app/models/user.rb

#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.
#

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable,
         :omniauthable, omniauth_providers: [:facebook, :google_oauth2]

  has_many :databundles, class_name: 'DataBundle'

  validates :email, presence: true, uniqueness: true

  def self.from_omniauth(auth)
    # Find user by omniauth
    # If exist user with uid, return it
    user = where(provider: auth.provider, uid: auth.uid).first
    return user if user

    # Or if exist user with email, return it
    user = where(email: auth.info.email).first
    return user if user

    # Create the user if it's a new registration
    create do |user|
      user.provider = auth.provider
      user.uid = auth.uid
      user.email = auth.info.email
      user.password = Devise.friendly_token[0, 20]
      user.firstname = auth.info.first_name
      user.lastname = auth.info.last_name
    end
  end
end