CMP-354 | Add an MCP generator to bootstrap an MCP server with Oauth

Gemfile.lock

@@ -94,6 +94,8 @@ GEM
       irb (~> 1.10)
       reline (>= 0.3.8)
     diff-lcs (1.6.2)
+    doorkeeper (5.9.0)
+      railties (>= 5)
     drb (2.2.3)
     erb (6.0.1)
     erubi (1.13.1)
@@ -124,7 +126,6 @@ GEM
       net-smtp
     marcel (1.1.0)
     mini_mime (1.1.5)
-    mini_portile2 (2.8.9)
     minitest (6.0.1)
       prism (~> 1.5)
     net-imap (0.6.2)
@@ -137,8 +138,7 @@ GEM
     net-smtp (0.5.1)
       net-protocol
     nio4r (2.7.5)
-    nokogiri (1.19.0)
-      mini_portile2 (~> 2.8.2)
+    nokogiri (1.19.0-arm64-darwin)
       racc (~> 1.4)
     nokogiri (1.19.0-x86_64-linux-gnu)
       racc (~> 1.4)
@@ -268,13 +268,15 @@ GEM
     zeitwerk (2.7.4)
 
 PLATFORMS
+  arm64-darwin-23
   arm64-darwin-25
   x86_64-linux
 
 DEPENDENCIES
   benchmark
   bundler (~> 4)
   debug (>= 1.0.0)
+  doorkeeper
   generator_spec (~> 0.10)
   pg
   propshaft

lib/generators/rolemodel/all_generator.rb

@@ -24,6 +24,7 @@ def run_all_the_generators
       generate 'rolemodel:editors'
       # generate 'rolemodel:tailored_select' # Not production ready
       generate 'rolemodel:lograge'
+      generate 'rolemodel:mcp'
     end
   end
 end

lib/generators/rolemodel/mcp/README.md

@@ -0,0 +1,13 @@
+# MCP Generator
+
+Install boilerplate for your very own MCP server.
+
+## What you get
+
+### Doorkeeper
+
+Oauth 2.1-enabled flow with dynamic application registration.
+
+### MCP
+
+A basic MCP controller that you can build on to serve tools, resources, and prompts.

lib/generators/rolemodel/mcp/USAGE

@@ -0,0 +1,22 @@
+Description:
+    Sets up our standard ActionMailer configuration with layout using CSS base styles
+
+Example:
+    rails generate rolemodel:mailers
+
+    This will create:
+        app/javascript/packs/mailer_stylesheets.scss
+        app/mailers/user_mailer.rb
+        app/views/layouts/mailer.html.slim
+        app/views/user_mailer/welcome_email.html.slim
+        config/initializers/premailer_rails.rb
+        public/logo.png
+        spec/mailers/previews/user_preview.rb
+
+    This will modify:
+        config/environments/development.rb
+        config/environments/production.rb
+
+    This will remove:
+        app/views/layouts/mailer.html.erb
+        app/views/layouts/mailer.text.erb

lib/generators/rolemodel/mcp/mcp_generator.rb

@@ -0,0 +1,90 @@
+# frozen_string_literal: true
+
+module Rolemodel
+  class MCPGenerator < BaseGenerator
+    source_root File.expand_path('templates', __dir__)
+
+    def install_mcp
+      bundle_command 'add mcp'
+      template 'app/controllers/mcp_controller.rb'
+      copy_file 'spec/requests/mcp_controller_spec.rb'
+
+      route <<~RUBY
+        match '/mcp', to: 'mcp#handle', via: %i[get post delete]
+      RUBY
+    end
+
+    def install_doorkeeper
+      bundle_command 'add doorkeeper'
+      generate 'doorkeeper:install'
+    end
+
+    def configure_doorkeeper
+      copy_file 'config/initializers/doorkeeper.rb', force: true
+      copy_file 'app/controllers/doorkeeper/base_controller.rb'
+
+      copy_file 'app/views/layouts/doorkeeper.html.slim'
+      template 'app/views/doorkeeper/authorizations/new.html.slim'
+      template 'app/views/doorkeeper/authorizations/error.html.slim'
+
+      copy_file 'app/assets/stylesheets/components/doorkeeper.css'
+
+      route 'use_doorkeeper'
+    end
+
+    def apply_doorkeeper_css
+      css_manifest = if File.exist?(File.join(destination_root, 'app/assets/stylesheets/application.scss'))
+        'app/assets/stylesheets/application.scss'
+      else
+        'app/assets/stylesheets/application.css'
+      end
+
+      return if File.read(File.join(destination_root, css_manifest)).include?("@import 'components/doorkeeper.css';")
+
+      append_to_file css_manifest, <<~CSS
+        @import 'components/doorkeeper.css';
+      CSS
+    end
+
+    def add_oauth_dynamic_registrations
+      copy_file 'app/controllers/oauth_registrations_controller.rb'
+      copy_file 'spec/requests/oauth_registrations_controller_spec.rb'
+      route <<~RUBY
+        post '/oauth/register', to: 'oauth_registrations#create'
+      RUBY
+    end
+
+    def add_well_known_route
+      copy_file 'app/controllers/well_known_controller.rb'
+      copy_file 'spec/requests/well_known_controller_spec.rb'
+      route <<~RUBY
+        get '/.well-known/oauth-protected-resource', to: 'well_known#oauth_protected_resource'
+        get '/.well-known/oauth-authorization-server', to: 'well_known#oauth_authorization_server'
+      RUBY
+    end
+
+    def update_inflections
+      inflections_path = File.join(destination_root, 'config/initializers/inflections.rb')
+      block_start = "\nActiveSupport::Inflector.inflections(:en) do |inflect|\n"
+
+      return if File.read(inflections_path).include?("inflect.acronym 'MCP'")
+
+      if File.read(inflections_path).include?(block_start)
+        inject_into_file inflections_path, "  inflect.acronym 'MCP'\n", after: block_start
+      else
+        append_to_file inflections_path, <<~RUBY
+
+          ActiveSupport::Inflector.inflections(:en) do |inflect|
+            inflect.acronym 'MCP'
+          end
+        RUBY
+      end
+    end
+
+    private
+
+    def application_name
+      Rails.application.class.try(:parent_name) || Rails.application.class.module_parent_name
+    end
+  end
+end

lib/generators/rolemodel/mcp/templates/app/assets/stylesheets/components/doorkeeper.css

@@ -0,0 +1,140 @@
+.doorkeeper {
+  position: fixed;
+  inset: 0;
+  box-sizing: border-box;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: var(--op-space-x-large) var(--op-space-large);
+  overflow: auto;
+  background-color: var(--op-color-neutral-plus-eight);
+  color: var(--op-color-neutral-minus-max);
+  font-family: var(--op-font-family);
+}
+
+.doorkeeper__card {
+  width: min(100%, 48rem);
+  background-color: var(--op-color-white);
+  border: var(--op-border-width) solid var(--op-color-neutral-plus-six);
+  border-radius: var(--op-radius-x-large);
+  box-shadow: var(--op-shadow-large);
+  display: flex;
+  flex-direction: column;
+  gap: var(--op-space-large);
+  padding: var(--op-space-2x-large);
+}
+
+.doorkeeper__brand {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: var(--op-space-large);
+  margin-bottom: var(--op-space-small);
+}
+
+.doorkeeper__logo {
+  width: 180px;
+  height: auto;
+}
+
+.doorkeeper__title {
+  margin: 0;
+  font-size: var(--op-font-2x-large);
+  font-weight: var(--op-font-weight-bold);
+  color: var(--op-color-primary-minus-two);
+  text-align: center;
+  letter-spacing: -0.04em;
+}
+
+.doorkeeper__prompt {
+  margin: 0;
+  font-size: var(--op-font-large);
+  line-height: var(--op-line-height-loose);
+  color: var(--op-color-neutral-minus-three);
+  text-align: center;
+}
+
+.doorkeeper__client-name {
+  color: var(--op-color-primary-base);
+  font-weight: var(--op-font-weight-bold);
+}
+
+.doorkeeper__permissions {
+  background-color: var(--op-color-primary-plus-eight);
+  border: var(--op-border-width) solid var(--op-color-primary-plus-six);
+  border-radius: var(--op-radius-medium);
+  padding: var(--op-space-large);
+  display: flex;
+  flex-direction: column;
+  gap: var(--op-space-medium);
+}
+
+.doorkeeper__permissions-label {
+  margin: 0;
+  font-size: var(--op-font-small);
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+  font-weight: var(--op-font-weight-bold);
+  color: var(--op-color-primary-minus-three);
+}
+
+.doorkeeper__scope-list {
+  margin: 0;
+  padding-left: var(--op-space-large);
+  display: grid;
+  gap: var(--op-space-small);
+  color: var(--op-color-primary-minus-max);
+}
+
+.doorkeeper__scope-item {
+  line-height: var(--op-line-height-base);
+  font-weight: var(--op-font-weight-medium);
+}
+
+.doorkeeper__actions {
+  display: flex;
+  flex-direction: column;
+  gap: var(--op-space-medium);
+  margin-top: var(--op-space-medium);
+}
+
+.doorkeeper__error {
+  align-self: stretch;
+}
+
+.doorkeeper__error-description {
+  margin: 0;
+  font-size: var(--op-font-medium);
+  line-height: var(--op-line-height-base);
+  white-space: pre-wrap;
+  overflow-wrap: anywhere;
+}
+
+.doorkeeper__form {
+  margin: 0;
+}
+
+.doorkeeper__button {
+  width: 100%;
+  justify-content: center;
+  font-weight: var(--op-font-weight-semi-bold);
+}
+
+@media (max-width: 640px) {
+  .doorkeeper {
+    padding: var(--op-space-large) var(--op-space-medium);
+  }
+
+  .doorkeeper__card {
+    padding: var(--op-space-large);
+    border-radius: var(--op-radius-large);
+  }
+
+  .doorkeeper__logo {
+    width: 140px;
+  }
+
+  .doorkeeper__title {
+    font-size: var(--op-font-x-large);
+  }
+}

lib/generators/rolemodel/mcp/templates/app/controllers/doorkeeper/base_controller.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+module Doorkeeper
+  class BaseController < ::ApplicationController
+    skip_before_action :authenticate_oauth, raise: false
+    skip_forgery_protection
+  end
+end