/* ==========================================================================
   APP SHELL — Navigation, Sidebar, Topbar Layout & Components
   Layout: Two-column grid with sidebar + main content area
   Sidebar: Role-scoped navigation with act switcher, nested nav groups
   Topbar: Notifications, user menu, responsive toggle
   ========================================================================== */

/* ---- Main shell grid layout ---- */
.nav-shell {
  display: grid;
  grid-template-columns: var(--sidebar-width, 280px) 1fr;
  min-height: 100vh;
  background-color: var(--color-bg);
}

.app-main {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* ---- Sidebar ---- */
.nav-sidebar {
  display: flex;
  flex-direction: column;
  background-color: var(--color-bg-subtle);
  border-right: 1px solid var(--color-border);
  overflow-y: auto;
  position: sticky;
  top: 0;
  max-height: 100vh;
}

.nav-brand {
  padding: var(--space-5) var(--space-4);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-weight: var(--weight-semibold);
  font-size: var(--text-md);
  color: var(--color-text);
}

.nav-brand a {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--color-text);
  text-decoration: none;
}

.nav-brand a:hover {
  opacity: 0.8;
}

.nav-brand .icon {
  width: 24px;
  height: 24px;
}

/* ---- Act Selector Dropdown ---- */
.act-selector {
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--color-border);
}

.act-selector-trigger {
  width: 100%;
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background-color: var(--color-surface);
  color: var(--color-text);
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  cursor: pointer;
  transition: all var(--duration-base) var(--ease-standard);
}

.act-selector-trigger:hover {
  background-color: var(--color-bg);
  border-color: var(--color-border-strong);
}

.act-selector-trigger[aria-expanded="true"] {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px var(--color-accent-subtle);
}

.act-selector-trigger .icon {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.act-name {
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  text-align: left;
}

.act-selector-menu {
  position: absolute;
  top: 100%;
  left: var(--space-4);
  right: var(--space-4);
  margin-top: var(--space-2);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  z-index: 100;
  min-width: 200px;
}

.act-selector-menu[hidden] {
  display: none;
}

.act-selector-item {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  padding: var(--space-3) var(--space-3);
  border-bottom: 1px solid var(--color-border);
  color: var(--color-text);
  text-decoration: none;
  font-size: var(--text-sm);
  transition: background-color var(--duration-base) var(--ease-standard);
}

.act-selector-item:last-child {
  border-bottom: none;
}

.act-selector-item:hover {
  background-color: var(--color-bg-subtle);
  text-decoration: none;
}

.act-selector-item.is-active {
  background-color: var(--color-accent-subtle);
  color: var(--color-accent);
  font-weight: var(--weight-semibold);
}

.act-item-name {
  font-weight: var(--weight-medium);
}

.act-item-role {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  font-weight: var(--weight-regular);
}

/* ---- Navigation Groups ---- */
.nav-groups {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-3) 0;
}

.nav-group {
  padding: 0 var(--space-2);
}

.nav-group + .nav-group {
  margin-top: var(--space-2);
}

.nav-group-label {
  padding: var(--space-3) var(--space-4);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--color-text-muted);
  opacity: 0.75;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  margin: 0 var(--space-2);
  border-radius: var(--radius-md);
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: var(--text-sm);
  font-weight: var(--weight-regular);
  transition: all var(--duration-base) var(--ease-standard);
  cursor: pointer;
}

.nav-link:hover {
  background-color: var(--color-bg);
  color: var(--color-text);
  text-decoration: none;
}

.nav-link.is-active {
  background-color: var(--color-accent-subtle);
  color: var(--color-accent);
  font-weight: var(--weight-medium);
}

.nav-link .icon {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

/* ---- Sidebar Footer ---- */
.nav-footer {
  padding: var(--space-3) 0 var(--space-4);
  border-top: 1px solid var(--color-border);
}

.nav-footer .nav-link {
  margin: 0 var(--space-2);
}

/* ---- Topbar ---- */
.app-topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-4) var(--space-5);
  background-color: var(--color-surface-raised);
  border-bottom: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
  flex-shrink: 0;
}

.topbar-left,
.topbar-right {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.topbar-item {
  position: relative;
}

/* ---- Icon Button Style ---- */
.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  padding: 0;
  border: 1px solid transparent;
  border-radius: var(--radius-md);
  background-color: transparent;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--duration-base) var(--ease-standard);
  font-size: 0; /* hide aria-label text */
}

.icon-btn:hover {
  background-color: var(--color-bg-subtle);
  color: var(--color-text);
}

.icon-btn:focus {
  outline: none;
  box-shadow: 0 0 0 3px var(--color-focus-ring);
}

.icon-btn .icon {
  width: 20px;
  height: 20px;
}

.sidebar-toggle {
  display: none; /* shown at mobile breakpoint */
}

/* ---- Notification Bell ---- */
.notification-bell {
  position: relative;
}

.notification-badge {
  position: absolute;
  top: -4px;
  right: -4px;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 20px;
  height: 20px;
  border-radius: var(--radius-pill);
  background-color: var(--color-danger);
  color: white;
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
}

.notification-badge[hidden] {
  display: none;
}

/* ---- Dropdown Menus ---- */
.dropdown {
  position: relative;
}

.dropdown-menu {
  position: absolute;
  top: 100%;
  right: 0;
  margin-top: var(--space-2);
  min-width: 280px;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  z-index: 200;
}

.dropdown-menu[hidden] {
  display: none;
}

.dropdown-header {
  padding: var(--space-3) var(--space-4);
  border-bottom: 1px solid var(--color-border);
  font-weight: var(--weight-semibold);
  font-size: var(--text-sm);
  color: var(--color-text);
}

.dropdown-content {
  padding: var(--space-3) var(--space-4);
}

.dropdown-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-4);
  color: var(--color-text);
  text-decoration: none;
  font-size: var(--text-sm);
  transition: background-color var(--duration-base) var(--ease-standard);
  background: none;
  border: none;
  width: 100%;
  text-align: left;
  cursor: pointer;
}

.dropdown-item:hover {
  background-color: var(--color-bg-subtle);
  text-decoration: none;
}

.dropdown-item .icon {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.dropdown-item.text-danger {
  color: var(--color-danger);
}

.dropdown-item.text-danger:hover {
  background-color: var(--color-danger-subtle);
}

.dropdown-divider {
  height: 1px;
  background-color: var(--color-border);
  margin: var(--space-2) 0;
}

.dropdown-footer {
  padding: var(--space-3) var(--space-4);
  border-top: 1px solid var(--color-border);
  font-size: var(--text-sm);
  text-align: center;
}

.dropdown-footer a {
  color: var(--color-accent);
  text-decoration: none;
}

.dropdown-footer a:hover {
  text-decoration: underline;
}

/* ---- User Button & Avatar ---- */
.user-button {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background-color: transparent;
  color: var(--color-text);
  font-size: var(--text-sm);
  cursor: pointer;
  transition: all var(--duration-base) var(--ease-standard);
}

.user-button:hover {
  background-color: var(--color-bg-subtle);
  border-color: var(--color-border-strong);
}

.user-button[aria-expanded="true"] {
  background-color: var(--color-bg-subtle);
  border-color: var(--color-accent);
}

.avatar {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 36px;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-pill);
  background: linear-gradient(135deg, var(--color-accent), #7c3aed);
  color: white;
  font-weight: var(--weight-semibold);
  font-size: var(--text-sm);
}

.avatar-sm {
  min-width: 32px;
  width: 32px;
  height: 32px;
  font-size: var(--text-xs);
}

/* ---- Notification Menu ---- */
.notification-menu .dropdown-content {
  max-height: 400px;
  overflow-y: auto;
}

.text-sm {
  font-size: var(--text-sm);
}

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

/* ---- Main Content Area ---- */
.app-content {
  flex: 1;
  overflow-y: auto;
  background-color: var(--color-bg);
}

/* ---- Responsive Behavior ---- */
@media (max-width: 1024px) {
  .nav-shell {
    grid-template-columns: 1fr;
  }

  .nav-sidebar {
    position: fixed;
    left: 0;
    top: 0;
    bottom: 0;
    width: 280px;
    z-index: 300;
    transform: translateX(-100%);
    transition: transform var(--duration-base) var(--ease-standard);
  }

  .nav-shell.sidebar-open .nav-sidebar {
    transform: translateX(0);
  }

  .sidebar-toggle {
    display: inline-flex;
  }
}

@media (max-width: 560px) {
  .app-topbar {
    padding: var(--space-3) var(--space-4);
  }

  .topbar-right {
    gap: var(--space-2);
  }

  .user-button span {
    display: none;
  }

  .user-button .icon {
    display: none;
  }

  .dropdown-menu {
    right: auto;
    left: 0;
    min-width: auto;
    max-width: calc(100vw - 16px);
  }

  .avatar {
    min-width: 32px;
    width: 32px;
    height: 32px;
  }
}