/**
 * Panel Components
 * ================
 * Shared styles for panel headers, loading states, empty states,
 * and other common panel patterns.
 */

/* ========================================
 * Unified Panel Header
 * ======================================== */

.panel-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-2) var(--space-3);
  border-bottom: 1px solid var(--color-border-default);
  background: var(--color-bg-secondary);
  min-height: 44px;
}

.panel-header__left {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.panel-header__title {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin: 0;
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.panel-header__icon {
  font-size: var(--font-size-base);
  color: var(--color-accent-primary);
}

.panel-header__badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 20px;
  height: 20px;
  padding: 0 var(--space-1);
  background: var(--color-accent-primary);
  border-radius: var(--radius-pill);
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-bold);
  color: var(--color-bg-primary);
}

.panel-header__right {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.panel-header__action {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  background: transparent;
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-sm);
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.panel-header__action:hover {
  background: var(--color-bg-tertiary);
  border-color: var(--color-accent-primary);
  color: var(--color-text-primary);
}

.panel-header__action:focus-visible {
  outline: 2px solid var(--color-accent-primary);
  outline-offset: 2px;
}

/* ========================================
 * Panel Content Area
 * ======================================== */

.panel-content {
  flex: 1;
  padding: var(--space-3);
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
}

.panel-content--compact {
  padding: var(--space-2);
}

.panel-content--flush {
  padding: 0;
}

/* ========================================
 * Panel Footer
 * ======================================== */

.panel-footer {
  padding: var(--space-2) var(--space-3);
  border-top: 1px solid var(--color-border-default);
  background: var(--color-bg-secondary);
}

.panel-footer__actions {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: var(--space-2);
}

.panel-footer__info {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: var(--font-size-xs);
  color: var(--color-text-secondary);
}

/* ========================================
 * Unified Empty State
 * ======================================== */

.panel-empty {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--space-6);
  text-align: center;
}

.panel-empty__icon {
  font-size: 48px;
  color: var(--color-text-muted);
  margin-bottom: var(--space-3);
  opacity: 0.5;
}

.panel-empty__title {
  margin: 0 0 var(--space-2) 0;
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-secondary);
}

.panel-empty__description {
  margin: 0;
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  max-width: 280px;
}

.panel-empty__action {
  margin-top: var(--space-4);
}

/* ========================================
 * Unified Loading State
 * ======================================== */

.panel-loading {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--space-6);
  gap: var(--space-3);
}

.panel-loading__spinner {
  width: 32px;
  height: 32px;
  border: 3px solid var(--color-bg-tertiary);
  border-top-color: var(--color-accent-primary);
  border-radius: 50%;
  animation: panel-spin 1s linear infinite;
}

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

.panel-loading__text {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
}

/* Skeleton loading for lists */
.panel-skeleton-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.panel-skeleton-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2);
  background: var(--color-bg-secondary);
  border-radius: var(--radius-md);
}

.panel-skeleton-avatar {
  width: 32px;
  height: 32px;
  background: linear-gradient(
    90deg,
    var(--color-bg-tertiary) 0%,
    var(--color-bg-hover) 50%,
    var(--color-bg-tertiary) 100%
  );
  background-size: 200% 100%;
  border-radius: var(--radius-md);
  animation: panel-shimmer 1.5s infinite;
}

.panel-skeleton-text {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.panel-skeleton-line {
  height: 12px;
  background: linear-gradient(
    90deg,
    var(--color-bg-tertiary) 0%,
    var(--color-bg-hover) 50%,
    var(--color-bg-tertiary) 100%
  );
  background-size: 200% 100%;
  border-radius: var(--radius-sm);
  animation: panel-shimmer 1.5s infinite;
}

.panel-skeleton-line--short {
  width: 60%;
}

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

/* ========================================
 * Panel Error State
 * ======================================== */

.panel-error {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--space-6);
  text-align: center;
}

.panel-error__icon {
  font-size: 32px;
  color: var(--color-accent-error);
  margin-bottom: var(--space-3);
}

.panel-error__title {
  margin: 0 0 var(--space-2) 0;
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-semibold);
  color: var(--color-accent-error);
}

.panel-error__description {
  margin: 0;
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  max-width: 280px;
}

.panel-error__retry {
  margin-top: var(--space-4);
  padding: var(--space-2) var(--space-4);
  background: transparent;
  border: 1px solid var(--color-accent-primary);
  border-radius: var(--radius-md);
  color: var(--color-accent-primary);
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.panel-error__retry:hover {
  background: var(--color-accent-primary);
  color: var(--color-bg-primary);
}

/* ========================================
 * Panel Section Dividers
 * ======================================== */

.panel-divider {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin: var(--space-3) 0;
}

.panel-divider__line {
  flex: 1;
  height: 1px;
  background: var(--color-border-subtle);
}

.panel-divider__text {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ========================================
 * Panel Tabs
 * ======================================== */

.panel-tabs {
  display: flex;
  gap: 0;
  padding: 0 var(--space-3);
  background: var(--color-bg-secondary);
  border-bottom: 1px solid var(--color-border-default);
}

.panel-tab {
  position: relative;
  display: flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-2) var(--space-3);
  background: transparent;
  border: none;
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  color: var(--color-text-secondary);
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

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

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

.panel-tab__badge {
  padding: 0 var(--space-1);
  background: var(--color-bg-tertiary);
  border-radius: var(--radius-pill);
  font-size: var(--font-size-xs);
}

.panel-tab--active .panel-tab__badge {
  background: color-mix(in srgb, var(--color-accent-primary) 20%, transparent);
  color: var(--color-accent-primary);
}

/* ========================================
 * Panel Collapse/Expand
 * ======================================== */

.panel-collapsible__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-2);
  background: var(--color-bg-tertiary);
  border-radius: var(--radius-sm);
  cursor: pointer;
  user-select: none;
}

.panel-collapsible__title {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-primary);
}

.panel-collapsible__chevron {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
  transition: transform var(--transition-fast);
}

.panel-collapsible--open .panel-collapsible__chevron {
  transform: rotate(180deg);
}

.panel-collapsible__content {
  padding: var(--space-2);
  display: none;
}

.panel-collapsible--open .panel-collapsible__content {
  display: block;
}

/* ========================================
 * Panel Search
 * ======================================== */

.panel-search {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  background: var(--color-bg-secondary);
  border-bottom: 1px solid var(--color-border-default);
}

.panel-search__input-wrapper {
  position: relative;
  flex: 1;
}

.panel-search__icon {
  position: absolute;
  left: var(--space-2);
  top: 50%;
  transform: translateY(-50%);
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
  pointer-events: none;
}

.panel-search__input {
  width: 100%;
  padding: var(--space-2) var(--space-2) var(--space-2) var(--space-6);
  background: var(--color-bg-primary);
  border: 1px solid var(--color-border-default);
  border-radius: var(--radius-md);
  color: var(--color-text-primary);
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  transition: border-color var(--transition-fast);
}

.panel-search__input:focus {
  outline: none;
  border-color: var(--color-accent-primary);
}

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

.panel-search__clear {
  position: absolute;
  right: var(--space-2);
  top: 50%;
  transform: translateY(-50%);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 20px;
  height: 20px;
  background: var(--color-bg-tertiary);
  border: none;
  border-radius: 50%;
  color: var(--color-text-muted);
  font-size: var(--font-size-xs);
  cursor: pointer;
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.panel-search__input:not(:placeholder-shown) + .panel-search__clear {
  opacity: 1;
}

.panel-search__clear:hover {
  background: var(--color-bg-hover);
  color: var(--color-text-primary);
}

/* ========================================
 * Responsive
 * ======================================== */

@media (max-width: 768px) {
  .panel-header {
    padding: var(--space-2);
  }

  .panel-content {
    padding: var(--space-2);
  }

  .panel-tabs {
    padding: 0 var(--space-2);
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }

  .panel-tab {
    padding: var(--space-2);
    white-space: nowrap;
  }

  .panel-header__action {
    width: 40px;
    height: 40px;
  }
}

/* ========================================
 * Reduced Motion
 * ======================================== */

@media (prefers-reduced-motion: reduce) {
  .panel-loading__spinner {
    animation: none;
  }

  .panel-skeleton-avatar,
  .panel-skeleton-line {
    animation: none;
  }
}