/**
 * ===============================================================================
 * BALAM AI - Skeleton Loading Component
 * ===============================================================================
 *
 * Shimmer-animated placeholders for perceived-performance improvement.
 * Replace spinners with skeleton shapes that mirror final content layout.
 *
 * Classes:
 *   .balam-skeleton           - Base shimmer (block-level, requires width/height)
 *   .balam-skeleton-text      - Text line placeholder (100% wide, 14px tall)
 *   .balam-skeleton-text.lg   - Heading placeholder (60% wide, 20px tall)
 *   .balam-skeleton-text.sm   - Caption placeholder (40% wide, 12px tall)
 *   .balam-skeleton-circle    - Avatar placeholder (40px default)
 *   .balam-skeleton-card      - Full card placeholder
 *   .balam-skeleton-row       - Table row placeholder
 *   .balam-skeleton-stat      - Dashboard stat card placeholder
 *
 * Accessibility:
 *   - prefers-reduced-motion: static gray, no animation
 *   - aria-hidden="true" recommended on skeleton containers
 *   - aria-busy="true" on the parent container being loaded
 *
 * @requires shared-variables.css
 * @version 1.0.0
 * ===============================================================================
 */

/* ─── Shimmer Animation ─────────────────────────────────────────────────────── */

@keyframes balam-shimmer {
    0% {
        background-position: 200% 0;
    }
    100% {
        background-position: -200% 0;
    }
}

/* ─── Base Skeleton ─────────────────────────────────────────────────────────── */

.balam-skeleton {
    display: block;
    background: linear-gradient(
        90deg,
        var(--balam-skeleton-base, #e5e7eb) 25%,
        var(--balam-skeleton-shine, #f3f4f6) 50%,
        var(--balam-skeleton-base, #e5e7eb) 75%
    );
    background-size: 200% 100%;
    animation: balam-shimmer 1.5s ease-in-out infinite;
    border-radius: 6px;
}

/* ─── Text Line ─────────────────────────────────────────────────────────────── */

.balam-skeleton-text {
    display: block;
    width: 100%;
    height: 14px;
    border-radius: 4px;
    background: linear-gradient(
        90deg,
        var(--balam-skeleton-base, #e5e7eb) 25%,
        var(--balam-skeleton-shine, #f3f4f6) 50%,
        var(--balam-skeleton-base, #e5e7eb) 75%
    );
    background-size: 200% 100%;
    animation: balam-shimmer 1.5s ease-in-out infinite;
}

.balam-skeleton-text.lg {
    width: 60%;
    height: 20px;
    border-radius: 5px;
}

.balam-skeleton-text.sm {
    width: 40%;
    height: 12px;
}

.balam-skeleton-text + .balam-skeleton-text {
    margin-top: 10px;
}

/* ─── Circle (Avatar) ───────────────────────────────────────────────────────── */

.balam-skeleton-circle {
    display: block;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    flex-shrink: 0;
    background: linear-gradient(
        90deg,
        var(--balam-skeleton-base, #e5e7eb) 25%,
        var(--balam-skeleton-shine, #f3f4f6) 50%,
        var(--balam-skeleton-base, #e5e7eb) 75%
    );
    background-size: 200% 100%;
    animation: balam-shimmer 1.5s ease-in-out infinite;
}

.balam-skeleton-circle.sm {
    width: 32px;
    height: 32px;
}

.balam-skeleton-circle.lg {
    width: 56px;
    height: 56px;
}

/* ─── Card Skeleton ─────────────────────────────────────────────────────────── */

.balam-skeleton-card {
    background: var(--balam-card-bg, #ffffff);
    border: 1px solid var(--balam-skeleton-border, #e5e7eb);
    border-radius: 12px;
    padding: 1.25rem;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.balam-skeleton-card .balam-skeleton-header {
    display: flex;
    align-items: center;
    gap: 12px;
}

.balam-skeleton-card .balam-skeleton-body {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

/* ─── Table Row Skeleton ────────────────────────────────────────────────────── */

.balam-skeleton-row {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 12px 16px;
    border-bottom: 1px solid var(--balam-skeleton-border, #e5e7eb);
}

.balam-skeleton-row .balam-skeleton-cell {
    height: 14px;
    border-radius: 4px;
    background: linear-gradient(
        90deg,
        var(--balam-skeleton-base, #e5e7eb) 25%,
        var(--balam-skeleton-shine, #f3f4f6) 50%,
        var(--balam-skeleton-base, #e5e7eb) 75%
    );
    background-size: 200% 100%;
    animation: balam-shimmer 1.5s ease-in-out infinite;
}

/* ─── Stat Card Skeleton ────────────────────────────────────────────────────── */

.balam-skeleton-stat {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 1.5rem 1.75rem;
    background: var(--balam-card-bg, #ffffff);
    border: 1px solid var(--balam-skeleton-border, #e5e7eb);
    border-radius: 16px;
}

.balam-skeleton-stat .balam-skeleton-icon {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    flex-shrink: 0;
    background: linear-gradient(
        90deg,
        var(--balam-skeleton-base, #e5e7eb) 25%,
        var(--balam-skeleton-shine, #f3f4f6) 50%,
        var(--balam-skeleton-base, #e5e7eb) 75%
    );
    background-size: 200% 100%;
    animation: balam-shimmer 1.5s ease-in-out infinite;
}

.balam-skeleton-stat .balam-skeleton-body {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

/* ─── Stagger Animation Delays ──────────────────────────────────────────────── */

.balam-skeleton-card:nth-child(2),
.balam-skeleton-row:nth-child(2),
.balam-skeleton-stat:nth-child(2) {
    animation-delay: 0.15s;
}

.balam-skeleton-card:nth-child(3),
.balam-skeleton-row:nth-child(3),
.balam-skeleton-stat:nth-child(3) {
    animation-delay: 0.3s;
}

.balam-skeleton-card:nth-child(4),
.balam-skeleton-row:nth-child(4),
.balam-skeleton-stat:nth-child(4) {
    animation-delay: 0.45s;
}

.balam-skeleton-card:nth-child(5),
.balam-skeleton-row:nth-child(5),
.balam-skeleton-stat:nth-child(5) {
    animation-delay: 0.6s;
}

/* ─── Content Fade-In Transition ────────────────────────────────────────────── */

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

.balam-fade-in {
    animation: balam-fadeSlideUp 0.3s ease forwards;
}

/* ─── Accessibility: Reduced Motion ─────────────────────────────────────────── */

@media (prefers-reduced-motion: reduce) {
    .balam-skeleton,
    .balam-skeleton-text,
    .balam-skeleton-circle,
    .balam-skeleton-row .balam-skeleton-cell,
    .balam-skeleton-stat .balam-skeleton-icon {
        animation: none;
        background: var(--balam-skeleton-base, #e5e7eb);
    }

    .balam-fade-in {
        animation: none;
        opacity: 1;
        transform: none;
    }
}