backend/models/User.js

const mongoose = require('mongoose');
const bcrypt = require('bcryptjs');

const userSchema = new mongoose.Schema({
  googleId: {
    type: String,
    sparse: true,
  },
  email: {
    type: String,
    required: true,
    unique: true,
    lowercase: true,
  },
  username: {
    type: String,
    required: true,
  },
  password: {
    type: String,
    required: function() {
      return !this.googleId;
    },
  },
  avatar: {
    type: String,
    default: '',
  },
  createdAt: {
    type: Date,
    default: Date.now,
  },
});

userSchema.pre('save', async function(next) {
  if (!this.isModified('password')) return next();
  
  if (this.password) {
    this.password = await bcrypt.hash(this.password, 10);
  }
  next();
});

userSchema.methods.comparePassword = async function(candidatePassword) {
  return await bcrypt.compare(candidatePassword, this.password);
};

module.exports = mongoose.model('User', userSchema);