btrc-hub/backend/app/services/post_version_recorder.rb

class PostVersionRecorder
  def self.record! post:, event_type:, created_by_user:
    new(post:, event_type:, created_by_user:).record!
  end

  def initialize post:, event_type:, created_by_user:
    @post = post
    @event_type = event_type
    @created_by_user = created_by_user
  end

  def record!
    @post.with_lock do
      latest = @post.post_versions.order(version_no: :desc).first
      attrs = snapshot_attributes

      return latest if @event_type == :update && latest && same_snapshot?(latest, attrs)

      PostVersion.create!(
          post: @post,
          version_no: (latest&.version_no || 0) + 1,
          event_type: @event_type,
          title: attrs[:title],
          url: attrs[:url],
          thumbnail_base: attrs[:thumbnail_base],
          tags: attrs[:tags],
          parent: attrs[:parent],
          original_created_from: attrs[:original_created_from],
          original_created_before: attrs[:original_created_before],
          created_at: Time.current,
          created_by_user: @created_by_user)
    end
  end

  private

  def snapshot_attributes
    { title: @post.title,
      url: @post.url,
      thumbnail_base: @post.thumbnail_base,
      tags: @post.snapshot_tag_names.join(' '),
      parent: @post.parent,
      original_created_from: @post.original_created_from,
      original_created_before: @post.original_created_before }
  end

  def same_snapshot? version, attrs
    true &&
        version.title == attrs[:title] &&
        version.url == attrs[:url] &&
        version.thumbnail_base == attrs[:thumbnail_base] &&
        version.tags == attrs[:tags] &&
        version.parent_id == attrs[:parent]&.id &&
        version.original_created_from == attrs[:original_created_from] &&
        version.original_created_before == attrs[:original_created_before]
  end
end