backend/src/controllers/chatController.js

const Message = require('../models/Message');
const Conversation = require('../models/Conversation');
const { generateAIResponse } = require('../services/aiService');
const Joi = require('joi');

// Validation schema
const sendMessageSchema = Joi.object({
  conversationId: Joi.string().required(),
  content: Joi.string().min(1).max(10000).required()
});

// Send message
exports.sendMessage = async (req, res) => {
  try {
    // Validate input
    const { error } = sendMessageSchema.validate(req.body);
    if (error) {
      return res.status(400).json({ error: error.details[0].message });
    }

    const { conversationId, content } = req.body;
    const userId = req.userId;

    // Verify conversation belongs to user
    const conversation = await Conversation.findOne({
      _id: conversationId,
      userId
    });

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

    // Create user message
    const userMessage = new Message({
      conversationId,
      sender: 'user',
      content
    });
    await userMessage.save();

    // Update conversation
    conversation.messageCount += 1;
    conversation.lastMessageAt = new Date();
    
    // Update title if it's the first message
    if (conversation.messageCount === 1) {
      conversation.title = content.substring(0, 50) + (content.length > 50 ? '...' : '');
    }
    
    await conversation.save();

    // Generate AI response
    const aiResponse = await generateAIResponse(content, conversationId);
    
    const assistantMessage = new Message({
      conversationId,
      sender: 'assistant',
      content: aiResponse.content,
      metadata: aiResponse.metadata
    });
    await assistantMessage.save();

    // Update conversation message count
    conversation.messageCount += 1;
    conversation.lastMessageAt = new Date();
    await conversation.save();

    // Emit to socket if available
    const io = req.app.get('socketio');
    if (io) {
      io.to(`user_${userId}`).emit('newMessage', {
        userMessage,
        assistantMessage
      });
    }

    res.json({
      userMessage,
      assistantMessage
    });
  } catch (error) {
    console.error('Send message error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
};

// Get messages for a conversation
exports.getMessages = async (req, res) => {
  try {
    const { conversationId } = req.params;
    const { page = 1, limit = 50 } = req.query;
    const userId = req.userId;

    // Verify conversation belongs to user
    const conversation = await Conversation.findOne({
      _id: conversationId,
      userId
    });

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

    // Get messages with pagination
    const messages = await Message.find({ conversationId })
      .sort({ createdAt: 1 })
      .limit(limit * 1)
      .skip((page - 1) * limit);

    const total = await Message.countDocuments({ conversationId });

    res.json({
      messages,
      pagination: {
        page: parseInt(page),
        limit: parseInt(limit),
        total,
        pages: Math.ceil(total / limit)
      }
    });
  } catch (error) {
    console.error('Get messages error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
};

// Delete message
exports.deleteMessage = async (req, res) => {
  try {
    const { messageId } = req.params;
    const userId = req.userId;

    // Find message and verify ownership
    const message = await Message.findById(messageId).populate({
      path: 'conversationId',
      select: 'userId'
    });

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

    if (message.conversationId.userId.toString() !== userId) {
      return res.status(403).json({ error: 'Unauthorized' });
    }

    await Message.findByIdAndDelete(messageId);

    // Update conversation message count
    await Conversation.findByIdAndUpdate(message.conversationId._id, {
      $inc: { messageCount: -1 }
    });

    res.json({ message: 'Message deleted successfully' });
  } catch (error) {
    console.error('Delete message error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
};