module ActiveAdmin

  # Shareable module to give a #display_on?(action) method
  # which returns true or false depending on an options hash.
  #
  # The options hash accepts:
  #
  # :only => :index
  # :only => [:index, :show]
  # :except => :index
  # :except => [:index, :show]
  #
  # call #normalize_display_options! after @options has been set
  # to ensure that the display options are setup correctly

  module OptionalDisplay
    def display_on?(action, render_context = self)
      return false if @options[:only]   && !@options[:only].include?(action.to_sym)
      return false if @options[:except] && @options[:except].include?(action.to_sym)

      case condition = @options[:if]
      when Symbol, String
        render_context.send condition
      when Proc
        render_context.instance_exec &condition
      else
        true
      end
    end

    private

    def normalize_display_options!
      @options[:only]   = Array(@options[:only])   if @options[:only]
      @options[:except] = Array(@options[:except]) if @options[:except]
    end
  end
end