document.addEventListener('DOMContentLoaded', () => {
    const uploadBtn = document.getElementById('upload-btn');
    const indexBtn = document.getElementById('index-btn');
    const sendBtn = document.getElementById('send-btn');
    const promptInput = document.getElementById('prompt-input');
    const chatContainer = document.getElementById('chat-container');
    const topKInput = document.getElementById('top-k');
    const statusMsg = document.getElementById('index-status');

    // Toggle helpers
    const toggleVector = document.getElementById('toggle-vector');
    const togglePage = document.getElementById('toggle-page');
    const toggleToc = document.getElementById('toggle-toc');

    function getActiveRagModes() {
        return {
            vector: toggleVector.checked,
            page: togglePage.checked,
            toc: toggleToc.checked
        };
    }

    function getRagModeString() {
        const m = getActiveRagModes();
        if (m.vector && m.page && m.toc) return 'all';
        const parts = [];
        if (m.page) parts.push('page');
        if (m.vector) parts.push('vector');
        if (m.toc) parts.push('toc');
        return parts.join(',') || 'all';
    }

    // Auto-resize textarea
    promptInput.addEventListener('input', function () {
        this.style.height = 'auto';
        this.style.height = (this.scrollHeight) + 'px';
        if (this.value.trim().length > 0) {
            sendBtn.removeAttribute('disabled');
        } else {
            sendBtn.setAttribute('disabled', 'true');
        }
    });

    promptInput.addEventListener('keydown', (e) => {
        if (e.key === 'Enter' && !e.shiftKey) {
            e.preventDefault();
            handleSend();
        }
    });

    sendBtn.addEventListener('click', handleSend);

    async function fetchDocuments() {
        const docList = document.getElementById('documents-list');
        try {
            const res = await fetch('/api/documents');
            const data = await res.json();

            docList.innerHTML = '';
            if (data.documents.length === 0) {
                docList.innerHTML = '<div style="font-size:0.8rem; color:var(--text-secondary); padding: 8px;">No documents uploaded.</div>';
                return;
            }

            data.documents.forEach(doc => {
                const card = document.createElement('div');
                card.className = 'document-card';

                const sizeKb = (doc.size / 1024).toFixed(1);

                let iconHtml = '';
                if (doc.thumbnail) {
                    iconHtml = `<img src="${doc.thumbnail}" alt="${doc.name}" class="doc-thumbnail" onerror="this.style.display='none'">`;
                } else {
                    const iconClass = doc.type === 'pdf' ? 'icon-pdf' :
                        doc.type === 'docx' ? 'icon-docx' :
                            doc.type === 'txt' ? 'icon-txt' : 'icon-default';
                    iconHtml = `<div class="doc-icon ${iconClass}">${doc.type.toUpperCase()}</div>`;
                }

                card.innerHTML = `
                    ${iconHtml}
                    <div class="doc-name" title="${doc.name}">${doc.name}</div>
                    <div class="doc-size">${sizeKb} KB</div>
                    <div style="display:flex; gap:4px; margin-top:4px;">
                        <button class="doc-tree-btn" title="View TOC Tree" onclick="event.stopPropagation()">🌳</button>
                    </div>
                `;

                // Tree button handler
                const treeBtn = card.querySelector('.doc-tree-btn');
                treeBtn.addEventListener('click', (e) => {
                    e.stopPropagation();
                    openTreeModal(doc.name);
                });

                // Add click handler to open embeddings viewer
                card.style.cursor = 'pointer';
                card.addEventListener('click', () => openChunksModal(doc.name));

                docList.appendChild(card);
            });
        } catch (e) {
            console.error("Failed to load documents", e);
        }
    }

    // Call once on load
    fetchDocuments();
    fetchStats();

    let isIndexing = false;
    let pollInterval = null;
    const overlay = document.getElementById('indexing-overlay');
    const overlayText = document.getElementById('overlay-text');

    async function checkIndexStatus() {
        try {
            const res = await fetch('/api/index/status');
            const data = await res.json();

            if (data.is_indexing) {
                if (data.progress) {
                    overlayText.textContent = data.progress;
                }
                if (!isIndexing) {
                    isIndexing = true;
                    statusMsg.innerHTML = '<span class="spinner"></span> Indexing in progress...';
                    statusMsg.style.color = 'var(--brand-color)';
                    indexBtn.disabled = true;
                    uploadBtn.disabled = true;
                    overlay.style.display = 'flex';
                    if (!pollInterval) {
                        pollInterval = setInterval(checkIndexStatus, 2000);
                    }
                }
            } else {
                if (isIndexing) {
                    isIndexing = false;
                    statusMsg.textContent = 'Ready.';
                    statusMsg.style.color = 'var(--text-secondary)';
                    indexBtn.disabled = false;
                    uploadBtn.disabled = false;
                    overlay.style.display = 'none';
                    if (pollInterval) {
                        clearInterval(pollInterval);
                        pollInterval = null;

                        // Wait a tiny bit and refresh so that thumbnails appear
                        setTimeout(fetchDocuments, 1000);
                    }
                }
            }
        } catch (e) {
            console.error("Failed to check index status", e);
        }
    }

    // Start polling if we are currently indexing
    checkIndexStatus();

    uploadBtn.addEventListener('click', async () => {
        const fileInput = document.getElementById('file-upload');
        if (fileInput.files.length === 0) return alert('Select files first.');

        const formData = new FormData();
        for (const file of fileInput.files) {
            formData.append('files', file);
        }

        formData.append('rag_mode', getRagModeString());

        uploadBtn.textContent = 'Uploading...';
        uploadBtn.disabled = true;

        try {
            const response = await fetch('/api/upload', {
                method: 'POST',
                body: formData
            });
            const result = await response.json();
            alert(result.message);
            fileInput.value = "";

            // Refresh documents list 
            fetchDocuments();
            // Force status check for auto-indexing
            checkIndexStatus();

        } catch (error) {
            console.error(error);
            alert('Upload failed.');
        } finally {
            uploadBtn.textContent = 'Upload';
            if (!isIndexing) uploadBtn.disabled = false;
        }
    });

    indexBtn.addEventListener('click', async () => {
        indexBtn.textContent = 'Starting...';
        indexBtn.disabled = true;
        statusMsg.innerHTML = '<span class="spinner"></span> Triggering index...';

        const ragMode = getRagModeString();

        try {
            const response = await fetch('/api/index', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ rag_mode: ragMode })
            });
            const result = await response.json();
            console.log(result.message);
            checkIndexStatus();
        } catch (error) {
            console.error(error);
            statusMsg.textContent = "Error triggering indexing.";
            indexBtn.disabled = false;
        } finally {
            indexBtn.textContent = 'Re-index All';
        }
    });

    const clearBtn = document.getElementById('clear-btn');
    clearBtn.addEventListener('click', async () => {
        if (!confirm('Are you sure you want to clear ALL indexed data? This action cannot be undone.')) {
            return;
        }

        clearBtn.textContent = 'Clearing...';
        clearBtn.disabled = true;
        try {
            const response = await fetch('/api/index/clear', { method: 'POST' });
            const result = await response.json();
            alert(result.message);
            fetchDocuments();
            fetchStats();
        } catch (error) {
            console.error(error);
            alert('Failed to clear database.');
        } finally {
            clearBtn.textContent = 'Clear All Data';
            clearBtn.disabled = false;
        }
    });

    async function fetchStats() {
        try {
            const response = await fetch('/api/stats');
            const data = await response.json();
            document.getElementById('stat-embed').textContent = data.tokens.embedding_tokens.toLocaleString();
            document.getElementById('stat-prompt').textContent = data.tokens.prompt_tokens.toLocaleString();
            document.getElementById('stat-response').textContent = data.tokens.completion_tokens.toLocaleString();
            document.getElementById('stat-toc').textContent = (data.tokens.toc_analysis_tokens || 0).toLocaleString();
            document.getElementById('stat-total').textContent = data.total_tokens.toLocaleString();
        } catch (error) {
            console.error('Error fetching stats:', error);
        }
    }

    function cleanMarkdown(text) {
        return marked.parse(text);
    }

    // ── History Management ───────────────────────────────────────────────────
    const MAX_HISTORY_TURNS = 10; // 5 user + 5 assistant

    function getHistory(ragMode) {
        try {
            const h = localStorage.getItem(`chat_history_${ragMode}`);
            return h ? JSON.parse(h) : [];
        } catch (e) {
            console.error('Error reading history', e);
            return [];
        }
    }

    function saveHistory(ragMode, history) {
        try {
            if (history.length > MAX_HISTORY_TURNS) {
                // Keep the most recent messages, taking care to keep user/assistant pairs intact if possible
                history = history.slice(history.length - MAX_HISTORY_TURNS);
            }
            localStorage.setItem(`chat_history_${ragMode}`, JSON.stringify(history));
            updateHistoryBadge(ragMode);
        } catch (e) {
            console.error('Error saving history', e);
        }
    }

    function appendToHistory(ragMode, userMsg, assistantMsg) {
        const history = getHistory(ragMode);
        history.push({ role: 'user', content: userMsg });
        history.push({ role: 'assistant', content: assistantMsg });
        saveHistory(ragMode, history);
    }

    function clearHistory() {
        localStorage.removeItem('chat_history_page');
        localStorage.removeItem('chat_history_vector');
        localStorage.removeItem('chat_history_toc');
        updateHistoryBadge('page');
        updateHistoryBadge('vector');
        updateHistoryBadge('toc');
        chatContainer.innerHTML = ''; // Optionally clear screen too
    }

    function updateHistoryBadge(mode) {
        // Will be implemented later if UI requires it. For now, it's a hook.
    }

    // Clear history button listener
    const clearHistoryBtn = document.getElementById('clear-history-btn');
    if (clearHistoryBtn) {
        clearHistoryBtn.addEventListener('click', () => {
            if (confirm("Are you sure you want to clear your local chat history?")) {
                clearHistory();
            }
        });
    }
    // ─────────────────────────────────────────────────────────────────────────

    function createResponseCard(title) {
        const card = document.createElement('div');
        card.className = 'response-card';
        card.innerHTML = `
            <div class="response-header">
                <svg width="20" height="20" viewBox="0 0 24 24" fill="none" class="ai-icon">
                    <path d="M12 2L2 7L12 12L22 7L12 2Z" stroke="currentColor" stroke-width="2" stroke-linejoin="round"/>
                    <path d="M2 17L12 22L22 17" stroke="currentColor" stroke-width="2" stroke-linejoin="round"/>
                    <path d="M2 12L12 17L22 12" stroke="currentColor" stroke-width="2" stroke-linejoin="round"/>
                </svg>
                <span>${title}</span>
            </div>
            <div class="response-content"><span class="typing-indicator"></span></div>
            <div class="metrics">
                <div class="metrics-row">
                    <div class="token-badges">
                        <span class="badge prompt-badge" style="display:none;" title="Prompt Tokens">Prompt: --</span>
                        <span class="badge completion-badge" style="display:none;" title="Completion Tokens">Response: --</span>
                    </div>
                    <button class="sources-toggle">View Sources ▼</button>
                </div>
                <div class="sources-list" style="display: none;"></div>
            </div>
        `;
        return card;
    }

    async function handleSend() {
        const query = promptInput.value.trim();
        if (!query) return;

        const modes = getActiveRagModes();
        if (!modes.vector && !modes.page && !modes.toc) {
            alert('Please enable at least one RAG mode.');
            return;
        }

        promptInput.value = '';
        promptInput.style.height = 'auto';
        sendBtn.disabled = true;

        // Create User Message
        const userMsg = document.createElement('div');
        userMsg.className = 'message user';
        userMsg.innerHTML = `<div class="user-bubble">${query}</div>`;
        chatContainer.appendChild(userMsg);

        // Create Container for Responses
        const sysMsg = document.createElement('div');
        sysMsg.className = 'message system';
        const responsesGrid = document.createElement('div');
        responsesGrid.className = 'system-responses';

        // Create Cards only for enabled modes
        const vectorCard = modes.vector ? createResponseCard('Vector RAG') : null;
        const pageCard = modes.page ? createResponseCard('Page Index RAG') : null;
        const tocCard = modes.toc ? createResponseCard('TOC Index RAG') : null;

        if (vectorCard) responsesGrid.appendChild(vectorCard);
        if (pageCard) responsesGrid.appendChild(pageCard);
        if (tocCard) responsesGrid.appendChild(tocCard);

        sysMsg.appendChild(responsesGrid);
        chatContainer.appendChild(sysMsg);

        chatContainer.scrollTop = chatContainer.scrollHeight;

        const topK = parseInt(topKInput.value) || 5;

        // Trigger chosen SSE calls
        if (vectorCard) {
            const history = getHistory('vector');
            fetchSSE('/api/chat/vector', { query, top_k: topK, chat_history: history }, vectorCard, 'vector', query);
        }
        if (pageCard) {
            const history = getHistory('page');
            fetchSSE('/api/chat/page', { query, top_k: topK, chat_history: history }, pageCard, 'page', query);
        }
        if (tocCard) {
            const history = getHistory('toc');
            fetchSSE('/api/chat/toc', { query, top_k: topK, chat_history: history }, tocCard, 'toc', query);
        }
    }

    async function fetchSSE(url, payload, cardElement, ragMode, userQuery) {
        const contentDiv = cardElement.querySelector('.response-content');
        const tokenDisplay = cardElement.querySelector('.prompt-tokens');
        const sourcesBtn = cardElement.querySelector('.sources-toggle');
        const sourcesList = cardElement.querySelector('.sources-list');

        sourcesBtn.addEventListener('click', () => {
            if (sourcesList.style.display === 'none') {
                sourcesList.style.display = 'block';
                sourcesBtn.textContent = 'Hide Sources ▲';
            } else {
                sourcesList.style.display = 'none';
                sourcesBtn.textContent = 'View Sources ▼';
            }
        });

        try {
            const response = await fetch(url, {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify(payload)
            });

            const reader = response.body.getReader();
            const decoder = new TextDecoder("utf-8");
            let fullText = "";
            let buffer = "";

            while (true) {
                const { done, value } = await reader.read();
                if (done) break;

                buffer += decoder.decode(value, { stream: true });
                const parts = buffer.split('\n\n');
                buffer = parts.pop();

                for (const part of parts) {
                    if (part.startsWith('data: ')) {
                        try {
                            const dataStr = part.substring(6);
                            if (!dataStr.trim()) continue;
                            const data = JSON.parse(dataStr);

                            if (data.type === 'token') {
                                fullText += data.content;
                                contentDiv.innerHTML = cleanMarkdown(fullText) + '<span class="typing-indicator"></span>';
                            } else if (data.type === 'sources') {
                                // Render sources
                                let sourcesHtml = '';
                                data.sources.forEach((s, idx) => {
                                    let label = s.chunk_index !== undefined ? `Chunk #${s.chunk_index}` : s.node_id !== undefined ? `Node ${s.node_id}: ${s.title || ''}` : `Page ${s.page_num}`;
                                    sourcesHtml += `
                                        <div class="source-item">
                                            <span class="source-meta">[${idx + 1}] ${s.source} — ${label} (score: ${s.score})</span>
                                            <span class="source-text">${s.text.substring(0, 150)}...</span>
                                        </div>
                                    `;
                                });
                                sourcesList.innerHTML = sourcesHtml || '<div class="source-item">No sources found.</div>';
                            } else if (data.type === 'stats') {
                                const promptBadge = cardElement.querySelector('.prompt-badge');
                                const completionBadge = cardElement.querySelector('.completion-badge');
                                if (promptBadge) {
                                    promptBadge.textContent = 'Prompt: ' + data.prompt_eval_count;
                                    promptBadge.style.display = 'inline-block';
                                }
                                if (completionBadge) {
                                    completionBadge.textContent = 'Response: ' + data.eval_count;
                                    completionBadge.style.display = 'inline-block';
                                }
                                fetchStats();
                            } else if (data.type === 'error') {
                                fullText += `\n\n**Error:** ${data.content}`;
                                contentDiv.innerHTML = cleanMarkdown(fullText);
                            }
                        } catch (e) {
                            console.error('JSON parse error:', e, part);
                        }
                    }
                }
                chatContainer.scrollTop = chatContainer.scrollHeight;
            }

            // Remove typing indicator at the end
            contentDiv.innerHTML = cleanMarkdown(fullText);

            // Save to history once complete
            if (fullText.trim()) {
                appendToHistory(ragMode, userQuery, fullText.trim());
            }

        } catch (error) {
            contentDiv.innerHTML = "<em>Connection error parsing stream.</em>";
            console.error(error);
        }
    }

    // Modal Logic
    const chunksModal = document.getElementById('chunks-modal');
    const modalTreeBtn = document.getElementById('modal-tree-btn');
    const closeModalBtn = document.getElementById('close-modal-btn');
    const modalDocTitle = document.getElementById('modal-doc-title');
    const pageChunksList = document.getElementById('page-chunks-list');
    const vectorChunksList = document.getElementById('vector-chunks-list');
    const tocChunksList = document.getElementById('toc-chunks-list');

    closeModalBtn.addEventListener('click', () => {
        chunksModal.style.display = 'none';
    });

    // Close if clicking outside
    window.addEventListener('click', (e) => {
        if (e.target === chunksModal) {
            chunksModal.style.display = 'none';
        }
    });

    async function openChunksModal(filename) {
        modalDocTitle.textContent = filename;
        pageChunksList.innerHTML = '<div class="spinner large-spinner"></div>';
        vectorChunksList.innerHTML = '<div class="spinner large-spinner"></div>';
        tocChunksList.innerHTML = '<div class="spinner large-spinner"></div>';
        chunksModal.style.display = 'flex';

        try {
            const docName = modalDocTitle.textContent;
            modalTreeBtn.onclick = () => openTreeModal(docName);

            const res = await fetch(`/api/documents/${encodeURIComponent(filename)}/chunks`);
            const data = await res.json();

            // Render Page Chunks
            pageChunksList.innerHTML = '';
            let totalPageTokens = 0;
            if (data.page_chunks && data.page_chunks.length > 0) {
                data.page_chunks.forEach(chunk => {
                    const el = document.createElement('div');
                    el.className = 'chunk-item';
                    el.innerHTML = `
                        <span class="chunk-meta" style="display:flex; justify-content:space-between;">
                            <span>Page ${chunk.page_num}</span>
                            <span style="color:var(--text-secondary); font-size:0.85em;">Tokens: ${chunk.tokens || 0}</span>
                        </span>
                        <div class="chunk-text">${chunk.text}</div>
                    `;
                    pageChunksList.appendChild(el);
                    totalPageTokens += (chunk.tokens || 0);
                });

                const totalEl = document.createElement('div');
                totalEl.style.marginTop = '16px';
                totalEl.style.padding = '12px';
                totalEl.style.backgroundColor = 'var(--bg-secondary)';
                totalEl.style.borderRadius = '6px';
                totalEl.style.fontWeight = 'bold';
                totalEl.style.display = 'flex';
                totalEl.style.justifyContent = 'space-between';
                totalEl.style.border = '1px solid var(--border-color)';
                totalEl.innerHTML = `<span>Total Page RAG Tokens:</span> <span>${totalPageTokens.toLocaleString()}</span>`;
                pageChunksList.appendChild(totalEl);
            } else {
                pageChunksList.innerHTML = '<div style="padding:16px;">No page chunks found.</div>';
            }

            // Render Vector Chunks
            vectorChunksList.innerHTML = '';
            let totalVectorTokens = 0;
            if (data.vector_chunks && data.vector_chunks.length > 0) {
                data.vector_chunks.forEach(chunk => {
                    const el = document.createElement('div');
                    el.className = 'chunk-item';
                    el.innerHTML = `
                        <span class="chunk-meta" style="display:flex; justify-content:space-between;">
                            <span>Chunk #${chunk.chunk_index}</span>
                            <span style="color:var(--text-secondary); font-size:0.85em;">Tokens: ${chunk.tokens || 0}</span>
                        </span>
                        <div class="chunk-text">${chunk.text}</div>
                    `;
                    vectorChunksList.appendChild(el);
                    totalVectorTokens += (chunk.tokens || 0);
                });

                const totalEl = document.createElement('div');
                totalEl.style.marginTop = '16px';
                totalEl.style.padding = '12px';
                totalEl.style.backgroundColor = 'var(--bg-secondary)';
                totalEl.style.borderRadius = '6px';
                totalEl.style.fontWeight = 'bold';
                totalEl.style.display = 'flex';
                totalEl.style.justifyContent = 'space-between';
                totalEl.style.border = '1px solid var(--border-color)';
                totalEl.innerHTML = `<span>Total Vector RAG Tokens:</span> <span>${totalVectorTokens.toLocaleString()}</span>`;
                vectorChunksList.appendChild(totalEl);
            } else {
                vectorChunksList.innerHTML = '<div style="padding:16px;">No vector chunks found.</div>';
            }

            // Render TOC Chunks
            tocChunksList.innerHTML = '';
            let totalTocTokens = 0;
            if (data.toc_chunks && data.toc_chunks.length > 0) {
                data.toc_chunks.forEach(chunk => {
                    const el = document.createElement('div');
                    el.className = 'chunk-item';
                    el.innerHTML = `
                        <span class="chunk-meta" style="display:flex; justify-content:space-between;">
                            <span>Node ${chunk.node_id}: ${chunk.title || ''}</span>
                            <span style="color:var(--text-secondary); font-size:0.85em;">Tokens: ${chunk.tokens || 0}</span>
                        </span>
                        <div class="chunk-text">${chunk.text}</div>
                    `;
                    tocChunksList.appendChild(el);
                    totalTocTokens += (chunk.tokens || 0);
                });

                const totalEl = document.createElement('div');
                totalEl.style.marginTop = '16px';
                totalEl.style.padding = '12px';
                totalEl.style.backgroundColor = 'var(--bg-secondary)';
                totalEl.style.borderRadius = '6px';
                totalEl.style.fontWeight = 'bold';
                totalEl.style.display = 'flex';
                totalEl.style.justifyContent = 'space-between';
                totalEl.style.border = '1px solid var(--border-color)';
                totalEl.innerHTML = `<span>Total TOC RAG Tokens:</span> <span>${totalTocTokens.toLocaleString()}</span>`;
                tocChunksList.appendChild(totalEl);
            } else {
                tocChunksList.innerHTML = '<div style="padding:16px;">No TOC nodes found.</div>';
            }

        } catch (error) {
            console.error(error);
            pageChunksList.innerHTML = '<div style="color:red; padding:16px;">Error loading data.</div>';
            vectorChunksList.innerHTML = '<div style="color:red; padding:16px;">Error loading data.</div>';
            tocChunksList.innerHTML = '<div style="color:red; padding:16px;">Error loading data.</div>';
        }
    }

    // ── Tree Viewer Modal Logic ──────────────────────────────────────────────
    const treeModal = document.getElementById('tree-modal');
    const closeTreeModalBtn = document.getElementById('close-tree-modal-btn');
    const treeModalTitle = document.getElementById('tree-modal-title');
    const treeContainer = document.getElementById('tree-container');

    closeTreeModalBtn.addEventListener('click', () => {
        treeModal.style.display = 'none';
    });

    window.addEventListener('click', (e) => {
        if (e.target === treeModal) {
            treeModal.style.display = 'none';
        }
    });

    function renderTreeNode(node) {
        const hasChildren = node.nodes && node.nodes.length > 0;
        const hasSummary = !!node.summary;
        const el = document.createElement('div');
        el.className = 'tree-node';

        // Header row
        const header = document.createElement('div');
        header.className = 'tree-node-header';

        // Show pointer if clickable
        if (hasChildren || hasSummary) {
            header.style.cursor = 'pointer';
        } else {
            header.style.cursor = 'default';
        }

        // Toggle arrow
        const toggle = document.createElement('span');
        toggle.className = 'tree-toggle' + (hasChildren ? '' : ' leaf');
        toggle.textContent = '▶';
        header.appendChild(toggle);

        // Node ID badge
        if (node.node_id) {
            const idBadge = document.createElement('span');
            idBadge.className = 'tree-node-id';
            idBadge.textContent = '#' + node.node_id;
            header.appendChild(idBadge);
        }

        // Title
        const title = document.createElement('span');
        title.className = 'tree-node-title';
        title.textContent = node.title || '(Untitled)';
        header.appendChild(title);

        // Page range
        if (node.start_index != null) {
            const pages = document.createElement('span');
            pages.className = 'tree-node-pages';
            pages.textContent = node.start_index === node.end_index
                ? `p.${node.start_index}`
                : `p.${node.start_index}–${node.end_index}`;
            header.appendChild(pages);
        }

        el.appendChild(header);

        // Summary details (shown on expand)
        if (hasSummary) {
            const details = document.createElement('div');
            details.className = 'tree-node-details';
            details.innerHTML = `<strong style="color:var(--brand-color); display:block; margin-bottom:4px;">Summary:</strong>${node.summary}`;
            el.appendChild(details);
        }

        // Children container
        if (hasChildren) {
            const childrenContainer = document.createElement('div');
            childrenContainer.className = 'tree-children';
            node.nodes.forEach(child => {
                childrenContainer.appendChild(renderTreeNode(child));
            });
            el.appendChild(childrenContainer);
        }

        // Click to expand/collapse
        header.addEventListener('click', () => {
            if (!hasChildren && !hasSummary) return;
            const children = el.querySelector('.tree-children');
            const details = el.querySelector('.tree-node-details');

            const isExpanded = (children && children.classList.contains('expanded')) ||
                (details && details.classList.contains('visible'));

            if (isExpanded) {
                if (children) {
                    children.classList.remove('expanded');
                    toggle.classList.remove('expanded');
                }
                if (details) details.classList.remove('visible');
            } else {
                if (children) {
                    children.classList.add('expanded');
                    toggle.classList.add('expanded');
                }
                if (details) details.classList.add('visible');
            }
        });

        return el;
    }

    async function openTreeModal(filename) {
        treeModalTitle.textContent = `🌳 ${filename}`;
        treeContainer.innerHTML = '<div class="spinner large-spinner"></div>';
        treeModal.style.display = 'flex';

        try {
            const res = await fetch(`/api/documents/${encodeURIComponent(filename)}/tree`);
            const data = await res.json();

            treeContainer.innerHTML = '';

            if (!data.tree || data.tree.length === 0) {
                treeContainer.innerHTML = `
                    <div class="tree-no-data">
                        <div>🌳</div>
                        <p>No tree structure available for this document.</p>
                        <p style="font-size:0.8rem; margin-top:8px;">Index this document with TOC RAG mode to generate a tree.</p>
                    </div>
                `;
                return;
            }

            data.tree.forEach(rootNode => {
                treeContainer.appendChild(renderTreeNode(rootNode));
            });

            // Auto-expand first level
            const firstLevelChildren = treeContainer.querySelectorAll(':scope > .tree-node > .tree-children');
            firstLevelChildren.forEach(c => {
                c.classList.add('expanded');
                const toggle = c.parentElement.querySelector('.tree-toggle');
                if (toggle) toggle.classList.add('expanded');
                const details = c.parentElement.querySelector('.tree-node-details');
                if (details) details.classList.add('visible');
            });

        } catch (error) {
            console.error(error);
            treeContainer.innerHTML = '<div style="color:red; padding:16px;">Error loading tree data.</div>';
        }
    }

    // Expose openTreeModal globally for inline onclick handlers
    window.openTreeModal = openTreeModal;
});