: none;
  }

  .logo-icon {
    font-size: 1.75rem;
  }
}

/* 深色模式 */
@media (prefers-color-scheme: dark) {
  :root {
    --header-bg: #2d3748;
  }

  .hamburger-line {
    background-color: var(--color-text-dark);
  }

  .search-input {
    background-color: #1a202c;
    color: var(--color-text-dark);
  }
}

/* 打印时隐藏header */
@media print {
  .site-header {
    display: none;
  }
}

/* 滚动时header隐藏效果（可选） */
.scroll-down .site-header {
  transform: translateY(-100%);
}

.scroll-up .site-header {
  transform: translateY(0);
}