discourse/app/models/email_token.rb

class EmailToken < ActiveRecord::Base
  belongs_to :user

  validates :token, :user_id, :email, presence: true

  before_validation(on: :create) do
    self.token = EmailToken.generate_token
    self.email = self.email.downcase if self.email
  end

  after_create do
    # Expire the previous tokens
    EmailToken.where(user_id: self.user_id)
      .where("id != ?", self.id)
      .update_all(expired: true)
  end

  def self.token_length
    16
  end

  def self.valid_after
    SiteSetting.email_token_valid_hours.hours.ago
  end

  def self.unconfirmed
    where(confirmed: false)
  end

  def self.active
    where(expired: false).where('created_at > ?', valid_after)
  end

  def self.generate_token
    SecureRandom.hex(EmailToken.token_length)
  end

  def self.valid_token_format?(token)
    token.present? && token =~ /\h{#{token.length / 2}}/i
  end

  def self.atomic_confirm(token)
    failure = { success: false }
    return failure unless valid_token_format?(token)

    email_token = confirmable(token)
    return failure if email_token.blank?

    user = email_token.user
    failure[:user] = user
    row_count = EmailToken.where(confirmed: false, id: email_token.id, expired: false).update_all 'confirmed = true'

    if row_count == 1
      { success: true, user: user, email_token: email_token }
    else
      failure
    end
  end

  def self.confirm(token)
    User.transaction do
      result = atomic_confirm(token)
      user = result[:user]
      if result[:success]
        # If we are activating the user, send the welcome message
        user.send_welcome_message = !user.active?
        user.active = true
        user.email = result[:email_token].email
        user.save!
        user.set_automatic_groups
      end

      if user
        return User.find_by_email(user.email) if Invite.redeem_from_email(user.email).present?
        user
      end
    end
  rescue ActiveRecord::RecordInvalid
    # If the user's email is already taken, just return nil (failure)
  end

  def self.confirmable(token)
    EmailToken.where(token: token)
      .where(expired: false, confirmed: false)
      .where("created_at >= ?", EmailToken.valid_after)
      .includes(:user)
      .first
  end
end

# == Schema Information
#
# Table name: email_tokens
#
#  id         :integer          not null, primary key
#  user_id    :integer          not null
#  email      :string(255)      not null
#  token      :string(255)      not null
#  confirmed  :boolean          default(FALSE), not null
#  expired    :boolean          default(FALSE), not null
#  created_at :datetime         not null
#  updated_at :datetime         not null
#
# Indexes
#
#  index_email_tokens_on_token    (token) UNIQUE
#  index_email_tokens_on_user_id  (user_id)
#