module ActsAsPreferenced
  module Store

    # This store holds preferences in a serialized field
    class Field < Base

      def initialize( klass, field, translation_scope = nil )
        super( klass, translation_scope )
        @field = field
        @klass.send( :define_method, "preferences" ) do
          prefs = read_attribute(field)
          unless prefs
            prefs = HashWithIndifferentAccess.new
            write_attribute(field, prefs)
          end
          return prefs
        end

        @klass.send( :define_method, "preferences=" ) do |new_prefs|
          self.class.all_preferences.each do |pref|
            # Hack to allow boolean preferences to be set to false. This looks
            # wrong from model point of view (if you mass assign preferences,
            # absent boolean ones will be set to false even though default is
            # true), but it works well for forms.
            # TODO: find a way to make it work properly both for defaults and
            # forms (if at all possible)
            new_prefs[pref.name] ||= false if pref.default == true 
          end
          write_attribute(field, new_prefs)
        end
      end

      def preference( name, options = {} )
        options.assert_valid_keys( :section, :label, :choices, :default )
        pref = Preference.new( self, name, options )
        if options[:choices] # Choice
          @klass.send( :define_method, "#{name}" ) do
            # This symbolizes strings and leave other values (eg. numbers)
            # intact
            value = preferences[name].is_a?( String ) ? preferences[name].to_sym : preferences[name]
            value || pref.default
          end
        else # Boolean
          @klass.send( :define_method, "#{name}?" ) do
            # We check for nil to allow "false" here
            preferences[name].nil? ?  pref.default : preferences[name]
          end
        end
        @klass.send( :define_method, "#{name}=" ) do |value|
          if pref.value_valid?( value )
            preferences[name] = value
          else
            raise ArgumentError, "Value #{value} invalid for preference #{pref.name}"
          end
        end

      end

    end
  end
end