(function () {
    'use strict';

    const state = {
        config: null,
        sessionId: null,
        messages: [],
        expandedMessages: new Set(),
        historyPage: 0,
        historyPageSize: 9999,
        historyTotal: 0,
        historyItems: [],
        model: '',
        outputMode: '流式输出 (Stream)',
        historyCount: 0,
        searchQuery: '',
        streaming: false,
    };

    const dom = {};

    document.addEventListener('DOMContentLoaded', init);

    async function init() {
        cacheDom();
        bindEvents();

        try {
            await loadConfig();
            const querySessionId = getSessionIdFromUrl();
            let loadedFromQuery = false;

            if (querySessionId !== null) {
                try {
                    await loadSession(querySessionId, { silent: true, updateUrl: true, replaceUrl: true });
                    loadedFromQuery = true;
                } catch (err) {
                    console.warn('Failed to load session from URL parameter:', err);
                    showToast('指定的会话不存在，已加载最新会话。', 'error');
                }
            }

            if (!loadedFromQuery) {
                await loadLatestSession({ updateUrl: true, replaceUrl: true });
            }

            await loadHistory();
        } catch (err) {
            showToast(err.message || '初始化失败', 'error');
        }

        renderSidebar();
        renderMessages();
        renderHistory();
    }

    function cacheDom() {
        dom.modelSelect = document.getElementById('model-select');
        dom.outputMode = document.getElementById('output-mode');
        dom.searchInput = document.getElementById('search-input');
        dom.searchFeedback = document.getElementById('search-feedback');
        dom.historyRange = document.getElementById('history-range');
        dom.historyRangeLabel = document.getElementById('history-range-label');
        dom.historyRangeValue = document.getElementById('history-range-value');
        dom.historyList = document.getElementById('history-list');
        dom.historyCount = document.getElementById('history-count');
        dom.historyPrev = document.getElementById('history-prev');
        dom.historyNext = document.getElementById('history-next');
        dom.newChatButton = document.getElementById('new-chat-btn');
        dom.chatMessages = document.getElementById('chat-messages');
        dom.chatForm = document.getElementById('chat-form');
        dom.chatInput = document.getElementById('chat-input');
        dom.sendButton = document.getElementById('send-btn');
        dom.fileInput = document.getElementById('file-input');
        dom.chatStatus = document.getElementById('chat-status');
        dom.toast = document.getElementById('toast');

        if (dom.sendButton && !dom.sendButton.dataset.defaultText) {
            dom.sendButton.dataset.defaultText = dom.sendButton.textContent || '发送';
        }
    }

    function bindEvents() {
        dom.modelSelect.addEventListener('change', () => {
            state.model = dom.modelSelect.value;
        });

        dom.outputMode.addEventListener('change', () => {
            state.outputMode = dom.outputMode.value;
        });

        dom.searchInput.addEventListener('input', () => {
            state.searchQuery = dom.searchInput.value.trim();
            state.expandedMessages = new Set();
            renderMessages();
        });

        dom.historyRange.addEventListener('input', () => {
            state.historyCount = Number(dom.historyRange.value || 0);
            updateHistorySlider();
        });

        dom.historyPrev.addEventListener('click', async () => {
            if (state.historyPage > 0) {
                state.historyPage -= 1;
                await loadHistory();
            }
        });

        dom.historyNext.addEventListener('click', async () => {
            const totalPages = Math.ceil(state.historyTotal / state.historyPageSize) || 1;
            if (state.historyPage < totalPages - 1) {
                state.historyPage += 1;
                await loadHistory();
            }
        });

        dom.newChatButton.addEventListener('click', async () => {
            if (state.streaming) {
                showToast('请等待当前回复完成后再新建会话', 'error');
                return;
            }
            try {
                const data = await fetchJSON('/api/session/new', { method: 'POST' });
                state.sessionId = data.session_id;
                state.messages = [];
                state.historyCount = 0;
                state.searchQuery = '';
                dom.searchInput.value = '';
                state.expandedMessages = new Set();
                state.historyPage = 0;
                renderSidebar();
                renderMessages();
                renderHistory();
                updateSessionInUrl(state.sessionId, { replace: false });
                showToast('当前会话已清空。', 'success');
                await loadHistory();
            } catch (err) {
                showToast(err.message || '新建会话失败', 'error');
            }
        });

        dom.chatForm.addEventListener('submit', handleSubmitMessage);

        dom.chatInput.addEventListener('keydown', (event) => {
            if (event.key === 'Enter' && !event.shiftKey && !event.ctrlKey && !event.altKey) {
                event.preventDefault();
                if (typeof dom.chatForm.requestSubmit === 'function') {
                    dom.chatForm.requestSubmit();
                } else if (dom.sendButton) {
                    dom.sendButton.click();
                }
            }
        });

        window.addEventListener('popstate', handlePopState);
    }

    async function loadConfig() {
        const config = await fetchJSON('/api/config');
        state.config = config;
        const models = Array.isArray(config.models) ? config.models : [];
        state.model = config.default_model || models[0] || '';
        populateSelect(dom.modelSelect, models, state.model);
        populateSelect(dom.outputMode, config.output_modes || [], state.outputMode);
    }

    function populateSelect(selectEl, values, selected) {
        selectEl.innerHTML = '';
        values.forEach((value) => {
            const option = document.createElement('option');
            option.value = value;
            option.textContent = value;
            if (value === selected) {
                option.selected = true;
            }
            selectEl.appendChild(option);
        });
        if (!values.length) {
            const option = document.createElement('option');
            option.value = '';
            option.textContent = '无可用选项';
            selectEl.appendChild(option);
        }
    }

    async function loadLatestSession(options = {}) {
        const { updateUrl = true, replaceUrl = false } = options;
        const data = await fetchJSON('/api/session/latest');
        state.sessionId = typeof data.session_id === 'number' ? data.session_id : 0;
        state.messages = Array.isArray(data.messages) ? data.messages : [];
        state.expandedMessages = new Set();
        state.historyCount = Math.min(state.historyCount, state.messages.length);
        state.searchQuery = '';
        dom.searchInput.value = '';
        state.historyPage = 0;
        renderSidebar();
        renderMessages();
        renderHistory();

        if (updateUrl) {
            updateSessionInUrl(state.sessionId, { replace: replaceUrl });
        }
    }

    async function loadSession(sessionId, options = {}) {
        const { silent = false, updateUrl = true, replaceUrl = false } = options;

        if (state.streaming) {
            if (!silent) {
                showToast('请等待当前回复完成后再切换会话', 'error');
            }
            return false;
        }

        try {
            const data = await fetchJSON(`/api/session/${sessionId}`);
            state.sessionId = data.session_id;
            state.messages = Array.isArray(data.messages) ? data.messages : [];
            state.historyCount = Math.min(state.historyCount, state.messages.length);
            state.expandedMessages = new Set();
            state.searchQuery = '';
            dom.searchInput.value = '';
            renderSidebar();
            renderMessages();
            renderHistory();

            if (updateUrl) {
                updateSessionInUrl(state.sessionId, { replace: replaceUrl });
            }

            return true;
        } catch (err) {
            if (!silent) {
                showToast(err.message || '加载会话失败', 'error');
            }
            throw err;
        }
    }

    async function loadHistory() {
        try {
            const data = await fetchJSON(`/api/history?page=${state.historyPage}&page_size=${state.historyPageSize}`);
            const total = data.total || 0;
            const items = Array.isArray(data.items) ? data.items : [];
            if (state.historyPage > 0 && items.length === 0 && total > 0) {
                const maxPage = Math.max(0, Math.ceil(total / state.historyPageSize) - 1);
                if (state.historyPage > maxPage) {
                    state.historyPage = maxPage;
                    await loadHistory();
                    return;
                }
            }
            state.historyTotal = total;
            state.historyItems = items;
            renderHistory();
        } catch (err) {
            showToast(err.message || '获取历史记录失败', 'error');
        }
    }

    function renderSidebar() {
        if (state.config) {
            populateSelect(dom.modelSelect, state.config.models || [], state.model);
            populateSelect(dom.outputMode, state.config.output_modes || [], state.outputMode);
        }
        updateHistorySlider();
        updateSearchFeedback();
    }

    function updateHistorySlider() {
        const total = state.messages.length;
        dom.historyRange.max = String(total);
        state.historyCount = Math.min(state.historyCount, total);
        dom.historyRange.value = String(state.historyCount);
        dom.historyRangeLabel.textContent = `选择使用的历史消息数量(共${total}条)`;
        dom.historyRangeValue.textContent = `您选择的历史消息数量是: ${state.historyCount}`;
    }

    function updateSearchFeedback() {
        if (!state.searchQuery) {
            dom.searchFeedback.textContent = '无匹配。';
            return;
        }
        const matches = state.messages.filter((msg) => messageMatches(msg.content, state.searchQuery)).length;
        dom.searchFeedback.textContent = `共找到 ${matches} 条匹配。`;
    }

    function setStatus(message, stateClass) {
        if (!dom.chatStatus) {
            return;
        }
        dom.chatStatus.textContent = message || '';
        dom.chatStatus.classList.remove('running', 'error');
        if (!message) {
            return;
        }
        if (stateClass) {
            dom.chatStatus.classList.add(stateClass);
        }
    }

    function setStreaming(active) {
        state.streaming = active;
        if (dom.sendButton) {
            dom.sendButton.disabled = active;
            const defaultText = dom.sendButton.dataset.defaultText || '发送';
            dom.sendButton.textContent = active ? '发送中…' : defaultText;
        }
        if (dom.newChatButton) {
            dom.newChatButton.disabled = active;
        }
        if (active) {
            setStatus('正在生成回复…', 'running');
        }
    }

    function renderHistory() {
        if (dom.historyCount) {
            const total = Number.isFinite(state.historyTotal) ? state.historyTotal : 0;
            dom.historyCount.textContent = `共 ${total} 条`;
        }

        dom.historyList.innerHTML = '';
        if (!state.historyItems.length) {
            const empty = document.createElement('div');
            empty.className = 'sidebar-help';
            empty.textContent = '无记录。';
            dom.historyList.appendChild(empty);
        } else {
            state.historyItems.forEach((item) => {
                const row = document.createElement('div');
                row.className = 'history-row';
                row.dataset.sessionId = String(item.session_id);
                row.setAttribute('role', 'listitem');
                if (item.session_id === state.sessionId) {
                    row.classList.add('active');
                }

                const loadLink = document.createElement('a');
                loadLink.className = 'history-title-link';
                loadLink.href = buildSessionUrl(item.session_id);
                const displayTitle = (item.title && item.title.trim()) ? item.title.trim() : `会话 #${item.session_id}`;
                const primary = document.createElement('span');
                primary.className = 'history-title-text';
                primary.textContent = displayTitle;
                loadLink.appendChild(primary);

                const subtitle = document.createElement('span');
                subtitle.className = 'history-subtitle';
                subtitle.textContent = item.filename ? item.filename : `会话 #${item.session_id}`;
                loadLink.appendChild(subtitle);
                loadLink.title = `会话 #${item.session_id} · 点击加载`;

                loadLink.addEventListener('click', async (event) => {
                    const isModified = event.metaKey || event.ctrlKey || event.shiftKey || event.altKey || event.button !== 0;
                    if (isModified) {
                        return;
                    }
                    event.preventDefault();
                    try {
                        await loadSession(item.session_id, { replaceUrl: false });
                    } catch (err) {
                        console.warn('Failed to load session from history list:', err);
                    }
                });
                row.appendChild(loadLink);

                const moveButton = document.createElement('button');
                moveButton.className = 'history-icon-button';
                moveButton.type = 'button';
                moveButton.textContent = '📦';
                moveButton.title = '移动到备份文件夹';
                moveButton.addEventListener('click', async (event) => {
                    event.stopPropagation();
                    try {
                        await fetchJSON('/api/history/move', {
                            method: 'POST',
                            body: { session_id: item.session_id },
                        });
                        showToast('已移动到备份。', 'success');
                        await loadHistory();
                    } catch (err) {
                        showToast(err.message || '移动失败', 'error');
                    }
                });
                row.appendChild(moveButton);

                const deleteButton = document.createElement('button');
                deleteButton.className = 'history-icon-button';
                deleteButton.type = 'button';
                deleteButton.textContent = '❌';
                deleteButton.title = '删除';
                deleteButton.addEventListener('click', async (event) => {
                    event.stopPropagation();
                    try {
                        await fetchJSON(`/api/history/${item.session_id}`, { method: 'DELETE' });
                        showToast('已删除。', 'success');
                        if (item.session_id === state.sessionId) {
                            await loadLatestSession();
                        }
                        await loadHistory();
                    } catch (err) {
                        showToast(err.message || '删除失败', 'error');
                    }
                });
                row.appendChild(deleteButton);

                dom.historyList.appendChild(row);
            });
        }

        const totalPages = Math.ceil(state.historyTotal / state.historyPageSize) || 1;
        dom.historyPrev.disabled = state.historyPage <= 0;
        dom.historyNext.disabled = state.historyPage >= totalPages - 1;
    }

    function renderMessages() {
        dom.chatMessages.innerHTML = '';
        const total = state.messages.length;
        const searching = Boolean(state.searchQuery);

        state.messages.forEach((message, index) => {
            const wrapper = document.createElement('div');
            wrapper.className = `message ${message.role === 'assistant' ? 'assistant' : 'user'}`;
            wrapper.dataset.index = String(index);

            const header = document.createElement('div');
            header.className = 'message-header';
            header.textContent = message.role === 'assistant' ? 'Assistant' : 'User';
            wrapper.appendChild(header);

            const contentEl = document.createElement('div');
            contentEl.className = 'message-content';
            const expanded = state.expandedMessages.has(index);
            const shouldClamp = !searching && index < total - 1 && !expanded;
            if (shouldClamp) {
                contentEl.classList.add('clamped');
            }

            const query = state.searchQuery && messageMatches(message.content, state.searchQuery)
                ? state.searchQuery
                : '';
            renderContent(message.content, contentEl, query);
            wrapper.appendChild(contentEl);

            const actions = document.createElement('div');
            actions.className = 'message-actions';

            if (!searching && index < total - 1) {
                const toggleButton = document.createElement('button');
                toggleButton.className = 'message-button';
                toggleButton.textContent = expanded ? '<<' : '>>';
                toggleButton.addEventListener('click', () => {
                    if (expanded) {
                        state.expandedMessages.delete(index);
                    } else {
                        state.expandedMessages.add(index);
                    }
                    renderMessages();
                });
                actions.appendChild(toggleButton);
            }

            if (message.role === 'assistant') {
                const exportButton = document.createElement('button');
                exportButton.className = 'message-button';
                exportButton.textContent = '导出';
                exportButton.addEventListener('click', async () => {
                    try {
                        await fetchJSON('/api/export', {
                            method: 'POST',
                            body: { content: message.content },
                        });
                        showToast('已导出到 blog 文件夹。', 'success');
                    } catch (err) {
                        showToast(err.message || '导出失败', 'error');
                    }
                });
                actions.appendChild(exportButton);
            }

            wrapper.appendChild(actions);
            dom.chatMessages.appendChild(wrapper);
        });

        updateSearchFeedback();
        scrollToBottom();
    }

    function renderContent(content, container, query) {
        container.innerHTML = '';
        const highlightQuery = query || '';

        if (typeof content === 'string' || content === null || content === undefined) {
            renderMarkdownContent(container, String(content || ''));
            applyHighlight(container, highlightQuery);
            return;
        }

        if (Array.isArray(content)) {
            content.forEach((part) => {
                if (part && part.type === 'text') {
                    const textContainer = document.createElement('div');
                    renderMarkdownContent(textContainer, String(part.text || ''));
                    container.appendChild(textContainer);
                } else if (part && part.type === 'image_url') {
                    const url = part.image_url && part.image_url.url ? part.image_url.url : '';
                    const img = document.createElement('img');
                    img.src = url;
                    img.alt = '上传的图片';
                    img.loading = 'lazy';
                    container.appendChild(img);
                } else {
                    const fallback = document.createElement('pre');
                    fallback.textContent = JSON.stringify(part, null, 2);
                    container.appendChild(fallback);
                }
            });
            applyHighlight(container, highlightQuery);
            return;
        }

        const pre = document.createElement('pre');
        pre.textContent = typeof content === 'object' ? JSON.stringify(content, null, 2) : String(content || '');
        container.appendChild(pre);
        applyHighlight(container, highlightQuery);
    }

    function renderMarkdownContent(container, text) {
        const normalized = String(text || '').replace(/\r\n/g, '\n');
        const lines = normalized.split('\n');
        let paragraphBuffer = [];
        let listBuffer = [];
        let blockquoteBuffer = [];
        let inCodeBlock = false;
        let codeLang = '';
        let codeBuffer = [];

        const flushParagraph = () => {
            if (!paragraphBuffer.length) {
                return;
            }
            const paragraphText = paragraphBuffer.join('\n');
            const paragraph = document.createElement('p');
            appendInlineMarkdown(paragraph, paragraphText);
            container.appendChild(paragraph);
            paragraphBuffer = [];
        };

        const flushList = () => {
            if (!listBuffer.length) {
                return;
            }
            const list = document.createElement('ul');
            listBuffer.forEach((item) => {
                const li = document.createElement('li');
                appendInlineMarkdown(li, item);
                list.appendChild(li);
            });
            container.appendChild(list);
            listBuffer = [];
        };

        const flushBlockquote = () => {
            if (!blockquoteBuffer.length) {
                return;
            }
            const blockquote = document.createElement('blockquote');
            const textContent = blockquoteBuffer.join('\n');
            appendInlineMarkdown(blockquote, textContent);
            container.appendChild(blockquote);
            blockquoteBuffer = [];
        };

        const flushCode = () => {
            const pre = document.createElement('pre');
            const code = document.createElement('code');
            if (codeLang) {
                code.dataset.lang = codeLang;
                code.className = `language-${codeLang}`;
            }
            code.textContent = codeBuffer.join('\n');
            pre.appendChild(code);
            container.appendChild(pre);
            codeBuffer = [];
            codeLang = '';
            inCodeBlock = false;
        };

        lines.forEach((rawLine) => {
            const line = rawLine;
            const fenceMatch = line.match(/^```([A-Za-z0-9_-]+)?\s*$/);
            if (fenceMatch) {
                if (inCodeBlock) {
                    flushCode();
                } else {
                    flushParagraph();
                    flushList();
                    flushBlockquote();
                    inCodeBlock = true;
                    codeLang = fenceMatch[1] ? fenceMatch[1].toLowerCase() : '';
                    codeBuffer = [];
                }
                return;
            }

            if (inCodeBlock) {
                codeBuffer.push(line);
                return;
            }

            const listMatch = line.match(/^\s*[-*+]\s+(.*)$/);
            if (listMatch) {
                flushParagraph();
                flushBlockquote();
                listBuffer.push(listMatch[1]);
                return;
            }

            const blockquoteMatch = line.match(/^>\s?(.*)$/);
            if (blockquoteMatch) {
                flushParagraph();
                flushList();
                blockquoteBuffer.push(blockquoteMatch[1]);
                return;
            }

            if (!line.trim()) {
                flushParagraph();
                flushList();
                flushBlockquote();
                return;
            }

            const headingMatch = line.match(/^(#{1,6})\s+(.*)$/);
            if (headingMatch) {
                flushParagraph();
                flushList();
                flushBlockquote();
                const level = Math.min(headingMatch[1].length, 6);
                const heading = document.createElement(`h${level}`);
                appendInlineMarkdown(heading, headingMatch[2]);
                container.appendChild(heading);
                return;
            }

            paragraphBuffer.push(line);
        });

        if (inCodeBlock) {
            flushCode();
        }
        flushParagraph();
        flushList();
        flushBlockquote();
    }

    function appendInlineMarkdown(parent, text) {
        const pattern = /(!?\[[^\]]*\]\([^\)]+\)|`[^`]*`|\*\*[^*]+\*\*|\*[^*]+\*|~~[^~]+~~)/g;
        let lastIndex = 0;
        let match;
        while ((match = pattern.exec(text)) !== null) {
            if (match.index > lastIndex) {
                appendTextNode(parent, text.slice(lastIndex, match.index));
            }
            appendMarkdownToken(parent, match[0]);
            lastIndex = pattern.lastIndex;
        }
        if (lastIndex < text.length) {
            appendTextNode(parent, text.slice(lastIndex));
        }
    }

    function appendMarkdownToken(parent, token) {
        if (token.startsWith('`') && token.endsWith('`')) {
            const code = document.createElement('code');
            code.textContent = token.slice(1, -1);
            parent.appendChild(code);
            return;
        }
        if (token.startsWith('**') && token.endsWith('**')) {
            const strong = document.createElement('strong');
            appendInlineMarkdown(strong, token.slice(2, -2));
            parent.appendChild(strong);
            return;
        }
        if (token.startsWith('*') && token.endsWith('*')) {
            const em = document.createElement('em');
            appendInlineMarkdown(em, token.slice(1, -1));
            parent.appendChild(em);
            return;
        }
        if (token.startsWith('~~') && token.endsWith('~~')) {
            const del = document.createElement('del');
            appendInlineMarkdown(del, token.slice(2, -2));
            parent.appendChild(del);
            return;
        }
        if (token.startsWith('![')) {
            const match = token.match(/^!\[([^\]]*)\]\(([^\)]+)\)$/);
            if (match) {
                const img = document.createElement('img');
                img.alt = match[1];
                img.src = match[2];
                img.loading = 'lazy';
                parent.appendChild(img);
                return;
            }
        }
        if (token.startsWith('[')) {
            const match = token.match(/^\[([^\]]+)\]\(([^\)]+)\)$/);
            if (match) {
                const anchor = document.createElement('a');
                anchor.href = match[2];
                anchor.target = '_blank';
                anchor.rel = 'noopener noreferrer';
                anchor.textContent = match[1];
                parent.appendChild(anchor);
                return;
            }
        }
        appendTextNode(parent, token);
    }

    function appendTextNode(parent, text) {
        if (!text) {
            return;
        }
        const fragments = String(text).split(/(\n)/);
        fragments.forEach((fragment) => {
            if (fragment === '\n') {
                parent.appendChild(document.createElement('br'));
            } else if (fragment) {
                parent.appendChild(document.createTextNode(fragment));
            }
        });
    }

    function clearHighlights(root) {
        if (!root) {
            return;
        }
        root.querySelectorAll('mark.hl').forEach((mark) => {
            const parent = mark.parentNode;
            if (!parent) {
                return;
            }
            while (mark.firstChild) {
                parent.insertBefore(mark.firstChild, mark);
            }
            parent.removeChild(mark);
            parent.normalize();
        });
    }

    function applyHighlight(root, query) {
        if (!root) {
            return;
        }
        clearHighlights(root);
        if (!query) {
            return;
        }
        const lowerQuery = query.toLowerCase();
        const walker = document.createTreeWalker(root, NodeFilter.SHOW_TEXT, null);
        const matches = [];
        while (walker.nextNode()) {
            const node = walker.currentNode;
            if (!node || !node.nodeValue || !node.nodeValue.trim()) {
                continue;
            }
            const text = node.nodeValue;
            const lowerText = text.toLowerCase();
            let index = lowerText.indexOf(lowerQuery);
            while (index !== -1) {
                matches.push({ node, start: index, end: index + query.length });
                index = lowerText.indexOf(lowerQuery, index + query.length);
            }
        }

        for (let i = matches.length - 1; i >= 0; i -= 1) {
            const { node, start, end } = matches[i];
            if (!node || !node.parentNode) {
                continue;
            }
            const range = document.createRange();
            range.setStart(node, start);
            range.setEnd(node, end);
            const mark = document.createElement('mark');
            mark.className = 'hl';
            range.surroundContents(mark);
        }
    }

    function messageMatches(content, query) {
        if (!query) {
            return false;
        }
        const lower = query.toLowerCase();
        if (typeof content === 'string') {
            return content.toLowerCase().includes(lower);
        }
        if (Array.isArray(content)) {
            return content.some((part) => {
                if (!part || part.type !== 'text') {
                    return false;
                }
                return String(part.text || '').toLowerCase().includes(lower);
            });
        }
        try {
            return JSON.stringify(content).toLowerCase().includes(lower);
        } catch (err) {
            return false;
        }
    }

    async function handleSubmitMessage(event) {
        event.preventDefault();
        if (state.streaming) {
            showToast('请等待当前回复完成', 'error');
            return;
        }

        const text = dom.chatInput.value.trim();
        const files = dom.fileInput.files;
        if (!text && (!files || files.length === 0)) {
            showToast('请输入内容或上传文件', 'error');
            return;
        }

        let uploads = [];
        const hasFiles = files && files.length > 0;
        if (hasFiles) {
            try {
                setStatus('正在上传文件…', 'running');
                uploads = await uploadAttachments(files);
            } catch (err) {
                const message = err.message || '文件上传失败';
                setStatus(message, 'error');
                showToast(message, 'error');
                return;
            }
        }

        const { content } = buildUserContent(text, uploads);
        if (!hasContent(content)) {
            setStatus('内容不能为空', 'error');
            showToast('内容不能为空', 'error');
            return;
        }

        setStatus('');
        state.expandedMessages = new Set();
        const userMessage = { role: 'user', content };
        state.messages.push(userMessage);
        renderMessages();
        scrollToBottom();

        dom.chatInput.value = '';
        dom.fileInput.value = '';

        const assistantMessage = { role: 'assistant', content: '' };
        state.messages.push(assistantMessage);
        const assistantIndex = state.messages.length - 1;
        renderMessages();
        scrollToBottom();

        const payload = {
            session_id: state.sessionId ?? 0,
            model: state.model,
            content,
            history_count: state.historyCount,
            stream: state.outputMode === '流式输出 (Stream)',
        };

        setStreaming(true);
        try {
            if (payload.stream) {
                await streamAssistantReply(payload, assistantMessage, assistantIndex);
            } else {
                const data = await fetchJSON('/api/chat', {
                    method: 'POST',
                    body: payload,
                });
                assistantMessage.content = data.message || '';
                updateMessageContent(assistantIndex, assistantMessage.content);
                showToast('已生成回复', 'success');
                setStatus('');
            }
        } catch (err) {
            state.messages.splice(assistantIndex, 1);
            renderMessages();
            const message = err.message || '发送失败';
            setStatus(message, 'error');
            showToast(message, 'error');
        } finally {
            try {
                state.historyPage = 0;
                await loadHistory();
            } catch (historyErr) {
                console.error('刷新历史记录失败', historyErr);
            } finally {
                updateHistorySlider();
                setStreaming(false);
            }
        }
    }

    function hasContent(content) {
        if (typeof content === 'string') {
            return Boolean(content.trim());
        }
        if (Array.isArray(content)) {
            return content.length > 1 || (content[0] && String(content[0].text || '').trim());
        }
        return Boolean(content);
    }

    async function uploadAttachments(fileList) {
        if (!fileList || fileList.length === 0) {
            return [];
        }
        const formData = new FormData();
        Array.from(fileList).forEach((file) => formData.append('files', file));
        const response = await fetch('/api/upload', {
            method: 'POST',
            body: formData,
        });
        if (!response.ok) {
            throw new Error('文件上传失败');
        }
        return await response.json();
    }

    function buildUserContent(text, uploads) {
        const results = Array.isArray(uploads) ? uploads : [];
        if (!results.length) {
            return { content: text };
        }

        const contentParts = [{ type: 'text', text: text }];
        let additionalPrompt = '';

        results.forEach((item) => {
            if (item.type === 'image' && item.data) {
                contentParts.push({
                    type: 'image_url',
                    image_url: { url: item.data },
                });
            } else if (item.type === 'file' && item.url) {
                additionalPrompt += `本次提问包含：${item.url} 文件\n`;
            }
        });

        const promptSuffix = additionalPrompt.trim();
        if (contentParts.length > 1) {
            const base = contentParts[0].text || '';
            contentParts[0].text = promptSuffix ? `${base}\n${promptSuffix}`.trim() : base;
            return { content: contentParts };
        }

        let combined = text || '';
        if (promptSuffix) {
            combined = combined ? `${combined}\n${promptSuffix}` : promptSuffix;
        }
        return { content: combined.trim() };
    }

    async function streamAssistantReply(payload, assistantMessage, assistantIndex) {
        const response = await fetch('/api/chat', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify(payload),
        });
        if (!response.ok || !response.body) {
            const errorText = await safeReadText(response);
            throw new Error(errorText || '生成失败');
        }

        const reader = response.body.getReader();
        const decoder = new TextDecoder('utf-8');
        let buffer = '';
        let done = false;

        while (!done) {
            const { value, done: streamDone } = await reader.read();
            done = streamDone;
            if (value) {
                buffer += decoder.decode(value, { stream: !done });
                let newlineIndex = buffer.indexOf('\n');
                while (newlineIndex !== -1) {
                    const line = buffer.slice(0, newlineIndex).trim();
                    buffer = buffer.slice(newlineIndex + 1);
                    if (line) {
                        const status = handleStreamLine(line, assistantMessage, assistantIndex);
                        if (status === 'end') {
                            return;
                        }
                    }
                    newlineIndex = buffer.indexOf('\n');
                }
            }
        }

        setStatus('');
    }

    function handleStreamLine(line, assistantMessage, assistantIndex) {
        let payload;
        try {
            payload = JSON.parse(line);
        } catch (err) {
            return;
        }

        if (payload.type === 'delta') {
            if (typeof assistantMessage.content !== 'string') {
                assistantMessage.content = '';
            }
            assistantMessage.content += payload.text || '';
            updateMessageContent(assistantIndex, assistantMessage.content);
            scrollToBottom();
            return null;
        } else if (payload.type === 'end') {
            showToast('已生成回复', 'success');
            setStatus('');
            return 'end';
        } else if (payload.type === 'error') {
            throw new Error(payload.message || '生成失败');
        }
    }

    function updateMessageContent(index, content) {
        const selector = `.message[data-index="${index}"] .message-content`;
        const node = dom.chatMessages.querySelector(selector);
        if (!node) {
            renderMessages();
            return;
        }
        node.classList.remove('clamped');
        renderContent(content, node, state.searchQuery && messageMatches(content, state.searchQuery) ? state.searchQuery : '');
    }

    function scrollToBottom() {
        dom.chatMessages.scrollTop = dom.chatMessages.scrollHeight;
    }

    function getSessionIdFromUrl() {
        const params = new URLSearchParams(window.location.search);
        const value = params.get('session');
        if (!value) {
            return null;
        }
        const parsed = Number(value);
        return Number.isInteger(parsed) && parsed >= 0 ? parsed : null;
    }

    function buildSessionUrl(sessionId) {
        const current = new URL(window.location.href);
        if (Number.isInteger(sessionId) && sessionId >= 0) {
            current.searchParams.set('session', String(sessionId));
        } else {
            current.searchParams.delete('session');
        }
        current.hash = '';
        const search = current.searchParams.toString();
        return `${current.pathname}${search ? `?${search}` : ''}`;
    }

    function updateSessionInUrl(sessionId, options = {}) {
        if (!window.history || typeof window.history.replaceState !== 'function') {
            return;
        }
        const { replace = false } = options;
        const target = buildSessionUrl(sessionId);
        const stateData = { sessionId };
        if (replace) {
            window.history.replaceState(stateData, '', target);
        } else {
            window.history.pushState(stateData, '', target);
        }
    }

    async function handlePopState(event) {
        if (state.streaming) {
            return;
        }

        const stateSessionId = event.state && Number.isInteger(event.state.sessionId)
            ? event.state.sessionId
            : getSessionIdFromUrl();

        try {
            if (stateSessionId !== null) {
                await loadSession(stateSessionId, { silent: true, updateUrl: false });
            } else {
                await loadLatestSession({ updateUrl: false });
            }
            await loadHistory();
        } catch (err) {
            console.warn('Failed to restore session from history navigation:', err);
        }
    }

    async function fetchJSON(url, options = {}) {
        const opts = { ...options };
        opts.headers = { ...(opts.headers || {}) };
        if (opts.body && !(opts.body instanceof FormData) && typeof opts.body !== 'string') {
            opts.headers['Content-Type'] = 'application/json';
            opts.body = JSON.stringify(opts.body);
        }
        const response = await fetch(url, opts);
        if (!response.ok) {
            const message = await readErrorMessage(response);
            throw new Error(message || '请求失败');
        }
        if (response.status === 204) {
            return {};
        }
        const text = await response.text();
        return text ? JSON.parse(text) : {};
    }

    async function readErrorMessage(response) {
        const text = await safeReadText(response);
        if (!text) {
            return response.statusText;
        }
        try {
            const data = JSON.parse(text);
            return data.detail || data.message || text;
        } catch (err) {
            return text;
        }
    }

    async function safeReadText(response) {
        try {
            return await response.text();
        } catch (err) {
            return '';
        }
    }

    let toastTimer;
    function showToast(message, type = 'success') {
        if (!dom.toast) {
            return;
        }
        dom.toast.textContent = message;
        dom.toast.classList.remove('hidden', 'success', 'error', 'show');
        dom.toast.classList.add(type, 'show');
        clearTimeout(toastTimer);
        toastTimer = setTimeout(() => {
            dom.toast.classList.remove('show');
            toastTimer = setTimeout(() => dom.toast.classList.add('hidden'), 300);
        }, 2500);
    }
})();