module ObjectIdentifier
  class Deidentifier
    attr_accessor :str, :options

    def initialize(str, options = {})
      @str     = str.to_s
      @options = options
    end

    # Class method for reconstructing an object or set of objects from its/their
    # self-identifying string(s).
    #
    # @overload self.identify(str)
    #   @param str [String] the String to deidentify
    # @overload self.identify(str, options)
    #   @param str [String] the object to identify
    #   @param [Hash] options the options for building a customized
    #     self-identifier
    #   @option options [String, nil] :klass object class name override
    #   @option options [Fixnum] :limit maximum number of objects to display
    #     from a collection
    #
    # @return [Object] the object represented by the identifier String
    def self.deidentify(obj, options = {})
      new(obj, options).deidentify
    end

    # @return [Object] the object represented by the identifier String
    def deidentify
      if multiple_objects_to_deidentify?
        # deidentify_multiple_objects
      else
        deidentify_single_object(str)
      end
    end

    private

    def deidentify_multiple_objects
    end

    def deidentify_single_object(object_str)
      klass = determine_class(object_str)
      attributes = extract_attributes(object_str)

      case (model = klass.constantize)
      when ActiveRecord::Base
        model.where(select_core_attributes(attributes)).first
      else
        model.new(attributes)
      end
    end

    def multiple_objects_to_deidentify?
      str.starts_with?("[") && str.ends_with?("]")
    end

    def determine_class(object_str)
      options.fetch(:klass) {
        object_str[/\A(\w+)/, 1]
      }
    end

    def extract_attributes(object_str)
      result = object_str[/\[(.+)\]/, 1]
      return if result == "no objects"
      JSON.parse(jsonify_attributes_str(result))
    end

    def jsonify_attributes_str(attributes_str)
      "{ #{attributes_str} }".gsub(/ (\w+):/, ' "\1":')
    end

    def select_core_attributes(attributes)
      attributes.select { |key, _| key.in?(klass.column_names) }
    end
  end
end