# -*- encoding : utf-8 -*-

class Card
  # {Card}'s names can be changed, and therefore _names_ should not be directly mentioned
  # in code, lest a name change break the application.
  #
  # Instead, a {Card} that needs specific code manipulations should be given a {Codename},
  # which will not change even if the card's name does.
  #
  # An administrator might add to the Company card via the RESTful web API with a url like
  #
  #     /update/CARDNAME?card[codename]=CODENAME
  #
  # ...or via the api like
  #
  #     Card[CARDNAME].update! codename: CODENAME
  #
  # Generally speaking, _codenames_ are represented by Symbols.
  #
  # The {Codename} class provides a fast cache for this slow-changing data.
  # Every process maintains a complete cache that is not frequently reset
  #
  class Codename
    class << self
      # returns codename for id and id for codename
      # @param codename [Integer, Symbol, String, Card::Name]
      # @return [Symbol]
      def [] codename
        case codename
        when Integer
          codehash[codename]
        when Symbol, String
          codehash.key?(codename.to_sym) ? codename.to_sym : nil
        end
      end

      def id codename
        case codename
        when Symbol, String
          codehash[codename.to_sym]
        when Integer
          codehash.key?(codename) ? codename : nil
        end
      end

      def name codename=nil
        return super() if codename.nil?

        name! codename
      rescue Error::CodenameNotFound => _e
        yield if block_given?
      end

      def card codename
        if (card_id = id(codename))
          Card[card_id]
        elsif block_given?
          yield
        end
      end

      def exist? codename
        id(codename).present?
      end

      alias_method :exists?, :exist?

      # a Hash in which Symbol keys have Integer values and vice versa
      # @return [Hash]
      def codehash
        @codehash ||= load_codehash
      end

      # clear cache both locally and in cache
      def reset_cache
        @codehash = nil
        ::Card.cache.delete "CODEHASH"
      end

      # @param codename [Symbol, String]
      # @return [Integer]
      def id! codename
        id(codename) || unknown_codename!(codename)
      end

      # @param codename [Symbol, String]
      # @return [Card::Name]
      def name! codename
        Card::Name[codename.to_sym]
      end

      def generate_id_constants
        # If a card has the codename _example_, then Card::ExampleID will
        # return the id for that card.
        codehash.each do |codename, id|
          next unless codename.is_a?(Symbol) && !codename.to_s.match?(/\W/)

          id_constant codename, id
        end
      end

      private

      # iterate through every card with a codename
      # @yieldparam codename [Symbol]
      # @yieldparam id [Integer]
      def each_codenamed_card
        sql = "select id, codename from cards where codename is not NULL"
        ActiveRecord::Base.connection.select_all(sql).each do |row|
          yield row["codename"].to_sym, row["id"].to_i
        end
      end

      # @todo remove duplicate checks here; should be caught upon creation
      def check_duplicates codehash, codename, card_id
        return unless codehash.key?(codename) || codehash.key?(card_id)

        Rails.logger.debug "dup codename: #{codename}, "\
                           "ID:#{card_id} (#{codehash[codename]})"
      end

      # generate Hash for @codehash and put it in the cache
      def load_codehash
        ::Card.cache.fetch("CODEHASH") do
          generate_codehash
        end
      end

      def generate_codehash
        hash = {}
        each_codenamed_card do |codename, card_id|
          check_duplicates hash, codename, card_id
          hash[codename] = card_id
          hash[card_id] = codename
        end
        hash
      end

      def unknown_codename! mark
        raise Card::Error::CodenameNotFound,
              ::I18n.t(:lib_exception_unknown_codename, codename: mark)
      end

      def id_constant codename, id=nil
        id ||= id! codename
        Card.const_get_or_set("#{codename.to_s.camelize}ID") { id }
      end
    end

    generate_id_constants
  end
end