feat: implement replicaset primitive

Makefile

@@ -122,6 +122,7 @@ build-examples: ## Build all example binaries.
 run-examples: ## Run all examples to verify they execute without error.
 	go run ./examples/deployment-primitive/.
 	go run ./examples/configmap-primitive/.
+	go run ./examples/replicaset-primitive/.
 	go run ./examples/rolebinding-primitive/.
 	go run ./examples/custom-resource-implementation/.
 	go run ./examples/hpa-primitive/.

docs/primitives.md

@@ -119,6 +119,7 @@ Editors provide scoped, typed APIs for modifying specific parts of a resource:
 | `ContainerEditor`       | Environment variables, arguments, resource limits, ports                          |
 | `PodSpecEditor`         | Volumes, tolerations, node selectors, service account, security context           |
 | `DeploymentSpecEditor`  | Replicas, update strategy, label selectors                                        |
+| `ReplicaSetSpecEditor`  | Replicas, min ready seconds                                                       |
 | `ConfigMapDataEditor`   | `.data` entries — set, remove, deep-merge YAML patches, raw access                |
 | `PolicyRulesEditor`     | `.rules` entries on Role and ClusterRole objects — add, remove, clear, raw access |
 | `BindingSubjectsEditor` | Subjects on RoleBinding or ClusterRoleBinding — ensure, remove, raw               |
@@ -148,6 +149,7 @@ have been applied. This means a single mutation can safely add a container and t
 | Primitive                           | Category    | Documentation                                             |
 | ----------------------------------- | ----------- | --------------------------------------------------------- |
 | `pkg/primitives/deployment`         | Workload    | [deployment.md](primitives/deployment.md)                 |
+| `pkg/primitives/replicaset`         | Workload    | [replicaset.md](primitives/replicaset.md)                 |
 | `pkg/primitives/cronjob`            | Integration | [cronjob.md](primitives/cronjob.md)                       |
 | `pkg/primitives/configmap`          | Static      | [configmap.md](primitives/configmap.md)                   |
 | `pkg/primitives/clusterrole`        | Static      | [clusterrole.md](primitives/clusterrole.md)               |
@@ -156,7 +158,6 @@ have been applied. This means a single mutation can safely add a container and t
 | `pkg/primitives/hpa`                | Integration | [hpa.md](primitives/hpa.md)                               |
 | `pkg/primitives/ingress`            | Integration | [ingress.md](primitives/ingress.md)                       |
 
-
 ## Usage Examples
 
 ### Creating a primitive

docs/primitives/replicaset.md

@@ -0,0 +1,178 @@
+# ReplicaSet Primitive
+
+The `replicaset` primitive is the framework's workload abstraction for managing Kubernetes `ReplicaSet` resources. It
+integrates fully with the component lifecycle and provides a rich mutation API for managing containers, pod specs, and
+metadata.
+
+ReplicaSets are rarely managed directly — operators typically use Deployments. This primitive is provided for operators
+that own ReplicaSets explicitly (e.g. custom rollout controllers).
+
+## Capabilities
+
+| Capability            | Detail                                                                                                                                        |
+| --------------------- | --------------------------------------------------------------------------------------------------------------------------------------------- |
+| **Health tracking**   | Verifies `ObservedGeneration` matches `Generation` before evaluating `ReadyReplicas`; reports `Healthy`, `Creating`, `Updating`, or `Scaling` |
+| **Suspension**        | Scales to zero replicas; reports `Suspending` / `Suspended`                                                                                   |
+| **Mutation pipeline** | Typed editors for metadata, replicaset spec, pod spec, and containers                                                                         |
+
+## Building a ReplicaSet Primitive
+
+```go
+import "github.com/sourcehawk/operator-component-framework/pkg/primitives/replicaset"
+
+base := &appsv1.ReplicaSet{
+    ObjectMeta: metav1.ObjectMeta{
+        Name:      "worker",
+        Namespace: owner.Namespace,
+    },
+    Spec: appsv1.ReplicaSetSpec{
+        Selector: &metav1.LabelSelector{
+            MatchLabels: map[string]string{"app": "worker"},
+        },
+        // baseline spec
+    },
+}
+
+resource, err := replicaset.NewBuilder(base).
+    WithMutation(MyFeatureMutation(owner.Spec.Version)).
+    Build()
+```
+
+## Mutations
+
+Mutations are the primary mechanism for modifying a `ReplicaSet` beyond its baseline. Each mutation is a named function
+that receives a `*Mutator` and records edit intent through typed editors.
+
+The `Feature` field controls when a mutation applies. Leaving it nil applies the mutation unconditionally. A feature
+with no version constraints and no `When()` conditions is also always enabled:
+
+```go
+func MyFeatureMutation(version string) replicaset.Mutation {
+    return replicaset.Mutation{
+        Name:    "my-feature",
+        Feature: feature.NewResourceFeature(version, nil), // always enabled
+        Mutate: func(m *replicaset.Mutator) error {
+            // record edits here
+            return nil
+        },
+    }
+}
+```
+
+Mutations are applied in the order they are registered with the builder.
+
+### Boolean-gated mutations
+
+Use `When(bool)` to gate a mutation on a runtime condition:
+
+```go
+func TracingMutation(version string, enabled bool) replicaset.Mutation {
+    return replicaset.Mutation{
+        Name:    "tracing",
+        Feature: feature.NewResourceFeature(version, nil).When(enabled),
+        Mutate: func(m *replicaset.Mutator) error {
+            m.EnsureContainer(corev1.Container{
+                Name:  "jaeger-agent",
+                Image: "jaegertracing/jaeger-agent:1.28",
+            })
+            return nil
+        },
+    }
+}
+```
+
+## Internal Mutation Ordering
+
+Within a single mutation, edit operations are grouped into categories and applied in a fixed sequence regardless of the
+order they are recorded:
+
+| Step | Category                    | What it affects                                                         |
+| ---- | --------------------------- | ----------------------------------------------------------------------- |
+| 1    | Object metadata edits       | Labels and annotations on the `ReplicaSet` object                       |
+| 2    | ReplicaSetSpec edits        | Replicas, min ready seconds                                             |
+| 3    | Pod template metadata edits | Labels and annotations on the pod template                              |
+| 4    | Pod spec edits              | Volumes, tolerations, node selectors, service account, security context |
+| 5    | Regular container presence  | Adding or removing containers from `spec.template.spec.containers`      |
+| 6    | Regular container edits     | Env vars, args, resources (snapshot taken after step 5)                 |
+| 7    | Init container presence     | Adding or removing containers from `spec.template.spec.initContainers`  |
+| 8    | Init container edits        | Env vars, args, resources (snapshot taken after step 7)                 |
+
+Container edits (steps 6 and 8) are evaluated against a snapshot taken _after_ presence operations in the same mutation.
+
+## Editors
+
+### ReplicaSetSpecEditor
+
+Controls replicaset-level settings via `m.EditReplicaSetSpec`.
+
+Available methods: `SetReplicas`, `SetMinReadySeconds`, `Raw`.
+
+```go
+m.EditReplicaSetSpec(func(e *editors.ReplicaSetSpecEditor) error {
+    e.SetReplicas(3)
+    e.SetMinReadySeconds(10)
+    return nil
+})
+```
+
+Note: `spec.selector` is immutable after creation and is not exposed by this editor. Set it via the desired object
+passed to `NewBuilder`.
+
+### PodSpecEditor
+
+Manages pod-level configuration via `m.EditPodSpec`.
+
+Available methods: `SetServiceAccountName`, `EnsureVolume`, `RemoveVolume`, `EnsureToleration`, `RemoveTolerations`,
+`EnsureNodeSelector`, `RemoveNodeSelector`, `EnsureImagePullSecret`, `RemoveImagePullSecret`, `SetPriorityClassName`,
+`SetHostNetwork`, `SetHostPID`, `SetHostIPC`, `SetSecurityContext`, `Raw`.
+
+```go
+m.EditPodSpec(func(e *editors.PodSpecEditor) error {
+    e.SetServiceAccountName("my-service-account")
+    return nil
+})
+```
+
+### ContainerEditor
+
+Modifies individual containers via `m.EditContainers` or `m.EditInitContainers`. Always used in combination with a
+[selector](../primitives.md#container-selectors).
+
+Available methods: `EnsureEnvVar`, `EnsureEnvVars`, `RemoveEnvVar`, `RemoveEnvVars`, `EnsureArg`, `EnsureArgs`,
+`RemoveArg`, `RemoveArgs`, `SetResourceLimit`, `SetResourceRequest`, `SetResources`, `Raw`.
+
+```go
+m.EditContainers(selectors.ContainerNamed("app"), func(e *editors.ContainerEditor) error {
+    e.EnsureEnvVar(corev1.EnvVar{Name: "LOG_LEVEL", Value: "info"})
+    return nil
+})
+```
+
+### ObjectMetaEditor
+
+Modifies labels and annotations. Use `m.EditObjectMetadata` to target the `ReplicaSet` object itself, or
+`m.EditPodTemplateMetadata` to target the pod template.
+
+Available methods: `EnsureLabel`, `RemoveLabel`, `EnsureAnnotation`, `RemoveAnnotation`, `Raw`.
+
+## Convenience Methods
+
+| Method                        | Equivalent to                                                 |
+| ----------------------------- | ------------------------------------------------------------- |
+| `EnsureReplicas(n)`           | `EditReplicaSetSpec` → `SetReplicas(n)`                       |
+| `EnsureContainerEnvVar(ev)`   | `EditContainers(AllContainers(), ...)` → `EnsureEnvVar(ev)`   |
+| `RemoveContainerEnvVar(name)` | `EditContainers(AllContainers(), ...)` → `RemoveEnvVar(name)` |
+| `EnsureContainerArg(arg)`     | `EditContainers(AllContainers(), ...)` → `EnsureArg(arg)`     |
+| `RemoveContainerArg(arg)`     | `EditContainers(AllContainers(), ...)` → `RemoveArg(arg)`     |
+
+## Guidance
+
+**`Feature: nil` applies unconditionally.** Omit `Feature` (leave it nil) for mutations that should always run.
+
+**Register mutations in dependency order.** If mutation B relies on a container added by mutation A, register A first.
+
+**Prefer `EnsureContainer` over direct slice manipulation.** The mutator tracks presence operations so that selectors in
+the same mutation resolve correctly and reconciliation remains idempotent.
+
+**Use selectors for precision.** Targeting `AllContainers()` when you only mean to modify the primary container can
+cause unexpected behavior if sidecar containers are present.

examples/replicaset-primitive/README.md

@@ -0,0 +1,33 @@
+# ReplicaSet Primitive Example
+
+This example demonstrates the usage of the `replicaset` primitive within the operator component framework. It shows how
+to manage a Kubernetes ReplicaSet as a component of a larger application, utilizing features like:
+
+- **Base Construction**: Initializing a ReplicaSet with basic metadata and spec.
+- **Feature Mutations**: Applying version-gated or conditional changes (sidecars, env vars, annotations) using the
+  `Mutator`.
+- **Data Extraction**: Harvesting information from the reconciled resource.
+
+## Directory Structure
+
+- `app/`: Defines the mock `ExampleApp` CRD and the controller that uses the component framework.
+- `features/`: Contains modular feature definitions:
+  - `mutations.go`: sidecar injection, env vars, and version-based image updates.
+- `resources/`: Contains the central `NewReplicaSetResource` factory that assembles all features using the
+  `replicaset.Builder`.
+- `main.go`: A standalone entry point that demonstrates a single reconciliation loop using a fake client.
+
+## Running the Example
+
+You can run this example directly using `go run`:
+
+```bash
+go run examples/replicaset-primitive/main.go
+```
+
+This will:
+
+1. Initialize a fake Kubernetes client.
+2. Create an `ExampleApp` owner object.
+3. Reconcile the `ExampleApp` components.
+4. Print the resulting status conditions.

examples/replicaset-primitive/app/controller.go

@@ -0,0 +1,54 @@
+// Package app provides a sample controller using the replicaset primitive.
+package app
+
+import (
+	"context"
+
+	"github.com/sourcehawk/operator-component-framework/pkg/component"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/client-go/tools/record"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+)
+
+// ExampleController reconciles an ExampleApp object using the component framework.
+type ExampleController struct {
+	client.Client
+	Scheme   *runtime.Scheme
+	Recorder record.EventRecorder
+	Metrics  component.Recorder
+
+	// NewReplicaSetResource is a factory function to create the replicaset resource.
+	// This allows us to inject the resource construction logic.
+	NewReplicaSetResource func(*ExampleApp) (component.Resource, error)
+}
+
+// Reconcile performs the reconciliation for a single ExampleApp.
+func (r *ExampleController) Reconcile(ctx context.Context, owner *ExampleApp) error {
+	// 1. Build the replicaset resource for this owner.
+	rsResource, err := r.NewReplicaSetResource(owner)
+	if err != nil {
+		return err
+	}
+
+	// 2. Build the component that manages the replicaset.
+	comp, err := component.NewComponentBuilder().
+		WithName("example-app").
+		WithConditionType("AppReady").
+		WithResource(rsResource, component.ResourceOptions{}).
+		Suspend(owner.Spec.Suspended).
+		Build()
+	if err != nil {
+		return err
+	}
+
+	// 3. Execute the component reconciliation.
+	resCtx := component.ReconcileContext{
+		Client:   r.Client,
+		Scheme:   r.Scheme,
+		Recorder: r.Recorder,
+		Metrics:  r.Metrics,
+		Owner:    owner,
+	}
+
+	return comp.Reconcile(ctx, resCtx)
+}

examples/replicaset-primitive/app/owner.go

@@ -0,0 +1,20 @@
+package app
+
+import (
+	sharedapp "github.com/sourcehawk/operator-component-framework/examples/shared/app"
+)
+
+// ExampleApp re-exports the shared CRD type so callers in this package need no import alias.
+type ExampleApp = sharedapp.ExampleApp
+
+// ExampleAppSpec re-exports the shared spec type.
+type ExampleAppSpec = sharedapp.ExampleAppSpec
+
+// ExampleAppStatus re-exports the shared status type.
+type ExampleAppStatus = sharedapp.ExampleAppStatus
+
+// ExampleAppList re-exports the shared list type.
+type ExampleAppList = sharedapp.ExampleAppList
+
+// AddToScheme registers the ExampleApp types with the given scheme.
+var AddToScheme = sharedapp.AddToScheme

examples/replicaset-primitive/features/mutations.go

@@ -0,0 +1,76 @@
+// Package features provides feature plan mutations for the replicaset-primitive example.
+package features
+
+import (
+	"fmt"
+
+	"github.com/sourcehawk/operator-component-framework/pkg/feature"
+	"github.com/sourcehawk/operator-component-framework/pkg/mutation/editors"
+	"github.com/sourcehawk/operator-component-framework/pkg/mutation/selectors"
+	"github.com/sourcehawk/operator-component-framework/pkg/primitives/replicaset"
+	corev1 "k8s.io/api/core/v1"
+)
+
+// TracingFeature adds a Jaeger sidecar to the replicaset.
+func TracingFeature(enabled bool) replicaset.Mutation {
+	return replicaset.Mutation{
+		Name:    "Tracing",
+		Feature: feature.NewResourceFeature("any", nil).When(enabled),
+		Mutate: func(m *replicaset.Mutator) error {
+			m.EnsureContainer(corev1.Container{
+				Name:  "jaeger-agent",
+				Image: "jaegertracing/jaeger-agent:1.28",
+			})
+
+			m.EnsureContainerEnvVar(corev1.EnvVar{
+				Name:  "JAEGER_AGENT_HOST",
+				Value: "localhost",
+			})
+
+			return nil
+		},
+	}
+}
+
+// MetricsFeature adds an exporter sidecar and some annotations.
+func MetricsFeature(enabled bool, port int) replicaset.Mutation {
+	return replicaset.Mutation{
+		Name:    "Metrics",
+		Feature: feature.NewResourceFeature("any", nil).When(enabled),
+		Mutate: func(m *replicaset.Mutator) error {
+			m.EnsureContainer(corev1.Container{
+				Name:  "prometheus-exporter",
+				Image: "prom/node-exporter:v1.3.1",
+			})
+
+			m.EditPodTemplateMetadata(func(meta *editors.ObjectMetaEditor) error {
+				meta.EnsureAnnotation("prometheus.io/scrape", "true")
+				meta.EnsureAnnotation("prometheus.io/port", fmt.Sprintf("%d", port))
+				return nil
+			})
+
+			return nil
+		},
+	}
+}
+
+// VersionFeature sets the image version and a label.
+func VersionFeature(version string) replicaset.Mutation {
+	return replicaset.Mutation{
+		Name:    "Version",
+		Feature: feature.NewResourceFeature(version, nil),
+		Mutate: func(m *replicaset.Mutator) error {
+			m.EditContainers(selectors.ContainerNamed("app"), func(ce *editors.ContainerEditor) error {
+				ce.Raw().Image = fmt.Sprintf("my-app:%s", version)
+				return nil
+			})
+
+			m.EditObjectMetadata(func(meta *editors.ObjectMetaEditor) error {
+				meta.EnsureLabel("app.kubernetes.io/version", version)
+				return nil
+			})
+
+			return nil
+		},
+	}
+}