internetee-registry/app/models/account_activity.rb

require 'csv'

class AccountActivity < ActiveRecord::Base
  include Versions
  belongs_to :account
  belongs_to :bank_transaction
  belongs_to :invoice

  CREATE = 'create'
  RENEW = 'renew'
  ADD_CREDIT = 'add_credit'

  after_create :update_balance
  def update_balance
    account.balance += sum
    account.save
  end

  class << self
    def types_for_select
      [CREATE, RENEW, ADD_CREDIT].map { |x| [I18n.t(x), x] }
    end

    def to_csv
      attributes = %w(description activity_type created_at sum)

      CSV.generate(headers: true) do |csv|
        csv << %w(description activity_type receipt_date sum)

        all.find_each do |x|
          csv << attributes.map { |attr| x.send(attr) }
        end
      end
    end
  end
end