require "abstract_controller/base"

module AbstractController
  class DoubleRenderError < Error
    DEFAULT_MESSAGE = "Render and/or redirect were called multiple times in this action. Please note that you may only call render OR redirect, and at most once per action. Also note that neither redirect nor render terminate execution of the action, so if you want to exit an action after redirecting, you need to do something like \"redirect_to(...) and return\"."

    def initialize(message = nil)
      super(message || DEFAULT_MESSAGE)
    end
  end

  module Rendering
    extend ActiveSupport::Concern

    included do
      extlib_inheritable_accessor :_view_paths
      self._view_paths ||= ActionView::PathSet.new
    end

    # An instance of a view class. The default view class is ActionView::Base
    #
    # The view class must have the following methods:
    # View.for_controller[controller] Create a new ActionView instance for a
    #   controller
    # View#render_partial[options]
    #   - responsible for setting options[:_template]
    #   - Returns String with the rendered partial
    #   options<Hash>:: see _render_partial in ActionView::Base
    # View#render_template[template, layout, options, partial]
    #   - Returns String with the rendered template
    #   template<ActionView::Template>:: The template to render
    #   layout<ActionView::Template>:: The layout to render around the template
    #   options<Hash>:: See _render_template_with_layout in ActionView::Base
    #   partial<Boolean>:: Whether or not the template to render is a partial
    #
    # Override this method in a to change the default behavior.
    def view_context
      @_view_context ||= ActionView::Base.for_controller(self)
    end

    # Mostly abstracts the fact that calling render twice is a DoubleRenderError.
    # Delegates render_to_body and sticks the result in self.response_body.
    def render(*args)
      if response_body
        raise AbstractController::DoubleRenderError, "OMG"
      end

      self.response_body = render_to_body(*args)
    end

    # Raw rendering of a template to a Rack-compatible body.
    #
    # ==== Options
    # _partial_object<Object>:: The object that is being rendered. If this
    #   exists, we are in the special case of rendering an object as a partial.
    #
    # :api: plugin
    def render_to_body(options = {})
      # TODO: Refactor so we can just use the normal template logic for this
      if options.key?(:partial)
        _render_partial(options)
      else
        _determine_template(options)
        _render_template(options)
      end
    end

    # Raw rendering of a template to a string. Just convert the results of
    # render_to_body into a String.
    #
    # :api: plugin
    def render_to_string(options = {})
      AbstractController::Rendering.body_to_s(render_to_body(options))
    end

    # Renders the template from an object.
    #
    # ==== Options
    # _template<ActionView::Template>:: The template to render
    # _layout<ActionView::Template>:: The layout to wrap the template in (optional)
    def _render_template(options)
      view_context.render_template(options)
    end

    # Renders the given partial.
    #
    # ==== Options
    # partial<String|Object>:: The partial name or the object to be rendered
    def _render_partial(options)
      view_context.render_partial(options)
    end

    # The list of view paths for this controller. See ActionView::ViewPathSet for
    # more details about writing custom view paths.
    def view_paths
      _view_paths
    end

    # Return a string representation of a Rack-compatible response body.
    def self.body_to_s(body)
      if body.respond_to?(:to_str)
        body
      else
        strings = []
        body.each { |part| strings << part.to_s }
        body.close if body.respond_to?(:close)
        strings.join
      end
    end

  private

    # Take in a set of options and determine the template to render
    #
    # ==== Options
    # _template<ActionView::Template>:: If this is provided, the search is over
    # _template_name<#to_s>:: The name of the template to look up. Otherwise,
    #   use the current action name.
    # _prefix<String>:: The prefix to look inside of. In a file system, this corresponds
    #   to a directory.
    # _partial<TrueClass, FalseClass>:: Whether or not the file to look up is a partial
    def _determine_template(options)
      if options.key?(:text)
        options[:_template] = ActionView::Template::Text.new(options[:text], format_for_text)
      elsif options.key?(:inline)
        handler  = ActionView::Template.handler_class_for_extension(options[:type] || "erb")
        template = ActionView::Template.new(options[:inline], "inline template", handler, {})
        options[:_template] = template
      elsif options.key?(:template)
        options[:_template_name] = options[:template]
      elsif options.key?(:file)
        options[:_template_name] = options[:file]
      end

      name = (options[:_template_name] || action_name).to_s

      options[:_template] ||= with_template_cache(name) do
        find_template(name, { :formats => formats }, options)
      end
    end

    def find_template(name, details, options)
      view_paths.find(name, details, options[:_prefix], options[:_partial])
    end

    def template_exists?(name, details, options)
      view_paths.exists?(name, details, options[:_prefix], options[:_partial])
    end

    def with_template_cache(name)
      yield
    end

    def format_for_text
      Mime[:text]
    end

    module ClassMethods
      def clear_template_caches!
      end

      # Append a path to the list of view paths for this controller.
      #
      # ==== Parameters
      # path<String, ViewPath>:: If a String is provided, it gets converted into
      # the default view path. You may also provide a custom view path
      # (see ActionView::ViewPathSet for more information)
      def append_view_path(path)
        self.view_paths << path
      end

      # Prepend a path to the list of view paths for this controller.
      #
      # ==== Parameters
      # path<String, ViewPath>:: If a String is provided, it gets converted into
      # the default view path. You may also provide a custom view path
      # (see ActionView::ViewPathSet for more information)
      def prepend_view_path(path)
        clear_template_caches!
        self.view_paths.unshift(path)
      end

      # A list of all of the default view paths for this controller.
      def view_paths
        self._view_paths
      end

      # Set the view paths.
      #
      # ==== Parameters
      # paths<ViewPathSet, Object>:: If a ViewPathSet is provided, use that;
      #   otherwise, process the parameter into a ViewPathSet.
      def view_paths=(paths)
        clear_template_caches!
        self._view_paths = paths.is_a?(ActionView::PathSet) ? paths : ActionView::Base.process_view_paths(paths)
      end
    end
  end
end