require 'set'
module Paperclip
  class << self
    attr_accessor :classes_with_attachments
    attr_writer :registered_attachments_styles_path
    def registered_attachments_styles_path
      @registered_attachments_styles_path ||= Rails.root.join('public/system/paperclip_attachments.yml').to_s
    end
  end

  self.classes_with_attachments = Set.new

  # Get list of styles saved on previous deploy (running rake paperclip:refresh:missing_styles)
  def self.get_registered_attachments_styles
    YAML.load_file(Paperclip.registered_attachments_styles_path)
  rescue Errno::ENOENT
    nil
  end
  private_class_method :get_registered_attachments_styles

  def self.save_current_attachments_styles!
    File.open(Paperclip.registered_attachments_styles_path, 'w') do |f|
      YAML.dump(current_attachments_styles, f)
    end
  end

  # Returns hash with styles for all classes using Paperclip.
  # Unfortunately current version does not work with lambda styles:(
  #   {
  #     :User => {:avatar => [:small, :big]},
  #     :Book => {
  #       :cover => [:thumb, :croppable]},
  #       :sample => [:thumb, :big]},
  #     }
  #   }
  def self.current_attachments_styles
    Hash.new.tap do |current_styles|
      Paperclip.classes_with_attachments.each do |klass_name|
        klass = Paperclip.class_for(klass_name)
        klass.attachment_definitions.each do |attachment_name, attachment_attributes|
          # TODO: is it even possible to take into account Procs?
          next if attachment_attributes[:styles].kind_of?(Proc)
          attachment_attributes[:styles].try(:keys).try(:each) do |style_name|
            klass_sym = klass.to_s.to_sym
            current_styles[klass_sym] ||= Hash.new
            current_styles[klass_sym][attachment_name.to_sym] ||= Array.new
            current_styles[klass_sym][attachment_name.to_sym] << style_name.to_sym
            current_styles[klass_sym][attachment_name.to_sym].map!(&:to_s).sort!.map!(&:to_sym).uniq!
          end
        end
      end
    end
  end
  private_class_method :current_attachments_styles

  # Returns hash with styles missing from recent run of rake paperclip:refresh:missing_styles
  #   {
  #     :User => {:avatar => [:big]},
  #     :Book => {
  #       :cover => [:croppable]},
  #     }
  #   }
  def self.missing_attachments_styles
    current_styles = current_attachments_styles
    registered_styles = get_registered_attachments_styles

    Hash.new.tap do |missing_styles|
      current_styles.each do |klass, attachment_definitions|
        attachment_definitions.each do |attachment_name, styles|
          registered = registered_styles[klass][attachment_name] || [] rescue []
          missed = styles - registered
          if missed.present?
            klass_sym = klass.to_s.to_sym
            missing_styles[klass_sym] ||= Hash.new
            missing_styles[klass_sym][attachment_name.to_sym] ||= Array.new
            missing_styles[klass_sym][attachment_name.to_sym].concat(missed.to_a)
            missing_styles[klass_sym][attachment_name.to_sym].map!(&:to_s).sort!.map!(&:to_sym).uniq!
          end
        end
      end
    end
  end
end