From 830226cca10c05765933ab1c9720d0bbea6e6467 Mon Sep 17 00:00:00 2001
From: Roman Samoilov <2270393+rsamoilov@users.noreply.github.com>
Date: Fri, 3 May 2024 12:30:48 +0100
Subject: [PATCH] Add `Cascade`

this allows to have both Rails and Rage controllers in one application
---
 lib/rage-rb.rb             |  4 ++++
 lib/rage/router/backend.rb | 14 ++++++++++----
 lib/rage/router/util.rb    | 15 +++++++++++++++
 3 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/lib/rage-rb.rb b/lib/rage-rb.rb
index 5a76bd8e..76131079 100644
--- a/lib/rage-rb.rb
+++ b/lib/rage-rb.rb
@@ -24,6 +24,10 @@ def self.application
     end
   end
 
+  def self.multi_application
+    Rage::Router::Util::Cascade.new(application, Rails.application)
+  end
+
   def self.routes
     Rage::Router::DSL.new(__router)
   end
diff --git a/lib/rage/router/backend.rb b/lib/rage/router/backend.rb
index 6979e92a..7dcd6d45 100644
--- a/lib/rage/router/backend.rb
+++ b/lib/rage/router/backend.rb
@@ -68,12 +68,18 @@ def on(method, path, handler, constraints: {}, defaults: nil)
       raise "Invalid route handler format, expected to match the 'controller#action' pattern" unless handler =~ STRING_HANDLER_REGEXP
 
       controller, action = Rage::Router::Util.path_to_class($1), $2
-      run_action_method_name = controller.__register_action(action.to_sym)
 
-      meta[:controller] = $1
-      meta[:action] = $2
+      if controller.ancestors.include?(RageController::API)
+        run_action_method_name = controller.__register_action(action.to_sym)
 
-      handler = eval("->(env, params) { #{controller}.new(env, params).#{run_action_method_name} }")
+        meta[:controller] = $1
+        meta[:action] = $2
+
+        handler = eval("->(env, params) { #{controller}.new(env, params).#{run_action_method_name} }")
+      else
+        # this is a Rails controller; notify `Rage::Router::Util::Cascade` to forward the request to Rails
+        handler = ->(_, _) { [404, { "X-Cascade" => "pass" }, []] }
+      end
     else
       raise "Non-string route handler should respond to `call`" unless handler.respond_to?(:call)
       # while regular handlers are expected to be called with the `env` and `params` objects,
diff --git a/lib/rage/router/util.rb b/lib/rage/router/util.rb
index 929d630e..9c9527b6 100644
--- a/lib/rage/router/util.rb
+++ b/lib/rage/router/util.rb
@@ -30,4 +30,19 @@ def path_to_name(str)
       end
     end
   end
+
+  # @private
+  class Cascade
+    def initialize(rage_app, rails_app)
+      @rage_app = rage_app
+      @rails_app = rails_app
+    end
+
+    def call(env)
+      result = @rage_app.call(env)
+      return result if result[0] == :__http_defer__ || result[1]["X-Cascade".freeze] != "pass".freeze
+
+      @rails_app.call(env)
+    end
+  end
 end