# coll = Product.find_all_by_kind('material') +
#   Product.find_all_by_kind('materialgroup') +
#   Product.find_all_by_kind('pricegroup') +
#   Product.find_all_by_kind('component')
# mass_translate(coll, [:name, :description], :en, :de)
# mass_translate(coll, [:name, :description], :de, [:en, :fr]) { |v, l| "#{v} (#{l})" }
#
# coll = Product.find_all_by_kind('product')
# mass_translate(coll, :name, :de, [:en, :fr])
#
# coll = Protoype.all + Taxon.all + Taxonomy .all
# mass_translate(coll, :name, :en, :de)
# mass_translate(coll, :name, :de, [:en, :fr]) { |v, l| "#{t} (#{l})" }
#
# coll = Property.all
# mass_translate(coll, :presentation, :en, :de)
# mass_translate(coll, :presentation, :de, [:en, :fr]) { |v, l| "#{v} (#{l})" }
#
def mass_translate(collection, attributes, from_locale, to_locales)
  default = I18n.locale
  attributes = [attributes] unless attributes.is_a? Array
  to_locales = [to_locales] unless to_locales.is_a? Array
  collection.each do |object|
    I18n.locale = from_locale
    values = Hash.new.tap do |hash|
      attributes.each do |attribute|
        hash[attribute] = object.send(attribute)
      end
    end
    attributes.each do |attribute|
      puts "read      (#{from_locale}): #{values[attribute]}"
      to_locales.each do |to_locale|
        I18n.locale = to_locale
        old_value = object.send(attribute)
        puts "overwrite (#{to_locale}): #{old_value}" unless old_value.nil?
        new_value = block_given? ? yield(values[attribute], to_locale) : values[attribute]
        new_value = "random#{Time.now.to_i}-#{rand(1000)}" if new_value.blank? # HACK!
        puts "write     (#{to_locale}): #{new_value}"
        object.update_attribute(attribute, new_value)
      end
    end
  end
  I18n.locale = default
end