# frozen_string_literal: true
# rubocop:todo all
# Copyright (C) 2009-2020 MongoDB Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

module BSON

  # Represents the Undefined BSON type
  #
  # @see http://bsonspec.org/#/specification
  #
  # @since 2.0.0
  class Undefined
    include JSON
    include Specialized

    # Undefined is type 0x06 in the BSON spec.
    #
    # @since 2.0.0
    BSON_TYPE = ::String.new(6.chr, encoding: BINARY).freeze

    # Determine if undefined is equal to another object.
    #
    # @example Check undefined equality.
    #   BSON::Undefined.new == object
    #
    # @param [ Object ] other The object to check against.
    #
    # @return [ true, false ] If the objects are equal.
    #
    # @since 2.0.0
    def ==(other)
      self.class == other.class
    end

    # Return a string representation of the BSON::Undefined for use in
    # application-level JSON serialization. This method is intentionally
    # different from #as_extended_json.
    #
    # @example Get the undefined as a JSON-serializable object.
    #   undefined.as_json
    #
    # @return [ nil ] The undefined as nil.
    def as_json(*args)
      nil
    end

    # Converts this object to a representation directly serializable to
    # Extended JSON (https://github.com/mongodb/specifications/blob/master/source/extended-json/extended-json.md).
    #
    # @option opts [ nil | :relaxed | :legacy ] :mode Serialization mode
    #   (default is canonical extended JSON)
    #
    # @return [ Hash ] The extended json representation.
    def as_extended_json(**options)
      { "$undefined" => true }
    end

    # Register this type when the module is loaded.
    #
    # @since 2.0.0
    Registry.register(BSON_TYPE, self)
  end
end