module AbstractInterface
  class << self
    inject :logger => :logger, :config => :config, :environment => :environment
    
    attr_accessor :plugin_name
    attr_accessor :layout_configurations_dir
    
    def generate_helper_methods *args
      AbstractInterface::ViewBuilder.generate_helper_methods *args
    end
    
    def available_themes; @available_themes ||= [] end
        
    def theme_metadata theme
      logger.warn "Complex calculation (AbstractInterface.theme_metadata) called in production!" if config.production?
      
      metadata = {}

      name = "/#{Crystal::Template::DIRECTORY_NAME}/#{THEMES_DIR}/#{theme}/metadata.rb"
      if environment.file_exist? name
        fname = environment.find_file name
        code = File.read fname
        metadata = eval code
        metadata.must_be.a Hash        
      end
      
      metadata.to_openobject
    end
    
    def layouts_defined?
      !!layout_configurations_dir
    end
    
    # Place definitions of your layouts into :layout_configurations_dir folder, you can have multiple such directories
    def layout_definitions_without_cache theme
      name = "#{layout_configurations_dir.must_be.present}/#{theme}.yml"
      raise "File '#{name}' not exist!" unless environment.file_exist? name
    
      result = {}
      environment.find_files(name).each do |fname|      
        lds = YAML.load_file(fname)
        validate_layout_definition!(lds, theme)
        result.merge! lds
      end
      result
    end
    cache_method_with_params_in_production :layout_definitions
    
    protected
      def validate_layout_definition! lds, theme
        lds.must_be.a Hash
        unless lds.include?('default')
          raise "No 'default' layout definition for '#{theme}' Theme (there always should be definition for 'default' layout)!"
        end
        lds.each do |theme_name, ld|
          ld.must_be.a Hash
          ld.must.include 'layout_template'
          ld.must.include 'slots'
          ld['slots'].must_be.a Hash
        end
      end
  end
    
end