/* ============================================
   BookNest — Clean & Simple Design System
   ============================================ */

/* --- Google Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

/* --- CSS Variables --- */
:root {
  --color-primary: #4f46e5;
  --color-primary-hover: #4338ca;
  --color-primary-light: #eef2ff;
  --color-success: #16a34a;
  --color-success-light: #f0fdf4;
  --color-warning: #d97706;
  --color-warning-light: #fffbeb;
  --color-danger: #dc2626;
  --color-danger-light: #fef2f2;
  --color-info: #2563eb;
  --color-info-light: #eff6ff;
  --color-gray-50: #f9fafb;
  --color-gray-100: #f3f4f6;
  --color-gray-200: #e5e7eb;
  --color-gray-300: #d1d5db;
  --color-gray-400: #9ca3af;
  --color-gray-500: #6b7280;
  --color-gray-600: #4b5563;
  --color-gray-700: #374151;
  --color-gray-800: #1f2937;
  --color-gray-900: #111827;
  --color-white: #ffffff;
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --radius: 6px;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
}

/* --- Reset & Base --- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: var(--font-family);
  color: var(--color-gray-800);
  background-color: var(--color-gray-50);
  line-height: 1.6;
}

a {
  color: var(--color-primary);
  text-decoration: none;
}

img {
  max-width: 100%;
}

/* --- Typography --- */
h1, h2, h3, h4 {
  font-weight: 700;
  color: var(--color-gray-900);
  line-height: 1.3;
}

h1 { font-size: 1.75rem; }
h2 { font-size: 1.375rem; }
h3 { font-size: 1.125rem; }
h4 { font-size: 1rem; }

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  font-family: var(--font-family);
  font-size: 0.875rem;
  font-weight: 500;
  border: 1px solid transparent;
  border-radius: var(--radius);
  cursor: pointer;
  transition: background-color 0.15s, border-color 0.15s;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-primary {
  background-color: var(--color-primary);
  color: var(--color-white);
}
.btn-primary:hover:not(:disabled) {
  background-color: var(--color-primary-hover);
}

.btn-secondary {
  background-color: var(--color-white);
  color: var(--color-gray-700);
  border-color: var(--color-gray-300);
}
.btn-secondary:hover:not(:disabled) {
  background-color: var(--color-gray-50);
}

.btn-danger {
  background-color: var(--color-danger);
  color: var(--color-white);
}
.btn-danger:hover:not(:disabled) {
  background-color: #b91c1c;
}

.btn-success {
  background-color: var(--color-success);
  color: var(--color-white);
}
.btn-success:hover:not(:disabled) {
  background-color: #15803d;
}

.btn-sm {
  padding: 0.35rem 0.75rem;
  font-size: 0.8rem;
}

.btn-lg {
  padding: 0.65rem 1.5rem;
  font-size: 1rem;
}

/* --- Form Elements --- */
.form-group {
  margin-bottom: 1rem;
}

.form-label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-gray-700);
  margin-bottom: 0.35rem;
}

.form-input, .form-select {
  width: 100%;
  padding: 0.5rem 0.75rem;
  font-family: var(--font-family);
  font-size: 0.875rem;
  color: var(--color-gray-800);
  background-color: var(--color-white);
  border: 1px solid var(--color-gray-300);
  border-radius: var(--radius);
  transition: border-color 0.15s;
}

.form-input:focus, .form-select:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.form-input::placeholder {
  color: var(--color-gray-400);
}

/* --- Cards --- */
.card {
  background-color: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius);
  padding: 1.25rem;
  box-shadow: var(--shadow-sm);
}

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--color-gray-200);
}

/* --- Tables --- */
.table-container {
  overflow-x: auto;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.875rem;
}

thead {
  background-color: var(--color-gray-50);
}

th {
  text-align: left;
  padding: 0.75rem 1rem;
  font-weight: 600;
  color: var(--color-gray-600);
  border-bottom: 2px solid var(--color-gray-200);
  white-space: nowrap;
}

td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--color-gray-100);
  color: var(--color-gray-700);
}

tr:hover {
  background-color: var(--color-gray-50);
}

/* --- Badges --- */
.badge {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: 9999px;
  text-transform: uppercase;
  letter-spacing: 0.025em;
}

.badge-success {
  background-color: var(--color-success-light);
  color: var(--color-success);
}

.badge-danger {
  background-color: var(--color-danger-light);
  color: var(--color-danger);
}

.badge-warning {
  background-color: var(--color-warning-light);
  color: var(--color-warning);
}

.badge-info {
  background-color: var(--color-info-light);
  color: var(--color-info);
}

.badge-gray {
  background-color: var(--color-gray-100);
  color: var(--color-gray-600);
}

/* --- Navigation Bar --- */
.navbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  height: 56px;
  background-color: var(--color-white);
  border-bottom: 1px solid var(--color-gray-200);
  box-shadow: var(--shadow-sm);
}

.navbar-brand {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-primary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.navbar-brand span {
  font-size: 1.4rem;
}

.navbar-links {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  list-style: none;
}

.navbar-links a {
  display: block;
  padding: 0.5rem 0.85rem;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-gray-600);
  border-radius: var(--radius);
  transition: background-color 0.15s, color 0.15s;
}

.navbar-links a:hover {
  background-color: var(--color-gray-100);
  color: var(--color-gray-900);
}

.navbar-links a.active {
  background-color: var(--color-primary-light);
  color: var(--color-primary);
}

.navbar-right {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.user-info {
  font-size: 0.8rem;
  color: var(--color-gray-500);
  text-align: right;
}

.user-info strong {
  display: block;
  color: var(--color-gray-800);
  font-size: 0.875rem;
}

/* --- Layout --- */
.main-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 1.5rem;
}

.page-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.5rem;
}

.page-header h1 {
  font-size: 1.5rem;
}

/* --- Login Page --- */
.login-page {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  background-color: var(--color-gray-100);
}

.login-card {
  width: 100%;
  max-width: 400px;
  background-color: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius);
  padding: 2rem;
  box-shadow: var(--shadow);
}

.login-card h1 {
  text-align: center;
  margin-bottom: 0.25rem;
}

.login-card .subtitle {
  text-align: center;
  font-size: 0.875rem;
  color: var(--color-gray-500);
  margin-bottom: 1.5rem;
}

.login-card .btn {
  width: 100%;
  margin-top: 0.5rem;
}

.toggle-link {
  display: block;
  text-align: center;
  margin-top: 1rem;
  font-size: 0.85rem;
  color: var(--color-primary);
  cursor: pointer;
}

.toggle-link:hover {
  text-decoration: underline;
}

/* --- Book Grid --- */
.book-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1rem;
}

.book-card {
  background-color: var(--color-white);
  border: 1px solid var(--color-gray-200);
  border-radius: var(--radius);
  padding: 1.25rem;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
}

.book-card h3 {
  margin-bottom: 0.25rem;
  font-size: 1rem;
}

.book-card .book-author {
  font-size: 0.85rem;
  color: var(--color-gray-500);
  margin-bottom: 0.75rem;
}

.book-card .book-meta {
  font-size: 0.8rem;
  color: var(--color-gray-600);
  margin-bottom: 0.25rem;
}

.book-card .book-footer {
  margin-top: auto;
  padding-top: 0.75rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px solid var(--color-gray-100);
}

/* --- Search / Filter Bar --- */
.filter-bar {
  display: flex;
  gap: 0.75rem;
  margin-bottom: 1.25rem;
  flex-wrap: wrap;
}

.filter-bar .form-input,
.filter-bar .form-select {
  max-width: 250px;
}

/* --- Pagination --- */
.pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  margin-top: 1.5rem;
  font-size: 0.875rem;
  color: var(--color-gray-600);
}

/* --- Modal --- */
.modal-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background-color: rgba(0,0,0,0.4);
  z-index: 1000;
  align-items: center;
  justify-content: center;
}

.modal-overlay.active {
  display: flex;
}

.modal {
  background-color: var(--color-white);
  border-radius: var(--radius);
  padding: 1.5rem;
  width: 90%;
  max-width: 480px;
  box-shadow: var(--shadow-md);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1rem;
}

.modal-header h2 {
  font-size: 1.125rem;
}

.modal-close {
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--color-gray-400);
  cursor: pointer;
  line-height: 1;
}

.modal-close:hover {
  color: var(--color-gray-600);
}

.modal-footer {
  display: flex;
  justify-content: flex-end;
  gap: 0.5rem;
  margin-top: 1.25rem;
}

/* --- Toast Notification --- */
.toast-container {
  position: fixed;
  top: 1rem;
  right: 1rem;
  z-index: 2000;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.toast {
  padding: 0.75rem 1rem;
  border-radius: var(--radius);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-white);
  min-width: 250px;
  box-shadow: var(--shadow);
  animation: toast-in 0.2s ease-out;
}

@keyframes toast-in {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}

.toast-success { background-color: var(--color-success); }
.toast-error { background-color: var(--color-danger); }
.toast-warning { background-color: var(--color-warning); }
.toast-info { background-color: var(--color-info); }

/* --- Loading Spinner --- */
.spinner {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 2px solid var(--color-gray-200);
  border-top-color: var(--color-primary);
  border-radius: 50%;
  animation: spin 0.5s linear infinite;
}

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

.loading-center {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 3rem;
  gap: 0.75rem;
  color: var(--color-gray-500);
  font-size: 0.875rem;
}

/* --- Empty State --- */
.empty-state {
  text-align: center;
  padding: 3rem 1rem;
  color: var(--color-gray-400);
}

.empty-state .empty-icon {
  font-size: 2.5rem;
  margin-bottom: 0.75rem;
}

.empty-state p {
  font-size: 0.9rem;
}

/* --- Section Divider --- */
.section {
  margin-bottom: 2rem;
}

.section-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-gray-700);
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--color-gray-200);
}

/* --- Inline Form Row --- */
.form-row {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.form-row .form-group {
  flex: 1;
  min-width: 180px;
}

/* --- Utility --- */
.hidden { display: none !important; }
.text-center { text-align: center; }
.text-right { text-align: right; }
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }

/* --- Responsive --- */
@media (max-width: 768px) {
  .navbar {
    padding: 0 1rem;
  }
  .navbar-links {
    gap: 0;
  }
  .navbar-links a {
    padding: 0.5rem 0.5rem;
    font-size: 0.8rem;
  }
  .user-info {
    display: none;
  }
  .main-content {
    padding: 1rem;
  }
  .filter-bar .form-input,
  .filter-bar .form-select {
    max-width: 100%;
  }
  .page-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.75rem;
  }
}