const Conversation = require('../models/Conversation');
const Message = require('../models/Message');
const User = require('../models/User');
const { generateInviteCode } = require('../utils/helpers');

exports.createConversation = async (req, res) => {
  try {
    const { type, name, description, participantIds } = req.body;
    const userId = req.user.userId;

    // Validate conversation type
    if (!['direct', 'group'].includes(type)) {
      return res.status(400).json({ error: 'Invalid conversation type' });
    }

    // For direct messages, check if conversation already exists
    if (type === 'direct') {
      if (!participantIds || participantIds.length !== 1) {
        return res.status(400).json({ error: 'Direct message requires exactly one participant' });
      }

      const existingConversation = await Conversation.findDirectConversation(userId, participantIds[0]);

      if (existingConversation) {
        await existingConversation.populate('participants.user', 'username displayName avatar status');
        return res.json({ 
          message: 'Conversation already exists',
          conversation: existingConversation 
        });
      }
    }

    // For group conversations, validate name
    if (type === 'group' && (!name || name.trim().length === 0)) {
      return res.status(400).json({ error: 'Group conversation requires a name' });
    }

    // Verify all participants exist
    const participants = await User.find({ 
      _id: { $in: participantIds } 
    }).select('_id');

    if (participants.length !== participantIds.length) {
      return res.status(400).json({ error: 'One or more participants not found' });
    }

    // Create conversation participants array
    const conversationParticipants = [
      { user: userId, role: 'owner' },
      ...participantIds.map(pid => ({ user: pid, role: 'member' }))
    ];

    const conversation = new Conversation({
      type,
      name: type === 'direct' ? null : name.trim(),
      description: type === 'direct' ? null : (description || '').trim(),
      createdBy: userId,
      participants: conversationParticipants
    });

    await conversation.save();
    await conversation.populate('participants.user', 'username displayName avatar status');
    await conversation.populate('createdBy', 'username displayName');

    res.status(201).json({
      message: 'Conversation created successfully',
      conversation
    });
  } catch (error) {
    console.error('❌ Create conversation error:', error);
    res.status(500).json({ error: 'Server error creating conversation' });
  }
};

exports.getUserConversations = async (req, res) => {
  try {
    const userId = req.user.userId;

    const conversations = await Conversation.find({
      'participants.user': userId
    })
    .populate('participants.user', 'username displayName avatar status lastSeen')
    .populate('lastMessage')
    .populate('createdBy', 'username displayName')
    .sort({ updatedAt: -1 });

    res.json({ conversations });
  } catch (error) {
    console.error('❌ Get conversations error:', error);
    res.status(500).json({ error: 'Server error fetching conversations' });
  }
};

exports.getConversation = async (req, res) => {
  try {
    const { conversationId } = req.params;
    const userId = req.user.userId;

    const conversation = await Conversation.findOne({
      _id: conversationId,
      'participants.user': userId
    })
    .populate('participants.user', 'username displayName avatar status lastSeen bio')
    .populate('createdBy', 'username displayName avatar')
    .populate('lastMessage');

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

    res.json({ conversation });
  } catch (error) {
    console.error('❌ Get conversation error:', error);
    res.status(500).json({ error: 'Server error fetching conversation' });
  }
};

exports.getConversationMessages = async (req, res) => {
  try {
    const { conversationId } = req.params;
    const { page = 1, limit = 50 } = req.query;
    const userId = req.user.userId;

    // Check if user is part of conversation
    const conversation = await Conversation.findOne({
      _id: conversationId,
      'participants.user': userId
    });

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

    const pageNum = Math.max(1, parseInt(page));
    const limitNum = Math.min(100, Math.max(1, parseInt(limit))); // Max 100 messages per request

    const messages = await Message.find({ conversation: conversationId })
      .populate('sender', 'username displayName avatar status')
      .populate('replyTo')
      .populate('reactions.user', 'username displayName')
      .sort({ createdAt: -1 })
      .limit(limitNum)
      .skip((pageNum - 1) * limitNum);

    // Reverse to get chronological order (oldest first)
    const sortedMessages = messages.reverse();

    const totalMessages = await Message.countDocuments({ conversation: conversationId });

    res.json({
      messages: sortedMessages,
      pagination: {
        page: pageNum,
        limit: limitNum,
        total: totalMessages,
        pages: Math.ceil(totalMessages / limitNum)
      }
    });
  } catch (error) {
    console.error('❌ Get messages error:', error);
    res.status(500).json({ error: 'Server error fetching messages' });
  }
};

// ADD THE MISSING FUNCTION
exports.updateConversation = async (req, res) => {
  try {
    const { conversationId } = req.params;
    const { name, description, settings } = req.body;
    const userId = req.user.userId;

    // Check if user is admin/owner of conversation
    const conversation = await Conversation.findOne({
      _id: conversationId,
      'participants.user': userId,
      'participants.role': { $in: ['admin', 'owner'] }
    });

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

    const updateData = {};
    if (name !== undefined) updateData.name = name;
    if (description !== undefined) updateData.description = description;
    if (settings) updateData.settings = { ...conversation.settings, ...settings };

    const updatedConversation = await Conversation.findByIdAndUpdate(
      conversationId,
      updateData,
      { new: true }
    ).populate('participants.user', 'username displayName avatar status');

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

    res.json({
      message: 'Conversation updated successfully',
      conversation: updatedConversation
    });
  } catch (error) {
    console.error('❌ Update conversation error:', error);
    res.status(500).json({ error: 'Server error updating conversation' });
  }
};

// ADD THE MISSING FUNCTION
exports.generateInviteLink = async (req, res) => {
  try {
    const { conversationId } = req.params;
    const { expiresIn = '7d', maxUses = null } = req.body;
    const userId = req.user.userId;

    // Check if user is admin/owner
    const conversation = await Conversation.findOne({
      _id: conversationId,
      'participants.user': userId,
      'participants.role': { $in: ['admin', 'owner'] }
    });

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

    const inviteCode = generateInviteCode();
    const expiresAt = new Date();
    expiresAt.setDate(expiresAt.getDate() + 7); // Default 7 days

    const inviteLink = {
      code: inviteCode,
      createdBy: userId,
      expiresAt,
      maxUses: maxUses || null,
      uses: 0,
      isActive: true
    };

    conversation.inviteLinks.push(inviteLink);
    await conversation.save();

    res.json({
      message: 'Invite link generated successfully',
      inviteLink: {
        code: inviteCode,
        url: `${process.env.CLIENT_URL || 'http://localhost:3000'}/join/${inviteCode}`,
        expiresAt,
        maxUses
      }
    });
  } catch (error) {
    console.error('❌ Generate invite link error:', error);
    res.status(500).json({ error: 'Server error generating invite link' });
  }
};