class Media < Tag
  NAME = ArchiveConfig.MEDIA_CATEGORY_NAME

  has_many :common_taggings, as: :filterable
  has_many :fandoms, -> { where(type: 'Fandom') }, through: :common_taggings, source: :common_tag

  after_create :expire_caches
  after_update :expire_caches, if: -> { saved_change_to_name? || saved_change_to_type? || saved_change_to_canonical? }
  after_destroy :expire_caches

  def expire_caches
    ActionController::Base.new.expire_fragment("menu-fandoms-version5")
    ActionController::Base.new.expire_fragment("homepage-fandoms-version2")
  end

  def child_types
    ['Fandom']
  end

  # The media tag for unwrangled fandoms
  def self.uncategorized
    tag = self.find_or_create_by_name(ArchiveConfig.MEDIA_UNCATEGORIZED_NAME)
    tag.update(canonical: true) unless tag.canonical
    tag
  end

  # The list of media used for the menu on every page. All media except "No
  # Media" and "Uncategorized Fandoms" are listed in order, and then
  # "Uncategorized Fandoms" is tacked onto the list at the end.
  def self.for_menu
    canonical.by_name.where.not(
      name: [ArchiveConfig.MEDIA_UNCATEGORIZED_NAME,
             ArchiveConfig.MEDIA_NO_TAG_NAME]
    ).to_a + [uncategorized]
  end
end