# frozen_string_literal: true

require "active_support/core_ext/object/duplicable"

module ThreadsafeAttributes
  def self.included(klass)
    klass.extend(ClassMethods)
  end

  module ClassMethods
    def threadsafe_attribute(*attrs)
      main_thread = Thread.main # remember this, because it could change after forking

      attrs.each do |attr|
        define_method attr do
          get_threadsafe_attribute(attr, main_thread)
        end

        define_method "#{attr}=" do |value|
          set_threadsafe_attribute(attr, value, main_thread)
        end

        define_method "#{attr}_defined?" do
          threadsafe_attribute_defined?(attr, main_thread)
        end
      end
    end
  end

  private

    def get_threadsafe_attribute(name, main_thread)
      if threadsafe_attribute_defined_by_thread?(name, Thread.current)
        get_threadsafe_attribute_by_thread(name, Thread.current)
      elsif threadsafe_attribute_defined_by_thread?(name, main_thread)
        value = get_threadsafe_attribute_by_thread(name, main_thread)
        value = value.dup if value.duplicable?
        set_threadsafe_attribute_by_thread(name, value, Thread.current)
        value
      end
    end

    def set_threadsafe_attribute(name, value, main_thread)
      set_threadsafe_attribute_by_thread(name, value, Thread.current)
      unless threadsafe_attribute_defined_by_thread?(name, main_thread)
        set_threadsafe_attribute_by_thread(name, value, main_thread)
      end
    end

    def threadsafe_attribute_defined?(name, main_thread)
      threadsafe_attribute_defined_by_thread?(name, Thread.current) || ((Thread.current != main_thread) && threadsafe_attribute_defined_by_thread?(name, main_thread))
    end

    def get_threadsafe_attribute_by_thread(name, thread)
      thread.thread_variable_get "active.resource.#{name}.#{self.object_id}"
    end

    def set_threadsafe_attribute_by_thread(name, value, thread)
      thread.thread_variable_set "active.resource.#{name}.#{self.object_id}.defined", true
      thread.thread_variable_set "active.resource.#{name}.#{self.object_id}", value
    end

    def threadsafe_attribute_defined_by_thread?(name, thread)
      thread.thread_variable_get "active.resource.#{name}.#{self.object_id}.defined"
    end
end