Refactor Doorkeeper::Rails::Helpers

Makes explicit what the public API is to inject doorkeeper behavior into
application endpoints.

This should be the only interface between Rails and doorkeeper. Other
frameworks can define their own interface and use doorkeeper too. This
is a step into decoupling doorkeeper from Rails, so that integration
is easier.

Related with #567.

lib/doorkeeper/rails/helpers.rb

@@ -3,53 +3,36 @@ module Rails
     module Helpers
       extend ActiveSupport::Concern
 
-      module ClassMethods
-        def doorkeeper_for(*args, &block)
-          fail Errors::DoorkeeperError, "`doorkeeper_for` no longer available", <<-eos
-\nStarting in version 2.0.0 of doorkeeper gem, `doorkeeper_for` is no longer
-available. Please change `doorkeeper_for` calls in your application with:
-
-  before_action :doorkeeper_authorize!
+      def doorkeeper_authorize!(*scopes)
+        @_doorkeeper_scopes = scopes || Doorkeeper.configuration.default_scopes
 
-For more information check the README:
-https://github.com/doorkeeper-gem/doorkeeper#protecting-resources-with-oauth-aka-your-api-endpoint\n
-          eos
+        if doorkeeper_token_is_invalid?
+          doorkeeper_render_error
         end
       end
 
-      def doorkeeper_token
-        @_doorkeeper_token ||= OAuth::Token.authenticate request, *Doorkeeper.configuration.access_token_methods
+      def doorkeeper_unauthorized_render_options
+        nil
       end
 
-      def valid_doorkeeper_token?(*scopes)
-        doorkeeper_token && doorkeeper_token.acceptable?(scopes)
+      def doorkeeper_forbidden_render_options
+        nil
       end
 
-      def doorkeeper_authorize!(*scopes)
-        scopes ||= Doorkeeper.configuration.default_scopes
-
-        unless valid_doorkeeper_token?(*scopes)
-          if !doorkeeper_token || !doorkeeper_token.accessible?
-            error = OAuth::InvalidTokenResponse.from_access_token(doorkeeper_token)
-            options = doorkeeper_unauthorized_render_options
-          else
-            error = OAuth::ForbiddenTokenResponse.from_scopes(scopes)
-            options = doorkeeper_forbidden_render_options
-          end
-          headers.merge!(error.headers.reject { |k| ['Content-Type'].include? k })
-          doorkeeper_error_renderer(error, options)
-        end
-      end
+      private
 
-      def doorkeeper_unauthorized_render_options
-        nil
+      def doorkeeper_token_is_invalid?
+        !doorkeeper_token || !doorkeeper_token.acceptable?(@_doorkeeper_scopes)
       end
 
-      def doorkeeper_forbidden_render_options
-        nil
+      def doorkeeper_render_error
+        error = doorkeeper_error
+        headers.merge! error.headers.reject { |k| "Content-Type" == k }
+        doorkeeper_render_error_with(error)
       end
 
-      def doorkeeper_error_renderer(error, options = {})
+      def doorkeeper_render_error_with(error)
+        options = doorkeeper_render_options
         if options.blank?
           head error.status
         else
@@ -58,6 +41,51 @@ def doorkeeper_error_renderer(error, options = {})
           render options
         end
       end
+
+      def doorkeeper_error
+        if doorkeeper_invalid_token_response?
+          OAuth::InvalidTokenResponse.from_access_token(doorkeeper_token)
+        else
+          OAuth::ForbiddenTokenResponse.from_scopes(@_doorkeeper_scopes)
+        end
+      end
+
+      def doorkeeper_render_options
+        if doorkeeper_invalid_token_response?
+          doorkeeper_unauthorized_render_options
+        else
+          doorkeeper_forbidden_render_options
+        end
+      end
+
+      def doorkeeper_invalid_token_response?
+        !doorkeeper_token || !doorkeeper_token.accessible?
+      end
+
+      def doorkeeper_token
+        @_doorkeeper_token ||= OAuth::Token.authenticate(
+          request,
+          *Doorkeeper.configuration.access_token_methods
+        )
+      end
+
+      module ClassMethods
+        def doorkeeper_for(*_args)
+          fail(
+            Errors::DoorkeeperError,
+            "`doorkeeper_for` no longer available",
+            <<-eos
+\nStarting in version 2.0.0 of doorkeeper gem, `doorkeeper_for` is no longer
+available. Please change `doorkeeper_for` calls in your application with:
+
+  before_action :doorkeeper_authorize!
+
+For more information check the README:
+https://github.com/doorkeeper-gem/doorkeeper#protecting-resources-with-oauth-aka-your-api-endpoint\n
+eos
+          )
+        end
+      end
     end
   end
 end