gistfile1.txt

class ConvertAgentNameToIds < ActiveRecord::Migration
  TYPES = ['created', 'modified', 'cancelled']
  
  def up
    @agents = Hash[*User.select([:first_name, :last_name, :username]).map {|i| ["#{i.first_name} #{i.last_name}", i.username]}.flatten]
    TYPES.each {|i| convert_agent(i)}
  end

  def down
    @agents = Hash[*User.select([:first_name, :last_name, :username]).map {|i| [i.username, "#{i.first_name} #{i.last_name}"]}.flatten]
    TYPES.each {|i| convert_agent(i)}
  end
  
  private
  
  def convert_agent(type)
    res = Reservation.where("#{type}_by IS NOT NULL")
    res.each do |r|
      agent = @agents[r.send("#{type}_by")]
      r.update_attribute("#{type}_by", agent) if agent.present?
    end
  end
end