improvements jan2025 (#6)

* feat(controller): add lazy watcher, improve resource usage and add pattern validation

- [x] Add cache sync health check for readiness probe verification
- [x] Create namespace lister with API reader support for fresh label queries
- [x] Add pattern validation with warning logs for invalid glob patterns
- [x] Implement lazy watcher initialization mode to scan for active resources
- [x] Add requeue delay to namespace reconciler for cache settlement
- [x] Replace custom containsString with slices.Contains from stdlib
- [x] Add structured logging context to reconcilers (kind, group, version)
- [x] Improve error variable naming for clarity in nested conditions
- [x] Add nil-safe label access in namespace reconciler setup
- [x] Add APIReader to namespace and source reconcilers for fresh data
- [x] Improve type assertions with proper error handling in mirror operations
- [x] Reorder struct fields for consistency and readability
- [x] Add comprehensive pattern validation tests and validation API

* feat(controller): add lazy watcher, improve resource usage and add pattern validation

- [x] Add circuit breaker for reconciliation failure tracking and prevention
- [x] Implement granular registration state tracking (not-registered, source-only, fully-registered)
- [x] Add lazy controller initialization for active resource types only
- [x] Consolidate namespace listing into single API call for efficiency
- [x] Add mirror creation verification to catch webhook rejections
- [x] Implement high-cardinality resource detection and warnings
- [x] Add source deletion check in mirror reconciler to prevent races
- [x] Preserve transformation annotations on errors in mirror reconciliation
- [x] Expand constants documentation with labels vs annotations design rationale
- [x] Add comprehensive test coverage for circuit breaker and registration states
- [x] Add mutation-safety tests for hash computation

* fixup! feat(controller): add lazy watcher, improve resource usage and add pattern validation

pkg/transformer/transformer_test.go

@@ -15,13 +15,13 @@ import (
 
 func TestTransformer_Transform(t *testing.T) {
 	tests := []struct {
-		name     string
-		source   runtime.Object
 		ctx      TransformContext
+		source   runtime.Object
+		validate func(t *testing.T, result runtime.Object)
+		name     string
+		errMsg   string
 		options  TransformOptions
 		wantErr  bool
-		errMsg   string
-		validate func(t *testing.T, result runtime.Object)
 	}{
 		// Good cases - Value rules
 		{
@@ -566,12 +566,12 @@ func TestParsePath(t *testing.T) {
 
 func TestSetNestedField(t *testing.T) {
 	tests := []struct {
-		name    string
-		obj     map[string]interface{}
-		path    []string
 		value   interface{}
-		wantErr bool
+		obj     map[string]interface{}
 		want    map[string]interface{}
+		name    string
+		path    []string
+		wantErr bool
 	}{
 		{
 			name:    "set top-level field",

pkg/transformer/types.go

@@ -13,46 +13,22 @@ type TransformRules struct {
 
 // Rule represents a single transformation rule.
 type Rule struct {
-	// Path is the JSONPath to the field to transform (e.g., "data.LOG_LEVEL", "metadata.labels.env")
-	Path string `yaml:"path"`
-
-	// Value sets a static value (mutually exclusive with Template, Merge, Delete)
-	Value *string `yaml:"value,omitempty"`
-
-	// Template uses Go templates to generate the value (mutually exclusive with Value, Merge, Delete)
-	Template *string `yaml:"template,omitempty"`
-
-	// Merge merges a map into the target field (mutually exclusive with Value, Template, Delete)
-	Merge map[string]interface{} `yaml:"merge,omitempty"`
-
-	// Delete removes the field (mutually exclusive with Value, Template, Merge)
-	Delete bool `yaml:"delete,omitempty"`
-
-	// NamespacePattern is an optional glob pattern that limits this rule to specific target namespaces
-	// Examples: "prod-*", "*-staging", "preprod-*"
-	// If not specified, the rule applies to all namespaces
-	NamespacePattern *string `yaml:"namespacePattern,omitempty"`
+	Value            *string                `yaml:"value,omitempty"`
+	Template         *string                `yaml:"template,omitempty"`
+	Merge            map[string]interface{} `yaml:"merge,omitempty"`
+	NamespacePattern *string                `yaml:"namespacePattern,omitempty"`
+	Path             string                 `yaml:"path"`
+	Delete           bool                   `yaml:"delete,omitempty"`
 }
 
 // TransformContext provides context variables for template evaluation.
 type TransformContext struct {
-	// TargetNamespace is the namespace where the mirror is being created
+	Labels          map[string]string
+	Annotations     map[string]string
 	TargetNamespace string
-
-	// SourceNamespace is the namespace of the source resource
 	SourceNamespace string
-
-	// SourceName is the name of the source resource
-	SourceName string
-
-	// TargetName is the name of the target resource (usually same as source)
-	TargetName string
-
-	// Labels is a copy of the source resource's labels
-	Labels map[string]string
-
-	// Annotations is a copy of the source resource's annotations
-	Annotations map[string]string
+	SourceName      string
+	TargetName      string
 }
 
 // TransformOptions configures the transformation behavior.

pkg/transformer/types_test.go

@@ -10,9 +10,9 @@ import (
 func TestRule_Validate(t *testing.T) {
 	tests := []struct {
 		name    string
+		errMsg  string
 		rule    Rule
 		wantErr bool
-		errMsg  string
 	}{
 		// Good cases
 		{
@@ -191,8 +191,8 @@ func TestRule_Type(t *testing.T) {
 func TestRuleType_String(t *testing.T) {
 	tests := []struct {
 		name     string
-		ruleType RuleType
 		want     string
+		ruleType RuleType
 	}{
 		{name: "value", ruleType: RuleTypeValue, want: "value"},
 		{name: "template", ruleType: RuleTypeTemplate, want: "template"},