module Fortitude
  module Support
    class InstanceVariableSet
      def initialize(target_object)
        @target_object = target_object
      end

      def [](name)
        target_object.instance_variable_get("@#{name}")
      end

      def []=(name, value)
        target_object.instance_variable_set("@#{name}", value)
      end

      def keys
        target_object.instance_variables.map do |instance_variable_name|
          $1.to_sym if instance_variable_name.to_s =~ /^@(.*)$/
        end.compact
      end

      def each
        keys.each { |k| yield k, self[k] }
      end

      def with_instance_variable_copying(widget)
        before_copy = widget.instance_variables
        skip_copy = before_copy - target_object.instance_variables

        copy_to_widget(widget)
        begin
          yield
        ensure
          copy_from_widget(widget, skip_copy)
        end
      end

      private
      def copy_to_widget(widget)
        needs = widget.needs_as_hash
        extras = widget.widget_extra_assigns

        target_object.instance_variables.each do |instance_variable_name|
          if instance_variable_name =~ /^@(.*)$/
            without_at = $1.to_sym
            next if needs.has_key?(without_at)
            next if extras.has_key?(without_at)

            value = target_object.instance_variable_get(instance_variable_name)
            widget.instance_variable_set(instance_variable_name, value)
          end
        end
      end

      def copy_from_widget(widget, exclude_variables = [ ])
        needs = widget.needs_as_hash
        extras = widget.widget_extra_assigns

        (widget.instance_variables - exclude_variables).each do |instance_variable_name|
          next if instance_variable_name =~ /^@_fortitude_/

          if instance_variable_name =~ /^@(.*)$/i
            without_at = $1.to_sym
            next if needs.has_key?(without_at)
            next if extras.has_key?(without_at)

            value = widget.instance_variable_get(instance_variable_name)
            target_object.instance_variable_set(instance_variable_name, value)
          end
        end
      end

      attr_reader :target_object
    end
  end
end