/* ==========================================================================
 *  Sidebar Base Styles - Modern Design
 *  ========================================================================== */
.sidebar {
    width: fit-content;
    min-width: 0;
    height: 100%;
    background: var(--bg-sidebar);
    border-right: 1px solid var(--border-sidebar);
    display: flex;
    flex-direction: column;
    z-index: 100;
    transition: width 0.35s cubic-bezier(0.4, 0, 0.2, 1), 
                min-width 0.35s cubic-bezier(0.4, 0, 0.2, 1), 
                transform 0.35s cubic-bezier(0.4, 0, 0.2, 1),
                opacity 0.25s ease-out;
}

.sidebar.collapsed {
    transform: translateX(-100%);
    opacity: 0;
    pointer-events: none;
}

.sidebar-header {
    padding: 16px;
    border-bottom: 1px solid var(--border-sidebar);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.sidebar-title {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.8px;
}

.sidebar-content {
    flex: 1;
    overflow-y: auto;
    padding: 8px;
}

.sidebar-footer {
    padding: 12px 16px;
    border-top: 1px solid var(--border-sidebar);
}

/* New Chat Button - Modern Style */
.new-chat-btn {
    width: 100%;
    padding: 12px 16px;
    background: var(--bg-tertiary);
    border: none;
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.new-chat-btn:hover {
    filter: brightness(1.15);
    transform: translateY(-1px);
    box-shadow: var(--shadow-soft);
}

.new-chat-btn svg {
    width: 18px;
    height: 18px;
}

/* ==========================================================================
 *  Two-Pane Sidebar Layout (Shared Structure)
 *  ========================================================================== */
.sidebar-inner-container {
    display: flex;
    height: 100%;
    width: 100%;
    overflow: hidden;
    background: var(--bg);
}

/* -----------------------------------------------------------------------------
 *  Pane 1: Category Navigator
 *  ----------------------------------------------------------------------------- */
.category-pane {
    width: 160px;
    min-width: 160px;
    background: var(--bg-dark);
    border-right: 1px solid var(--border-sidebar);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    flex-shrink: 0;
    transition: width 0.3s ease, transform 0.3s ease;
}

.category-header {
    padding: 16px 12px;
    border-bottom: 1px solid var(--border-sidebar);
}

.category-header h3 {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    font-weight: 600;
}

.category-list {
    flex: 1;
    overflow-y: auto;
    padding: 8px;
}

.category-item {
    display: flex;
    align-items: center;
    gap: 10px;
    width: 100%;
    padding: 10px 12px;
    background: transparent;
    border: none;
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-size: 0.9rem;
    cursor: pointer;
    text-align: left;
    transition: all 0.15s ease;
    margin-bottom: 4px;
}

.category-item:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.category-item.active {
    background: rgba(var(--primary-rgb), 0.15);
    color: var(--accent);
    font-weight: 600;
}

.category-item-icon {
    width: 18px;
    height: 18px;
    opacity: 0.9;
    flex-shrink: 0;
}

.category-item-name {
    flex: 1;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

/* -----------------------------------------------------------------------------
 *  Pane 2: Chat List
 *  ----------------------------------------------------------------------------- */
.chat-pane {
    flex: none;
    width: 300px;
    display: flex;
    flex-direction: column;
    min-width: 0;
    position: relative;
    background: var(--bg-sidebar);
    transition: transform 0.3s ease;
}

.chat-pane-header {
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0 16px;
    border-bottom: 1px solid var(--border-sidebar);
    flex-shrink: 0;
    cursor: pointer;
    user-select: none;
    position: relative;
    transition: background 0.2s;
}

.chat-pane-header:hover {
    background: var(--bg-tertiary);
}

.category-back-arrow {
    position: absolute;
    left: 16px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    display: none;
}

#chat-pane-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    pointer-events: none;
}

.category-group-header {
    display: flex;
    align-items: center;
    padding: 10px 12px 5px;
    margin-top: 5px;
    cursor: pointer;
    user-select: none;
    color: var(--text-muted);
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.category-group-header .chevron {
    margin-right: 6px;
    transition: transform 0.2s ease;
    opacity: 0.5;
}

.category-group-header .chevron.collapsed {
    transform: rotate(-90deg);
}

.category-group-content {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.category-group-content .category-item {
    margin-left: 4px;
}

/* ==========================================================================
 *  Mobile Styles (< 768px) - Fullscreen Sidebar
 *  ========================================================================== */
@media (max-width: 768px) {
    .sidebar {
        position: fixed;
        left: 0;
        top: 0;
        width: 100% !important;
        min-width: 100% !important;
        height: 100vh;
        z-index: 1000;
        transform: translateX(-100%);
        border-right: none;
    }

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

    .sidebar-inner-container {
        width: 100%;
        height: 100%;
    }

    .category-pane,
    .chat-pane {
        position: absolute;
        top: 0;
        left: 0;
        width: 100% !important;
        min-width: 100% !important;
        height: 100%;
        border: none;
    }

    .chat-pane {
        transform: translateX(0);
        z-index: 2;
    }

    .category-pane {
        transform: translateX(-100%);
        z-index: 1;
    }

    .category-pane.open {
        transform: translateX(0);
    }

    .category-pane.open ~ .chat-pane {
        transform: translateX(100%);
    }

    .chat-pane-header {
        background: linear-gradient(180deg, var(--bg-tertiary) 0%, var(--bg-sidebar) 100%);
        display: flex;
    }

    .category-back-arrow {
        display: block;
    }

    .category-handle {
        display: none;
    }
}

/* ==========================================================================
 *  Desktop Styles (>= 769px)
 *  ========================================================================== */
@media (min-width: 769px) {
    .sidebar {
        position: relative;
        transform: none;
        width: fit-content;
        min-width: 0;
    }

    .sidebar.desktop-hidden {
        width: 0 !important;
        min-width: 0 !important;
        flex: 0 0 0 !important;
        opacity: 0;
        overflow: hidden;
        padding: 0 !important;
        margin: 0 !important;
        border: none;
    }

    .category-pane {
        position: relative;
        width: 160px;
        min-width: 160px;
        transform: none;
        transition: none;
    }

    .category-pane.collapsed {
        width: 0 !important;
        min-width: 0 !important;
        overflow: hidden;
        border: none;
        margin: 0;
        padding: 0;
    }

    .chat-pane {
        position: relative;
        flex: none;
        width: 300px;
        transform: none;
    }

    .chat-pane-header {
        display: none;
    }

    .category-pane.open,
    .category-pane.open ~ .chat-pane {
        transform: none;
    }

    .category-handle {
        width: 6px;
        cursor: pointer;
        background: transparent;
        transition: all 0.2s ease;
        z-index: 30;
        flex-shrink: 0;
        border-left: 1px solid transparent;
        border-right: 1px solid transparent;
    }

    .category-handle:hover {
        background: rgba(var(--accent-rgb, 0, 123, 255), 0.1);
        border-left: 1px solid var(--accent);
        border-right: 1px solid var(--accent);
    }

    .app-wrapper {
        transition: grid-template-columns 0.3s ease;
    }

    .app-wrapper.sidebar-hidden {
        grid-template-columns: 0 1fr !important;
    }

    .main-content {
        transition: margin-left 0.3s ease, width 0.3s ease;
    }
}

/* ==========================================================================
 *  Chat List & Items - Modern Design
 *  ========================================================================== */
.chat-list {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.chat-item {
    padding: 12px 14px;
    background: var(--bg-tertiary);
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: background-color 0.2s ease, 
                border-color 0.2s ease, 
                transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1),
                box-shadow 0.2s ease;
    display: flex;
    flex-direction: column;
    gap: 4px;
    max-height: 10rem;
    flex-shrink: 0;
}

.chat-item:hover {
    background: var(--bg-secondary);
    border-color: var(--border-color);
    transform: translateX(4px);
}

.chat-item.active {
    background: var(--bg-secondary);
    border-color: var(--accent);
    box-shadow: 0 0 0 1px var(--accent-glow), inset 0 0 0 1px var(--accent);
}

/* Smooth chat item entrance animation */
@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(-20px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.chat-item.animate-in {
    animation: slideInRight 0.3s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}

.chat-item-title {
    font-size: 0.9rem;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    font-weight: 500;
    line-height: 1.3;
    height: 24px;
}

.chat-item-meta {
    font-size: 0.75rem;
    color: var(--text-muted);
    display: flex;
    margin-top: auto;
    justify-content: space-between;
    align-items: center;
}

.chat-item-snippet {
    font-size: 0.75rem;
    color: var(--text-muted);
    font-style: italic;
    line-height: 1.2;
    margin-top: 2px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.chat-item-actions {
    display: flex;
    gap: 4px;
    opacity: 0;
    transition: opacity 0.2s;
}

.chat-item:hover .chat-item-actions {
    opacity: 1;
}

.chat-action-btn {
    padding: 4px 8px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 0.7rem;
    cursor: pointer;
    transition: all 0.15s;
}

.chat-action-btn:hover {
    background: var(--bg-secondary);
    color: var(--text-primary);
    border-color: var(--accent);
}

.chat-action-btn.delete:hover {
    border-color: var(--error);
    color: var(--error);
}

.chat-group-content {
    display: flex;
    flex-direction: column;
    gap: 2px;
    padding: 0;
    margin: 0;
}

.chat-section-divider {
    height: 1px;
    background: var(--border-light);
    margin: 10px 15px;
    opacity: 0.5;
}

.chat-group-header {
    display: flex;
    align-items: center;
    padding: 10px 15px 5px;
    cursor: pointer;
    user-select: none;
    color: var(--text-muted);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.chat-group-header:hover {
    color: var(--text-secondary);
}

.header-icon {
    width: 16px;
    height: 16px;
    margin-right: 8px;
    opacity: 0.8;
    display: flex;
    align-items: center;
    justify-content: center;
}

.chat-group-header .chevron {
    margin-right: 8px;
    transition: transform 0.2s ease;
    opacity: 0.5;
}

.chat-group-header .chevron.collapsed {
    transform: rotate(-90deg);
}

.chat-group-header.category-default {
    color: var(--text-muted);
}

.chat-group-header.category-character {
    color: var(--primary-color);
    background: rgba(var(--primary-rgb), 0.05);
}

/* ==========================================================================
 *  Sidebar Overlay
 *  ========================================================================== */
.sidebar-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 99;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s, visibility 0.3s;
}

.sidebar-overlay.show {
    opacity: 1;
    visibility: visible;
}

/* ==========================================================================
 *  Hybrid Sidebar Layout (Category Strip)
 *  ========================================================================== */
.sidebar-container {
    display: flex;
    height: 100%;
    width: 100%;
    overflow: hidden;
    background: var(--bg);
}

#sidebar-nav-strip {
    width: 60px;
    min-width: 60px;
    background: var(--bg-dark);
    border-right: 1px solid var(--border-light);
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 10px 0;
    gap: 5px;
    overflow-y: auto;
    overflow-x: hidden;
    z-index: 5;
}

.category-btn {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    background: var(--bg);
    border: 2px solid transparent;
    color: var(--text-muted);
    transition: all 0.2s;
    font-weight: 600;
    font-size: 1.1rem;
}

.category-btn:hover {
    background: var(--hover-bg);
    color: var(--text-primary);
}

.category-btn.active {
    border-color: var(--primary-color);
    color: var(--primary-color);
    background: rgba(var(--primary-rgb), 0.1);
}

.category-btn svg {
    width: 20px;
    height: 20px;
}

/* ==========================================================================
 *  Sidebar Search & Tags
 *  ========================================================================== */
.sidebar-search {
    padding: 10px;
    border-bottom: 1px solid var(--border-sidebar);
    position: relative;
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.sidebar-search-input {
    flex: 1;
    min-width: 0;
    padding: 9px 12px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 0.85rem;
    outline: none;
    transition: all 0.2s ease;
    height: 36px;
}

.sidebar-search-input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px color-mix(in srgb, var(--accent) 15%, transparent);
}

.chat-item.hidden-by-search,
.chat-item.hidden-by-tag {
    display: none;
}

.search-btn-group {
    display: flex;
    gap: 4px;
}

.search-action-btn {
    width: 36px;
    height: 36px;
    padding: 0;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.search-action-btn:hover {
    background: var(--bg-secondary);
    color: var(--text-primary);
    border-color: var(--border-color);
}

.search-action-btn.active {
    background: var(--accent);
    border-color: var(--accent);
    color: var(--bg-primary);
}

.tag-dropdown {
    width: 100%;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    margin-top: 4px;
    padding: 8px;
    box-shadow: var(--shadow-soft);
    z-index: 50;
    max-height: 250px;
    overflow-y: auto;
}

.tag-dropdown.hidden {
    display: none;
}

.tag-dropdown-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 4px 4px 8px 4px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    color: var(--text-muted);
    border-bottom: 1px solid var(--border-light);
    margin-bottom: 8px;
}

.tag-list {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.tag-dropdown .clear-filter-btn {
    display: none;
    width: 20px;
    height: 20px;
    padding: 0;
    background: transparent;
    border: none;
    color: var(--text-muted);
}

.tag-dropdown .clear-filter-btn:hover {
    color: var(--error);
}

.tag-chip {
    display: inline-flex;
    align-items: center;
    padding: 4px 10px;
    font-size: 0.75rem;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.2s ease;
    color: var(--text-secondary);
}

.tag-chip:hover {
    background: var(--bg);
    border-color: var(--text-muted);
}

.tag-chip.active {
    background: var(--accent);
    border-color: var(--accent);
    color: var(--bg-primary);
}

/* ==========================================================================
 *  Drag and Drop Styling
 *  ========================================================================== */
.chat-item {
    cursor: default;
    user-select: none;
    -webkit-user-select: none;
    pointer-events: auto;
}

.chat-item.dragging {
    cursor: grabbing;
    opacity: 0;
}

.category-item {
    transition: background-color 0.2s ease, border-color 0.2s ease;
    position: relative;
}

.category-item.drag-over {
    background-color: var(--accent);
    color: var(--bg-primary);
}

/* ==========================================================================
 *  Category Pane Footer
 *  ========================================================================== */
.category-footer {
    padding: 12px;
    border-top: 1px solid var(--border-sidebar);
    margin-top: auto;
}

.category-logout-btn {
    width: 100%;
    padding: 10px;
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 0.9rem;
}

.category-logout-btn:hover {
    background: var(--error-bg);
    color: white;
    border-color: var(--error);
}