noesya/osuny

module Sluggable
  extend ActiveSupport::Concern

  # Filenames uses 255 bytes so should have 255 characters max. To be safe, we limit to 100.
  # Source: https://askubuntu.com/questions/166764/how-long-can-file-names-be/166767#166767
  SLUG_MAX_LENGTH = 100

  included do
    validates :slug, presence: true, unless: :skip_slug_validation?
    validate :slug_must_be_unique, unless: :skip_slug_validation?
    validates :slug, format: { with: /\A[a-z0-9\-]+\z/, message: I18n.t('slug_error') }, unless: :skip_slug_validation?

    before_validation :set_slug
  end

  def set_slug
    self.slug = to_s.parameterize if self.slug.blank?
    adjust_slug_length
    current_slug = self.slug
    n = 0
    while slug_unavailable?(self.slug)
      n += 1
      self.slug = [current_slug, n].join('-')
    end
  end

  protected

  def adjust_slug_length
    return unless self.slug.length > SLUG_MAX_LENGTH
    # "my-very-long-and-detailed-first-blog-post" => "my-very-long-and-detailed-first-"
    self.slug = self.slug[0, SLUG_MAX_LENGTH]
    # "my-very-long-and-detailed-first-" => "my-very-long-and-detailed-first"
    self.slug.chop! if self.slug.ends_with?('-')
  end

  def slug_unavailable?(slug)
    existence_params = { slug: slug }
    existence_params[:university_id] = self.university_id if respond_to?(:university_id)
    existence_params[:language_id] = self.language_id if respond_to?(:language_id)

    self.class.unscoped
              .where(**existence_params)
              .where.not(id: self.id)
              .exists?
  end

  def slug_must_be_unique
    errors.add(:slug, :taken) if slug_unavailable?(slug)
  end

  def skip_slug_validation?
    false
  end
end