api: framework api to register user sync() func

pkg/api/framework/api.go

@@ -0,0 +1,57 @@
+package framework
+
+import (
+	"context"
+
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+/*
+'framework' asks only the user business logic to handle resource events.
+It hides all nitty-gritty of k8s controller loop.
+
+An example:
+```main.go
+	func main() {
+		framework.RegisterSync(
+			SyncCallback{
+				SyncFunc:   syncEtcdCluster,
+				ResourceType: &etcdapi.EtcdCluster{},
+			},
+		)
+		framework.Run(context.TODO())
+	}
+
+	func syncEtcdCluster(obj runtime.Object, existed bool) error {
+		if !existed {
+			destroyEtcdCluster()
+			return nil
+		}
+		ec := obj.(*etcdapi.EtcdCluster)
+		reconcile(ec)
+		return nil
+	}
+```
+*/
+
+// SyncCallback defines user business logic for when resource events are triggered.
+type SyncCallback struct {
+	// SyncFunc defines the func to sync a resource event.
+	// 'obj' is the current state of the resource on the event.
+	// 'existed' indicates whether this object still exists. If not, its relevant resources
+	// should be destroyed.
+	SyncFunc func(obj runtime.Object, existed bool) error
+	// ResourceType is used to decide what resource to watch and sync events
+	// It is an instantiation of the resource object which will be used to decide type at runtime.
+	ResourceType runtime.Object
+}
+
+// RegisterSync registers the callbacks where user business logic is defined.
+func RegisterSync(cbs ...SyncCallback) {
+	panic("TODO: unimplemented")
+}
+
+// Run is the main entry point.
+func Run(ctx context.Context) error {
+	panic("TODO: unimplemented")
+}