/**
 * StackLogix Chatbot — Frontend Logic with Streaming SSE
 */

// --- Config ---
const API_BASE = window.location.origin;
let sessionId = generateSessionId();
let isStreaming = false;

// --- DOM Elements ---
const messagesContainer = document.getElementById('messagesContainer');
const messagesList = document.getElementById('messagesList');
const welcomeScreen = document.getElementById('welcomeScreen');
const userInput = document.getElementById('userInput');
const sendBtn = document.getElementById('sendBtn');
const newChatBtn = document.getElementById('newChatBtn');
const ingestBtn = document.getElementById('ingestBtn');
const statusDot = document.getElementById('statusDot');
const docsCount = document.getElementById('docsCount');
const sessionDisplay = document.getElementById('sessionDisplay');

// --- Init ---
document.addEventListener('DOMContentLoaded', () => {
    sessionDisplay.textContent = sessionId.slice(0, 12) + '...';
    checkHealth();
    fetchCollectionInfo();
    setupEventListeners();
});

// --- Event Listeners ---
function setupEventListeners() {
    sendBtn.addEventListener('click', sendMessage);

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

    userInput.addEventListener('input', () => {
        userInput.style.height = 'auto';
        userInput.style.height = Math.min(userInput.scrollHeight, 120) + 'px';
        sendBtn.disabled = !userInput.value.trim() || isStreaming;
    });

    newChatBtn.addEventListener('click', startNewChat);
    ingestBtn.addEventListener('click', triggerIngest);

    document.querySelectorAll('.prompt-chip, .suggestion-card').forEach(btn => {
        btn.addEventListener('click', () => {
            const prompt = btn.getAttribute('data-prompt');
            if (prompt && !isStreaming) {
                userInput.value = prompt;
                sendBtn.disabled = false;
                sendMessage();
            }
        });
    });
}

// --- Core: Streaming Chat ---

async function sendMessage() {
    const message = userInput.value.trim();
    if (!message || isStreaming) return;

    // Hide welcome screen
    welcomeScreen.classList.add('hidden');

    // Clear input
    userInput.value = '';
    userInput.style.height = 'auto';
    sendBtn.disabled = true;
    isStreaming = true;

    // Add user message
    appendUserMessage(message);

    // Show typing indicator
    const typingEl = showTypingIndicator();

    try {
        const response = await fetch(`${API_BASE}/chat/stream`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({
                session_id: sessionId,
                user_message: message,
            }),
        });

        if (!response.ok) throw new Error(`HTTP ${response.status}`);

        // Remove typing indicator, create assistant message bubble
        typingEl.remove();
        const { bubbleEl, contentEl, messageDiv } = createAssistantMessage();

        const reader = response.body.getReader();
        const decoder = new TextDecoder();
        let fullText = '';
        let sources = null;
        let followUp = null;
        let buffer = '';

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

            buffer += decoder.decode(value, { stream: true });

            // Process complete SSE lines
            const lines = buffer.split('\n');
            buffer = lines.pop() || ''; // Keep incomplete line in buffer

            for (const line of lines) {
                if (!line.startsWith('data: ')) continue;

                try {
                    const event = JSON.parse(line.slice(6));

                    if (event.type === 'token') {
                        fullText += event.content;
                        contentEl.innerHTML = formatContent(fullText);
                        scrollToBottom();
                    } else if (event.type === 'sources') {
                        sources = event.sources;
                    } else if (event.type === 'follow_up') {
                        followUp = event.content;
                    } else if (event.type === 'error') {
                        fullText = event.content;
                        contentEl.innerHTML = formatContent(fullText);
                    } else if (event.type === 'done') {
                        // Append sources below the bubble
                        if (sources && sources.length > 0) {
                            const sourcesEl = createSourcesElement(sources);
                            messageDiv.querySelector('.message-content').appendChild(sourcesEl);
                        }
                        // Append follow-up question
                        if (followUp) {
                            const followUpEl = createFollowUpElement(followUp);
                            messageDiv.querySelector('.message-content').appendChild(followUpEl);
                        }
                        // Add timestamp
                        const timeEl = document.createElement('div');
                        timeEl.classList.add('message-time');
                        timeEl.textContent = new Date().toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' });
                        messageDiv.querySelector('.message-content').appendChild(timeEl);

                        scrollToBottom();
                    }
                } catch (e) {
                    // Skip malformed JSON
                }
            }
        }

    } catch (error) {
        console.error('Chat error:', error);
        typingEl?.remove();
        appendSimpleAssistantMessage('Sorry, something went wrong. Please try again.');
        showToast('Failed to get response. Check if the server is running.', 'error');
    } finally {
        isStreaming = false;
        sendBtn.disabled = !userInput.value.trim();
    }
}

// --- Message Rendering ---

function appendUserMessage(content) {
    const messageDiv = document.createElement('div');
    messageDiv.classList.add('message', 'user');
    const time = new Date().toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' });

    messageDiv.innerHTML = `
        <div class="message-avatar">U</div>
        <div class="message-content">
            <div class="message-bubble"><p>${escapeHtml(content)}</p></div>
            <div class="message-time">${time}</div>
        </div>
    `;
    messagesList.appendChild(messageDiv);
    scrollToBottom();
}

function createAssistantMessage() {
    const messageDiv = document.createElement('div');
    messageDiv.classList.add('message', 'assistant');

    const bubbleEl = document.createElement('div');
    bubbleEl.classList.add('message-bubble');
    const contentEl = document.createElement('div');
    contentEl.classList.add('streaming-content');
    contentEl.innerHTML = '<span class="cursor-blink"></span>';
    bubbleEl.appendChild(contentEl);

    messageDiv.innerHTML = `
        <div class="message-avatar">S</div>
        <div class="message-content"></div>
    `;
    messageDiv.querySelector('.message-content').appendChild(bubbleEl);
    messagesList.appendChild(messageDiv);
    scrollToBottom();

    return { bubbleEl, contentEl, messageDiv };
}

function appendSimpleAssistantMessage(content) {
    const messageDiv = document.createElement('div');
    messageDiv.classList.add('message', 'assistant');
    const time = new Date().toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' });

    messageDiv.innerHTML = `
        <div class="message-avatar">S</div>
        <div class="message-content">
            <div class="message-bubble"><p>${escapeHtml(content)}</p></div>
            <div class="message-time">${time}</div>
        </div>
    `;
    messagesList.appendChild(messageDiv);
    scrollToBottom();
}

function createSourcesElement(sources) {
    const el = document.createElement('div');
    el.classList.add('sources-container');

    let html = '<div class="sources-header"><svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><path d="M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z"></path><polyline points="14 2 14 8 20 8"></polyline></svg> Sources</div>';
    html += '<div class="sources-list">';
    for (const src of sources) {
        const scorePercent = Math.round(src.score * 100);
        const scoreClass = scorePercent >= 60 ? 'high' : scorePercent >= 40 ? 'medium' : 'low';
        html += `
            <div class="source-item">
                <span class="source-file">${escapeHtml(src.file)}</span>
                <span class="source-folder">${escapeHtml(src.folder)}</span>
                <span class="source-score ${scoreClass}">${scorePercent}%</span>
            </div>
        `;
    }
    html += '</div>';
    el.innerHTML = html;
    return el;
}

function createFollowUpElement(question) {
    const el = document.createElement('div');
    el.classList.add('follow-up');
    el.setAttribute('data-question', question);
    el.onclick = function () { askFollowUp(this); };
    el.innerHTML = `
        <div class="follow-up-label">Suggested Follow-up</div>
        <div class="follow-up-text">${escapeHtml(question)}</div>
    `;
    return el;
}

function formatContent(text) {
    let html = escapeHtml(text);

    // Bold: **text**
    html = html.replace(/\*\*(.*?)\*\*/g, '<strong>$1</strong>');

    // Bullet points
    html = html.replace(/^[-•]\s+(.+)$/gm, '<li>$1</li>');
    html = html.replace(/(<li>.*<\/li>)/s, '<ul>$1</ul>');

    // Numbered lists
    html = html.replace(/^\d+\.\s+(.+)$/gm, '<li>$1</li>');

    // Paragraphs
    html = html.replace(/\n\n/g, '</p><p>');
    html = html.replace(/\n/g, '<br>');

    if (!html.startsWith('<')) {
        html = '<p>' + html + '</p>';
    }

    return html;
}

function showTypingIndicator() {
    const typing = document.createElement('div');
    typing.classList.add('typing-indicator');
    typing.innerHTML = `
        <div class="message-avatar">S</div>
        <div class="typing-dots">
            <span></span><span></span><span></span>
        </div>
    `;
    messagesList.appendChild(typing);
    scrollToBottom();
    return typing;
}

function scrollToBottom() {
    messagesContainer.scrollTop = messagesContainer.scrollHeight;
}

// --- Follow-up ---
function askFollowUp(el) {
    const question = el.getAttribute('data-question');
    if (question && !isStreaming) {
        userInput.value = question;
        sendBtn.disabled = false;
        sendMessage();
    }
}
window.askFollowUp = askFollowUp;

// --- New Chat ---
function startNewChat() {
    if (isStreaming) return;
    sessionId = generateSessionId();
    sessionDisplay.textContent = sessionId.slice(0, 12) + '...';
    messagesList.innerHTML = '';
    welcomeScreen.classList.remove('hidden');
    showToast('New conversation started', 'info');
}

// --- Ingest ---
async function triggerIngest() {
    if (ingestBtn.classList.contains('loading')) return;

    ingestBtn.classList.add('loading');
    ingestBtn.textContent = 'Ingesting...';
    showToast('Document ingestion started. This may take a minute...', 'info');

    try {
        const response = await fetch(`${API_BASE}/ingest`, { method: 'POST' });
        const data = await response.json();

        if (response.ok) {
            showToast('Documents ingested successfully!', 'success');
            fetchCollectionInfo();
        } else {
            showToast(`Ingestion failed: ${data.detail}`, 'error');
        }
    } catch (error) {
        showToast('Failed to trigger ingestion. Is the server running?', 'error');
    } finally {
        ingestBtn.classList.remove('loading');
        ingestBtn.innerHTML = `
            <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
                <path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4"></path>
                <polyline points="17 8 12 3 7 8"></polyline>
                <line x1="12" y1="3" x2="12" y2="15"></line>
            </svg>
            Re-ingest Documents
        `;
    }
}

// --- Health & Info ---
async function checkHealth() {
    try {
        const response = await fetch(`${API_BASE}/health`);
        if (response.ok) {
            statusDot.textContent = 'Online';
            statusDot.classList.add('online');
        } else {
            throw new Error();
        }
    } catch {
        statusDot.textContent = 'Offline';
        statusDot.classList.add('offline');
    }
}

async function fetchCollectionInfo() {
    try {
        const response = await fetch(`${API_BASE}/collection-info`);
        const data = await response.json();
        if (data.points_count !== undefined) {
            docsCount.textContent = `${data.points_count} chunks`;
        } else {
            docsCount.textContent = 'Not loaded';
        }
    } catch {
        docsCount.textContent = '—';
    }
}

// --- Utilities ---
function generateSessionId() {
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (c) => {
        const r = (Math.random() * 16) | 0;
        const v = c === 'x' ? r : (r & 0x3) | 0x8;
        return v.toString(16);
    });
}

function escapeHtml(text) {
    const div = document.createElement('div');
    div.textContent = text;
    return div.innerHTML;
}

function showToast(message, type = 'info') {
    const toast = document.createElement('div');
    toast.classList.add('toast', type);
    toast.textContent = message;
    document.body.appendChild(toast);

    setTimeout(() => {
        toast.classList.add('hiding');
        setTimeout(() => toast.remove(), 300);
    }, 4000);
}