Add builder pattern

This builder pattern refactors things so that we can use the same
code to generate manifests/etc.  This means that if we make sure
that we exclusively use those, we can do testing there and keep
something common.

Change-Id: Ibc39f9b9e3e21b18fb255ba2a67d2d8ba3b5c585

builders/deployment.go

@@ -0,0 +1,59 @@
+package builders
+
+import (
+	appsv1 "k8s.io/api/apps/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/utils/pointer"
+	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
+)
+
+// DeploymentBuilder defines the interface to build a deployment
+type DeploymentBuilder struct {
+	obj             *appsv1.Deployment
+	podTemplateSpec *PodTemplateSpecBuilder
+	owner           metav1.Object
+	scheme          *runtime.Scheme
+	labels          map[string]string
+}
+
+// Deployment returns a new deployment builder
+func Deployment(existing *appsv1.Deployment, owner metav1.Object, scheme *runtime.Scheme) *DeploymentBuilder {
+	return &DeploymentBuilder{
+		obj:    existing,
+		labels: map[string]string{},
+		owner:  owner,
+		scheme: scheme,
+	}
+}
+
+// Labels specifies labels for the deployment
+func (d *DeploymentBuilder) Labels(labels map[string]string) *DeploymentBuilder {
+	d.labels = labels
+	d.obj.ObjectMeta.Labels = d.labels
+	d.obj.Spec.Selector = &metav1.LabelSelector{MatchLabels: d.labels}
+	return d
+}
+
+// Replicas defines the number of replicas
+func (d *DeploymentBuilder) Replicas(replicas int32) *DeploymentBuilder {
+	d.obj.Spec.Replicas = pointer.Int32Ptr(replicas)
+	return d
+}
+
+// PodTemplateSpec defines a builder for the pod template spec
+func (d *DeploymentBuilder) PodTemplateSpec(podTemplateSpec *PodTemplateSpecBuilder) *DeploymentBuilder {
+	d.podTemplateSpec = podTemplateSpec
+	return d
+}
+
+// Build creates a final deployment objet
+func (d *DeploymentBuilder) Build() error {
+	podTemplateSpec, err := d.podTemplateSpec.Labels(d.labels).Build()
+	if err != nil {
+		return err
+	}
+
+	d.obj.Spec.Template = podTemplateSpec
+	return controllerutil.SetControllerReference(d.owner, d.obj, d.scheme)
+}