module RailsConnector
  # This class provides methods used to retrieve objects from CMS based an entry
  # in CMS of the obj_class <tt>NamedLink</tt>.
  # @api public
  class NamedLink
    LINKLIST_NAME = "related_links".freeze

    # @api public
    class NotFound < StandardError
    end

    @@named_links_cache = nil
    @@updated_at = nil
    @@cache_expiry_time = nil

    # Generates a cache of named links based on the CMS objects related link list.
    # Raises exceptions if zero or more than one objects have this obj_class
    def self.generate_named_links_cache
      return if @@named_links_cache

      # add method for get related_links attiribute for simply Obj-instance
      attributes = RailsConnector::Attribute.where(attribute_name: LINKLIST_NAME)
      if attributes.length != 0
        Obj.send(:define_attribute, LINKLIST_NAME, ActiveRecord::Type::String.new)
        Obj.send(:delegate, LINKLIST_NAME.to_sym, to: :attr_dict)
      else
        Rails.logger.warn "Check if you NamedLink class is defined properly. Attibute related_links does not exist."
        # there is not attribute named 'related_links' defined
        @@named_links_cache = []
        @@updated_at = Time.now
        return nil
      end

      found_objects = BasicObj.where(obj_class: "NamedLink")
      Rails.logger.warn "Couldn't find NamedLink CMS Object!" if found_objects.empty?
      Rails.logger.warn "More than one NamedLink CMS Object found!" if found_objects.size > 1

      @@named_links_cache = found_objects
                            .sort_by(&:valid_from)
                            .reverse
                            .flat_map(&:related_links)
                            .each_with_object({}) do |link_obj, temp|
        temp[link_obj.title] = link_obj.destination_object
      end

      @@updated_at = Time.now
      nil
    end

    # Sets the time in minutes after which the cache will be expired.
    # The default expiry time is set to 1 minute
    # @api public
    def self.cache_expiry_time=(value)
      @@cache_expiry_time = value
    end

    def self.cache_expiry_time
      @@cache_expiry_time || 1
    end

    def self.cache_expired?
      @@updated_at.nil? || @@updated_at <= cache_expiry_time.minute.ago
    end

    # Returns the CMS object mapped to the given title or nil.
    # The title can be a string of symbol.
    # If :cache => false is provided, the object will not be fetched from the cache.
    # @api public
    def self.get_object(title, options = {})
      object = named_links[title.to_s]
      raise NotFound, "The NamedLink '#{title}' does not exist" if object.nil?

      options[:cache] == false ? object.reload : object
    end

    def self.reset_cache
      @@named_links_cache = nil
    end

    def self.named_links
      reset_cache if cache_expired?
      generate_named_links_cache unless named_links_cache
      named_links_cache
    end

    def self.named_links_cache
      @@named_links_cache
    end
  end
end