/**
 * Modern Sidebar Navigation CSS
 * Optimized for Cumulative Layout Shift (CLS) reduction
 * Uses BEM methodology for maintainability
 */

/* CSS Custom Properties for theming */
:root {
  /* Base colors */
  --sidebar-bg: #1a1a1a;
  --sidebar-border: #403f3f;
  --sidebar-item-border: #454645;
  --sidebar-text: #ffffff;
  --sidebar-text-hover: #cccccc;
  --sidebar-accent: #666666;
  --sidebar-header-bg: #2a2a2a;
  --sidebar-content-bg: #2a2a2a;
  --sidebar-title-color: #ffffff;

  /* Hover states */
  --sidebar-hover-bg: rgba(255, 255, 255, 0.05);
  --sidebar-link-hover-bg: rgba(255, 255, 255, 0.03);

  /* Focus/accessibility colors */
  --sidebar-focus-color: #d8d8d8;

  /* Transitions */
  --sidebar-transition: 0.15s ease-out;
}

/* Sidebar Container */
.sidebar-nav {
  contain: layout; /* Isolate layout changes for better CLS */
  background: var(--sidebar-bg);
  border: 1px solid var(--sidebar-border);
  border-radius: 0;
  margin-left: 0; /* Remove left margin which has been added by some global styles */
  overflow: hidden;
}

.sidebar-nav__title {
  background: var(--sidebar-header-bg);
  color: var(--sidebar-title-color);
  padding: 12px 15px;
  margin: 0;
  font-size: 1rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.3px;
}

/* Accordion Structure */
.sidebar-nav__accordion {
  /* Container for accordion items - no additional styling needed */
}

.sidebar-nav__item {
  border-bottom: 1px solid var(--sidebar-item-border);
}

.sidebar-nav__item:last-child {
  border-bottom: none;
}

/* Category Header */
.sidebar-nav__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 5px 12px 15px;
  min-height: 44px; /* WCAG 2.1 minimum touch target */
  background: transparent;
  border: none;
  width: 100%;
  text-align: left;
  cursor: pointer;
  font-size: 1rem;
  color: var(--sidebar-text);
  text-transform: capitalize;
  text-decoration: none;
  transition: background-color var(--sidebar-transition), color var(--sidebar-transition);
  position: relative;
}

.sidebar-nav__header:hover {
  color: var(--sidebar-text);
  background-color: black;
}

.sidebar-nav__header--link {
  cursor: pointer;
}

/* Text container for category names */
.sidebar-nav__header > span:first-child {
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  padding-right: 8px; /* Space between text and icon */
}

/* Icon for expandable items */
.sidebar-nav__icon {
  font-family: FontAwesome;
  font-size: 12px;
  color: var(--sidebar-text);
  transition: transform var(--sidebar-transition);
  min-width: 16px;
  text-align: center;
}

.sidebar-nav__icon--down::before {
  content: "\f107";
}

.sidebar-nav__icon--up::before {
  content: "\f106";
}

/* Rotate icon when expanded */
.sidebar-nav__item--expanded .sidebar-nav__icon {
  transform: rotate(180deg);
}

/* Content Panel */
.sidebar-nav__content {
  max-height: 0;
  overflow: hidden;
  background: var(--sidebar-content-bg);
  transition: max-height var(--sidebar-transition),
              padding var(--sidebar-transition);
  will-change: max-height; /* Optimize for animations */
  transform: translateZ(0); /* Create new layer for better performance */
}

.sidebar-nav__content--expanded {
  max-height: 500px; /* Reasonable upper bound for dynamic content */
  padding: 5px 0;
}

/* Sub-navigation List */
.sidebar-nav__list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.sidebar-nav__subitem {
  border-bottom: 1px solid var(--sidebar-item-border);
}

.sidebar-nav__subitem:last-child {
  border-bottom: none;
}

.sidebar-nav__link {
  display: flex;
  align-items: center;
  padding: 10px 25px;
  min-height: 36px; /* Improved touch target size */
  color: var(--sidebar-text);
  text-decoration: none;
  font-size: 0.9rem;
  transition: background-color var(--sidebar-transition),
              color var(--sidebar-transition);
  overflow: hidden;
}

.sidebar-nav__link:hover {
  background-color: var(--sidebar-link-hover-bg);
  color: var(--sidebar-text);
}

/* No dropdown items (items without children) */
.sidebar-nav__header--no-dropdown .sidebar-nav__icon {
  display: none;
}

/* Responsive Design */
@media (max-width: 768px) {
  .sidebar-nav {
    border-radius: 0;
    border-left: none;
    border-right: none;
  }

  .sidebar-nav__header {
    padding: 8px 12px;
  }

  .sidebar-nav__link {
    padding: 6px 20px;
  }
}

/* Print styles */
@media print {
  .sidebar-nav {
    display: none;
  }
}

/* Accessibility improvements */
@media (prefers-reduced-motion: reduce) {
  .sidebar-nav__header,
  .sidebar-nav__content,
  .sidebar-nav__icon,
  .sidebar-nav__link {
    transition: none;
  }
}

/* Focus states for keyboard navigation */
.sidebar-nav__header:focus-visible,
.sidebar-nav__link:focus-visible {
  outline: 3px solid var(--sidebar-focus-color);
  outline-offset: 2px;
  box-shadow: 0 0 0 1px var(--sidebar-focus-color);
  color: var(--sidebar-title-color);
}

/* Fallback for browsers without focus-visible support */
.sidebar-nav__header:focus:not(:focus-visible),
.sidebar-nav__link:focus:not(:focus-visible) {
  outline: 2px solid var(--sidebar-focus-color);
  outline-offset: 1px;
  color: var(--sidebar-title-color);
}

/* Ensure keyboard focus is always visible */
.sidebar-nav__header:focus,
.sidebar-nav__link:focus {
  outline: 2px solid var(--sidebar-focus-color);
  outline-offset: 1px;
  color: var(--sidebar-title-color);
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  .sidebar-nav {
    border: 2px solid;
  }

  .sidebar-nav__item {
    border-bottom: 1px solid;
  }
}