const express = require('express');
const Database = require('better-sqlite3');
const cors = require('cors');
const fs = require('fs');

const app = express();

// Parse ALLOWED_ORIGINS from Hugging Face secrets (environment variables)
let allowedOrigins = '*'; // Default fallback to allow all if secret is not set
if (process.env.ALLOWED_ORIGINS) {
    // Splits a comma-separated string like "https://example.com,https://app.example.com"
    allowedOrigins = process.env.ALLOWED_ORIGINS.split(',').map(url => url.trim());
    console.log(`🔒 CORS Restricted to Origins:`, allowedOrigins);
} else {
    console.log(`⚠️ CORS is globally accessible (*). Set ALLOWED_ORIGINS secret to secure.`);
}

// CORS Middleware Configuration
app.use(cors({
    origin: allowedOrigins,
    methods: ['GET', 'POST', 'PUT', 'DELETE', 'PATCH', 'OPTIONS'],
    allowedHeaders: ['Content-Type', 'X-User-ID', 'X-User-Email']
}));

app.use(express.json({ limit: '50mb' }));

// ============================================
// LOGGING MIDDLEWARE
// ============================================

const logRequest = (req, res, next) => {
    const timestamp = new Date().toISOString();
    const userId = req.headers['x-user-id'] || 'NO_USER_ID';
    const userEmail = req.headers['x-user-email'] || '';
    
    console.log(`\n📥 [${timestamp}] ${req.method} ${req.path}`);
    console.log(`   👤 User ID: ${userId}${userEmail ? ` (${userEmail})` : ''}`);
    console.log(`   🔗 Origin: ${req.headers.origin || 'Unknown'}`);
    console.log(`   📍 IP: ${req.ip}`);
    
    if (req.method === 'POST' || req.method === 'PATCH') {
        console.log(`   📦 Request Body:`, JSON.stringify(req.body, null, 2).substring(0, 500));
    }
    
    if (req.query && Object.keys(req.query).length > 0) {
        console.log(`   🔍 Query Params:`, req.query);
    }
    
    // Store original send function
    const originalSend = res.send;
    res.send = function(body) {
        const responseTime = Date.now() - req.startTime;
        console.log(`\n📤 [${timestamp}] ${req.method} ${req.path} → ${res.statusCode}`);
        console.log(`   ⏱️  Response Time: ${responseTime}ms`);
        
        if (res.statusCode >= 400) {
            console.log(`   ❌ Error Response:`, body);
        } else {
            if (typeof body === 'string') {
                try {
                    const parsed = JSON.parse(body);
                    console.log(`   ✅ Success Response:`, JSON.stringify(parsed, null, 2).substring(0, 300));
                } catch {
                    console.log(`   ✅ Success Response: ${body.substring(0, 100)}...`);
                }
            } else if (typeof body === 'object') {
                console.log(`   ✅ Success Response:`, JSON.stringify(body, null, 2).substring(0, 300));
            }
        }
        
        originalSend.call(this, body);
    };
    
    req.startTime = Date.now();
    next();
};

app.use(logRequest);

// ============================================
// DATABASE INITIALIZATION
// ============================================

const path = require('path');

let databaseDir;
if (fs.existsSync('/data')) {
    databaseDir = '/data';
    console.log("✅ PRODUCTION MODE: Using Persistent Storage at /data");
} else {
    databaseDir = path.join(process.cwd(), "data");
    if (!fs.existsSync(databaseDir)) {
        fs.mkdirSync(databaseDir, { recursive: true });
    }
    console.log(`⚠️ LOCAL MODE: Using local storage at ${databaseDir}`);
}

// Initialize Database
const dbPath = path.join(databaseDir, 'chat_storage.db');
console.log(`💾 Initializing database at: ${dbPath}`);

try {
    const db = new Database(dbPath);
    console.log('✅ Database connection established');

    // Database settings
    db.pragma('journal_mode = WAL');
    db.pragma('foreign_keys = ON');
    console.log('🔧 Database pragmas set');

    // Schema
    const initSchema = () => {
        const schema = `
        CREATE TABLE IF NOT EXISTS chats (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id TEXT NOT NULL,
            title TEXT NOT NULL,
            model TEXT DEFAULT 'default',
            created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
            updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
        );
        
        CREATE TABLE IF NOT EXISTS messages (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            chat_id INTEGER NOT NULL,
            role TEXT CHECK( role IN ('user','assistant') ) NOT NULL,
            content TEXT NOT NULL,
            model TEXT,
            timestamp DATETIME DEFAULT CURRENT_TIMESTAMP,
            FOREIGN KEY (chat_id) REFERENCES chats (id) ON DELETE CASCADE
        );

        CREATE TABLE IF NOT EXISTS chat_workspaces (
            chat_id INTEGER PRIMARY KEY,
            content TEXT NOT NULL DEFAULT '',
            updated_at DATETIME DEFAULT CURRENT_TIMESTAMP,
            FOREIGN KEY (chat_id) REFERENCES chats (id) ON DELETE CASCADE
        );
        
        CREATE INDEX IF NOT EXISTS idx_chats_user ON chats(user_id, updated_at DESC);
        CREATE INDEX IF NOT EXISTS idx_messages_chat ON messages(chat_id);
        CREATE INDEX IF NOT EXISTS idx_chat_workspaces_updated ON chat_workspaces(updated_at DESC);

        /* ── Ant-Editor Document Storage ── */
        CREATE TABLE IF NOT EXISTS documents (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id TEXT NOT NULL,
            title TEXT NOT NULL DEFAULT 'Untitled Document',
            content TEXT NOT NULL DEFAULT '',
            language TEXT NOT NULL DEFAULT 'en',
            created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
            updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
        );

        CREATE INDEX IF NOT EXISTS idx_documents_user ON documents(user_id, updated_at DESC);

        /* ── User Identity Tracking ── */
        /* Maps user_id (UUID from Cloudflare KV) to email for traceability. */
        /* The proxy (catchall.js) verifies the session and sends both headers. */
        CREATE TABLE IF NOT EXISTS users (
            user_id TEXT PRIMARY KEY,
            email TEXT NOT NULL DEFAULT '',
            first_seen_at DATETIME DEFAULT CURRENT_TIMESTAMP,
            last_seen_at DATETIME DEFAULT CURRENT_TIMESTAMP
        );

        CREATE INDEX IF NOT EXISTS idx_users_email ON users(email);

        /* ── Document Sharing ── */
        /* Maps a random share_token (UUID) to a document ID.            */
        /* Anyone with the token can read/write the document — no auth.  */
        /* ON DELETE CASCADE: deleting the source document nukes shares. */
        CREATE TABLE IF NOT EXISTS shared_documents (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            share_token TEXT NOT NULL UNIQUE,
            document_id INTEGER NOT NULL,
            created_by TEXT NOT NULL,
            created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
            FOREIGN KEY (document_id) REFERENCES documents(id) ON DELETE CASCADE
        );

        CREATE UNIQUE INDEX IF NOT EXISTS idx_shared_token ON shared_documents(share_token);
        CREATE INDEX IF NOT EXISTS idx_shared_doc_id ON shared_documents(document_id);
        `;

        db.exec(schema);
        console.log('✅ Database schema initialized');
        
        // Log existing data counts
        const chatCount = db.prepare('SELECT COUNT(*) as count FROM chats').get().count;
        const messageCount = db.prepare('SELECT COUNT(*) as count FROM messages').get().count;
        console.log(`📊 Database Stats: ${chatCount} chats, ${messageCount} messages`);
    };

    initSchema();

    // ============================================
    // HELPER FUNCTIONS
    // ============================================

    // Middleware to get user ID + canonical email-based identity resolution.
    //
    // Problem: The same Google account gets a DIFFERENT random UUID in each
    // Cloudflare environment (dev vs prod) because each has its own KV store.
    // But they all share this single backend. Without resolution, the same
    // person's documents are split across multiple user_ids.
    //
    // Solution: The `users` table tracks the FIRST user_id we ever saw for
    // a given email. On subsequent requests, if the email arrives with a
    // DIFFERENT user_id (from another environment), we:
    //   1. Auto-migrate their documents and chats to the canonical user_id
    //   2. Override req.userId to the canonical one
    //
    // This ensures one email = one identity = one set of documents, always.
    const requireUser = (req, res, next) => {
        // Accept user ID from header OR query param (for sendBeacon)
        const incomingUserId = req.headers['x-user-id'] || req.query.user_id;
        
        if (!incomingUserId || typeof incomingUserId !== 'string') {
            console.log(`❌ Missing or invalid X-User-ID header`);
            return res.status(401).json({ error: 'User identity required' });
        }

        // Read verified email from proxy (if session was valid)
        const userEmail = req.headers['x-user-email'] || '';
        req.userEmail = userEmail;

        // ── Canonical user resolution ──
        // If we have an email, check if this email already has a canonical user_id
        let canonicalUserId = incomingUserId;

        if (userEmail) {
            try {
                // Look up the FIRST user_id ever registered for this email
                const existing = db.prepare(
                    `SELECT user_id FROM users WHERE email = ? ORDER BY first_seen_at ASC LIMIT 1`
                ).get(userEmail);

                if (existing && existing.user_id !== incomingUserId) {
                    // This email already has a canonical user_id from a different environment.
                    // Use the canonical one and migrate any orphaned data.
                    canonicalUserId = existing.user_id;
                    console.log(
                        `🔄 [identity] Email ${userEmail} → canonical user ${canonicalUserId.substring(0, 8)}… ` +
                        `(incoming ${incomingUserId.substring(0, 8)}… will be merged)`
                    );

                    // Auto-migrate documents from the incoming (non-canonical) user_id
                    const docMigration = db.prepare(
                        `UPDATE documents SET user_id = ? WHERE user_id = ?`
                    ).run(canonicalUserId, incomingUserId);

                    if (docMigration.changes > 0) {
                        console.log(`   📄 Migrated ${docMigration.changes} document(s) → ${canonicalUserId.substring(0, 8)}…`);
                    }

                    // Auto-migrate chats from the incoming user_id
                    const chatMigration = db.prepare(
                        `UPDATE chats SET user_id = ? WHERE user_id = ?`
                    ).run(canonicalUserId, incomingUserId);

                    if (chatMigration.changes > 0) {
                        console.log(`   💬 Migrated ${chatMigration.changes} chat(s) → ${canonicalUserId.substring(0, 8)}…`);
                    }

                    // Clean up the non-canonical user record if it exists
                    db.prepare(`DELETE FROM users WHERE user_id = ? AND email = ?`)
                        .run(incomingUserId, userEmail);
                } else if (!existing) {
                    // First time this email is seen — register the canonical mapping
                    db.prepare(`
                        INSERT INTO users (user_id, email, first_seen_at, last_seen_at)
                        VALUES (?, ?, CURRENT_TIMESTAMP, CURRENT_TIMESTAMP)
                    `).run(incomingUserId, userEmail);
                } else {
                    // Same user_id as canonical — just update last_seen
                    db.prepare(`
                        UPDATE users SET last_seen_at = CURRENT_TIMESTAMP WHERE user_id = ?
                    `).run(canonicalUserId);
                }
            } catch (err) {
                // Non-fatal: don't block the request if identity resolution fails
                console.warn(`⚠️ Identity resolution failed:`, err.message);
            }
        }

        req.userId = canonicalUserId;
        console.log(`✅ User authenticated: ${canonicalUserId.substring(0, 10)}...${userEmail ? ` (${userEmail})` : ' (guest)'}`);
        next();
    };


    app.get('/health', (req, res) => {
        console.log('❤️ Health check requested');
        try {
            // Test database connection
            db.prepare('SELECT 1 as test').get();
            res.json({ 
                status: 'active', 
                database: 'connected',
                timestamp: new Date().toISOString(),
                uptime: process.uptime()
            });
        } catch (error) {
            console.error('❌ Health check failed:', error);
            res.status(500).json({ 
                status: 'degraded', 
                database: 'disconnected',
                error: error.message 
            });
        }
    });

    // Debug stats endpoint
    app.get('/debug/stats', (req, res) => {
        try {
            console.log('📊 Debug stats requested');
            
            // Get user count
            const userCountStmt = db.prepare(`
                SELECT COUNT(DISTINCT user_id) as user_count FROM chats
            `);
            const userCount = userCountStmt.get().user_count;
            
            // Get chat count by user
            const chatsByUserStmt = db.prepare(`
                SELECT user_id, COUNT(*) as chat_count 
                FROM chats 
                GROUP BY user_id 
                ORDER BY chat_count DESC
                LIMIT 10
            `);
            const topUsers = chatsByUserStmt.all();
            
            // Get message count by chat
            const messagesByChatStmt = db.prepare(`
                SELECT chat_id, COUNT(*) as message_count 
                FROM messages 
                GROUP BY chat_id 
                ORDER BY message_count DESC
                LIMIT 10
            `);
            const topChats = messagesByChatStmt.all();
            
            // Get recent activity
            const recentChatsStmt = db.prepare(`
                SELECT id, user_id, title, updated_at 
                FROM chats 
                ORDER BY updated_at DESC 
                LIMIT 5
            `);
            const recentChats = recentChatsStmt.all();
            
            res.json({
                database: dbPath,
                users: {
                    total: userCount,
                    top: topUsers
                },
                chats: {
                    total: db.prepare('SELECT COUNT(*) as count FROM chats').get().count,
                    recent: recentChats
                },
                messages: {
                    total: db.prepare('SELECT COUNT(*) as count FROM messages').get().count,
                    top_chats: topChats
                },
                chat_workspaces: {
                    total: db.prepare('SELECT COUNT(*) as count FROM chat_workspaces').get().count
                },
                documents: {
                    total: db.prepare('SELECT COUNT(*) as count FROM documents').get().count
                },
                timestamp: new Date().toISOString()
            });
        } catch (error) {
            console.error('❌ Debug stats error:', error);
            res.status(500).json({ error: error.message });
        }
    });

    app.get('/api/chats', requireUser, (req, res) => {
        try {
            console.log(`📋 Fetching chats for user: ${req.userId.substring(0, 10)}...`);
            const limit = Math.min(parseInt(req.query.limit) || 50, 100);
            const offset = parseInt(req.query.offset) || 0;
            
            const stmt = db.prepare(`
                SELECT id, title, model, created_at, updated_at 
                FROM chats 
                WHERE user_id = ? 
                ORDER BY updated_at DESC 
                LIMIT ? OFFSET ?
            `);
            
            const chats = stmt.all(req.userId, limit, offset);
            console.log(`✅ Found ${chats.length} chats for user`);
            
            res.json(chats);
        } catch (err) {
            console.error(`❌ Error fetching chats for user ${req.userId}:`, err);
            res.status(500).json({ error: err.message });
        }
    });

    app.post('/api/chats', requireUser, (req, res) => {
        try {
            const { title, model } = req.body;
            console.log(`📝 Creating new chat for user ${req.userId.substring(0, 10)}...`);
            console.log(`   Title: ${title}, Model: ${model || 'default'}`);
            
            if (!title || typeof title !== 'string') {
                console.log(`❌ Invalid title: ${title}`);
                return res.status(400).json({ error: 'Valid title required' });
            }
            
            const stmt = db.prepare(`
                INSERT INTO chats (user_id, title, model) 
                VALUES (?, ?, ?)
            `);
            
            const info = stmt.run(req.userId, title.trim(), model || 'default');
            console.log(`✅ Chat created with ID: ${info.lastInsertRowid}`);
            
            const newChat = db.prepare(`
                SELECT * FROM chats WHERE id = ?
            `).get(info.lastInsertRowid);
            
            console.log(`📊 New chat details:`, newChat);
            res.status(201).json(newChat);
        } catch (err) {
            console.error(`❌ Error creating chat for user ${req.userId}:`, err);
            res.status(500).json({ error: err.message });
        }
    });

    app.get('/api/chats/:id/messages', requireUser, (req, res) => {
        try {
            const chatId = req.params.id;
            console.log(`📩 Fetching messages for chat ${chatId} (user: ${req.userId.substring(0, 10)}...)`);
            
            // Verify ownership
            const chat = db.prepare(`
                SELECT id, title, user_id FROM chats 
                WHERE id = ? AND user_id = ?
            `).get(chatId, req.userId);
            
            if (!chat) {
                console.log(`❌ Chat ${chatId} not found or not owned by user ${req.userId}`);
                return res.status(404).json({ error: 'Chat not found' });
            }
            
            console.log(`✅ Chat found: "${chat.title}" (ID: ${chat.id})`);
            
            const messages = db.prepare(`
                SELECT * FROM messages 
                WHERE chat_id = ? 
                ORDER BY timestamp ASC
            `).all(chatId);
            
            console.log(`✅ Found ${messages.length} messages for chat ${chatId}`);
            
            // Log first few messages
            if (messages.length > 0) {
                console.log(`   Sample messages:`);
                messages.slice(0, 3).forEach(msg => {
                    console.log(`   - ${msg.role}: ${msg.content.substring(0, 50)}...`);
                });
                if (messages.length > 3) {
                    console.log(`   ... and ${messages.length - 3} more`);
                }
            }
            
            res.json(messages);
        } catch (err) {
            console.error(`❌ Error fetching messages for chat ${req.params.id}:`, err);
            res.status(500).json({ error: err.message });
        }
    });

    app.post('/api/messages', requireUser, (req, res) => {
        try {
            const { chatId, role, content, model } = req.body;
            console.log(`💾 Saving message to chat ${chatId}`);
            console.log(`   Role: ${role}, Model: ${model || 'none'}`);
            console.log(`   Content preview: ${content.substring(0, 100)}...`);
            
            if (!chatId || !role || !content) {
                console.log(`❌ Invalid message data: chatId=${chatId}, role=${role}, content=${content ? 'present' : 'missing'}`);
                return res.status(400).json({ error: 'Invalid message data' });
            }
            
            // Verify ownership
            const chat = db.prepare(`
                SELECT id, title, user_id FROM chats 
                WHERE id = ? AND user_id = ?
            `).get(chatId, req.userId);
            
            if (!chat) {
                console.log(`❌ Chat ${chatId} not found or not owned by user ${req.userId}`);
                return res.status(404).json({ error: 'Chat not found' });
            }
            
            console.log(`✅ Chat verified: "${chat.title}"`);
            
            // Insert message
            const insertStmt = db.prepare(`
                INSERT INTO messages (chat_id, role, content, model) 
                VALUES (?, ?, ?, ?)
            `);
            
            const info = insertStmt.run(chatId, role, content, model || null);
            console.log(`✅ Message saved with ID: ${info.lastInsertRowid}`);
            
            // Update chat timestamp
            db.prepare(`
                UPDATE chats 
                SET updated_at = CURRENT_TIMESTAMP 
                WHERE id = ?
            `).run(chatId);
            console.log(`🕒 Updated chat ${chatId} timestamp`);
            
            // Return the saved message
            const newMessage = db.prepare(`
                SELECT * FROM messages 
                WHERE id = ?
            `).get(info.lastInsertRowid);
            
            console.log(`📤 Returning saved message with ID: ${newMessage.id}`);
            res.status(201).json(newMessage);
        } catch (err) {
            console.error(`❌ Error saving message:`, err);
            res.status(500).json({ error: err.message });
        }
    });

    app.get('/api/chats/:id', requireUser, (req, res) => {
        try {
            const chatId = req.params.id;
            console.log(`🔍 Fetching chat ${chatId} details for user ${req.userId.substring(0, 10)}...`);
            
            const chat = db.prepare(`
                SELECT * FROM chats 
                WHERE id = ? AND user_id = ?
            `).get(chatId, req.userId);
            
            if (!chat) {
                console.log(`❌ Chat ${chatId} not found`);
                return res.status(404).json({ error: 'Chat not found' });
            }
            
            console.log(`✅ Chat found:`, chat);
            res.json(chat);
        } catch (err) {
            console.error(`❌ Error fetching chat ${req.params.id}:`, err);
            res.status(500).json({ error: err.message });
        }
    });

    app.delete('/api/chats/:id', requireUser, (req, res) => {
        try {
            const chatId = req.params.id;
            console.log(`🗑️ Deleting chat ${chatId} for user ${req.userId.substring(0, 10)}...`);
            
            // First, get chat info for logging
            const chat = db.prepare(`
                SELECT title FROM chats 
                WHERE id = ? AND user_id = ?
            `).get(chatId, req.userId);
            
            if (!chat) {
                console.log(`❌ Chat ${chatId} not found or not owned by user`);
                return res.status(404).json({ error: 'Chat not found' });
            }
            
            console.log(`   Deleting chat: "${chat.title}"`);
            
            // Count messages before deletion
            const messageCount = db.prepare(`
                SELECT COUNT(*) as count FROM messages WHERE chat_id = ?
            `).get(chatId).count;
            
            console.log(`   This will delete ${messageCount} messages`);
            
            const stmt = db.prepare(`
                DELETE FROM chats 
                WHERE id = ? AND user_id = ?
            `);
            
            const info = stmt.run(req.params.id, req.userId);
            
            if (info.changes === 0) {
                console.log(`❌ No rows deleted`);
                return res.status(404).json({ error: 'Chat not found' });
            }
            
            console.log(`✅ Deleted chat ${chatId} and ${messageCount} messages`);
            res.json({ 
                success: true,
                chatId: chatId,
                messagesDeleted: messageCount
            });
        } catch (err) {
            console.error(`❌ Error deleting chat ${req.params.id}:`, err);
            res.status(500).json({ error: err.message });
        }
    });

    app.patch('/api/chats/:id', requireUser, (req, res) => {
        try {
            const { title } = req.body;
            const chatId = req.params.id;
            
            console.log(`✏️ Renaming chat ${chatId} for user ${req.userId.substring(0, 10)}...`);
            console.log(`   New title: ${title}`);
            
            if (!title || typeof title !== 'string') {
                console.log(`❌ Invalid title: ${title}`);
                return res.status(400).json({ error: 'Valid title required' });
            }
            
            // Get old title for logging
            const oldChat = db.prepare(`
                SELECT title FROM chats 
                WHERE id = ? AND user_id = ?
            `).get(chatId, req.userId);
            
            if (!oldChat) {
                console.log(`❌ Chat ${chatId} not found`);
                return res.status(404).json({ error: 'Chat not found' });
            }
            
            console.log(`   Old title: "${oldChat.title}"`);
            
            const stmt = db.prepare(`
                UPDATE chats 
                SET title = ?, updated_at = CURRENT_TIMESTAMP 
                WHERE id = ? AND user_id = ?
            `);
            
            const info = stmt.run(title.trim(), req.params.id, req.userId);
            
            if (info.changes === 0) {
                console.log(`❌ No rows updated`);
                return res.status(404).json({ error: 'Chat not found' });
            }
            
            console.log(`✅ Chat renamed from "${oldChat.title}" to "${title}"`);
            res.json({ 
                success: true,
                oldTitle: oldChat.title,
                newTitle: title
            });
        } catch (err) {
            console.error(`❌ Error renaming chat ${req.params.id}:`, err);
            res.status(500).json({ error: err.message });
        }
    });

    app.get('/api/chats/:id/workspace', requireUser, (req, res) => {
        try {
            const chatId = req.params.id;
            const chat = db.prepare(`
                SELECT id, title
                FROM chats
                WHERE id = ? AND user_id = ?
            `).get(chatId, req.userId);

            if (!chat) {
                return res.status(404).json({ error: 'Chat not found' });
            }

            const workspace = db.prepare(`
                SELECT chat_id, content, updated_at
                FROM chat_workspaces
                WHERE chat_id = ?
            `).get(chatId);

            res.json({
                chat_id: chatId,
                content: workspace?.content ?? '',
                updated_at: workspace?.updated_at ?? null
            });
        } catch (err) {
            console.error(`❌ Error fetching workspace for chat ${req.params.id}:`, err);
            res.status(500).json({ error: err.message });
        }
    });

    app.put('/api/chats/:id/workspace', requireUser, (req, res) => {
        try {
            const chatId = req.params.id;
            const { content } = req.body;

            if (typeof content !== 'string') {
                return res.status(400).json({ error: 'Workspace content must be a string' });
            }

            if (content.length > 5_000_000) {
                return res.status(413).json({ error: 'Workspace content too large' });
            }

            const chat = db.prepare(`
                SELECT id, title
                FROM chats
                WHERE id = ? AND user_id = ?
            `).get(chatId, req.userId);

            if (!chat) {
                return res.status(404).json({ error: 'Chat not found' });
            }

            db.prepare(`
                INSERT INTO chat_workspaces (chat_id, content, updated_at)
                VALUES (?, ?, CURRENT_TIMESTAMP)
                ON CONFLICT(chat_id) DO UPDATE SET
                    content = excluded.content,
                    updated_at = CURRENT_TIMESTAMP
            `).run(chatId, content);

            const updated = db.prepare(`
                SELECT chat_id, content, updated_at
                FROM chat_workspaces
                WHERE chat_id = ?
            `).get(chatId);

            res.json(updated);
        } catch (err) {
            console.error(`❌ Error saving workspace for chat ${req.params.id}:`, err);
            res.status(500).json({ error: err.message });
        }
    });

    // ============================================
    // ANT-EDITOR DOCUMENT ENDPOINTS
    // These are completely separate from the chat system.
    // ============================================

    // List all documents for a user
    app.get('/api/documents', requireUser, (req, res) => {
        try {
            const limit = Math.min(parseInt(req.query.limit) || 50, 200);
            const offset = Math.max(parseInt(req.query.offset) || 0, 0);

            const stmt = db.prepare(`
                SELECT id, title, language, created_at, updated_at,
                       LENGTH(content) as content_length
                FROM documents
                WHERE user_id = ?
                ORDER BY updated_at DESC
                LIMIT ? OFFSET ?
            `);

            const documents = stmt.all(req.userId, limit, offset);

            const countStmt = db.prepare('SELECT COUNT(*) as total FROM documents WHERE user_id = ?');
            const { total } = countStmt.get(req.userId);

            res.json({ documents, total, limit, offset });
        } catch (err) {
            res.status(500).json({ error: err.message });
        }
    });

    // List all active shared links for the current user (with document titles)
    // IMPORTANT: Must be registered BEFORE /api/documents/:id to prevent
    // Express from matching 'shared-links' as the :id parameter.
    app.get('/api/documents/shared-links', requireUser, (req, res) => {
        try {
            const stmt = db.prepare(`
                SELECT
                    sd.share_token,
                    sd.document_id,
                    sd.created_at,
                    d.title AS document_title
                FROM shared_documents sd
                JOIN documents d ON d.id = sd.document_id
                WHERE sd.created_by = ?
                ORDER BY sd.created_at DESC
            `);

            const links = stmt.all(req.userId);

            console.log(`🔗 Listed ${links.length} shared link(s) for user ${req.userId.substring(0, 8)}…`);
            res.json({ shared_links: links });
        } catch (err) {
            console.error('Failed to list shared links:', err);
            res.status(500).json({ error: err.message });
        }
    });

    // Get a single document (with full content)
    app.get('/api/documents/:id', requireUser, (req, res) => {
        try {
            const doc = db.prepare(`
                SELECT * FROM documents
                WHERE id = ? AND user_id = ?
            `).get(req.params.id, req.userId);

            if (!doc) {
                return res.status(404).json({ error: 'Document not found' });
            }

            res.json(doc);
        } catch (err) {
            res.status(500).json({ error: err.message });
        }
    });

    // Create a new document
    app.post('/api/documents', requireUser, (req, res) => {
        try {
            const { title, content, language } = req.body;

            const docTitle = (title && typeof title === 'string') ? title.trim() : 'Untitled Document';
            const docContent = (content && typeof content === 'string') ? content : '';
            const docLanguage = (language && typeof language === 'string') ? language.trim().substring(0, 2) : 'en';

            const stmt = db.prepare(`
                INSERT INTO documents (user_id, title, content, language)
                VALUES (?, ?, ?, ?)
            `);

            const info = stmt.run(req.userId, docTitle, docContent, docLanguage);

            const newDoc = db.prepare('SELECT * FROM documents WHERE id = ?').get(info.lastInsertRowid);

            res.status(201).json(newDoc);
        } catch (err) {
            res.status(500).json({ error: err.message });
        }
    });

    // Update a document (full save — title + content)
    app.put('/api/documents/:id', requireUser, (req, res) => {
        try {
            const { title, content, language } = req.body;

            // Verify ownership
            const existing = db.prepare(`
                SELECT id FROM documents WHERE id = ? AND user_id = ?
            `).get(req.params.id, req.userId);

            if (!existing) {
                return res.status(404).json({ error: 'Document not found' });
            }

            const updates = [];
            const params = [];

            if (title !== undefined) {
                updates.push('title = ?');
                params.push(typeof title === 'string' ? title.trim() : 'Untitled Document');
            }
            if (content !== undefined) {
                updates.push('content = ?');
                params.push(typeof content === 'string' ? content : '');
            }
            if (language !== undefined) {
                updates.push('language = ?');
                params.push(typeof language === 'string' ? language.trim().substring(0, 2) : 'en');
            }

            if (updates.length === 0) {
                return res.status(400).json({ error: 'No fields to update' });
            }

            updates.push('updated_at = CURRENT_TIMESTAMP');
            params.push(req.params.id, req.userId);

            db.prepare(`
                UPDATE documents SET ${updates.join(', ')}
                WHERE id = ? AND user_id = ?
            `).run(...params);

            const updatedDoc = db.prepare('SELECT * FROM documents WHERE id = ?').get(req.params.id);
            res.json(updatedDoc);
        } catch (err) {
            res.status(500).json({ error: err.message });
        }
    });

    // Rename a document (title only)
    app.patch('/api/documents/:id', requireUser, (req, res) => {
        try {
            const { title } = req.body;

            if (!title || typeof title !== 'string') {
                return res.status(400).json({ error: 'Valid title required' });
            }

            const stmt = db.prepare(`
                UPDATE documents
                SET title = ?, updated_at = CURRENT_TIMESTAMP
                WHERE id = ? AND user_id = ?
            `);

            const info = stmt.run(title.trim(), req.params.id, req.userId);

            if (info.changes === 0) {
                return res.status(404).json({ error: 'Document not found' });
            }

            res.json({ success: true });
        } catch (err) {
            res.status(500).json({ error: err.message });
        }
    });

    // Delete a document
    app.delete('/api/documents/:id', requireUser, (req, res) => {
        try {
            const stmt = db.prepare(`
                DELETE FROM documents
                WHERE id = ? AND user_id = ?
            `);

            const info = stmt.run(req.params.id, req.userId);

            if (info.changes === 0) {
                return res.status(404).json({ error: 'Document not found' });
            }

            res.json({ success: true });
        } catch (err) {
            res.status(500).json({ error: err.message });
        }
    });

    // ============================================
    // DOCUMENT SHARING ENDPOINTS
    // Share a document via a randomly generated token.
    // Create/delete share requires auth. Access via token is public.
    // ============================================

    const crypto = require('crypto');


    // Create (or return existing) share link for a document
    app.post('/api/documents/:id/share', requireUser, (req, res) => {
        try {
            const docId = req.params.id;

            // Verify ownership
            const doc = db.prepare(
                'SELECT id, title FROM documents WHERE id = ? AND user_id = ?'
            ).get(docId, req.userId);

            if (!doc) {
                return res.status(404).json({ error: 'Document not found' });
            }

            // Check if a share link already exists for this doc
            const existing = db.prepare(
                'SELECT share_token FROM shared_documents WHERE document_id = ? AND created_by = ?'
            ).get(docId, req.userId);

            if (existing) {
                return res.json({ share_token: existing.share_token });
            }

            // Generate a new share token (URL-safe UUID)
            const shareToken = crypto.randomUUID();

            db.prepare(
                'INSERT INTO shared_documents (share_token, document_id, created_by) VALUES (?, ?, ?)'
            ).run(shareToken, docId, req.userId);

            console.log(`🔗 Share link created for doc ${docId} → token ${shareToken.substring(0, 8)}…`);

            res.status(201).json({ share_token: shareToken });
        } catch (err) {
            console.error('Failed to create share link:', err);
            res.status(500).json({ error: err.message });
        }
    });

    // Revoke a share link
    app.delete('/api/documents/:id/share', requireUser, (req, res) => {
        try {
            const docId = req.params.id;

            // Verify ownership
            const doc = db.prepare(
                'SELECT id FROM documents WHERE id = ? AND user_id = ?'
            ).get(docId, req.userId);

            if (!doc) {
                return res.status(404).json({ error: 'Document not found' });
            }

            const info = db.prepare(
                'DELETE FROM shared_documents WHERE document_id = ? AND created_by = ?'
            ).run(docId, req.userId);

            if (info.changes === 0) {
                return res.status(404).json({ error: 'No share link found for this document' });
            }

            console.log(`🔗❌ Share link revoked for doc ${docId}`);
            res.json({ success: true });
        } catch (err) {
            res.status(500).json({ error: err.message });
        }
    });

    // ── Public shared document access (NO auth) ──

    // Get a shared document by token
    app.get('/api/shared/:token', (req, res) => {
        try {
            const token = req.params.token;

            // Validate token format (UUID)
            if (!token || typeof token !== 'string' || token.length < 10) {
                return res.status(400).json({ error: 'Invalid share token' });
            }

            const share = db.prepare(
                'SELECT document_id FROM shared_documents WHERE share_token = ?'
            ).get(token);

            if (!share) {
                return res.status(404).json({ error: 'Shared document not found or link has been revoked' });
            }

            const doc = db.prepare(
                'SELECT id, title, content, language, created_at, updated_at FROM documents WHERE id = ?'
            ).get(share.document_id);

            if (!doc) {
                // Document was deleted — clean up orphaned share record
                db.prepare('DELETE FROM shared_documents WHERE share_token = ?').run(token);
                return res.status(404).json({ error: 'The shared document no longer exists' });
            }

            // Return document WITHOUT user_id (privacy)
            res.json({
                id: doc.id,
                title: doc.title,
                content: doc.content,
                language: doc.language,
                content_length: (doc.content || '').length,
                created_at: doc.created_at,
                updated_at: doc.updated_at,
            });
        } catch (err) {
            console.error('Failed to fetch shared document:', err);
            res.status(500).json({ error: err.message });
        }
    });

    // Save edits to a shared document by token (public — no auth)
    app.put('/api/shared/:token', (req, res) => {
        try {
            const token = req.params.token;
            const { title, content } = req.body;

            // Validate token format
            if (!token || typeof token !== 'string' || token.length < 10) {
                return res.status(400).json({ error: 'Invalid share token' });
            }

            const share = db.prepare(
                'SELECT document_id FROM shared_documents WHERE share_token = ?'
            ).get(token);

            if (!share) {
                return res.status(404).json({ error: 'Shared document not found or link has been revoked' });
            }

            const updates = [];
            const params = [];

            if (title !== undefined) {
                updates.push('title = ?');
                params.push(typeof title === 'string' ? title.trim() : 'Untitled Document');
            }
            if (content !== undefined) {
                updates.push('content = ?');
                params.push(typeof content === 'string' ? content : '');
            }

            if (updates.length === 0) {
                return res.status(400).json({ error: 'No fields to update' });
            }

            updates.push('updated_at = CURRENT_TIMESTAMP');
            params.push(share.document_id);

            db.prepare(
                `UPDATE documents SET ${updates.join(', ')} WHERE id = ?`
            ).run(...params);

            const updatedDoc = db.prepare(
                'SELECT id, title, content, language, created_at, updated_at FROM documents WHERE id = ?'
            ).get(share.document_id);

            res.json({
                id: updatedDoc.id,
                title: updatedDoc.title,
                content: updatedDoc.content,
                language: updatedDoc.language,
                content_length: (updatedDoc.content || '').length,
                created_at: updatedDoc.created_at,
                updated_at: updatedDoc.updated_at,
            });
        } catch (err) {
            console.error('Failed to save shared document:', err);
            res.status(500).json({ error: err.message });
        }
    });

    // Beacon-save for shared documents (for page close via navigator.sendBeacon)
    app.post('/api/shared/:token/beacon-save', (req, res) => {
        try {
            const token = req.params.token;
            const { title, content } = req.body;

            if (!token || typeof token !== 'string' || token.length < 10) {
                return res.status(400).json({ error: 'Invalid share token' });
            }

            const share = db.prepare(
                'SELECT document_id FROM shared_documents WHERE share_token = ?'
            ).get(token);

            if (!share) {
                return res.status(404).json({ error: 'Shared document not found' });
            }

            const updates = [];
            const params = [];

            if (title !== undefined) {
                updates.push('title = ?');
                params.push(typeof title === 'string' ? title.trim() : 'Untitled Document');
            }
            if (content !== undefined) {
                updates.push('content = ?');
                params.push(typeof content === 'string' ? content : '');
            }

            if (updates.length > 0) {
                updates.push('updated_at = CURRENT_TIMESTAMP');
                params.push(share.document_id);

                db.prepare(
                    `UPDATE documents SET ${updates.join(', ')} WHERE id = ?`
                ).run(...params);
            }

            res.json({ success: true });
        } catch (err) {
            res.status(500).json({ error: err.message });
        }
    });

    // Beacon-save endpoint (POST because sendBeacon only supports POST)
    // Used for saving on page close via navigator.sendBeacon()
    app.post('/api/documents/:id/beacon-save', requireUser, (req, res) => {
        try {
            const { title, content } = req.body;

            const existing = db.prepare(`
                SELECT id FROM documents WHERE id = ? AND user_id = ?
            `).get(req.params.id, req.userId);

            if (!existing) {
                return res.status(404).json({ error: 'Document not found' });
            }

            const updates = [];
            const params = [];

            if (title !== undefined) {
                updates.push('title = ?');
                params.push(typeof title === 'string' ? title.trim() : 'Untitled Document');
            }
            if (content !== undefined) {
                updates.push('content = ?');
                params.push(typeof content === 'string' ? content : '');
            }

            if (updates.length > 0) {
                updates.push('updated_at = CURRENT_TIMESTAMP');
                params.push(req.params.id, req.userId);

                db.prepare(`
                    UPDATE documents SET ${updates.join(', ')}
                    WHERE id = ? AND user_id = ?
                `).run(...params);
            }

            res.json({ success: true });
        } catch (err) {
            res.status(500).json({ error: err.message });
        }
    });

    // ============================================
    // ERROR HANDLING MIDDLEWARE
    // ============================================

    app.use((req, res, next) => {
        console.log(`❌ Route not found: ${req.method} ${req.url}`);
        res.status(404).json({ 
            error: 'Route not found',
            method: req.method,
            path: req.url 
        });
    });

    app.use((err, req, res, next) => {
        console.error(`🔥 Unhandled error:`, err);
        console.error(`   Request: ${req.method} ${req.url}`);
        console.error(`   User ID: ${req.userId || 'unknown'}`);
        
        res.status(500).json({ 
            error: 'Internal server error',
            message: err.message,
            timestamp: new Date().toISOString()
        });
    });

    // ============================================
    // START SERVER
    // ============================================

    const port = process.env.PORT || 7860;
    app.listen(port, () => {
        console.log(`\n🚀 ===========================================`);
        console.log(`🚀 NeuralStream Chat Storage v2.0.0`);
        console.log(`🚀 Listening on port ${port}`);
        console.log(`🚀 Database: ${dbPath}`);
        console.log(`🚀 Logging: COMPREHENSIVE`);
        console.log(`🚀 ===========================================\n`);
        
        // Log startup timestamp and environment
        console.log(`📅 Server started at: ${new Date().toISOString()}`);
        console.log(`🌍 Environment: ${process.env.NODE_ENV || 'development'}`);
        console.log(`💻 Platform: ${process.platform}`);
        console.log(`👤 User: ${require('os').userInfo().username}`);
        
        // Test database with sample query
        try {
            const testResult = db.prepare('SELECT sqlite_version() as version').get();
            console.log(`💾 SQLite version: ${testResult.version}`);
        } catch (error) {
            console.error(`❌ Database test failed:`, error);
        }
    });

} catch (error) {
    console.error(`❌ Failed to initialize database:`, error);
    process.exit(1);
}