otvorenesudy/otvorenesudy-api

module Formattable
  extend ActiveSupport::Concern

  module ClassMethods
    def formatters
      @formatters ||= Hash.new
    end

    protected

    def formattable(attribute, options = {})
      define_method attribute do |pattern = nil|
        value = read_attribute(attribute)

        return value if !value.nil? && (pattern.nil? || pattern == options[:default])

        formatter = (self.class.formatters[attribute] ||= Formatter.new data = yield(self), options)
        cache     = (formatted[attribute] ||= Cache.new data || yield(self))

        cache.get formatter, pattern
      end

      define_method "invalidate_#{attribute}" do
        formatted[attribute] = nil
      end
    end
  end

  private

  def formatted
    @formatted ||= {}
  end

  public

  class Formatter
    attr_reader :default,
                :directives,
                :remove,
                :squeeze,
                :strip

    def initialize(data, options = {})
      @default    = options[:default] || raise
      @directives = data.keys.map { |key| key[1].to_sym }
      @regexp     = /\%[#{@directives.join}]/

      @remove  = options[:remove]
      @squeeze = options[:squeeze] == false ? nil : options[:squeeze] || ' '
      @strip   = options[:strip] == nil ? true : options[:strip]
    end

    def format(pattern, data)
      value = (pattern || default).gsub(@regexp, data)

      value.gsub! @remove, '' if @remove
      value.squeeze! @squeeze if @squeeze
      value.strip! if @strip
      value
    end
  end

  class Cache
    attr_reader :values

    def initialize(data)
      @data  = data
      @cache = {}
    end

    def get(formatter, pattern)
      @cache[pattern] ||= formatter.format pattern, @data
    end
  end
end