/**
 * Components CSS
 * Styles for all UI components
 */

/* ==========================================================================
   CSS Variables
   ========================================================================== */

:root {
  /* Colors */
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-secondary: #64748b;
  --color-accent: #f59e0b;
  --color-success: #10b981;
  --color-error: #ef4444;

  --color-text: #1e293b;
  --color-text-muted: #64748b;
  --color-text-light: #94a3b8;

  --color-bg: #ffffff;
  --color-bg-secondary: #f8fafc;
  --color-bg-tertiary: #f1f5f9;

  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;

  /* Typography */
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-serif: Georgia, 'Times New Roman', serif;

  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 2rem;

  /* Borders */
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 200ms ease;
  --transition-slow: 300ms ease;
}

/* ==========================================================================
   Mode Toggle
   ========================================================================== */

.mode-toggle {
  display: inline-flex;
  background: var(--color-bg-tertiary);
  border-radius: var(--radius-full);
  padding: 4px;
  gap: 4px;
}

.mode-toggle button {
  padding: 8px 16px;
  border: none;
  background: transparent;
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.mode-toggle button:hover {
  color: var(--color-text);
}

.mode-toggle button.active {
  background: var(--color-bg);
  color: var(--color-primary);
  box-shadow: var(--shadow-sm);
}

/* ==========================================================================
   Intent Chips
   ========================================================================== */

.intent-chips {
  display: flex;
  gap: var(--space-sm);
  padding: var(--space-md) 0;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

.intent-chips::-webkit-scrollbar {
  display: none;
}

.intent-chip {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 10px 16px;
  border: 2px solid var(--color-border);
  background: var(--color-bg);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text);
  cursor: pointer;
  white-space: nowrap;
  transition: all var(--transition-fast);
  flex-shrink: 0;
}

.intent-chip:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.intent-chip.active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: white;
}

.intent-chip .chip-icon {
  font-size: 1.1em;
}

.intent-chip .chip-label {
  font-weight: 500;
}

/* ==========================================================================
   Search UI
   ========================================================================== */

.search-container {
  position: relative;
  width: 100%;
  max-width: 600px;
}

.search-input-wrapper {
  position: relative;
}

.search-input {
  width: 100%;
  padding: 14px 20px;
  padding-left: 48px;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-full);
  font-size: var(--text-base);
  color: var(--color-text);
  background: var(--color-bg);
  transition: all var(--transition-fast);
}

.search-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.search-input::placeholder {
  color: var(--color-text-light);
  transition: opacity var(--transition-fast);
}

.search-input.placeholder-fade::placeholder {
  opacity: 0;
}

.search-icon {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--color-text-muted);
  pointer-events: none;
}

/* Search Dropdown */
.search-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  right: 0;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  max-height: 400px;
  overflow-y: auto;
  z-index: 100;
  display: none;
}

.search-dropdown.show {
  display: block;
}

.suggestion-item {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 12px 16px;
  cursor: pointer;
  transition: background var(--transition-fast);
}

.suggestion-item:hover,
.suggestion-item.active {
  background: var(--color-bg-secondary);
}

.suggestion-icon {
  font-size: 1.2em;
  flex-shrink: 0;
}

.suggestion-text {
  flex: 1;
  font-size: var(--text-sm);
  color: var(--color-text);
}

.suggestion-text mark {
  background: rgba(37, 99, 235, 0.15);
  color: var(--color-primary);
  padding: 0 2px;
  border-radius: 2px;
}

.suggestion-subtext {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  flex-shrink: 0;
}

/* ==========================================================================
   Books Grid
   ========================================================================== */

.books-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
  gap: var(--space-lg);
  padding: var(--space-md) 0;
}

@media (min-width: 640px) {
  .books-grid {
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  }
}

@media (min-width: 1024px) {
  .books-grid {
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  }
}

/* Book Card */
.book-card {
  display: flex;
  flex-direction: column;
  background: var(--color-bg);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-sm);
}

.book-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.book-card .book-link {
  display: flex;
  flex-direction: column;
  text-decoration: none;
  color: inherit;
  height: 100%;
}

.book-cover {
  position: relative;
  aspect-ratio: 2 / 3;
  overflow: hidden;
  background: var(--color-bg-tertiary);
}

.book-cover img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--transition-slow);
}

.book-card:hover .book-cover img {
  transform: scale(1.05);
}

/* Effort Badge */
.effort-badge {
  position: absolute;
  top: var(--space-sm);
  left: var(--space-sm);
  padding: 4px 8px;
  font-size: var(--text-xs);
  font-weight: 600;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(4px);
}

.effort-badge.beginner {
  color: var(--color-success);
}

.effort-badge.intermediate {
  color: var(--color-accent);
}

.effort-badge.advanced {
  color: var(--color-error);
}

/* Book Info */
.book-info {
  padding: var(--space-md);
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
  flex: 1;
}

.book-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  margin: 0;
}

.book-author {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin: 0;
}

.why-it-matters {
  font-size: var(--text-xs);
  color: var(--color-secondary);
  line-height: 1.5;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  margin: var(--space-xs) 0 0;
}

.book-meta {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-top: auto;
  padding-top: var(--space-sm);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

.book-meta .effort {
  display: flex;
  align-items: center;
  gap: 4px;
}

.book-meta .rating {
  color: var(--color-accent);
}

/* Subject Tags (Academic Mode) */
.subject-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  margin-top: var(--space-xs);
}

.subject-tag {
  font-size: 10px;
  padding: 2px 6px;
  background: var(--color-bg-tertiary);
  color: var(--color-text-muted);
  border-radius: var(--radius-sm);
}

/* ==========================================================================
   Filter Modal
   ========================================================================== */

.filter-modal {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: 1000;
  display: flex;
  align-items: flex-end;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-base);
}

.filter-modal.open {
  opacity: 1;
  visibility: visible;
}

.filter-modal .modal-content {
  width: 100%;
  max-width: 500px;
  max-height: 90vh;
  background: var(--color-bg);
  border-radius: var(--radius-xl) var(--radius-xl) 0 0;
  display: flex;
  flex-direction: column;
  transform: translateY(100%);
  transition: transform var(--transition-base);
}

.filter-modal.open .modal-content {
  transform: translateY(0);
}

@media (min-width: 640px) {
  .filter-modal {
    align-items: center;
  }

  .filter-modal .modal-content {
    border-radius: var(--radius-xl);
    max-height: 80vh;
  }
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-lg);
  border-bottom: 1px solid var(--color-border);
}

.modal-header h2 {
  font-size: var(--text-lg);
  font-weight: 600;
  margin: 0;
}

.modal-close {
  width: 32px;
  height: 32px;
  border: none;
  background: var(--color-bg-tertiary);
  border-radius: var(--radius-full);
  font-size: var(--text-lg);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-muted);
  transition: all var(--transition-fast);
}

.modal-close:hover {
  background: var(--color-bg-secondary);
  color: var(--color-text);
}

.modal-body {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-lg);
}

.modal-footer {
  display: flex;
  gap: var(--space-md);
  padding: var(--space-lg);
  border-top: 1px solid var(--color-border);
}

.modal-footer .btn {
  flex: 1;
}

/* Filter Groups */
.filter-group {
  margin-bottom: var(--space-xl);
}

.filter-group:last-child {
  margin-bottom: 0;
}

.filter-group-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text);
  margin: 0 0 var(--space-md);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.filter-options {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.filter-options label {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-sm);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: background var(--transition-fast);
}

.filter-options label:hover {
  background: var(--color-bg-secondary);
}

.filter-options input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--color-primary);
}

/* ==========================================================================
   Buttons
   ========================================================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 12px 20px;
  border: none;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-primary {
  background: var(--color-primary);
  color: white;
}

.btn-primary:hover {
  background: var(--color-primary-dark);
}

.btn-secondary {
  background: var(--color-bg-tertiary);
  color: var(--color-text);
}

.btn-secondary:hover {
  background: var(--color-border);
}

/* Refine Button */
.refine-trigger {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 8px 16px;
  border: 1px solid var(--color-border);
  background: var(--color-bg);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.refine-trigger:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.refine-badge,
.filter-count {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 20px;
  height: 20px;
  padding: 0 6px;
  background: var(--color-primary);
  color: white;
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 600;
}

/* ==========================================================================
   Empty State
   ========================================================================== */

.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--space-2xl);
  text-align: center;
  color: var(--color-text-muted);
}

.empty-state p {
  margin: 0;
  font-size: var(--text-base);
}

/* ==========================================================================
   Skeleton Loading
   ========================================================================== */

.skeleton {
  position: relative;
  overflow: hidden;
}

.skeleton::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(
    90deg,
    transparent,
    rgba(255, 255, 255, 0.5),
    transparent
  );
  animation: skeleton-shimmer 1.5s infinite;
}

@keyframes skeleton-shimmer {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}

.skeleton-cover {
  aspect-ratio: 2 / 3;
  background: var(--color-bg-tertiary);
}

.skeleton-title {
  height: 16px;
  width: 80%;
  background: var(--color-bg-tertiary);
  border-radius: var(--radius-sm);
}

.skeleton-author {
  height: 12px;
  width: 60%;
  background: var(--color-bg-tertiary);
  border-radius: var(--radius-sm);
  margin-top: var(--space-xs);
}

.skeleton-meta {
  height: 12px;
  width: 40%;
  background: var(--color-bg-tertiary);
  border-radius: var(--radius-sm);
  margin-top: var(--space-sm);
}

/* ==========================================================================
   Utility Classes
   ========================================================================== */

.modal-open {
  overflow: hidden;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* ==========================================================================
   Site Header
   ========================================================================== */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  padding: var(--space-sm) var(--space-md);
}

.header-container {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
}

.logo {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
}

.logo:hover {
  color: var(--color-primary);
}

/* Header Navigation */
.header-nav {
  display: flex;
  gap: var(--space-md);
}

.header-nav a {
  color: var(--color-text);
  text-decoration: none;
  font-size: var(--text-sm);
  font-weight: 500;
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  transition: background var(--transition-fast), color var(--transition-fast);
}

.header-nav a:hover {
  background: var(--color-bg-secondary);
  color: var(--color-primary);
}

@media (max-width: 640px) {
  .header-nav {
    display: none;
  }
}

/* ==========================================================================
   Site Footer
   ========================================================================== */

.site-footer {
  background: var(--color-bg-secondary);
  border-top: 1px solid var(--color-border);
  padding: var(--space-xl) var(--space-md);
  margin-top: var(--space-2xl);
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
  text-align: center;
}

.footer-content p {
  margin: 0 0 var(--space-xs);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}

.footer-note {
  font-size: var(--text-xs);
  color: var(--color-text-light);
}

.footer-links {
  margin-top: var(--space-sm);
  font-size: var(--text-xs);
}

.footer-links a {
  color: var(--color-text-muted);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--color-primary);
  text-decoration: underline;
}

/* ==========================================================================
   Main Content Container
   ========================================================================== */

.main-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--space-md);
}

@media (min-width: 768px) {
  .main-content {
    padding: var(--space-xl);
  }
}

/* ==========================================================================
   Burger Menu Button
   ========================================================================== */

.burger-menu {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 40px;
  height: 40px;
  padding: 8px;
  background: transparent;
  border: none;
  cursor: pointer;
  gap: 4px;
}

.burger-line {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--color-text);
  border-radius: 1px;
  transition: all 0.2s ease;
}

.burger-menu:hover .burger-line {
  background: var(--color-primary);
}

/* Hide burger menu on desktop */
@media (min-width: 641px) {
  .burger-menu {
    display: none;
  }
}

/* ==========================================================================
   Mobile Navigation Drawer
   ========================================================================== */

.mobile-nav-drawer {
  position: fixed;
  top: 0;
  left: 0;
  width: 280px;
  max-width: 85vw;
  height: 100vh;
  background: var(--color-bg);
  box-shadow: var(--shadow-xl);
  z-index: 1000;
  transform: translateX(-100%);
  transition: transform 0.3s ease;
  display: flex;
  flex-direction: column;
}

.mobile-nav-drawer.is-open {
  transform: translateX(0);
}

.nav-drawer-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-md) var(--space-lg);
  border-bottom: 1px solid var(--color-border);
}

.nav-drawer-title {
  font-size: var(--text-lg);
  font-weight: 600;
  color: var(--color-text);
}

.nav-drawer-close {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: transparent;
  border: none;
  font-size: 1.5rem;
  color: var(--color-text-muted);
  cursor: pointer;
  border-radius: var(--radius-md);
}

.nav-drawer-close:hover {
  background: var(--color-bg-secondary);
  color: var(--color-text);
}

.nav-drawer-links {
  list-style: none;
  padding: var(--space-md) 0;
  margin: 0;
  flex: 1;
  overflow-y: auto;
}

.nav-drawer-links li {
  margin: 0;
}

.nav-drawer-links a {
  display: block;
  padding: var(--space-md) var(--space-lg);
  color: var(--color-text);
  text-decoration: none;
  font-size: var(--text-base);
  font-weight: 500;
  transition: background 0.15s ease, color 0.15s ease;
}

.nav-drawer-links a:hover {
  background: var(--color-bg-secondary);
  color: var(--color-primary);
}

/* Navigation Drawer Overlay */
.nav-drawer-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: 999;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease, visibility 0.3s ease;
}

.nav-drawer-overlay.is-visible {
  opacity: 1;
  visibility: visible;
}

/* Hide mobile nav drawer elements on desktop */
@media (min-width: 641px) {
  .mobile-nav-drawer,
  .nav-drawer-overlay {
    display: none;
  }
}