module Plate
  # The Dsl class provides the methods available in plugin files in order to extend
  # the functionality a generated site.
  class Dsl
    class << self
      # Evaluate the given file path into the {Plate::Dsl dsl} instance.
      def evaluate_plugin(file_path)
        instance_eval_plugin(read_plugin_file(file_path))
      end

      # Performs evaluation of the file's content
      def instance_eval_plugin(content)
        new.instance_eval(content)
      end

      # Read the given plugin file path into a string
      #
      # @return [String] The plugin file's contents
      def read_plugin_file(file_path)
        File.read(file_path)
      rescue
        raise PluginNotReadable
      end
    end

    # Register a new callback for the given object and event.
    #
    # @example Run block after rendering a site
    #     callback :site, :after_render do
    #       puts 'done!'
    #     end
    #
    # @example Run block before rendering a page
    #     callback :page, :before_render do |page|
    #       puts "Rendering page #{page.path}"
    #     end
    #
    # @example Run a method on the site after write
    #     class Site
    #       def finished!
    #         log('All done.')
    #       end
    #     end
    #
    #     callback :site, :after_write, :finished!
    #
    def callback(object, event, method_name = nil, &block)
      if Symbol === object
        object = "Plate::#{object.to_s.classify}".constantize
      end

      object.register_callback(event, method_name, &block)
    end
    alias :register_callback :callback

    # Set up a new engine designed for rendering dynamic assets.
    # Engines should be compatible with the Tilt::Template syntax.
    def register_asset_engine(extension, klass)
      Plate.register_asset_engine(extension, klass)
    end

    # Set up a new engine designed for rendering dynamic assets.
    # Engines should be compatible with the Tilt::Template syntax.
    def register_template_engine(extension, klass)
      Plate.register_template_engine(extension, klass)
    end
  end
end