Add explanatory comments for provider interfaces

Signed-off-by: Danil Grigorev <danil.grigorev@suse.com>

cmd/plugin/cmd/delete.go

@@ -308,12 +308,6 @@ func deleteProviders(ctx context.Context, client ctrlclient.Client, providerList
 	for _, provider := range providerList.GetItems() {
 		log.Info(fmt.Sprintf("Deleting %s %s/%s", provider.GetType(), provider.GetName(), provider.GetNamespace()))
 
-		provider, ok := provider.(generic.Provider)
-		if !ok {
-			log.Info(fmt.Sprintf("Expected to get GenericProvider for %s", gvk))
-			continue
-		}
-
 		if err := client.DeleteAllOf(ctx, provider, ctrlclient.InNamespace(provider.GetNamespace())); err != nil {
 			return false, fmt.Errorf("unable to issue delete for %s: %w", gvk, err)
 		}

internal/controller/generic/interfaces.go

@@ -26,32 +26,38 @@ import (
 	"sigs.k8s.io/controller-runtime/pkg/reconcile"
 )
 
-type Provider interface {
-	operatorv1.GenericProvider
-}
+// Provider is an GenericProvider.
+type Provider = operatorv1.GenericProvider
 
+// ProviderList is a GenericProviderList satisfying ObjectList interface.
 type ProviderList interface {
 	client.ObjectList
 	operatorv1.GenericProviderList
 }
 
+// Getter is a base interface for provider reconcilers.
 type Getter interface {
 	ClusterctlProviderType() clusterctlv1.ProviderType
 	GenericProvider() Provider
 	GetProviderList() ProviderList
 }
 
+// Connector is a base interface for building phase reconcile and accessing cluster via client.
 type Connector interface {
 	GetClient() client.Client
 	GetConfig() *rest.Config
 }
 
+// GroupBuilder implementation allows to build a generic Group acting on specific provider type,
+// preserving the type info.
 type GroupBuilder[P Provider] interface {
 	Connector
 	Getter
 	ClusterctlProvider(provider P) *clusterctlv1.Provider
 }
 
+// Group is a generic interface with access to typed Provider object.
+// Each reconciler phase expected to work with a Provider Group.
 type Group[P Provider] interface {
 	Connector
 	Getter
@@ -62,6 +68,14 @@ type Group[P Provider] interface {
 // NewGroup is a function that creates a new group.
 type NewGroup[P Provider] func(P, ProviderList, GroupBuilder[P]) Group[P]
 
+// ProviderReconciler is a reconciler methods interface related to specified provider
+// The reconcile is split into 4 stages, each executed after another, and accepting any Provider object.
+// Each stage will return a list of phases for controller execution, typed for defined Provider:
+//
+// - PreflightChecks(ctx context.Context, provider P) []ReconcileFn[P, Group[P]]
+// - ReconcileNormal(ctx context.Context, provider P) []ReconcileFn[P, Group[P]]
+// - ReportStatus(ctx context.Context, provider P) []ReconcileFn[P, Group[P]]
+// - ReconcileDelete(ctx context.Context, provider P) []ReconcileFn[P, Group[P]].
 type ProviderReconciler[P Provider] interface {
 	GroupBuilder[P]
 	Init()
@@ -74,12 +88,27 @@ type ProviderReconciler[P Provider] interface {
 // ReconcileFn is a function that represent a phase of the reconciliation.
 type ReconcileFn[P Provider, G Group[P]] func(context.Context, G) (reconcile.Result, error)
 
+// NewReconcileFnList created a list of reconcile phases, with a typed group working with a defined provider only
+// Example:
+//
+//	generic.NewReconcileFnList(r.corePreflightChecks) // Will only compile when passed to core provider reconciler working on CoreProvider
+//
+//	func (r *CoreProviderReconciler) corePreflightChecks(ctx context.Context, phase generic.Group[*operatorv1.CoreProvider]) (ctrl.Result, error) {
+//			var p *operatorv1.CoreProvider
+//			// getting actual core provider instead of interface for resource specific operations or validation
+//			p = phase.GetProvider() // this works
+//	}
 func NewReconcileFnList[P Provider, G Group[P]](phaseFunc ...ReconcileFn[P, G]) []ReconcileFn[P, G] {
 	return phaseFunc
 }
 
+// ProviderReconcilers is a storage of registered provider reconcilers on controller startup.
+// It is used to access reconciler specific methods, allowing to map Clusterctl provider type
+// on an actual Provider object, which represents it.
 var ProviderReconcilers = map[clusterctlv1.ProviderType]Getter{}
 
+// GetBuilder provides an initialized reconciler to fetch component in the domail of provider, like
+// provider list type, clusterctl provider, etc. without need to maintain an evergrowing switch statement.
 func GetBuilder[P Provider](_ P) GroupBuilder[P] {
 	for _, reconciler := range ProviderReconcilers {
 		if r, ok := reconciler.(ProviderReconciler[P]); ok {