class Roda
  module RodaPlugins
    # The class_level_routing plugin adds routing methods at the class level, which can
    # be used instead of or in addition to using the normal +route+ method to start the
    # routing tree.  If a request is not matched by the normal routing tree, the class
    # level routes will be tried.  This offers a more Sinatra-like API, while
    # still allowing you to use a routing tree inside individual actions.
    #
    # Here's the first example from the README, modified to use the class_level_routing
    # plugin:
    #
    #   class App < Roda
    #     plugin :class_level_routing
    #
    #     # GET / request
    #     root do
    #       request.redirect "/hello"
    #     end
    #
    #     # GET /hello/world request
    #     get "hello/world" do
    #       "Hello world!"
    #     end
    #
    #     # /hello request
    #     is "hello" do
    #       # GET /hello request
    #       request.get do
    #         "Hello!"
    #       end
    #
    #       # POST /hello request
    #       request.post do
    #         puts "Someone said hello!"
    #         request.redirect
    #       end
    #     end
    #   end
    #
    # When using the the class_level_routing plugin with nested routes, you may also want to use the
    # delegate plugin to delegate certain instance methods to the request object, so you don't have
    # to continually use +request.+ in your routing blocks.
    #
    # Note that class level routing is implemented via a simple array of routes, so routing performance
    # will degrade linearly as the number of routes increases.  For best performance, you should use
    # the normal +route+ class method to define your routing tree.  This plugin does make it simpler to
    # add additional routes after the routing tree has already been defined, though.
    module ClassLevelRouting
      # Initialize the class_routes array when the plugin is loaded.  Also, if the application doesn't
      # currently have a routing block, setup an empty routing block so that things will still work if
      # a routing block isn't added.
      def self.configure(app)
        app.route{} unless app.route_block
        app.opts[:class_level_routes] ||= []
      end

      module ClassMethods
        # Define routing methods that will store class level routes.
        [:root, :on, :is, :get, :post, :delete, :head, :options, :link, :patch, :put, :trace, :unlink].each do |meth|
          define_method(meth) do |*args, &block|
            opts[:class_level_routes] << [meth, args, block].freeze
          end
        end

        # Freeze the class level routes so that there can be no thread safety issues at runtime.
        def freeze
          opts[:class_level_routes].freeze
          super
        end
      end

      module InstanceMethods
        # If the normal routing tree doesn't handle an action, try each class level route
        # to see if it matches.
        def call
          result = super

          if result[0] == 404 && (v = result[2]).is_a?(Array) && v.empty?
            # Reset the response so it doesn't inherit the status or any headers from
            # the original response.
            @_response = self.class::RodaResponse.new
            super do |r|
              opts[:class_level_routes].each do |meth, args, blk|
                r.send(meth, *args) do |*a|
                  instance_exec(*a, &blk)
                end
              end
            end
          else
            result
          end
        end
      end
    end

    register_plugin(:class_level_routing, ClassLevelRouting)
  end
end