// ==UserScript==
// @name         豆包用户消息气泡导航
// @namespace    https://github.com/yourname/doubao-nav
// @version      2.0.1.2
// @description  基于DOM结构，在豆包虚拟滚动技术下，为豆包网页版增加一个目录功能，更适合从0到n的新建对话。v2.1: sessionStorage 持久化、精准 scroller 跳转、快速扫描、总数估算。
// @author       你
// @match        https://www.doubao.com/*
// @grant        none
// @tag          导航
// @tag          目录
// @tag          工具
// @tag          豆包
// ==/UserScript==

(function () {
    'use strict';

    // ============================================================
    // 0. 常量
    // ============================================================
    const SCROLLER_SEL = '.v_list_scroller-BxcoIX';
    const FALLBACK_SCROLLER_SEL = '.scrollable-Se7zNt';
    const SCROLL_HOLDER_SEL = '.scroll_holder';
    const V_LIST_ROW_SEL = '.v_list_row[data-observe-row]';
    const USER_BUBBLE_SEL = 'div[class*="send-msg-bubble"]';
    const STORAGE_PREFIX = 'db_nav_v10_';
    const EST_ROW_HEIGHT = 120; // 估计平均每条消息的渲染高度（px）

    // ============================================================
    // 1. 样式 — 完全对齐稳定版
    // ============================================================
    const CSS = `
.usr-nav-native {
    position: fixed; right: 10px; top: 50%; transform: translateY(-50%);
    z-index: 10; pointer-events: none;
}
.usr-nav-indicator {
    width: 16px;
    transition: width 0.3s cubic-bezier(0.25, 0.8, 0.25, 1),
                background 0.3s ease, box-shadow 0.3s ease,
                backdrop-filter 0.3s ease;
    overflow: hidden; background: transparent;
    backdrop-filter: none; box-shadow: none;
    border-radius: 10px 0 0 10px;
    display: flex; flex-direction: column; align-items: stretch;
    max-height: 288px; cursor: pointer; pointer-events: auto;
    scroll-behavior: smooth;
    border-left: 0.5px solid rgba(0,0,0,0.04);
}
.usr-nav-indicator:hover {
    width: 260px; overflow-y: auto;
    background: linear-gradient(135deg, rgba(255,255,255,0.55) 0%, rgba(255,255,255,0.35) 100%);
    backdrop-filter: blur(20px) saturate(180%);
    -webkit-backdrop-filter: blur(20px) saturate(180%);
    box-shadow: -4px 0 24px rgba(0,0,0,0.06), 0 0 0 0.5px rgba(255,255,255,0.6) inset;
}
.usr-nav-item {
    height: 40px; width: 100%; position: relative;
    display: flex; align-items: center; flex-shrink: 0;
    padding-left: 6px; box-sizing: border-box;
    border-radius: 6px; transition: background 0.15s ease, border-radius 0.15s ease;
}
.usr-nav-dash-marker {
    position: absolute; right: 3px; top: 50%; transform: translateY(-50%);
    width: 10px; height: 3px; border-radius: 3px;
    background: var(--s-color-text-tertiary, rgba(100, 110, 125, 0.55));
    transition: all 0.25s cubic-bezier(0.34, 1.56, 0.64, 1); z-index: 2;
}
.usr-nav-item.active .usr-nav-dash-marker {
    width: 14px; height: 4px;
    background: linear-gradient(90deg, #165DFF, #4080FF);
    box-shadow: 0 0 6px rgba(22,93,255,0.35); border-radius: 3px;
}
.usr-nav-item .usr-nav-text { display: none; }
.usr-nav-indicator:hover .usr-nav-text { display: block; }
.usr-nav-text {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    font-size: 13px; font-weight: 400; line-height: 1.5;
    color: color-mix(in srgb, var(--s-color-text-primary, #1d1d1f) 45%, transparent);
    white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
    padding-right: 16px; margin-left: 6px;
    transition: color 0.15s ease, transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
    transform: translateX(-4px);
    -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale;
}
.usr-nav-indicator:hover .usr-nav-text { transform: translateX(0); }
.usr-nav-indicator:hover .usr-nav-item.active .usr-nav-text { color: #165DFF; font-weight: 500; }
.usr-nav-indicator:hover .usr-nav-item:hover:not(.active) { border-radius: 8px; }
.usr-nav-indicator:hover .usr-nav-item:hover:not(.active) .usr-nav-text {
    color: var(--s-color-text-primary, #1d1d1f);
}
.usr-nav-indicator:hover .usr-nav-item:hover .usr-nav-dash-marker {
    background: rgba(22,93,255,0.4); width: 12px; height: 3.5px;
}
.usr-nav-indicator::-webkit-scrollbar { width: 3px; }
.usr-nav-indicator::-webkit-scrollbar-thumb { background: rgba(0,0,0,0.12); border-radius: 3px; }
.usr-nav-indicator::-webkit-scrollbar-thumb:hover { background: rgba(0,0,0,0.2); }
.usr-nav-indicator::-webkit-scrollbar-track { background: transparent; }

/* 扫描按钮 */
.usr-nav-scan-btn {
    display: none; height: 28px; width: 100%; flex-shrink: 0;
    align-items: center; justify-content: center;
    font-size: 12px; font-weight: 500; cursor: pointer;
    color: #165DFF; background: rgba(22,93,255,0.06);
    border-radius: 6px; margin-bottom: 4px;
    transition: background 0.15s ease;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    -webkit-font-smoothing: antialiased;
}
.usr-nav-indicator:hover .usr-nav-scan-btn { display: flex; }
.usr-nav-scan-btn:hover { background: rgba(22,93,255,0.12); }
.usr-nav-scan-btn.scanning { color: #FF9500; background: rgba(255,149,0,0.08); pointer-events: none; }

/* 扫描进度条 */
.usr-nav-scan-progress {
    display: none; height: 2px; width: 100%; flex-shrink: 0;
    background: rgba(0,0,0,0.06); border-radius: 1px; margin-bottom: 4px;
    overflow: hidden;
}
.usr-nav-scan-progress.active { display: block; }
.usr-nav-scan-progress .fill {
    height: 100%; width: 0%;
    background: linear-gradient(90deg, #165DFF, #4080FF);
    border-radius: 1px; transition: width 0.3s ease;
}

/* 底部统计 */
.usr-nav-footer {
    display: none; flex-shrink: 0;
    font-size: 11px; color: var(--s-color-text-quaternary, rgba(0,0,0,0.3));
    text-align: center; padding: 4px 8px 8px 8px;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    -webkit-font-smoothing: antialiased;
    white-space: nowrap;
}
.usr-nav-indicator:hover .usr-nav-footer { display: block; }
`;
    document.head.appendChild(Object.assign(document.createElement('style'), { textContent: CSS }));

    // ============================================================
    // 2. DOM 工具
    // ============================================================
    let indicator = null;

    function getScroller() {
        return document.querySelector(SCROLLER_SEL) || document.querySelector(FALLBACK_SCROLLER_SEL);
    }

    function getScrollHolder() {
        const s = getScroller();
        return s ? s.querySelector(SCROLL_HOLDER_SEL) : null;
    }

    function getMessageId(bubble) {
        const msgEl = bubble.closest('[data-message-id]');
        return msgEl ? msgEl.dataset.messageId : null;
    }

    function getCurrentBubbles() {
        const bubbles = document.querySelectorAll(USER_BUBBLE_SEL);
        const result = [];
        bubbles.forEach(b => {
            const id = getMessageId(b);
            if (id) result.push({ id, bubble: b });
        });
        return result;
    }

    /**
     * 读取当前已渲染的 v_list_row，收集其 --vlist-row-transform-y 作为定位锚点
     * 返回 [{ id: messageId, y: px }, ...]，按 y 升序
     */
    function getVisibleAnchors() {
        const rows = document.querySelectorAll(V_LIST_ROW_SEL);
        const anchors = [];
        rows.forEach(row => {
            const observeData = row.dataset.observeRow; // "block_12345"
            if (!observeData || !observeData.startsWith('block_')) return;
            const msgId = observeData.slice(6); // 去掉 "block_" 前缀
            const y = getComputedStyle(row).getPropertyValue('--vlist-row-transform-y').trim();
            const py = parseFloat(y);
            if (!isNaN(py)) {
                anchors.push({ id: msgId, y: py });
            }
        });
        anchors.sort((a, b) => a.y - b.y);
        return anchors;
    }

    /**
     * 根据已知锚点，用线性插值估算 targetId 的 scrollTop
     * 返回 null 表示无法估算
     */
    function estimateScrollTop(targetId, p) {
        const anchors = getVisibleAnchors();
        if (anchors.length === 0) return null;

        const targetIdx = p.idOrder.indexOf(targetId);
        if (targetIdx < 0) return null;

        // 按 idOrder 索引排序锚点
        const indexed = anchors
            .map(a => ({ ...a, idx: p.idOrder.indexOf(a.id) }))
            .filter(a => a.idx >= 0)
            .sort((a, b) => a.idx - b.idx);

        if (indexed.length === 0) return null;

        // 找包围 targetIdx 的两个锚点
        let before = null, after = null;
        for (const a of indexed) {
            if (a.idx <= targetIdx) before = a;
            if (a.idx >= targetIdx && !after) after = a;
        }

        if (before && after && before.idx !== after.idx) {
            // 线性插值
            const ratio = (targetIdx - before.idx) / (after.idx - before.idx);
            return before.y + (after.y - before.y) * ratio;
        } else if (before && before.idx === targetIdx) {
            return before.y;
        } else if (before) {
            // 目标在所有锚点之后：外推
            return before.y + EST_ROW_HEIGHT * (targetIdx - before.idx);
        } else if (after) {
            // 目标在所有锚点之前：外推
            return Math.max(0, after.y - EST_ROW_HEIGHT * (after.idx - targetIdx));
        }

        return null;
    }

    /**
     * 获取 scroller 当前可视区域的中心对应的 scrollTop
     */
    function getViewCenterScrollTop() {
        const s = getScroller();
        if (!s) return 0;
        return s.scrollTop + s.clientHeight / 2;
    }

    // ============================================================
    // 2b. IntersectionObserver — 高亮跟踪主要机制（对齐稳定版）
    // ============================================================
    const io = new IntersectionObserver((entries) => {
        let bestId = null, bestRatio = 0;
        entries.forEach(e => {
            if (e.isIntersecting && e.intersectionRatio > bestRatio) {
                bestRatio = e.intersectionRatio;
                const id = getMessageId(e.target);
                if (id) bestId = id;
            }
        });
        if (bestId && bestId !== activeId) {
            setActive(bestId);
        }
    }, { threshold: [0, 0.2, 0.5, 1.0] });

    function observeBubbles() {
        io.disconnect();
        document.querySelectorAll(USER_BUBBLE_SEL).forEach(b => {
            if (getMessageId(b)) io.observe(b);
        });
    }

    // ============================================================
    // 3. 多会话存储池 — 按 conversation_id 分池，切换对话自动换池
    //    v2.1: 集成 sessionStorage 持久化
    // ============================================================
    function getConversationId() {
        const match = window.location.pathname.match(/^\/chat\/(\d+)/);
        return match ? match[1] : null;
    }

    const pools = new Map();       // convId → { registry: Map, idOrder: [], activeId: null }
    let currentConvId = null;
    let activeId = null;          // 当前池的激活消息 ID
    let switchCooldown = 0;       // 对话切换后 1.5s 冷却期，防止轮询读到旧 DOM
    let savePending = false;      // 防抖保存标记

    function savePool(convId, p) {
        try {
            const data = {
                idOrder: p.idOrder.slice(),
                registry: {}
            };
            p.registry.forEach((entry, id) => {
                data.registry[id] = { label: entry.label };
            });
            sessionStorage.setItem(STORAGE_PREFIX + convId, JSON.stringify(data));
        } catch (e) {
            // sessionStorage 满或不可用，静默失败
        }
    }

    function schedulePoolSave() {
        if (savePending) return;
        savePending = true;
        setTimeout(() => {
            savePending = false;
            const convId = getConversationId() || '__default__';
            const p = pools.get(convId);
            if (p) savePool(convId, p);
        }, 500);
    }

    function loadPool(convId) {
        try {
            const raw = sessionStorage.getItem(STORAGE_PREFIX + convId);
            if (!raw) return null;
            const data = JSON.parse(raw);
            if (!data.idOrder || !data.registry) return null;
            const registry = new Map();
            Object.entries(data.registry).forEach(([id, entry]) => {
                registry.set(id, { label: entry.label, row: null });
            });
            return { registry, idOrder: data.idOrder, activeId: null };
        } catch (e) {
            return null;
        }
    }

    function switchToConversation(convId) {
        if (convId === currentConvId) return;

        // 先保存当前池
        if (currentConvId) {
            const oldP = pools.get(currentConvId);
            if (oldP) savePool(currentConvId, oldP);
        }

        // 尝试从 sessionStorage 恢复
        const restored = loadPool(convId);
        if (restored) {
            pools.set(convId, restored);
            currentConvId = convId;
            activeId = restored.activeId || null;
            rebuildPanel();
            updateEstimatedCount();
            switchCooldown = Date.now() + 1500;
            return;
        }

        // 新建空池
        currentConvId = convId;
        pools.set(convId, {
            registry: new Map(),
            idOrder: [],
            activeId: null
        });
        activeId = null;
        if (indicator) {
            indicator.querySelectorAll('.usr-nav-item, .usr-nav-scan-btn, .usr-nav-scan-progress, .usr-nav-footer').forEach(el => {
                if (!el.classList.contains('usr-nav-scan-btn') &&
                    !el.classList.contains('usr-nav-scan-progress') &&
                    !el.classList.contains('usr-nav-footer')) {
                    el.remove();
                }
            });
            // 保留扫描按钮和底部统计（innerHTML 重置会丢），改为清空 nav items
            const items = indicator.querySelectorAll('.usr-nav-item');
            items.forEach(el => el.remove());
        }
        switchCooldown = Date.now() + 1500; // 冷却 1.5s，等 React 更新 DOM
    }

    function pool() {
        const convId = getConversationId() || '__default__';
        if (convId !== currentConvId) {
            switchToConversation(convId);
        }
        return pools.get(currentConvId);
    }

    // 将 visible 中新发现的 ID 按 DOM-relative 位置插入 idOrder
    // DOM 顺序即时间序（聊天页面保证），比 BigInt 排序更可靠
    function mergeNewIds(p, visible) {
        let added = false;
        visible.forEach(({ id }, i) => {
            if (p.idOrder.includes(id)) return;

            // 找 DOM 中左侧最近的已知邻居
            let pred = null;
            for (let j = i - 1; j >= 0; j--) {
                if (p.idOrder.includes(visible[j].id)) { pred = visible[j].id; break; }
            }
            // 找 DOM 中右侧最近的已知邻居
            let succ = null;
            for (let j = i + 1; j < visible.length; j++) {
                if (p.idOrder.includes(visible[j].id)) { succ = visible[j].id; break; }
            }

            if (pred) {
                p.idOrder.splice(p.idOrder.indexOf(pred) + 1, 0, id);
            } else if (succ) {
                p.idOrder.splice(p.idOrder.indexOf(succ), 0, id);
            } else {
                p.idOrder.push(id);
            }
            added = true;
        });
        return added;
    }

    function ingest() {
        if (Date.now() < switchCooldown) return; // 对话切换冷却期，等 React 更新 DOM
        const p = pool();
        if (!p) return;

        const visible = getCurrentBubbles();

        // 先注册所有可见 ID（不插入 idOrder，由 mergeNewIds 统一处理）
        visible.forEach(({ id, bubble }) => {
            const label = bubble.textContent.trim().slice(0, 22);
            if (p.registry.has(id)) {
                p.registry.get(id).label = label;
            } else {
                p.registry.set(id, { label, row: null });
            }
        });

        // 按 DOM 相对位置插入新 ID
        const changed = mergeNewIds(p, visible);
        if (changed) {
            rebuildPanel();
            schedulePoolSave();
        } else {
            updateLabelsInPlace();
        }
        updateActiveByScroll();
        updateEstimatedCount();
        observeBubbles();
    }

    // ============================================================
    // 4. 面板构建 — 增量复用 DOM，仅在顺序变化时重建
    // ============================================================
    function createNavItem(id, label, index) {
        const item = document.createElement('div');
        item.className = 'usr-nav-item';
        item.dataset.messageId = id;

        const marker = document.createElement('span');
        marker.className = 'usr-nav-dash-marker';

        const text = document.createElement('span');
        text.className = 'usr-nav-text';
        text.textContent = `${index + 1}. ${label}`;

        item.appendChild(marker);
        item.appendChild(text);
        return item;
    }

    function rebuildPanel() {
        const p = pool();
        if (!p || !indicator) return;

        const oldMap = new Map();
        indicator.querySelectorAll('.usr-nav-item').forEach(el => {
            oldMap.set(el.dataset.messageId, el);
        });

        // 先移除旧 items（保留 scan-btn、scan-progress、footer）
        const scanBtn = indicator.querySelector('.usr-nav-scan-btn');
        const scanProg = indicator.querySelector('.usr-nav-scan-progress');
        const footer = indicator.querySelector('.usr-nav-footer');

        const frag = document.createDocumentFragment();
        // 确保扫描按钮在最前
        if (scanBtn) frag.appendChild(scanBtn);
        if (scanProg) frag.appendChild(scanProg);

        p.idOrder.forEach((id, i) => {
            const entry = p.registry.get(id);
            if (!entry) return;

            let item = oldMap.get(id);
            if (item) {
                oldMap.delete(id);
            } else {
                item = createNavItem(id, entry.label, i);
            }
            entry.row = item;

            const textEl = item.querySelector('.usr-nav-text');
            if (textEl) textEl.textContent = `${i + 1}. ${entry.label}`;

            frag.appendChild(item);
        });

        oldMap.forEach(el => el.remove());

        // 确保 footer 在最后
        if (footer) frag.appendChild(footer);

        indicator.innerHTML = '';
        indicator.appendChild(frag);

        // 重建后重新挂载 active 类（DOM 已全新，旧类丢失）
        if (activeId) {
            const cur = indicator.querySelector(`.usr-nav-item[data-message-id="${activeId}"]`);
            if (cur) cur.classList.add('active');
        }

        updateEstimatedCount();
    }

    function updateLabelsInPlace() {
        const p = pool();
        if (!p) return;

        const items = indicator.querySelectorAll('.usr-nav-item');
        items.forEach((item) => {
            const id = item.dataset.messageId;
            const entry = p.registry.get(id);
            if (!entry) return;
            entry.row = item;
            const idx = p.idOrder.indexOf(id);
            if (idx < 0) return;
            const textEl = item.querySelector('.usr-nav-text');
            if (textEl) textEl.textContent = `${idx + 1}. ${entry.label}`;
        });
    }

    // ============================================================
    // 5. 激活高亮（lastActiveId 模式）
    // ============================================================
    function updateActiveByScroll() {
        const visible = getCurrentBubbles();
        if (visible.length === 0) return;

        const scroller = getScroller();
        const viewCenter = scroller
            ? scroller.scrollTop + scroller.clientHeight / 2
            : window.innerHeight / 2;

        let bestId = null, bestDist = Infinity;

        visible.forEach(({ id, bubble }) => {
            const s = getScroller();
            let bubbleCenter;
            if (s) {
                const sRect = s.getBoundingClientRect();
                const bRect = bubble.getBoundingClientRect();
                bubbleCenter = s.scrollTop + (bRect.top - sRect.top) + bRect.height / 2;
            } else {
                const rect = bubble.getBoundingClientRect();
                bubbleCenter = rect.top + rect.height / 2;
            }

            if (bubble.getBoundingClientRect().height === 0) return;
            const dist = Math.abs(bubbleCenter - viewCenter);
            if (dist < bestDist) { bestDist = dist; bestId = id; }
        });

        if (bestId && bestId !== activeId) {
            setActive(bestId);
        }
    }

    function setActive(id) {
        if (activeId) {
            const prev = indicator.querySelector(`.usr-nav-item[data-message-id="${activeId}"]`);
            if (prev) prev.classList.remove('active');
        }
        if (id) {
            const next = indicator.querySelector(`.usr-nav-item[data-message-id="${id}"]`);
            if (next) {
                next.classList.add('active');
                setTimeout(() => {
                    next.scrollIntoView({ block: 'center', behavior: 'smooth' });
                }, 10);
                activeId = id;
                return;
            }
        }
        activeId = null;
    }

    // ============================================================
    // 6. 跳转 — v2.1: 使用 scroller + 锚点估算替代 window.scrollBy
    // ============================================================
    function scrollToMessage(id) {
        const scroller = getScroller();
        const visible = getCurrentBubbles();
        const match = visible.find(b => b.id === id);

        if (match) {
            // 目标在 DOM：直接用 scroller 滚动到目标
            if (scroller) {
                const sRect = scroller.getBoundingClientRect();
                const bRect = match.bubble.getBoundingClientRect();
                const targetScroll = scroller.scrollTop + (bRect.top - sRect.top) - scroller.clientHeight / 2 + bRect.height / 2;
                scroller.scrollTo({ top: targetScroll, behavior: 'smooth' });
            } else {
                match.bubble.scrollIntoView({ behavior: 'smooth', block: 'center' });
            }
            match.bubble.style.transition = 'box-shadow 0.2s';
            match.bubble.style.boxShadow = '0 0 0 3px rgba(22,93,255,0.4)';
            setTimeout(() => { match.bubble.style.boxShadow = ''; }, 1500);
            return;
        }

        // 虚拟滚动：目标不在当前 DOM，用锚点估算位置直接跳转
        const p = pool();
        if (!p) return;
        const targetIdx = p.idOrder.indexOf(id);
        if (targetIdx < 0) return;

        const estimated = estimateScrollTop(id, p);

        if (estimated !== null && scroller) {
            // 用估算位置直接跳转
            scroller.scrollTo({ top: estimated, behavior: 'smooth' });
            // 跳转后等待虚拟列表渲染，尝试一次微调
            setTimeout(() => {
                const retry = getCurrentBubbles().find(b => b.id === id);
                if (retry && scroller) {
                    const sRect = scroller.getBoundingClientRect();
                    const bRect = retry.bubble.getBoundingClientRect();
                    const targetScroll = scroller.scrollTop + (bRect.top - sRect.top) - scroller.clientHeight / 2 + bRect.height / 2;
                    scroller.scrollTo({ top: targetScroll, behavior: 'smooth' });
                    retry.bubble.style.transition = 'box-shadow 0.2s';
                    retry.bubble.style.boxShadow = '0 0 0 3px rgba(22,93,255,0.4)';
                    setTimeout(() => { retry.bubble.style.boxShadow = ''; }, 1500);
                }
            }, 350);
            return;
        }

        // 回退：方向性滚动（使用 scroller 而非 window）
        const visibleIds = visible.map(b => b.id);
        if (visibleIds.length === 0) return;
        const visFirst = p.idOrder.indexOf(visibleIds[0]);
        const visLast = p.idOrder.indexOf(visibleIds[visibleIds.length - 1]);

        if (targetIdx < visFirst) {
            if (scroller) {
                scroller.scrollBy({ top: -(scroller.clientHeight * 0.7), behavior: 'smooth' });
            } else {
                window.scrollBy(0, -(window.innerHeight * 0.7));
            }
        } else if (targetIdx > visLast) {
            if (scroller) {
                scroller.scrollBy({ top: scroller.clientHeight * 0.7, behavior: 'smooth' });
            } else {
                window.scrollBy(0, window.innerHeight * 0.7);
            }
        } else {
            return;
        }
        setTimeout(() => scrollToMessage(id), 400);
    }

    // ============================================================
    // 7. 快速扫描模式 — v2.1 新增
    // ============================================================
    let scanActive = false;
    let scanAbortController = null;

    async function startScan() {
        if (scanActive) return;
        scanActive = true;

        const scroller = getScroller();
        if (!scroller) { scanActive = false; return; }

        const scrollHolder = getScrollHolder();
        if (!scrollHolder) { scanActive = false; return; }

        const totalY = parseFloat(
            getComputedStyle(scrollHolder).getPropertyValue('--vlist-row-transform-y').trim()
        );
        if (!totalY || totalY <= 0) { scanActive = false; return; }

        const viewHeight = scroller.clientHeight;
        const stepSize = viewHeight * 1.5;
        const totalSteps = Math.ceil(totalY / stepSize);

        // 更新按钮状态
        const btn = indicator.querySelector('.usr-nav-scan-btn');
        const progBar = indicator.querySelector('.usr-nav-scan-progress');
        const progFill = progBar ? progBar.querySelector('.fill') : null;
        if (btn) btn.classList.add('scanning');
        if (progBar) progBar.classList.add('active');

        let currentStep = 0;

        return new Promise((resolve) => {
            scanAbortController = resolve;

            function step() {
                if (!scanActive) {
                    // 扫描被中止
                    if (btn) btn.classList.remove('scanning');
                    if (progBar) progBar.classList.remove('active');
                    if (progFill) progFill.style.width = '0%';
                    return;
                }

                currentStep++;
                const pos = Math.min(currentStep * stepSize, totalY);

                // 更新进度
                const pct = Math.min(100, Math.round((pos / totalY) * 100));
                if (progFill) progFill.style.width = pct + '%';
                if (btn) btn.textContent = `扫描中 ${pct}%`;

                if (pos >= totalY) {
                    // 扫描完成
                    scanActive = false;
                    if (btn) {
                        btn.classList.remove('scanning');
                        btn.style.display = 'none';
                    }
                    if (progBar) progBar.classList.remove('active');
                    if (progFill) progFill.style.width = '0%';
                    scheduleSync();
                    updateEstimatedCount();
                    return;
                }

                scroller.scrollTop = pos;

                // 等待虚拟列表渲染 + 同步
                setTimeout(() => {
                    scheduleSync();
                    setTimeout(step, 150);
                }, 250);
            }

            step();
        });
    }

    function stopScan() {
        scanActive = false;
        if (scanAbortController) {
            scanAbortController();
            scanAbortController = null;
        }
        const btn = indicator.querySelector('.usr-nav-scan-btn');
        const progBar = indicator.querySelector('.usr-nav-scan-progress');
        const progFill = progBar ? progBar.querySelector('.fill') : null;
        if (btn) {
            btn.classList.remove('scanning');
            btn.textContent = '🔍 扫描目录';
        }
        if (progBar) progBar.classList.remove('active');
        if (progFill) progFill.style.width = '0%';
    }

    function createScanButton() {
        const btn = document.createElement('div');
        btn.className = 'usr-nav-scan-btn';
        btn.textContent = '🔍 扫描目录';
        btn.addEventListener('click', (e) => {
            e.stopPropagation();
            if (scanActive) {
                stopScan();
            } else {
                startScan();
            }
        });

        const progBar = document.createElement('div');
        progBar.className = 'usr-nav-scan-progress';
        const progFill = document.createElement('div');
        progFill.className = 'fill';
        progBar.appendChild(progFill);

        return { btn, progBar };
    }

    // ============================================================
    // 8. 消息总数估算 — v2.1 新增
    // ============================================================
    function updateEstimatedCount() {
        const footer = indicator.querySelector('.usr-nav-footer');
        if (!footer) return;

        const p = pool();
        if (!p) { footer.textContent = ''; return; }

        const discovered = p.idOrder.length;

        const scrollHolder = getScrollHolder();
        let estimatedTotal = null;
        if (scrollHolder) {
            const totalY = parseFloat(
                getComputedStyle(scrollHolder).getPropertyValue('--vlist-row-transform-y').trim()
            );
            if (totalY && totalY > 0) {
                estimatedTotal = Math.round(totalY / EST_ROW_HEIGHT);
            }
        }

        if (estimatedTotal !== null) {
            footer.textContent = `≈${estimatedTotal} 条消息 · 已发现 ${discovered} 条`;
        } else if (discovered > 0) {
            footer.textContent = `已发现 ${discovered} 条消息`;
        } else {
            footer.textContent = '';
        }
    }

    function createFooter() {
        const footer = document.createElement('div');
        footer.className = 'usr-nav-footer';
        return footer;
    }

    // ============================================================
    // 9. 事件系统
    // ============================================================
    let scrollTimer;

    let pending = false;
    function scheduleSync() {
        if (pending) return;
        pending = true;
        requestAnimationFrame(() => {
            ingest();
            pending = false;
        });
    }

    // ============================================================
    // 10. 初始化 — v2.1: 使用 v_list_scroller 作为主 scroller
    // ============================================================
    function watchUrlChanges() {
        const origPush = history.pushState;
        const origReplace = history.replaceState;

        function onUrlChange() {
            const newConvId = getConversationId() || '__default__';
            if (newConvId !== currentConvId) {
                // 立即切池+清面板，但不主动 sync
                // DOM 更新后 MutationObserver 会自然触发 ingest，避免读到旧 DOM
                switchToConversation(newConvId);
            }
        }

        history.pushState = function (...args) {
            origPush.apply(this, args);
            onUrlChange();
        };
        history.replaceState = function (...args) {
            origReplace.apply(this, args);
            onUrlChange();
        };
        window.addEventListener('popstate', onUrlChange);
    }

    async function init() {
        for (let i = 0; i < 100; i++) {
            const hasChat = getScroller() ||
                            document.querySelector('.scrollable-Se7zNt') ||
                            document.querySelector('[data-message-id]');
            if (hasChat) break;
            await new Promise(r => setTimeout(r, 300));
        }

        const outer = document.createElement('div');
        outer.className = 'usr-nav-native';
        indicator = document.createElement('div');
        indicator.className = 'usr-nav-indicator';
        outer.appendChild(indicator);
        document.body.appendChild(outer);

        // 创建扫描按钮和进度条
        const { btn: scanBtn, progBar } = createScanButton();
        indicator.appendChild(scanBtn);
        indicator.appendChild(progBar);

        // 创建底部统计
        const footer = createFooter();
        indicator.appendChild(footer);

        // 事件委托：点击导航项 → 跳转到对应消息
        indicator.addEventListener('click', (e) => {
            const item = e.target.closest('.usr-nav-item');
            if (item && item.dataset.messageId) {
                scrollToMessage(item.dataset.messageId);
            }
        });

        // 监听 SPA 路由切换（pushState / replaceState / popstate）
        watchUrlChanges();

        ingest();

        // 挂载 scroller 滚动监听
        const scroller = getScroller();
        if (scroller && !scroller._usrNavScrollBound) {
            scroller._usrNavScrollBound = true;
            scroller.addEventListener('scroll', () => {
                clearTimeout(scrollTimer);
                scrollTimer = setTimeout(updateActiveByScroll, 80);
            }, { passive: true });
        }

        // 聊天容器 MutationObserver
        const chat = scroller ||
                     document.querySelector('.scrollable-Se7zNt') ||
                     document.querySelector('[data-message-id]')?.closest('div[class*="scroll"]');
        if (chat) {
            const mo = new MutationObserver(() => scheduleSync());
            mo.observe(chat, { childList: true, subtree: true });
            // 如果 chat 不是 scroller 且有独立滚动，监听其 scroll
            if (chat !== scroller) {
                chat.addEventListener('scroll', () => {
                    clearTimeout(scrollTimer);
                    scrollTimer = setTimeout(updateActiveByScroll, 80);
                }, { passive: true });
            }
        }

        // 兜底：容器重绑定
        let currentChat = chat;
        const bodyMo = new MutationObserver(() => {
            const newScroller = getScroller();
            const newChat = newScroller || document.querySelector('.scrollable-Se7zNt');
            if (newChat && newChat !== currentChat) {
                currentChat = newChat;
                const mo = new MutationObserver(() => scheduleSync());
                mo.observe(newChat, { childList: true, subtree: true });
                if (!newChat._usrNavScrollBound) {
                    newChat._usrNavScrollBound = true;
                    newChat.addEventListener('scroll', () => {
                        clearTimeout(scrollTimer);
                        scrollTimer = setTimeout(updateActiveByScroll, 80);
                    }, { passive: true });
                }
                scheduleSync();
            }
        });
        bodyMo.observe(document.body, { childList: true, subtree: true });

        // window scroll 回退
        window.addEventListener('scroll', () => {
            clearTimeout(scrollTimer);
            scrollTimer = setTimeout(updateActiveByScroll, 80);
        }, { passive: true });

        // 终极兜底：每 4 秒轮询一次，MutationObserver 失效时仍能同步
        // scheduleSync 自带 rAF 防抖，ingest 无新消息时仅轻量更新，开销可忽略
        setInterval(() => scheduleSync(), 4000);
    }

    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded', () => setTimeout(init, 100));
    } else {
        setTimeout(init, 100);
    }
})();