Process one installment at a time in background jobs

Instead of attempting to process multiple installments at a time, which
increases the chances something might go wrong, we are now only processing
one installment at a time.

This also improves the extension's performance, because the installments
can be processed in parallel.

6 files changed, 27 insertions, 57 deletions

diff --git a/app/jobs/solidus_subscriptions/process_installment_job.rb b/app/jobs/solidus_subscriptions/process_installment_job.rb
new file mode 100644
index 0000000..6beeec6
--- /dev/null
+++ b/app/jobs/solidus_subscriptions/process_installment_job.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module SolidusSubscriptions
+  class ProcessInstallmentJob < ApplicationJob
+    queue_as SolidusSubscriptions.configuration.processing_queue
+
+    def perform(installment)
+      Checkout.new([installment]).process
+    end
+  end
+end
diff --git a/app/jobs/solidus_subscriptions/process_installments_job.rb b/app/jobs/solidus_subscriptions/process_installments_job.rb
deleted file mode 100644
index e7e1f63..0000000
--- a/app/jobs/solidus_subscriptions/process_installments_job.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-# frozen_string_literal: true
-
-# This job is responsible for creating a consolidated installment from a
-# list of installments and processing it.
-
-module SolidusSubscriptions
-  class ProcessInstallmentsJob < ApplicationJob
-    queue_as SolidusSubscriptions.configuration.processing_queue
-
-    # Process a collection of installments
-    #
-    # @param installment_ids [Array<Integer>] The ids of the
-    #   installments to be processed together and fulfilled by the same order
-    #
-    # @return [Spree::Order] The order which fulfills the list of installments
-    def perform(installment_ids)
-      return if installment_ids.empty?
-
-      installments = SolidusSubscriptions::Installment.where(id: installment_ids).
-                     includes(subscription: [:line_items, :user])
-      Checkout.new(installments).process
-    end
-  end
-end
diff --git a/lib/solidus_subscriptions/processor.rb b/lib/solidus_subscriptions/processor.rb
index 4547cec..b5aaa70 100644
--- a/lib/solidus_subscriptions/processor.rb
+++ b/lib/solidus_subscriptions/processor.rb
@@ -29,7 +29,7 @@ module SolidusSubscriptions
       end
 
       def process_installment(installment)
-        ProcessInstallmentsJob.perform_later(installment)
+        ProcessInstallmentJob.perform_later(installment)
       end
     end
   end
diff --git a/spec/jobs/solidus_subscriptions/process_installment_job_spec.rb b/spec/jobs/solidus_subscriptions/process_installment_job_spec.rb
new file mode 100644
index 0000000..4a33819
--- /dev/null
+++ b/spec/jobs/solidus_subscriptions/process_installment_job_spec.rb
@@ -0,0 +1,11 @@
+RSpec.describe SolidusSubscriptions::ProcessInstallmentJob do
+  it 'processes checkout for the installment' do
+    installment = build_stubbed(:installment)
+    checkout = instance_spy(SolidusSubscriptions::Checkout)
+    allow(SolidusSubscriptions::Checkout).to receive(:new).with(installment).and_return(checkout)
+
+    described_class.perform_now(installment)
+
+    expect(checkout).to have_received(:process)
+  end
+end
diff --git a/spec/jobs/solidus_subscriptions/process_installments_job_spec.rb b/spec/jobs/solidus_subscriptions/process_installments_job_spec.rb
deleted file mode 100644
index 111fc05..0000000
--- a/spec/jobs/solidus_subscriptions/process_installments_job_spec.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-require 'spec_helper'
-
-RSpec.describe SolidusSubscriptions::ProcessInstallmentsJob do
-  let(:root_order) { create :completed_order_with_pending_payment }
-  let(:installments) do
-    traits = {
-      subscription_traits: [{
-        user: root_order.user,
-        line_item_traits: [{
-          spree_line_item: root_order.line_items.first
-        }]
-      }]
-    }
-
-    create_list(:installment, 2, traits)
-  end
-
-  describe '#perform' do
-    subject { described_class.new.perform(installments) }
-
-    it 'processes the consolidated installment' do
-      expect_any_instance_of(SolidusSubscriptions::Checkout).
-        to receive(:process).once
-
-      subject
-    end
-  end
-end
diff --git a/spec/lib/solidus_subscriptions/processor_spec.rb b/spec/lib/solidus_subscriptions/processor_spec.rb
index a7301f0..03be168 100644
--- a/spec/lib/solidus_subscriptions/processor_spec.rb
+++ b/spec/lib/solidus_subscriptions/processor_spec.rb
@@ -46,8 +46,8 @@ RSpec.describe SolidusSubscriptions::Processor, :checkout do
 
       described_class.run
 
-      expect(SolidusSubscriptions::ProcessInstallmentsJob).to have_been_enqueued
-        .with([subscription.installments.last])
+      expect(SolidusSubscriptions::ProcessInstallmentJob).to have_been_enqueued
+        .with(subscription.installments.last)
     end
 
     it 'schedules other actionable installments for processing' do
@@ -55,8 +55,8 @@ RSpec.describe SolidusSubscriptions::Processor, :checkout do
 
       described_class.run
 
-      expect(SolidusSubscriptions::ProcessInstallmentsJob).to have_been_enqueued
-        .with([actionable_installment])
+      expect(SolidusSubscriptions::ProcessInstallmentJob).to have_been_enqueued
+        .with(actionable_installment)
     end
   end