# Stores slugs used to prettify URLs. For more information, see the
# {Slugalicious} mixin.
#
# As new slugs are created, old ones are marked as inactive and kept around for
# redirect purposes. Once a slug is old enough, it is deleted and its value can
# be used for new records (no longer redirects).
#
# h2. Associations
#
# | @sluggable@ | The record that this slug references. |
#
# h2. Properties
#
# | @slug@ | The slug, lowercased and normalized. Slugs must be unique to their @sluggable_type@ and @scope@. |
# | @active@ | Whether this is the most recently generated slug for the sluggable. |
# | @scope@ | Freeform data scoping this slug to a certain subset of records within the model. |

class Slug < ActiveRecord::Base
  belongs_to :sluggable, polymorphic: true

  scope :for, ->(object_or_type, object_id=nil) {
    object_type = object_id ? object_or_type : object_or_type.class.to_s
    object_id ||= object_or_type.id
    where(sluggable_type: object_type, sluggable_id: object_id)
  }
  scope :for_class, ->(model) { where(sluggable_type: model.to_s) }
  scope :from_slug, ->(klass, scope, slug) {
    where(sluggable_type: klass.to_s, slug: slug, scope: scope)
  }
  scope :active, where(active: true)
  scope :inactive, where(active: false)

  validates :sluggable_type,
            presence: true
  validates :sluggable_id,
            presence: true,
            numericality: { only_integer: true }
  validates :slug,
            presence: true,
            length: { maximum: 126 },
            uniqueness: { case_sensitive: false, scope: [ :scope, :sluggable_type ] } #TODO validate scope case-insensitively
  validates :scope,
            length: { maximum: 126 },
            allow_blank: true
  validate :one_active_slug_per_object
  
  after_save :invalidate_cache
  after_destroy :invalidate_cache
  
  # Marks a slug as active and deactivates all other slugs assigned to the
  # record.

  def activate!
    self.class.transaction do
      Slug.for(sluggable_type, sluggable_id).update_all(active: false)
      update_attribute :active, true
    end
  end

  private

  def one_active_slug_per_object
    return unless new_record? or (active? and active_changed?)
    errors.add(:active, :one_per_sluggable) if active? and Slug.active.for(sluggable_type, sluggable_id).count > 0
  end
  
  def invalidate_cache
    Rails.cache.delete "Slug/#{sluggable_type}/#{sluggable_id}/slug"
    Rails.cache.delete "Slug/#{sluggable_type}/#{sluggable_id}/slug_with_path"
  end
end