Monkey patch gruf interceptor

Gemfile.lock

@@ -3,6 +3,7 @@ PATH
   specs:
     grpc-rest (0.1.21)
       grpc
+      gruf
       rails (>= 6.0)
 
 GEM

README.md

@@ -154,9 +154,22 @@ service MyService {
 
 ## Gruf Interceptors
 
-grpc-rest supports [gruf](https://github.com/bigcommerce/gruf) Interceptors. As long as you're not using a custom interceptor
+grpc-rest supports [gruf](https://github.com/bigcommerce/gruf) Interceptors through a custom `GrpcRest::BaseInterceptor` class. As long as you're not using a custom interceptor
 registry, your interceptors will be called normally around the controller.
 
+```ruby
+module Interceptors
+  # Interceptor for catching errors from controllers
+  class ErrorInterceptor < GrpcRest::BaseInterceptor
+
+    def call
+      # Your code here
+    end
+
+  end
+end
+```
+
 ## To Do
 
 * Replace Go implementation with Ruby (+ executable)

grpc-rest.gemspec

@@ -20,6 +20,7 @@ Gem::Specification.new do |spec|
 
   spec.add_runtime_dependency('grpc')
   spec.add_runtime_dependency('rails', '>= 6.0')
+  spec.add_runtime_dependency('gruf')
 
   spec.add_development_dependency('rspec-rails')
   spec.add_development_dependency('gruf')

lib/grpc_rest.rb

@@ -1,6 +1,7 @@
 require 'google/protobuf/well_known_types'
 require 'grpc'
 require 'grpc/core/status_codes'
+require 'interceptors/base_interceptor'
 
 module GrpcRest
   class << self

lib/interceptors/base_interceptor.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require 'gruf'
+
+module GrpcRest
+    # This is a monkey-patch that fixes an issue we were having with using the fail! method in
+    # interceptors where an active call was not instantiated yet.
+    # Basically, we overloaded this function: https://github.com/bigcommerce/gruf/blob/main/lib/gruf/errors/helpers.rb#L34
+  class BaseInterceptor < ::Gruf::Interceptors::ServerInterceptor
+    def fail!(error_code, _app_code = 500, message = 'unkown error', metadata = {})
+      raise grpc_error(error_code, message.to_s, metadata)
+    end
+
+    private
+
+    # Ported from https://github.com/flipp-oss/grpc-rest/blob/main/lib/grpc_rest.rb#L142
+    def grpc_error(error_code, message, metadata)
+      case error_code
+      when :ok
+        GRPC::Ok.new(message, metadata)
+      when 499
+        GRPC::Cancelled.new(message, metadata)
+      when :bad_request, :invalid_argument
+        GRPC::InvalidArgument.new(message, metadata)
+      when :gateway_timeout
+        GRPC::DeadlineExceeded.new(message, metadata)
+      when :not_found
+        GRPC::NotFound.new(message, metadata)
+      when :conflict
+        GRPC::AlreadyExists.new(message, metadata)
+      when :forbidden
+        GRPC::PermissionDenied.new(message, metadata)
+      when :unauthorized
+        GRPC::Unauthenticated.new(message, metadata)
+      when :too_many_requests
+        GRPC::ResourceExhausted.new(message, metadata)
+      when :not_implemented
+        GRPC::Unimplemented.new(message, metadata)
+      when :service_unavailable
+        GRPC::Unavailable.new(message, metadata)
+      else
+        GRPC::Internal.new(message, metadata)
+      end
+    end
+  end
+end