styles.css

/* ===========================================
   Library Manager - Frontend Styles
   Session 18: Connecting Frontend to API
   =========================================== */

/* -----------------------------------------
   CSS Variables (Theme Colors)
   ----------------------------------------- */
:root {
    /* Primary Colors */
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --primary-light: #eef2ff;

    /* Status Colors */
    --success-color: #22c55e;
    --success-light: #dcfce7;
    --error-color: #ef4444;
    --error-light: #fee2e2;
    --warning-color: #f59e0b;
    --warning-light: #fef3c7;

    /* Neutral Colors */
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --text-muted: #9ca3af;
    --border-color: #e5e7eb;
    --background: #f9fafb;
    --card-background: #ffffff;

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

    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;

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

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 300ms ease;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* -----------------------------------------
   Layout
   ----------------------------------------- */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-lg);
}

/* -----------------------------------------
   Header
   ----------------------------------------- */
header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

header h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: var(--spacing-xs);
}

header .subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Connection Status Indicator */
.connection-status {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    background-color: var(--card-background);
    border-radius: 999px;
    margin-top: var(--spacing-md);
    box-shadow: var(--shadow-sm);
}

.status-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background-color: var(--warning-color);
    animation: pulse 2s infinite;
}

.connection-status.connected .status-dot {
    background-color: var(--success-color);
    animation: none;
}

.connection-status.disconnected .status-dot {
    background-color: var(--error-color);
    animation: none;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

/* -----------------------------------------
   Cards
   ----------------------------------------- */
.card {
    background-color: var(--card-background);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
}

.card h2 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

/* -----------------------------------------
   Forms
   ----------------------------------------- */
.form-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.form-group label {
    font-weight: 600;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.form-group input {
    padding: var(--spacing-sm) var(--spacing-md);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

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

.form-group input:invalid:not(:placeholder-shown) {
    border-color: var(--error-color);
}

.error-message {
    font-size: 0.75rem;
    color: var(--error-color);
    min-height: 1rem;
}

/* -----------------------------------------
   Buttons
   ----------------------------------------- */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-lg);
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    min-width: 100px;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

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

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

.btn-secondary {
    background-color: var(--background);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover:not(:disabled) {
    background-color: var(--border-color);
}

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

.btn-danger:hover:not(:disabled) {
    background-color: #dc2626;
}

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

.btn-success:hover:not(:disabled) {
    background-color: #16a34a;
}

.btn-small {
    padding: var(--spacing-xs) var(--spacing-md);
    font-size: 0.875rem;
    min-width: auto;
}

/* Button Spinner */
.btn .spinner {
    width: 16px;
    height: 16px;
    border: 2px solid transparent;
    border-top-color: currentColor;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

.btn .spinner.hidden {
    display: none;
}

.btn .button-text.hidden {
    display: none;
}

/* -----------------------------------------
   Search Section
   ----------------------------------------- */
.search-section {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
    align-items: center;
    justify-content: space-between;
}

.search-box {
    flex: 1;
    min-width: 250px;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.search-box input {
    padding: var(--spacing-sm) var(--spacing-md);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
}

.search-box input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--primary-light);
}

.filter-options {
    display: flex;
    gap: var(--spacing-md);
}

.filter-options label {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    cursor: pointer;
    font-size: 0.875rem;
}

/* -----------------------------------------
   Section Header
   ----------------------------------------- */
.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-lg);
}

.section-header h2 {
    margin: 0;
    font-size: 1.5rem;
}

/* -----------------------------------------
   Loading State
   ----------------------------------------- */
.loading-state {
    text-align: center;
    padding: var(--spacing-xl) 0;
}

.spinner-large {
    width: 48px;
    height: 48px;
    border: 4px solid var(--border-color);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto var(--spacing-md);
}

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

.loading-state p {
    color: var(--text-secondary);
}

/* -----------------------------------------
   Error State
   ----------------------------------------- */
.error-state {
    text-align: center;
    padding: var(--spacing-xl);
    background-color: var(--error-light);
    border-radius: var(--radius-lg);
}

.error-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto var(--spacing-md);
    background-color: var(--error-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    font-weight: bold;
}

.error-state h3 {
    color: var(--error-color);
    margin-bottom: var(--spacing-sm);
}

.error-help {
    text-align: left;
    background-color: white;
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    margin: var(--spacing-md) 0;
}

.error-help ul {
    margin-left: var(--spacing-lg);
    margin-top: var(--spacing-sm);
}

.error-help li {
    margin-bottom: var(--spacing-xs);
}

/* -----------------------------------------
   Empty State
   ----------------------------------------- */
.empty-state {
    text-align: center;
    padding: var(--spacing-xl);
    background-color: var(--primary-light);
    border-radius: var(--radius-lg);
}

.empty-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--spacing-md);
    background-color: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: bold;
}

.empty-state h3 {
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
}

/* -----------------------------------------
   Books Grid
   ----------------------------------------- */
.books-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-lg);
}

/* -----------------------------------------
   Book Card
   ----------------------------------------- */
.book-card {
    background-color: var(--card-background);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-sm);
    border: 2px solid var(--border-color);
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

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

/* Status Indicator Strip */
.book-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background-color: var(--success-color);
}

.book-card.checked-out::before {
    background-color: var(--warning-color);
}

.book-card h3 {
    font-size: 1.1rem;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
    line-height: 1.3;
}

.book-card .author {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: var(--spacing-xs);
}

.book-card .pages {
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-bottom: var(--spacing-md);
}

.book-card .status {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: 999px;
    font-size: 0.75rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
}

.book-card .status.available {
    background-color: var(--success-light);
    color: #15803d;
}

.book-card .status.checked-out {
    background-color: var(--warning-light);
    color: #b45309;
}

/* Book Actions */
.book-actions {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border-color);
}

.book-actions button {
    flex: 1;
    min-width: 80px;
    padding: var(--spacing-xs) var(--spacing-sm);
    font-size: 0.8rem;
}

/* -----------------------------------------
   Modal
   ----------------------------------------- */
.modal {
    position: fixed;
    inset: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.modal.hidden {
    display: none;
}

.modal-overlay {
    position: absolute;
    inset: 0;
    background-color: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
}

.modal-content {
    position: relative;
    background-color: var(--card-background);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    width: 90%;
    max-width: 500px;
    box-shadow: var(--shadow-lg);
    animation: modalSlideIn 0.3s ease;
}

.modal-small {
    max-width: 400px;
}

@keyframes modalSlideIn {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-lg);
}

.modal-header h2 {
    margin: 0;
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-muted);
    padding: var(--spacing-xs);
    line-height: 1;
}

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

.modal-body {
    margin-bottom: var(--spacing-lg);
}

.modal-body .warning-text {
    color: var(--error-color);
    font-size: 0.875rem;
    margin-top: var(--spacing-sm);
}

.modal-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: flex-end;
}

/* -----------------------------------------
   Toast Notifications
   ----------------------------------------- */
.toast {
    position: fixed;
    bottom: var(--spacing-lg);
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--text-primary);
    color: white;
    padding: var(--spacing-md) var(--spacing-lg);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    z-index: 2000;
    animation: toastSlideUp 0.3s ease;
}

.toast.hidden {
    display: none;
}

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

.toast.error {
    background-color: var(--error-color);
}

@keyframes toastSlideUp {
    from {
        opacity: 0;
        transform: translateX(-50%) translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateX(-50%) translateY(0);
    }
}

/* -----------------------------------------
   Utility Classes
   ----------------------------------------- */
.hidden {
    display: none !important;
}

.text-center {
    text-align: center;
}

.text-muted {
    color: var(--text-muted);
}

/* -----------------------------------------
   Responsive Design
   ----------------------------------------- */
@media (max-width: 768px) {
    .container {
        padding: var(--spacing-md);
    }

    header h1 {
        font-size: 1.75rem;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

    .search-section {
        flex-direction: column;
        align-items: stretch;
    }

    .filter-options {
        justify-content: center;
    }

    .books-grid {
        grid-template-columns: 1fr;
    }

    .modal-content {
        width: 95%;
        margin: var(--spacing-md);
    }

    .modal-buttons {
        flex-direction: column;
    }

    .modal-buttons button {
        width: 100%;
    }
}

/* -----------------------------------------
   Skeleton Loading (Bonus Feature)
   ----------------------------------------- */
.skeleton {
    background: linear-gradient(90deg, var(--border-color) 25%, var(--background) 50%, var(--border-color) 75%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
    border-radius: var(--radius-sm);
}

.skeleton-title {
    height: 24px;
    width: 80%;
    margin-bottom: var(--spacing-sm);
}

.skeleton-text {
    height: 16px;
    width: 60%;
    margin-bottom: var(--spacing-xs);
}

.skeleton-button {
    height: 32px;
    width: 100px;
}

@keyframes shimmer {
    to {
        background-position: -200% 0;
    }
}

/* -----------------------------------------
   Print Styles
   ----------------------------------------- */
@media print {
    .add-book-section,
    .search-section,
    .book-actions,
    .modal,
    .toast {
        display: none !important;
    }

    .book-card {
        break-inside: avoid;
        box-shadow: none;
        border: 1px solid #000;
    }
}