/* ========================================================================== */
/* 侧边栏头部与导航选项卡 (Sidebar Header & Navigation Tabs) */
/* ========================================================================== */

.sidebar-header {
    padding-block: var(--spacing-2);
}

.nav-tabs {
    display: flex;
    justify-content: space-around;
    padding-block-start: var(--spacing-3);
}

.nav-tab {
    padding: var(--spacing-2) var(--spacing-3);
    border: none;
    border-bottom: 2px solid transparent;
    background: none;
    cursor: pointer;
    color: var(--text-secondary);
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    transition: color var(--transition-duration-normal) ease-out, border-bottom-color var(--transition-duration-normal) ease-out;
}

.nav-tab:hover {
    color: var(--brand-bg);
}

.nav-tab.active {
    border-bottom-color: var(--brand-bg);
    color: var(--brand-bg);
}

/* ========================================================================== */
/* 聊天列表 (Chat List) */
/* ========================================================================== */

.chat-list-container {
    flex-grow: 1;
    overflow-y: auto;
}

#chatListNav {
    list-style: none;
}

.chat-list-item {
    display: flex;
    align-items: center;
    padding: var(--spacing-3) var(--spacing-4);
    border-bottom: var(--border-width-standard) solid var(--border-color);
    cursor: pointer;
    transition: background-color var(--transition-duration-fast) ease-out;
}

.chat-list-item:hover {
    background-color: var(--surface-hover-bg);
}

.chat-list-item.active {
    background-color: var(--surface-active-bg);
}

.chat-list-item.active .chat-list-name:not(.special-contact .chat-list-name) {
    font-weight: var(--font-weight-bold);
}

.chat-list-info {
    flex-grow: 1;
    overflow: hidden;
}

.chat-list-name {
    display: flex;
    align-items: center;
    margin-bottom: 2px;
    overflow: hidden;
    white-space: nowrap;
    text-overflow: ellipsis;
    font-size: var(--font-size-md);
    font-weight: var(--font-weight-semibold);
    color: var(--text-primary);
    transition: color var(--transition-duration-slow) ease-out;
}

.chat-list-preview {
    overflow: hidden;
    white-space: nowrap;
    text-overflow: ellipsis;
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
}

.chat-list-meta {
    min-width: 50px;
    text-align: end;
}

.chat-list-time {
    margin-bottom: var(--spacing-1);
    color: var(--text-secondary);
    font-size: var(--font-size-xs);
}

.chat-list-badge {
    display: inline-block;
    min-width: 18px;
    padding: 2px 6px;
    border-radius: 10px;
    background-color: var(--success-bg);
    color: var(--text-on-success);
    text-align: center;
    font-size: var(--font-size-xs);
    font-weight: var(--font-weight-bold);
}

.chat-list-item-empty {
    padding: var(--spacing-5);
    color: var(--text-secondary);
    text-align: center;
}

.chat-list-avatar {
    width: var(--avatar-size-md);
    height: var(--avatar-size-md);
    margin-inline-end: var(--spacing-3);
    font-size: var(--font-size-xl);
}

/* ========================================================================== */
/* 新建聊天悬浮按钮 (New Chat FAB) */
/* ========================================================================== */

.new-chat-fab {
    position: absolute;
    z-index: var(--z-index-content);
    inset-block-end: 20px;
    inset-inline-start: calc(var(--sidebar-width) - 70px);
    display: flex;
    align-items: center;
    justify-content: center;
    width: 50px;
    height: 50px;
    border: none;
    border-radius: var(--border-radius-circle);
    background-color: var(--brand-bg);
    box-shadow: 0 2px 10px rgba(var(--black-rgb), 0.2);
    cursor: pointer;
    color: var(--text-on-brand);
    font-size: var(--font-size-icon-lg);
    transition: background-color var(--transition-duration-normal) ease-out, transform var(--transition-duration-normal) ease-out;
}

.new-chat-fab:hover {
    background-color: var(--brand-bg-dark);
    transform: scale(1.05);
}

/* ========================================================================== */
/* 人员大厅相关 (People Lobby Related) */
/* ========================================================================== */

.lobby-content {
    display: flex;
    flex-direction: column;
    height: 100%;
}

#peopleLobbyList {
    flex-grow: 1;
    overflow-y: auto;
}

#peopleLobbyRefreshBtn.loading {
    animation: spin 1s linear infinite;
    pointer-events: none;
    opacity: 0.7;
}

/* ========================================================================== */
/* 列表项状态修饰符 (List Item State Modifiers) */
/* ========================================================================== */

.chat-list-item.group .chat-list-avatar {
    background-color: var(--success-bg);
}

.chat-list-item.active.special-contact .chat-list-name {
    color: var(--character-theme-primary);
    font-weight: var(--font-weight-bold);
}

.chat-list-item.special-contact .chat-list-avatar {
    background-color: var(--character-avatar-bg);
    color: var(--character-avatar-text-color);
}

/* ========================================================================== */
/* 响应式设计 (Responsive Design) */
/* ========================================================================== */

@media screen and (max-width: 768px) {
    .new-chat-fab {
        inset-inline-start: auto;
        inset-inline-end: 20px;
    }
}