From cc642512bb046a70b6c7435ee627346fbc9c7879 Mon Sep 17 00:00:00 2001
From: Ryan Zhang <yangzhangrice@hotmail.com>
Date: Thu, 14 Jul 2022 18:13:53 -0700
Subject: [PATCH] feat: skeleton of the resource change contrtoller (#164)

Co-authored-by: Ryan Zhang <zhangryan@microsoft.com>
---
 .../resourcechange_controller.go              | 94 +++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 pkg/controllers/resourcechange/resourcechange_controller.go

diff --git a/pkg/controllers/resourcechange/resourcechange_controller.go b/pkg/controllers/resourcechange/resourcechange_controller.go
new file mode 100644
index 000000000..6c02c6a42
--- /dev/null
+++ b/pkg/controllers/resourcechange/resourcechange_controller.go
@@ -0,0 +1,94 @@
+/*
+Copyright (c) Microsoft Corporation.
+Licensed under the MIT license.
+*/
+
+package resourcechange
+
+import (
+	"context"
+	"fmt"
+
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/api/meta"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/client-go/dynamic"
+	"k8s.io/client-go/tools/record"
+	"k8s.io/klog/v2"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+
+	fleetv1alpha1 "go.goms.io/fleet/apis/v1alpha1"
+	"go.goms.io/fleet/pkg/utils"
+	"go.goms.io/fleet/pkg/utils/controller"
+	"go.goms.io/fleet/pkg/utils/keys"
+)
+
+// Reconciler finds the placements that reference to any resource.
+type Reconciler struct {
+	// Client is used to retrieve objects, it is often more convenient than lister.
+	Client client.Client
+
+	Recorder record.EventRecorder
+
+	// DynamicClient used to fetch arbitrary resources.
+	DynamicClient dynamic.Interface
+
+	RestMapper meta.RESTMapper
+
+	InformerManager utils.InformerManager
+
+	// the handler of the placement controller
+	PlacementController controller.Controller
+}
+
+func (r *Reconciler) Reconcile(ctx context.Context, key controller.QueueKey) (ctrl.Result, error) {
+	clusterWideKey, ok := key.(keys.ClusterWideKey)
+	if !ok {
+		err := fmt.Errorf("got a resource key %+v not of type cluster wide key", key)
+		klog.ErrorS(err, "we have encountered a fatal error that can't be retried")
+		return ctrl.Result{}, err
+	}
+	klog.V(2).InfoS("Reconciling object", "key", clusterWideKey)
+
+	object, err := r.getUnstructuredObject(ctx, clusterWideKey)
+	if err != nil {
+		if !apierrors.IsNotFound(err) {
+			klog.ErrorS(err, "Failed to get unstructured object", "key", clusterWideKey)
+		}
+		return ctrl.Result{}, client.IgnoreNotFound(err)
+	}
+
+	_, err = r.findMatchedPolicies(object)
+	return ctrl.Result{}, err
+}
+
+// getUnstructuredObject retrieves an unstructured object by its gvknn key, this will hit the informer cache
+func (r *Reconciler) getUnstructuredObject(ctx context.Context, objectKey keys.ClusterWideKey) (*unstructured.Unstructured, error) {
+	restMapping, err := r.RestMapper.RESTMapping(objectKey.GroupKind(), objectKey.Version)
+	if err != nil {
+		klog.Errorf("Failed to get GVR of object: %s, error: %v", objectKey, err)
+		return nil, err
+	}
+	gvr := restMapping.Resource
+	if !r.InformerManager.IsInformerSynced(gvr) {
+		return nil, fmt.Errorf("informer cache for %+v is not synced yet", restMapping.Resource)
+	}
+
+	lister := r.InformerManager.Lister(gvr)
+	obj, err := lister.ByNamespace(objectKey.Namespace).Get(objectKey.Name)
+	if err != nil {
+		if apierrors.IsNotFound(err) {
+			return nil, err
+		}
+		// print logs only for real error.
+		klog.ErrorS(err, "Failed to get obj", "object", objectKey)
+		return nil, err
+	}
+	return obj.(*unstructured.Unstructured), nil
+}
+
+// findMatchedPolicies find all the polices that this unstructured object is referenced
+func (r *Reconciler) findMatchedPolicies(object *unstructured.Unstructured) ([]*fleetv1alpha1.ClusterResourcePlacement, error) {
+	return nil, nil
+}