class ActiveRecord::Associations::Builder::BelongsTo

def self.add_counter_cache_callbacks(model, reflection)
  cache_column = reflection.counter_cache_column
  model.after_update lambda { |record|
    association = association(reflection.name)
    if association.saved_change_to_target?
      association.increment_counters
      association.decrement_counters_before_last_save
    end
  }
  klass = reflection.class_name.safe_constantize
  klass.attr_readonly cache_column if klass && klass.respond_to?(:attr_readonly)
end

def self.add_default_callbacks(model, reflection)
  model.before_validation lambda { |o|
    o.association(reflection.name).default(&reflection.options[:default])
  }
end

def self.add_destroy_callbacks(model, reflection)
  model.after_destroy lambda { |o| o.association(reflection.name).handle_dependency }
end

def self.add_touch_callbacks(model, reflection)
  foreign_key = reflection.foreign_key
  name        = reflection.name
  touch       = reflection.options[:touch]
  callback = lambda { |changes_method| lambda { |record|
    BelongsTo.touch_record(record, record.send(changes_method), foreign_key, name, touch, belongs_to_touch_method)
  }}
  if reflection.counter_cache_column
    touch_callback = callback.(:saved_changes)
    update_callback = lambda { |record|
      instance_exec(record, &touch_callback) unless association(reflection.name).saved_change_to_target?
    }
    model.after_update update_callback, if: :saved_changes?
  else
    model.after_create callback.(:saved_changes), if: :saved_changes?
    model.after_update callback.(:saved_changes), if: :saved_changes?
    model.after_destroy callback.(:changes_to_save)
  end
  model.after_touch callback.(:changes_to_save)
end

def self.define_callbacks(model, reflection)
  super
  add_counter_cache_callbacks(model, reflection) if reflection.options[:counter_cache]
  add_touch_callbacks(model, reflection)         if reflection.options[:touch]
  add_default_callbacks(model, reflection)       if reflection.options[:default]
end

def self.define_change_tracking_methods(model, reflection)
  model.generated_association_methods.class_eval <<-CODE, __FILE__, __LINE__ + 1
    def #{reflection.name}_changed?
      association(:#{reflection.name}).target_changed?
    end
    def #{reflection.name}_previously_changed?
      association(:#{reflection.name}).target_previously_changed?
    end
  CODE
end

def self.define_validations(model, reflection)
  if reflection.options.key?(:required)
    reflection.options[:optional] = !reflection.options.delete(:required)
  end
  if reflection.options[:optional].nil?
    required = model.belongs_to_required_by_default
  else
    required = !reflection.options[:optional]
  end
  super
  if required
    model.validates_presence_of reflection.name, message: :required
  end
end

def self.macro
  :belongs_to
end

def self.touch_record(o, changes, foreign_key, name, touch, touch_method) # :nodoc:
  old_foreign_id = changes[foreign_key] && changes[foreign_key].first
  if old_foreign_id
    association = o.association(name)
    reflection = association.reflection
    if reflection.polymorphic?
      foreign_type = reflection.foreign_type
      klass = changes[foreign_type] && changes[foreign_type].first || o.public_send(foreign_type)
      klass = o.class.polymorphic_class_for(klass)
    else
      klass = association.klass
    end
    primary_key = reflection.association_primary_key(klass)
    old_record = klass.find_by(primary_key => old_foreign_id)
    if old_record
      if touch != true
        old_record.public_send(touch_method, touch)
      else
        old_record.public_send(touch_method)
      end
    end
  end
  record = o.public_send name
  if record && record.persisted?
    if touch != true
      record.public_send(touch_method, touch)
    else
      record.public_send(touch_method)
    end
  end
end

def self.valid_dependent_options
  [:destroy, :delete, :destroy_async]
end

def self.valid_options(options)
  valid = super + [:polymorphic, :counter_cache, :optional, :default]
  valid += [:foreign_type] if options[:polymorphic]
  valid += [:ensuring_owner_was] if options[:dependent] == :destroy_async
  valid
end