# lib/active_record/real_delete_discreetly.rb
module RealDeleteDiscreetly
  extend ActiveSupport::Concern

  def delete_discreetly
    relation_exist = false
    self.class.confirm_relations.each do |confirm_relation|
      if destroyed_by_association
        if destroyed_by_association.active_record == confirm_relation.to_s.classify.constantize
          relation_exist = false
          break
        end
      else
        if reflection = self.class.reflections[confirm_relation].presence
          send_method = case reflection.macro
                    when :has_many
                      :exists?
                    else
                      :present?
                    end

          if send(confirm_relation).send(send_method)
            relation_exist = true
            break
          end
        else
          raise ArgumentError, "#{confirm_relation} is not Reflection"
        end
      end
    end

    unless relation_exist
      self.class.delete_all!(self.class.primary_key.to_sym => id)
    end
  end

  module ClassMethods
    def real_delete_discreetly(options = {})
      class_attribute :confirm_relations
      self.confirm_relations = options.delete(:confirm_relations)

      acts_as_paranoid options
      after_destroy :delete_discreetly
    end
  end
end

# spec support
shared_examples_for 'real delete discreetly' do |opts|
  let(:base_instance) { opts[:base_instance] }
  let(:confirm_relations) { opts[:confirm_relations] }
  let(:paranoid_column) { opts[:paranoid_column] || :delete_flag }
  let(:paranoid_column_type) { opts[:paranoid_column_type] || :boolean }

  before do
    @model = base_instance.dup
    @model.save
    case paranoid_column_type.to_sym
    when :boolean
      @from = false
      @to = true
    else
      time = Time.now
      Time.stub(:now).and_return(time)
      @from = nil
      @to = time
    end
  end

  context 'relation exists' do
    before do
      confirm_relation = confirm_relations.first
      case @model.class.reflections[confirm_relation].macro
      when :has_many
        @model.send(confirm_relation).send(:build)
      else
        @model.send("build_#{confirm_relation}")
      end
    end

    it 'soft deleted' do
      expect { @model.destroy }.to change { @model.send(paranoid_column) }.from(@from).to(@to)
    end

    it 'not real deleted' do
      expect { @model.destroy }.to change(@model.class.unscoped, :count).by(0)
    end
  end

  context 'when relation not exists' do
    it 'real deleted' do
      expect { @model.destroy }.to change(@model.class.unscoped, :count).by(-1)
    end
  end
end

# Usage
## in Model
class UserProfile < ActiveRecord::Base
  belongs_to :user
  real_delete_discreetly column: :del_flg, column_type: 'boolean', confirm_relations: [:user]
end

## rspec
require 'rails_helper'

RSpec.describe UserProfile, type: :model do
 include_examples 'real delete discreetly',
 base_instance: UserProfile.create(user_id: nil_or_exist_id),
 confirm_relations: [:user]
end