backend/src/models/Conversation.js

const mongoose = require('mongoose');

const conversationSchema = new mongoose.Schema({
  title: {
    type: String,
    required: true,
    trim: true,
    maxlength: 100
  },
  userId: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'User',
    required: true
  },
  messageCount: {
    type: Number,
    default: 0
  },
  lastMessageAt: {
    type: Date,
    default: Date.now
  },
  isArchived: {
    type: Boolean,
    default: false
  },
  tags: [{
    type: String,
    trim: true
  }]
}, {
  timestamps: true
});

// Index for better query performance
conversationSchema.index({ userId: 1, createdAt: -1 });
conversationSchema.index({ userId: 1, lastMessageAt: -1 });

module.exports = mongoose.model('Conversation', conversationSchema);