Creates destroy cluster service

The service will later on receive params and extend its functionality
to either simply remove the cluster or remove cluster and its
resources depending on the params sent by the frontend

app/controllers/clusters/clusters_controller.rb

@@ -92,13 +92,12 @@ class Clusters::ClustersController < Clusters::BaseController
   end
 
   def destroy
-    if cluster.destroy
-      flash[:notice] = _('Kubernetes cluster integration was successfully removed.')
+    response = Clusters::DestroyService
+      .new(current_user, destroy_params)
+      .execute(cluster)
+
+    flash[:notice] = response[:message]
     redirect_to clusterable.index_path, status: :found
-    else
-      flash[:notice] = _('Kubernetes cluster integration was not removed.')
-      render :show
-    end
   end
 
   def create_gcp
@@ -143,6 +142,14 @@ class Clusters::ClustersController < Clusters::BaseController
 
   private
 
+  def destroy_params
+    # To be uncomented on https://gitlab.com/gitlab-org/gitlab/merge_requests/16954
+    # This MR got split into other since it was too big.
+    #
+    # params.permit(:cleanup)
+    {}
+  end
+
   def update_params
     if cluster.provided_by_user?
       params.require(:cluster).permit(

app/services/clusters/destroy_service.rb

+# frozen_string_literal: true
+
+module Clusters
+  class DestroyService
+    attr_reader :current_user, :params
+
+    def initialize(user = nil, params = {})
+      @current_user, @params = user, params.dup
+      @response = {}
+    end
+
+    def execute(cluster)
+      cleanup? ? start_cleanup!(cluster) : destroy_cluster!(cluster)
+
+      @response
+    end
+
+    private
+
+    def cleanup?
+      Gitlab::Utils.to_boolean(params[:cleanup])
+    end
+
+    def start_cleanup!(cluster)
+      cluster.start_cleanup!
+      @response[:message] = _('Kubernetes cluster integration and resources are being removed.')
+    end
+
+    def destroy_cluster!(cluster)
+      cluster.destroy!
+      @response[:message] = _('Kubernetes cluster integration was successfully removed.')
+    end
+  end
+end

locale/gitlab.pot

@@ -9679,7 +9679,7 @@ msgstr ""
 msgid "Kubernetes cluster creation time exceeds timeout; %{timeout}"
 msgstr ""
 
-msgid "Kubernetes cluster integration was not removed."
+msgid "Kubernetes cluster integration and resources are being removed."
 msgstr ""
 
 msgid "Kubernetes cluster integration was successfully removed."

spec/services/clusters/destroy_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Clusters::DestroyService do
+  describe '#execute' do
+    subject { described_class.new(cluster.user, params).execute(cluster) }
+
+    let!(:cluster) { create(:cluster, :project, :provided_by_user) }
+
+    context 'when correct params' do
+      shared_examples 'only removes cluster' do
+        it 'does not start cleanup' do
+          expect(cluster).not_to receive(:start_cleanup)
+          subject
+        end
+
+        it 'destroys the cluster' do
+          subject
+          expect { cluster.reload }.to raise_error ActiveRecord::RecordNotFound
+        end
+      end
+
+      context 'when params are empty' do
+        let(:params) { {} }
+
+        it_behaves_like 'only removes cluster'
+      end
+
+      context 'when cleanup param is false' do
+        let(:params) { { cleanup: 'false' } }
+
+        it_behaves_like 'only removes cluster'
+      end
+
+      context 'when cleanup param is true' do
+        let(:params) { { cleanup: 'true' } }
+
+        before do
+          allow(Clusters::Cleanup::AppWorker).to receive(:perform_async)
+        end
+
+        it 'does not destroy cluster' do
+          subject
+          expect(Clusters::Cluster.where(id: cluster.id).exists?).not_to be_falsey
+        end
+
+        it 'transition cluster#cleanup_status from cleanup_not_started to uninstalling_applications' do
+          expect { subject }.to change { cluster.cleanup_status_name }
+            .from(:cleanup_not_started)
+            .to(:cleanup_uninstalling_applications)
+        end
+      end
+    end
+  end
+end