/**
 * Commerce Learning Hub - Layout Styles
 * 
 * Contains: Page structure, header, sidebar, footer, grid, containers,
 *           mobile drawer, back-to-top button
 */

/* ============================================
   PAGE STRUCTURE
   ============================================ */
.app {
  display: grid;
  grid-template-rows: auto 1fr auto;
  grid-template-columns: auto 1fr;
  grid-template-areas:
    "header header"
    "sidebar main"
    "footer footer";
  min-height: 100vh;
}

/* ============================================
   SKIP LINK
   ============================================ */
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--color-primary);
  color: var(--color-text-inverse);
  padding: var(--space-2) var(--space-4);
  z-index: var(--z-tooltip);
  transition: top var(--transition-fast);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.skip-link:focus {
  top: 0;
}

/* ============================================
   HEADER
   ============================================ */
.header {
  grid-area: header;
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  background: var(--glass-bg);
  backdrop-filter: blur(var(--glass-blur));
  -webkit-backdrop-filter: blur(var(--glass-blur));
  border-bottom: 1px solid var(--glass-border);
  height: var(--header-height);
  display: flex;
  align-items: center;
  padding: 0 var(--container-padding);
}

.header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  gap: var(--space-4);
}

.header__brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-weight: var(--font-bold);
  font-size: var(--text-lg);
  color: var(--color-text);
  flex-shrink: 0;
}

.header__logo {
  width: 2.25rem;
  height: 2.25rem;
  background: linear-gradient(135deg, var(--color-primary), var(--color-secondary));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: var(--text-lg);
  box-shadow: var(--shadow-sm);
}

.header__nav {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex: 1;
  justify-content: center;
}

.header__menu {
  display: flex;
  gap: var(--space-1);
  align-items: center;
}

.header__menu-item {
  position: relative;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  color: var(--color-text-secondary);
  font-weight: var(--font-medium);
  font-size: var(--text-sm);
  transition: all var(--transition-fast);
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  background: transparent;
  border: none;
  cursor: pointer;
}

.header__menu-item:hover {
  background: var(--color-surface-elevated);
  color: var(--color-text);
  text-decoration: none;
}

.header__actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex-shrink: 0;
}

.header__search {
  position: relative;
}

.header__search-input {
  width: 220px;
  padding: var(--space-2) var(--space-3) var(--space-2) 2.25rem;
  background: var(--color-surface-elevated);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  transition: all var(--transition-fast);
}

.header__search-input:focus {
  outline: none;
  border-color: var(--color-primary);
  background: var(--color-surface);
  width: 280px;
  box-shadow: 0 0 0 3px var(--color-primary-light);
}

.header__search-icon {
  position: absolute;
  left: 0.75rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--color-text-muted);
  pointer-events: none;
  font-size: var(--text-sm);
}

/* Mobile menu toggle */
.header__mobile-toggle {
  display: none;
  width: 2.5rem;
  height: 2.5rem;
  border-radius: var(--radius-md);
  background: var(--color-surface-elevated);
  align-items: center;
  justify-content: center;
  cursor: pointer;
  border: 1px solid var(--color-border);
  font-size: var(--text-lg);
}

/* ============================================
   SIDEBAR
   ============================================ */
.sidebar {
  grid-area: sidebar;
  position: sticky;
  top: var(--header-height);
  height: calc(100vh - var(--header-height));
  align-self: start;
  width: var(--sidebar-width);
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  overflow-y: auto;
  padding: var(--space-4);
  z-index: var(--z-sidebar);
  transition: transform var(--transition-base);
}

.sidebar__section {
  margin-bottom: var(--space-6);
}

.sidebar__title {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-2);
  padding: 0 var(--space-2);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.sidebar__title-action {
  font-size: var(--text-xs);
  color: var(--color-primary);
  cursor: pointer;
  text-transform: none;
  letter-spacing: normal;
  font-weight: var(--font-medium);
}

.sidebar__title-action:hover {
  text-decoration: underline;
}

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

.sidebar__link {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  color: var(--color-text-secondary);
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  transition: all var(--transition-fast);
}

.sidebar__link:hover {
  background: var(--color-surface-elevated);
  color: var(--color-text);
  text-decoration: none;
}

.sidebar__link--active {
  background: var(--color-primary-light);
  color: var(--color-primary);
}

.sidebar__icon {
  font-size: var(--text-lg);
  width: 1.5rem;
  text-align: center;
  flex-shrink: 0;
}

.sidebar__empty {
  padding: var(--space-3);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  font-style: italic;
  text-align: center;
}

/* Sidebar overlay (mobile) */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: calc(var(--z-sidebar) - 1);
  opacity: 0;
  transition: opacity var(--transition-base);
}

.sidebar-overlay--visible {
  display: block;
  opacity: 1;
}

/* ============================================
   MAIN CONTENT
   ============================================ */
.main {
  grid-area: main;
  position: relative;
  z-index: var(--z-base);
  padding: var(--space-8);
  max-width: 100%;
  overflow-x: hidden;
  min-width: 0;
}

.main__inner {
  max-width: var(--container-max);
  margin: 0 auto;
}

/* ============================================
   FOOTER
   ============================================ */
.footer {
  grid-area: footer;
  position: relative;
  z-index: 500;
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: var(--space-12) var(--container-padding) var(--space-6);
}

.footer__inner {
  max-width: var(--container-max);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 2fr repeat(3, 1fr);
  gap: var(--space-8);
}

.footer__brand {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.footer__brand-name {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-weight: var(--font-bold);
  font-size: var(--text-lg);
  color: var(--color-text);
}

.footer__brand-logo {
  width: 2rem;
  height: 2rem;
  background: linear-gradient(135deg, var(--color-primary), var(--color-secondary));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-base);
}

.footer__brand-description {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: var(--leading-relaxed);
  max-width: 320px;
}

.footer__social {
  display: flex;
  gap: var(--space-2);
  margin-top: var(--space-2);
}

.footer__social-link {
  width: 2.25rem;
  height: 2.25rem;
  border-radius: var(--radius-md);
  background: var(--color-surface-elevated);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-secondary);
  transition: all var(--transition-fast);
  font-size: var(--text-base);
}

.footer__social-link:hover {
  background: var(--color-primary);
  color: var(--color-text-inverse);
  transform: translateY(-2px);
  text-decoration: none;
}

.footer__section h4 {
  font-size: var(--text-sm);
  font-weight: var(--font-semibold);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text);
  margin-bottom: var(--space-3);
}

.footer__links {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.footer__link {
  color: var(--color-text-secondary);
  font-size: var(--text-sm);
  transition: color var(--transition-fast);
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
}

.footer__link:hover {
  color: var(--color-primary);
  text-decoration: none;
}

.footer__bottom {
  max-width: var(--container-max);
  margin: var(--space-8) auto 0;
  padding-top: var(--space-6);
  border-top: 1px solid var(--color-border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-3);
  color: var(--color-text-muted);
  font-size: var(--text-sm);
}

.footer__bottom-links {
  display: flex;
  gap: var(--space-4);
}

.footer__bottom-links a {
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
}

.footer__bottom-links a:hover {
  color: var(--color-primary);
  text-decoration: none;
}

/* ============================================
   BACK TO TOP BUTTON
   ============================================ */
.back-to-top {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  width: 3rem;
  height: 3rem;
  border-radius: var(--radius-full);
  background: var(--color-primary);
  color: var(--color-text-inverse);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  border: none;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: all var(--transition-base);
  z-index: var(--z-sticky);
  font-size: var(--text-lg);
}

.back-to-top--visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  background: var(--color-primary-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow-xl);
}

/* ============================================
   CONTAINER
   ============================================ */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
}

/* ============================================
   GRID SYSTEM
   ============================================ */
.grid {
  display: grid;
  gap: var(--space-6);
}

.grid--2 { grid-template-columns: repeat(2, 1fr); }
.grid--3 { grid-template-columns: repeat(3, 1fr); }
.grid--4 { grid-template-columns: repeat(4, 1fr); }

/* ============================================
   RESPONSIVE
   ============================================ */
@media (max-width: 1024px) {
  .grid--4 { grid-template-columns: repeat(3, 1fr); }
  .footer__inner { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .app {
    grid-template-columns: 1fr;
    grid-template-areas:
      "header"
      "main"
      "footer";
  }
  
  .header__nav { display: none; }
  .header__search-input { width: 140px; }
  .header__search-input:focus { width: 180px; }
  .header__mobile-toggle { display: flex; }
  
  .sidebar {
    position: fixed;
    left: 0;
    top: var(--header-height);
    width: 85%;
    max-width: 320px;
    height: calc(100vh - var(--header-height));
    transform: translateX(-100%);
    box-shadow: var(--shadow-xl);
  }
  
  .sidebar--open {
    transform: translateX(0);
  }
  
  .main {
    padding: var(--space-4);
  }
  
  .grid--2, .grid--3, .grid--4 {
    grid-template-columns: 1fr;
  }
  
  .footer__inner {
    grid-template-columns: 1fr;
    gap: var(--space-6);
  }
  
  .footer__bottom {
    flex-direction: column;
    text-align: center;
  }
  
  .back-to-top {
    bottom: var(--space-4);
    right: var(--space-4);
  }
}

@media (max-width: 480px) {
  :root {
    --container-padding: 1rem;
  }
  
  h1 { font-size: var(--text-3xl); }
  h2 { font-size: var(--text-2xl); }
  h3 { font-size: var(--text-xl); }
  
  .header__search { display: none; }
}