class I18n::Railtie

def self.include_fallbacks_module
  I18n.backend.class.send(:include, I18n::Backend::Fallbacks)
end

def self.init_fallbacks(fallbacks)
  include_fallbacks_module
  args = case fallbacks
  when ActiveSupport::OrderedOptions
    [*(fallbacks[:defaults] || []) << fallbacks[:map]].compact
  when Hash, Array
    Array.wrap(fallbacks)
  else # TrueClass
    []
  end
  I18n.fallbacks = I18n::Locale::Fallbacks.new(*args)
end

def self.initialize_i18n(app)
  return if @i18n_inited
  fallbacks = app.config.i18n.delete(:fallbacks)
  # Avoid issues with setting the default_locale by disabling available locales
  # check while configuring.
  enforce_available_locales = app.config.i18n.delete(:enforce_available_locales)
  enforce_available_locales = I18n.enforce_available_locales unless I18n.enforce_available_locales.nil?
  I18n.enforce_available_locales = false
  app.config.i18n.each do |setting, value|
    case setting
    when :railties_load_path
      app.config.i18n.load_path.unshift(*value)
    when :load_path
      I18n.load_path += value
    else
      I18n.send("#{setting}=", value)
    end
  end
  init_fallbacks(fallbacks) if fallbacks && validate_fallbacks(fallbacks)
  # Restore available locales check so it will take place from now on.
  I18n.enforce_available_locales = enforce_available_locales
  reloader = ActiveSupport::FileUpdateChecker.new(I18n.load_path.dup){ I18n.reload! }
  app.reloaders << reloader
  ActionDispatch::Reloader.to_prepare { reloader.execute_if_updated }
  reloader.execute
  @i18n_inited = true
end

def self.validate_fallbacks(fallbacks)
  case fallbacks
  when ActiveSupport::OrderedOptions
    !fallbacks.empty?
  when TrueClass, Array, Hash
    true
  else
    raise "Unexpected fallback type #{fallbacks.inspect}"
  end
end