Handle Zendesk API errors in /support-tickets

Otherwise 500 error is returned. The Client apps can then handle those
appropriately.

Ideally calling Zendesk API should be done in a worker that would handle all
possible Zendesk API errors with appropriate retry logic (e.g. don’t retry on
409 :conflict). The controller should respond with 202 :accepted status rather
than 201 :created.
It is not implemented at this time due to change in delivery priorities (and
this work being reprioritised).

app/controllers/support_tickets_controller.rb

@@ -1,4 +1,8 @@
 class SupportTicketsController < ApplicationController
+  rescue_from ZendeskAPI::Error::RecordInvalid, with: :handle_as_validation_error
+
+  rescue_from ZendeskAPI::Error::NetworkError, with: :cast_zendesk_api_error
+
   def create
     support_ticket = SupportTicket.new(support_ticket_attributes)
 
@@ -13,6 +17,14 @@ def create
 
 private
 
+  def handle_as_validation_error(error)
+    render json: { status: "error", errors: error.message }, status: :unprocessable_entity
+  end
+
+  def cast_zendesk_api_error(error)
+    render json: { status: "error", errors: error.message }, status: error.response[:status]
+  end
+
   def support_ticket_attributes
     params.slice(
       :subject, :description, :priority, :requester, :collaborators, :tags, :custom_fields, :ticket_form_id

spec/helpers/zendesk_test_helpers.rb

@@ -38,6 +38,14 @@ def zendesk_has_valid_user_with_email(email)
                    headers: { "Content-Type" => "application/json" })
     end
 
+    def stub_zendesk_returns_record_invalid
+      stub_request(:any, /#{zendesk_endpoint}\/.*/).to_return(status: 422)
+    end
+
+    def stub_zendesk_is_unavailable
+      stub_request(:any, /#{zendesk_endpoint}\/.*/).to_return(status: 503)
+    end
+
     def zendesk_endpoint
       "https://govuk.zendesk.com/api/v2"
     end

spec/requests/support_tickets_spec.rb

@@ -67,6 +67,32 @@
     expect(response_hash).to include("errors" => include("description" => include("can't be blank")))
   end
 
+  it "sends validation error response if ZendeskAPI::Error::RecordInvalid occurs" do
+    stub_zendesk_returns_record_invalid
+    post "/support-tickets",
+         params: {
+           subject: "Feedback for app",
+           description: "Ticket body",
+           requester: { email: "a@b.com" },
+         }
+
+    expect(response.code).to eq("422")
+    expect(response_hash).to include("status" => "error")
+  end
+
+  it "casts the error responses if ZendeskAPI::Error::NetworkError occurs" do
+    stub_zendesk_is_unavailable
+
+    post "/support-tickets",
+         params: {
+           subject: "Feedback for app",
+           description: "Ticket body",
+         }
+
+    expect(response.code).to eq("503")
+    expect(response_hash).to include("status" => "error")
+  end
+
   def response_hash
     JSON.parse(response.body)
   end