require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'mongoid', '9.0.8'
end

Mongoid.configure do |config|
  config.clients.default = {
    hosts: ['localhost:27017'],
    database: 'mongoid_test',
  }
end

class Post
  include Mongoid::Document

  has_many :comments, inverse_of: :post

  accepts_nested_attributes_for :comments, allow_destroy: true

  field :title, type: String
end

class Comment
  include Mongoid::Document

  belongs_to :post, inverse_of: :comments

  belongs_to :parent, class_name: 'Comment', inverse_of: :comments, optional: true

  has_many :comments, inverse_of: :parent

  accepts_nested_attributes_for :comments, allow_destroy: true

  validates :title, presence: true

  field :title, type: String
end

post = Post.create(title: 'Post 1')
comment1 = post.comments.create!(title: 'Comment 1')

puts 'Before:'
puts post.inspect
puts "  #{comment1.inspect}"
puts "    #{comment1.comments.to_a}"
puts ''

post.update!(
  comments_attributes: [
    {
      _id: comment1.id,
      comments_attributes: [
        {
          title: nil
        }
      ]
    }
  ]
)

puts 'After:'
puts post.reload.inspect
puts "  #{comment1.reload.inspect}"
puts "    #{comment1.comments.to_a}"