ActiveStorage callbacks

module ActiveStorage
  class Attached
    def perform_attachment(attachables)
      return yield unless record.class.respond_to?(:attachment_callbacks)
      callbacks = record.class.attachment_callbacks[name.to_sym]
      return yield unless callbacks
      [callbacks[:before]].flatten.each { |cb| record.send(cb, self, [attachables].flatten) if cb }
      yield
      [callbacks[:after]].flatten.each { |cb| record.send(cb, self, [attachables].flatten) if cb }
    end
  end

  class Attached::Many < Attached
    def attach(*attachables)
      perform_attachment(attachables.flatten) do
        attachables.flatten.map do |attachable|
          if record.new_record?
            attachments.build(record: record, blob: create_blob_from(attachable))
          else
            attachments.create!(record: record, blob: create_blob_from(attachable))
          end
        end
      end
    end
  end

  class Attached::One < Attached
    def attach(attachable)
      perform_attachment(attachable) do
        blob_was = blob if attached?
        blob = create_blob_from(attachable)
        unless blob == blob_was
          transaction do
            detach
            write_attachment build_attachment(blob: blob)
          end
          blob_was.purge_later if blob_was && dependent == :purge_later
        end
      end
    end
  end
end

module ActiveStorageCallbacks
  extend ActiveSupport::Concern

  included do
    cattr_accessor :attachment_callbacks
    extend ActiveModel::Callbacks
    define_model_callbacks :attach, only: %i[after before]
    after_attach -> {}
    before_attach -> {}
    class << self
      def perform_attach(callbacks)
        self.attachment_callbacks = callbacks
      end
    end
  end
end