/* ═══════════════════════════════════════════════════════════════
   TF Study Shelf — Component Library
   Reusable UI component styles following PRD 05 design system
   ═══════════════════════════════════════════════════════════════ */

/* ─── Buttons ─────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 12px 24px;
  border-radius: var(--radius-md);
  font: 500 14px/20px var(--font-primary);
  transition: all var(--transition-fast);
  white-space: nowrap;
  cursor: pointer;
  border: none;
  outline: none;
  position: relative;
  overflow: hidden;
  min-height: 44px;
}

.btn-primary {
  background: var(--accent);
  color: var(--accent-on);
}
.btn-primary:hover { background: var(--color-accent-hover); transform: translateY(-1px); }
.btn-primary:active { background: var(--color-accent-pressed); transform: translateY(0); }

.btn-secondary {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--accent);
}
.btn-secondary:hover { background: var(--color-accent-subtle); }
.btn-secondary:active { background: rgba(255, 119, 89, 0.2); }

.btn-text {
  background: transparent;
  color: var(--accent);
  padding: 8px 16px;
}
.btn-text:hover { background: var(--color-accent-subtle); }

.btn-gradient {
  background: var(--gradient-primary);
  color: var(--accent-on);
  border: none;
  font-weight: 600;
}
.btn-gradient:hover { opacity: 0.9; transform: translateY(-1px); box-shadow: var(--shadow-2); }

.btn-danger {
  background: #dc3545;
  color: #fff;
}
.btn-danger:hover { background: #c82333; }

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
}
.btn-ghost:hover { background: var(--bg-elevated); color: var(--text-primary); }

.btn-sm { padding: 8px 16px; font-size: 12px; min-height: 36px; }
.btn-lg { padding: 16px 32px; font-size: 16px; min-height: 52px; }
.btn-full { width: 100%; }
.btn-icon { padding: 10px; border-radius: var(--radius-sm); min-height: auto; }

.btn:disabled, .btn.disabled {
  opacity: 0.38;
  cursor: not-allowed;
  pointer-events: none;
}

/* ─── Cards ───────────────────────────────────────────────── */
.card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  box-shadow: var(--shadow-1);
  transition: all var(--transition-fast);
}

.card-hover:hover {
  box-shadow: var(--shadow-2);
  transform: translateY(-2px);
  border-color: var(--color-accent-subtle);
}

.card-elevated {
  background: var(--bg-surface);
  border: none;
  box-shadow: var(--shadow-2);
}

.card-accent {
  border-left: 3px solid var(--accent);
}

.card-gradient {
  background: var(--gradient-accent-soft);
  border: 1px solid var(--color-accent-subtle);
}

/* ─── Book Card ───────────────────────────────────────────── */
.book-card {
  display: flex;
  flex-direction: column;
  background: var(--bg-surface);
  border: 1px solid rgba(33, 33, 33, 0.08);
  border-radius: var(--radius-md);
  padding: 12px;
  box-shadow: var(--shadow-1);
  transition: all var(--transition-fast);
  cursor: pointer;
}

.book-card:hover {
  box-shadow: var(--shadow-2);
  transform: translateY(-3px);
}

.book-card__cover {
  width: 100%;
  aspect-ratio: 3/4;
  border-radius: var(--radius-sm);
  background: var(--bg-elevated);
  overflow: hidden;
  margin-bottom: var(--space-sm);
}

.book-card__cover img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.book-card__title {
  font: 600 14px/20px var(--font-primary);
  color: var(--text-primary);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  margin-bottom: 4px;
}

.book-card__author {
  font: 400 12px/16px var(--font-primary);
  color: var(--text-secondary);
  margin-bottom: var(--space-sm);
}

.book-card__meta {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font: 400 12px/16px var(--font-primary);
  color: var(--text-tertiary);
}

.book-card__badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 8px;
  background: var(--color-accent-subtle);
  color: var(--accent);
  border-radius: var(--radius-sm);
  font: 500 10px/14px var(--font-primary);
}

/* ─── Input Fields ────────────────────────────────────────── */
.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
}

.form-label {
  font: 500 12px/16px var(--font-primary);
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.form-input {
  width: 100%;
  padding: 12px 16px;
  border: 1px solid var(--color-input-border);
  border-radius: var(--radius-md);
  background: var(--bg-surface);
  color: var(--text-primary);
  font: 400 14px/20px var(--font-primary);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form-input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--color-accent-subtle);
}

.form-input::placeholder {
  color: var(--color-input-placeholder);
}

.form-input.error {
  border-color: #dc3545;
  box-shadow: 0 0 0 3px rgba(220, 53, 69, 0.1);
}

.form-error {
  font: 400 12px/16px var(--font-primary);
  color: #dc3545;
}

.form-input-icon {
  position: relative;
}
.form-input-icon .form-input { padding-left: 44px; }
.form-input-icon .icon {
  position: absolute;
  left: 14px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-tertiary);
  pointer-events: none;
}

textarea.form-input {
  min-height: 120px;
  resize: vertical;
}

select.form-input {
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%23999' stroke-width='2'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 14px center;
  padding-right: 36px;
}

/* ─── Search Bar ──────────────────────────────────────────── */
.search-bar {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 10px 16px;
  background: var(--color-input-bg);
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  transition: all var(--transition-fast);
}

.search-bar:focus-within {
  background: var(--bg-surface);
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--color-accent-subtle);
}

.search-bar input {
  flex: 1;
  border: none;
  background: transparent;
  outline: none;
  font: 400 14px/20px var(--font-primary);
  color: var(--text-primary);
}

.search-bar input::placeholder { color: var(--color-input-placeholder); }
.search-bar .icon { color: var(--text-tertiary); flex-shrink: 0; }

/* ─── Chips & Badges ──────────────────────────────────────── */
.chip {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 6px 12px;
  background: var(--color-accent-subtle);
  color: var(--accent);
  border-radius: var(--radius-sm);
  font: 500 12px/16px var(--font-primary);
  cursor: pointer;
  transition: all var(--transition-fast);
  border: 1px solid transparent;
}

.chip:hover { background: rgba(255, 119, 89, 0.2); }

.chip.active {
  background: var(--accent);
  color: var(--accent-on);
}

.chip-outline {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-secondary);
}
.chip-outline:hover { border-color: var(--accent); color: var(--accent); }
.chip-outline.active { border-color: var(--accent); background: var(--color-accent-subtle); color: var(--accent); }

.badge {
  display: inline-flex;
  align-items: center;
  padding: 4px 10px;
  border-radius: var(--radius-full);
  font: 500 11px/14px var(--font-primary);
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.badge-published { background: var(--color-accent-subtle); color: var(--accent); }
.badge-draft { background: var(--bg-elevated); color: var(--text-secondary); }
.badge-unpublished { background: rgba(220, 53, 69, 0.1); color: #dc3545; }
.badge-active { background: rgba(40, 167, 69, 0.1); color: #28a745; }

/* ─── Stat Card ───────────────────────────────────────────── */
.stat-card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.stat-card__value {
  font: 700 28px/36px var(--font-mono);
  color: var(--text-primary);
}

.stat-card__label {
  font: 400 13px/18px var(--font-primary);
  color: var(--text-secondary);
}

.stat-card__icon {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  background: var(--color-accent-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent);
  margin-bottom: var(--space-xs);
}

/* ─── Progress Bar ────────────────────────────────────────── */
.progress-bar {
  width: 100%;
  height: 4px;
  background: rgba(33, 33, 33, 0.1);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.progress-bar__fill {
  height: 100%;
  background: var(--gradient-primary);
  border-radius: var(--radius-full);
  transition: width var(--transition-slow);
}

.progress-bar--thick { height: 8px; }

.progress-label {
  font: 500 14px/20px var(--font-mono);
  color: var(--text-secondary);
}

/* ─── Table ───────────────────────────────────────────────── */
.table-wrapper {
  overflow-x: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
}

.table {
  width: 100%;
  border-collapse: collapse;
}

.table th {
  text-align: left;
  padding: 12px 16px;
  font: 500 12px/16px var(--font-primary);
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
}

.table td {
  padding: 12px 16px;
  font: 400 14px/20px var(--font-primary);
  border-bottom: 1px solid var(--border);
  vertical-align: middle;
}

.table tr:last-child td { border-bottom: none; }
.table tr:hover td { background: var(--bg-elevated); }

/* ─── Modal / Dialog ──────────────────────────────────────── */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--color-overlay);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-normal);
}

.modal-overlay.active {
  opacity: 1;
  visibility: visible;
}

.modal {
  background: var(--bg-surface);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  max-width: 480px;
  width: 90%;
  max-height: 85vh;
  overflow-y: auto;
  box-shadow: var(--shadow-3);
  transform: translateY(20px) scale(0.95);
  transition: transform var(--transition-sheet);
}

.modal-overlay.active .modal {
  transform: translateY(0) scale(1);
}

.modal__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-md);
}

.modal__title { font: 600 18px/24px var(--font-primary); }

.modal__close {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}
.modal__close:hover { background: var(--bg-elevated); color: var(--text-primary); }

.modal__actions {
  display: flex;
  gap: var(--space-sm);
  justify-content: flex-end;
  margin-top: var(--space-lg);
}

/* ─── Toast Notifications ─────────────────────────────────── */
.toast-container {
  position: fixed;
  top: var(--space-lg);
  right: var(--space-lg);
  z-index: 2000;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.toast {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 12px 20px;
  box-shadow: var(--shadow-3);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  min-width: 300px;
  max-width: 440px;
  animation: toastIn 300ms ease-out forwards;
  font: 400 14px/20px var(--font-primary);
}

.toast-success { border-left: 3px solid #28a745; }
.toast-error { border-left: 3px solid #dc3545; }
.toast-warning { border-left: 3px solid #ffc107; }
.toast-info { border-left: 3px solid var(--accent); }

@keyframes toastIn {
  from { opacity: 0; transform: translateX(40px); }
  to { opacity: 1; transform: translateX(0); }
}

.toast-exit {
  animation: toastOut 200ms ease-in forwards;
}

@keyframes toastOut {
  to { opacity: 0; transform: translateX(40px); }
}

/* ─── Empty State ─────────────────────────────────────────── */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--space-3xl) var(--space-lg);
  text-align: center;
}

.empty-state__icon {
  width: 64px;
  height: 64px;
  border-radius: var(--radius-lg);
  background: var(--gradient-accent-soft);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-lg);
  font-size: 28px;
}

.empty-state__title {
  font: 600 18px/24px var(--font-primary);
  color: var(--text-primary);
  margin-bottom: var(--space-sm);
}

.empty-state__message {
  font: 400 14px/20px var(--font-primary);
  color: var(--text-secondary);
  margin-bottom: var(--space-lg);
  max-width: 360px;
}

/* ─── Tabs ────────────────────────────────────────────────── */
.tabs {
  display: flex;
  gap: 0;
  border-bottom: 1px solid var(--border);
  overflow-x: auto;
  scrollbar-width: none;
}
.tabs::-webkit-scrollbar { display: none; }

.tab {
  padding: 12px 20px;
  font: 500 14px/20px var(--font-primary);
  color: var(--text-secondary);
  border-bottom: 2px solid transparent;
  transition: all var(--transition-fast);
  white-space: nowrap;
  cursor: pointer;
}

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

.tab.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

/* ─── Pagination ──────────────────────────────────────────── */
.pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  margin-top: var(--space-xl);
}

.pagination__btn {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  font: 500 13px/18px var(--font-primary);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.pagination__btn:hover { background: var(--bg-elevated); color: var(--text-primary); }

.pagination__btn.active {
  background: var(--accent);
  color: var(--accent-on);
}

.pagination__btn:disabled {
  opacity: 0.3;
  cursor: not-allowed;
}

/* ─── Toggle Switch ───────────────────────────────────────── */
.toggle {
  position: relative;
  width: 44px;
  height: 24px;
  border-radius: var(--radius-full);
  background: var(--color-disabled);
  cursor: pointer;
  transition: background var(--transition-fast);
}

.toggle.active { background: var(--accent); }

.toggle::after {
  content: '';
  position: absolute;
  top: 2px;
  left: 2px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: white;
  box-shadow: var(--shadow-1);
  transition: transform var(--transition-fast);
}

.toggle.active::after { transform: translateX(20px); }

/* ─── Dropdown ────────────────────────────────────────────── */
.dropdown {
  position: relative;
  display: inline-block;
}

.dropdown__menu {
  position: absolute;
  top: calc(100% + 4px);
  right: 0;
  min-width: 200px;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-3);
  z-index: 100;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-8px);
  transition: all var(--transition-fast);
  overflow: hidden;
}

.dropdown.open .dropdown__menu {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.dropdown__item {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 10px 16px;
  font: 400 14px/20px var(--font-primary);
  color: var(--text-primary);
  cursor: pointer;
  transition: background var(--transition-fast);
}

.dropdown__item:hover { background: var(--bg-elevated); }
.dropdown__item--danger { color: #dc3545; }
.dropdown__divider { height: 1px; background: var(--border); margin: 4px 0; }

/* ─── Loading Spinner ─────────────────────────────────────── */
.spinner {
  width: 32px;
  height: 32px;
  border: 3px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

.spinner-sm { width: 18px; height: 18px; border-width: 2px; }
.spinner-lg { width: 48px; height: 48px; border-width: 4px; }

@keyframes spin {
  to { transform: rotate(360deg); }
}

.loading-overlay {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 200px;
}

/* ─── Avatar ──────────────────────────────────────────────── */
.avatar {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-full);
  background: var(--gradient-primary);
  color: var(--accent-on);
  display: flex;
  align-items: center;
  justify-content: center;
  font: 600 14px/20px var(--font-primary);
  flex-shrink: 0;
}
.avatar-sm { width: 28px; height: 28px; font-size: 11px; }
.avatar-lg { width: 48px; height: 48px; font-size: 18px; }

/* ─── Checkbox & Radio ────────────────────────────────────── */
.checkbox-label, .radio-label {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  cursor: pointer;
  font: 400 14px/20px var(--font-primary);
}

.checkbox-label input[type="checkbox"],
.radio-label input[type="radio"] {
  width: 18px;
  height: 18px;
  accent-color: var(--accent);
  cursor: pointer;
}