/**
 * Loading Skeletons
 * Reusable skeleton loader styles for better perceived performance
 */

/* Base skeleton styles */
.skeleton {
    background: linear-gradient(
        90deg,
        #f0f0f0 0%,
        #e0e0e0 20%,
        #f0f0f0 40%,
        #f0f0f0 100%
    );
    background-size: 200% 100%;
    animation: skeleton-loading 1.5s ease-in-out infinite;
    border-radius: 4px;
}

.dark .skeleton {
    background: linear-gradient(
        90deg,
        #2d3748 0%,
        #1a202c 20%,
        #2d3748 40%,
        #2d3748 100%
    );
    background-size: 200% 100%;
}

@keyframes skeleton-loading {
    0% {
        background-position: 200% 0;
    }
    100% {
        background-position: -200% 0;
    }
}

/* Skeleton shapes */
.skeleton-text {
    height: 1rem;
    margin-bottom: 0.5rem;
}

.skeleton-text-sm {
    height: 0.75rem;
    margin-bottom: 0.25rem;
}

.skeleton-text-lg {
    height: 1.5rem;
    margin-bottom: 0.75rem;
}

.skeleton-title {
    height: 2rem;
    margin-bottom: 1rem;
    width: 60%;
}

.skeleton-avatar {
    width: 3rem;
    height: 3rem;
    border-radius: 50%;
}

.skeleton-avatar-sm {
    width: 2rem;
    height: 2rem;
    border-radius: 50%;
}

.skeleton-avatar-lg {
    width: 5rem;
    height: 5rem;
    border-radius: 50%;
}

.skeleton-button {
    height: 2.5rem;
    width: 6rem;
    border-radius: 0.5rem;
}

.skeleton-image {
    width: 100%;
    height: 12rem;
    border-radius: 0.5rem;
}

/* Course card skeleton */
.skeleton-course-card {
    background: white;
    border: 1px solid #e2e8f0;
    border-radius: 0.5rem;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.dark .skeleton-course-card {
    background: #1e293b;
    border-color: #334155;
}

.skeleton-course-card .skeleton-image {
    height: 12rem;
    border-radius: 0;
}

.skeleton-course-card .skeleton-content {
    padding: 1.5rem;
}

.skeleton-course-card .skeleton-title {
    width: 80%;
    margin-bottom: 1rem;
}

.skeleton-course-card .skeleton-text {
    width: 100%;
}

.skeleton-course-card .skeleton-text:last-child {
    width: 60%;
}

/* List item skeleton */
.skeleton-list-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem;
    background: white;
    border: 1px solid #e2e8f0;
    border-radius: 0.5rem;
    margin-bottom: 0.5rem;
}

.dark .skeleton-list-item {
    background: #1e293b;
    border-color: #334155;
}

.skeleton-list-item .skeleton-avatar {
    flex-shrink: 0;
}

.skeleton-list-item .skeleton-content {
    flex: 1;
}

/* Table row skeleton */
.skeleton-table-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
    gap: 1rem;
    padding: 1rem;
    border-bottom: 1px solid #e2e8f0;
}

.dark .skeleton-table-row {
    border-color: #334155;
}

/* Grid skeleton */
.skeleton-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
}

/* Lazy loading states */
.lazy-image {
    transition: opacity 0.3s ease-in-out;
    opacity: 0.5;
}

.lazy-loading {
    opacity: 0.5;
    filter: blur(5px);
}

.lazy-loaded {
    opacity: 1;
    filter: blur(0);
}

.lazy-error {
    opacity: 0.3;
    background-color: #fee;
}

.dark .lazy-error {
    background-color: #422;
}

/* Fade in animation for loaded content */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.fade-in {
    animation: fadeIn 0.3s ease-in-out;
}

/* Loading spinner */
.spinner {
    border: 3px solid #f3f3f3;
    border-top: 3px solid #3498db;
    border-radius: 50%;
    width: 40px;
    height: 40px;
    animation: spin 1s linear infinite;
}

.dark .spinner {
    border-color: #334155;
    border-top-color: #60a5fa;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.spinner-sm {
    width: 20px;
    height: 20px;
    border-width: 2px;
}

.spinner-lg {
    width: 60px;
    height: 60px;
    border-width: 4px;
}

/* Loading overlay */
.loading-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(255, 255, 255, 0.8);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 10;
}

.dark .loading-overlay {
    background: rgba(0, 0, 0, 0.6);
}

/* Pulse animation for loading states */
@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.5;
    }
}

.pulse {
    animation: pulse 2s cubic-bezier(0.4, 0, 0.6, 1) infinite;
}