module Mobility
  module Backend
=begin

Stores attribute translation as attribute/value pair on a shared translations
table, using a polymorphic relationship between a translation class and models
using the backend. By default, two tables are assumed to be present supporting
string and text translations: a +mobility_text_translations+ table for text-valued translations and a
+mobility_string_translations+ table for string-valued translations (the only
difference being the column type of the +value+ column on the table).

==Backend Options

===+association_name+

Name of association on model. Defaults to +mobility_text_translations+ (if
+type+ is +:text+) or +mobility_string_translations+ (if +type+ is +:string+).
If specified, ensure name does not overlap with other methods on model or with
the association name used by other backends on model (otherwise one will
overwrite the other).

===+type+

Currently, either +:text+ or +:string+ is supported. Determines which class to
use for translations, which in turn determines which table to use to store
translations (by default +mobility_text_translations+ for text type,
+mobility_string_translations+ for string type).

===+class_name+

Class to use for translations when defining association. By default,
{Mobility::ActiveRecord::TextTranslation} or
{Mobility::ActiveRecord::StringTranslation} for ActiveRecord models (similar
for Sequel models). If string is passed in, it will be constantized to get the
class.

@see Mobility::Backend::ActiveRecord::KeyValue
@see Mobility::Backend::Sequel::KeyValue

=end
    module KeyValue
      include OrmDelegator

      # Simple cache to memoize translations as a hash so they can be fetched
      # quickly.
      class TranslationsCache
        # @param backend Instance of KeyValue backend to cache
        # @return [TranslationsCache]
        def initialize(backend)
          @cache = Hash.new { |hash, locale| hash[locale] = backend.translation_for(locale) }
        end

        # @param locale [Symbol] Locale to fetch
        def [](locale)
          @cache[locale].value
        end

        # @param locale [Symbol] Locale to set
        # @param value [String] Value to set
        def []=(locale, value)
          @cache[locale].value = value
        end

        # @yield [locale, translation]
        def each_translation &block
          @cache.each_value &block
        end
      end
    end
  end
end