Need to refactor but how?

ugly_hashes.rb

# Want to take a DELEGATIONS hash like this:
#
# {
#   object1: [ attribute11, attribute12 ],
#   object2: [ attribute21, attribute22 ]
# }
#
# and turn it into a REVERSE_DELEGATIONS hash like this:
#
# {
#   object1_attribute11: [ object1, attribute11 ],
#   object1_attribute12: [ object1, attribute12 ],
#   object2_attribute21: [ object2, attribute21 ],
#   object2_attribute22: [ object2, attribute22 ]
# }

class RegistrationForm
  DELEGATIONS = {
    user: [
      :first_name, :first_name=,
      :last_name, :last_name=,
      :email, :email=,
      :password, :password=,
      :password_confirmation, :password_confirmation=
    ],

    organization: [
      :name, :name=
    ]
  }

  REVERSE_DELEGATIONS = DELEGATIONS.inject({}) do |reverse_delegations, delegation|
    klass = delegation.first
    attrs = delegation.last

    attrs.map { |attr| [ :"#{klass}_#{attr}", attr ] }.each do |lookup, attr|
      reverse_delegations[lookup] = [ klass, attr ]
    end

    reverse_delegations
  end


  def self.human_attribute_name(method)
    REVERSE_DELEGATIONS.has_key?(method) ? REVERSE_DELEGATIONS[method].first.to_s.camelize.constantize.send(:human_attribute_name, REVERSE_DELEGATIONS[method].last) : method.to_s.humanize
  end

end