module Sluger

# File lib/sluger.rb, line 7
def sluger(*args)
  options = { limit: 255 }
  title_column = args.length > 0 ? args[0] : :title
  slug_column = args.length > 1 ? args[1] : :slug
  options.merge!(args[2]) if args.length > 2 && args[2].is_a?(Hash)
  has_limit = options[:limit] > 0

  self.class_eval do
    before_validation :process_slugering
  end

  define_singleton_method(:slugering) do |entity, title|
    return nil if title.blank?

    new_slug = title.parameterize
    new_slug = title[0, options[:limit]] if has_limit && new_slug.length > options[:limit]

    pk = self.primary_key
    relation = self
    relation = relation.where.not(pk => entity[pk]) unless entity.new_record?

    index = 0
    base_slug = new_slug
    while relation.where("#{slug_column} = ?", new_slug).count > 0 do
      index += 1
      new_slug = base_slug[0, options[:limit] - index.to_s.length - 1] if has_limit
      new_slug = "#{new_slug}-#{index}"
    end
    new_slug
  end

  define_method(:process_slugering) do
    return unless self[slug_column].blank?
    new_value = self[title_column]
    self[slug_column] = self.class.send(:slugering, self, new_value)
  end

  define_method(:to_param) do
    self[slug_column]
  end
end