feat: implement pod primitive

docs/primitives.md

@@ -156,6 +156,7 @@ have been applied. This means a single mutation can safely add a container and t
 | `pkg/primitives/statefulset`        | Workload    | [statefulset.md](primitives/statefulset.md)               |
 | `pkg/primitives/replicaset`         | Workload    | [replicaset.md](primitives/replicaset.md)                 |
 | `pkg/primitives/daemonset`          | Workload    | [daemonset.md](primitives/daemonset.md)                   |
+| `pkg/primitives/pod`                | Workload    | [pod.md](primitives/pod.md)                               |
 | `pkg/primitives/job`                | Task        | [job.md](primitives/job.md)                               |
 | `pkg/primitives/cronjob`            | Integration | [cronjob.md](primitives/cronjob.md)                       |
 | `pkg/primitives/configmap`          | Static      | [configmap.md](primitives/configmap.md)                   |

docs/primitives/pod.md

@@ -0,0 +1,226 @@
+# Pod Primitive
+
+The `pod` primitive is the framework's built-in workload abstraction for managing Kubernetes `Pod` resources directly.
+It integrates fully with the component lifecycle and provides a mutation API for managing containers, pod specs, and
+metadata.
+
+Pods are rarely managed directly by operators; this primitive is provided for completeness and for operators that manage
+pod objects (e.g. debugging utilities, node-local agents).
+
+## Capabilities
+
+| Capability            | Detail                                                                                             |
+| --------------------- | -------------------------------------------------------------------------------------------------- |
+| **Health tracking**   | Monitors pod phase and container statuses; reports `Healthy`, `Creating`, `Updating`, or `Failing` |
+| **Graceful rollouts** | Detects degraded or down states via grace status handler                                           |
+| **Suspension**        | Deletes the pod (pods cannot be paused); reports `Suspended`                                       |
+| **Mutation pipeline** | Typed editors for metadata, pod spec, and containers                                               |
+
+## Building a Pod Primitive
+
+```go
+import "github.com/sourcehawk/operator-component-framework/pkg/primitives/pod"
+
+base := &corev1.Pod{
+    ObjectMeta: metav1.ObjectMeta{
+        Name:      "debug-pod",
+        Namespace: owner.Namespace,
+    },
+    Spec: corev1.PodSpec{
+        Containers: []corev1.Container{
+            {
+                Name:  "debug",
+                Image: "busybox:latest",
+            },
+        },
+    },
+}
+
+resource, err := pod.NewBuilder(base).
+    WithMutation(MyFeatureMutation(owner.Spec.Version)).
+    Build()
+```
+
+## Mutations
+
+Mutations are the primary mechanism for modifying a `Pod` 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) pod.Mutation {
+    return pod.Mutation{
+        Name:    "my-feature",
+        Feature: feature.NewResourceFeature(version, nil), // always enabled
+        Mutate: func(m *pod.Mutator) error {
+            // record edits here
+            return nil
+        },
+    }
+}
+```
+
+Mutations are applied in the order they are registered with the builder. If one mutation depends on a change made by
+another, register the dependency first.
+
+### Boolean-gated mutations
+
+Use `When(bool)` to gate a mutation on a runtime condition:
+
+```go
+func DebugMutation(version string, enabled bool) pod.Mutation {
+    return pod.Mutation{
+        Name:    "debug-mode",
+        Feature: feature.NewResourceFeature(version, nil).When(enabled),
+        Mutate: func(m *pod.Mutator) error {
+            m.EnsureContainerEnvVar(corev1.EnvVar{Name: "DEBUG", Value: "true"})
+            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. This ensures structural consistency across mutations.
+
+| Step | Category                   | What it affects                                                         |
+| ---- | -------------------------- | ----------------------------------------------------------------------- |
+| 1    | Object metadata edits      | Labels and annotations on the `Pod` object                              |
+| 2    | Pod spec edits             | Volumes, tolerations, node selectors, service account, security context |
+| 3    | Regular container presence | Adding or removing containers from `spec.containers`                    |
+| 4    | Regular container edits    | Env vars, args, resources (snapshot taken after step 3)                 |
+| 5    | Init container presence    | Adding or removing containers from `spec.initContainers`                |
+| 6    | Init container edits       | Env vars, args, resources (snapshot taken after step 5)                 |
+
+Container edits (steps 4 and 6) are evaluated against a snapshot taken _after_ presence operations in the same mutation.
+This means a single mutation can add a container and then configure it without selector resolution issues.
+
+**Kubernetes immutability note:** most fields in `Pod.spec` are immutable after creation, including the overall
+structure of `spec.containers` and `spec.initContainers` and the majority of per-container fields (such as `env`,
+`args`, resources, ports, and probes). Presence operations such as `EnsureContainer` / `RemoveContainer` (and the
+corresponding init container operations) are intended for use when constructing a new Pod or when recreating the Pod,
+not for in-place updates to an existing Pod. If a mutation attempts to add or remove containers on an existing Pod, the
+Kubernetes API server will reject the update. In practice, the set of fields that can be updated in-place on an existing
+Pod is very small (primarily container images, plus a few feature-gated fields such as resources with in-place resize);
+treat Pods as effectively immutable and use delete-and-recreate when you need to change other container attributes.
+
+## Editors
+
+### 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`. `RemoveTolerations` accepts a predicate
+function (`match func(corev1.Toleration) bool`) and removes all tolerations for which `match` returns `true`.
+
+```go
+m.EditPodSpec(func(e *editors.PodSpecEditor) error {
+    e.SetServiceAccountName("my-service-account")
+    e.EnsureVolume(corev1.Volume{
+        Name: "config",
+        VolumeSource: corev1.VolumeSource{
+            ConfigMap: &corev1.ConfigMapVolumeSource{
+                LocalObjectReference: corev1.LocalObjectReference{Name: "app-config"},
+            },
+        },
+    })
+    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"})
+    e.EnsureArg("--metrics-port=9090")
+    e.SetResourceLimit(corev1.ResourceCPU, resource.MustParse("500m"))
+    return nil
+})
+```
+
+For fields not covered by the typed API (such as volume mounts), use `Raw()`:
+
+```go
+m.EditContainers(selectors.ContainerNamed("app"), func(e *editors.ContainerEditor) error {
+    e.Raw().VolumeMounts = append(e.Raw().VolumeMounts, corev1.VolumeMount{
+        Name:      "config",
+        MountPath: "/etc/config",
+    })
+    return nil
+})
+```
+
+### ObjectMetaEditor
+
+Modifies labels and annotations via `m.EditObjectMetadata`.
+
+Available methods: `EnsureLabel`, `RemoveLabel`, `EnsureAnnotation`, `RemoveAnnotation`, `Raw`.
+
+```go
+m.EditObjectMetadata(func(e *editors.ObjectMetaEditor) error {
+    e.EnsureLabel("app.kubernetes.io/version", version)
+    return nil
+})
+```
+
+### Raw Escape Hatch
+
+All editors provide a `.Raw()` method for direct access to the underlying Kubernetes struct when the typed API is
+insufficient. The mutation remains scoped to the editor's target — you cannot accidentally modify unrelated parts of the
+spec.
+
+```go
+m.EditContainers(selectors.ContainerNamed("app"), func(e *editors.ContainerEditor) error {
+    e.Raw().SecurityContext = &corev1.SecurityContext{
+        ReadOnlyRootFilesystem: ptr.To(true),
+    }
+    return nil
+})
+```
+
+## Convenience Methods
+
+The `Mutator` also exposes convenience wrappers that target all containers at once:
+
+| Method                        | Equivalent to                                                 |
+| ----------------------------- | ------------------------------------------------------------- |
+| `EnsureContainerEnvVar(ev)`   | `EditContainers(AllContainers(), ...)` → `EnsureEnvVar(ev)`   |
+| `RemoveContainerEnvVar(name)` | `EditContainers(AllContainers(), ...)` → `RemoveEnvVar(name)` |
+| `EnsureContainerArg(arg)`     | `EditContainers(AllContainers(), ...)` → `EnsureArg(arg)`     |
+| `RemoveContainerArg(arg)`     | `EditContainers(AllContainers(), ...)` → `RemoveArg(arg)`     |
+
+## Suspension
+
+Pods cannot be paused. The default behavior deletes the pod when the component is suspended.
+
+- `DefaultDeleteOnSuspendHandler`: returns `true` — pod is deleted on suspend.
+- `DefaultSuspendMutationHandler`: no-op (deletion is handled by the framework).
+- `DefaultSuspensionStatusHandler`: always returns `{Suspended, "Pod deleted on suspend"}`.
+
+## Guidance
+
+**`Feature: nil` applies unconditionally.** Omit `Feature` (leave it nil) for mutations that should always run. Use
+`feature.NewResourceFeature(version, constraints)` when version-based gating is needed, and chain `.When(bool)` for
+boolean conditions.
+
+**Register mutations in dependency order.** If mutation B relies on a container added by mutation A, register A first.
+The internal ordering within each mutation handles intra-mutation dependencies automatically.
+
+**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/pod-primitive/README.md

@@ -0,0 +1,32 @@
+# Pod Primitive Example
+
+This example demonstrates the usage of the `pod` primitive within the operator component framework. It shows how to
+manage a Kubernetes Pod as a component of a larger application, utilizing features like:
+
+- **Base Construction**: Initializing a Pod with basic metadata and spec.
+- **Feature Mutations**: Applying version-gated or conditional metadata changes (labels) using the `Mutator`.
+- **Suspension**: Deleting the pod when the component is suspended (pods cannot be paused).
+- **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`: label mutations applied to the Pod using the `Mutator`.
+- `resources/`: Contains the central `NewPodResource` factory that assembles all features using the `pod.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/pod-primitive/main.go
+```
+
+This will:
+
+1. Initialize a fake Kubernetes client.
+2. Create an `ExampleApp` owner object.
+3. Reconcile the `ExampleApp` components through multiple spec changes.
+4. Print the resulting status conditions.

examples/pod-primitive/app/controller.go

@@ -0,0 +1,54 @@
+// Package app provides a sample controller using the pod 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
+
+	// NewPodResource is a factory function to create the pod resource.
+	// This allows us to inject the resource construction logic.
+	NewPodResource 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 pod resource for this owner.
+	podResource, err := r.NewPodResource(owner)
+	if err != nil {
+		return err
+	}
+
+	// 2. Build the component that manages the pod.
+	comp, err := component.NewComponentBuilder().
+		WithName("example-app").
+		WithConditionType("AppReady").
+		WithResource(podResource, 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/pod-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/pod-primitive/features/mutations.go

@@ -0,0 +1,47 @@
+// Package features provides sample mutations for the pod primitive example.
+//
+// These examples only mutate object metadata because most Pod spec fields
+// are immutable after creation. Kubernetes does allow a small set of in-place
+// updates (notably container images), but other fields such as env, args, and
+// resources require the Pod to be deleted and recreated.
+package features
+
+import (
+	"github.com/sourcehawk/operator-component-framework/pkg/feature"
+	"github.com/sourcehawk/operator-component-framework/pkg/mutation/editors"
+	"github.com/sourcehawk/operator-component-framework/pkg/primitives/pod"
+)
+
+// TracingFeature marks the pod as tracing-enabled via metadata.
+// Controllers or sidecar injectors can watch the label and handle
+// any required Pod replacement or injection.
+func TracingFeature(enabled bool) pod.Mutation {
+	return pod.Mutation{
+		Name:    "Tracing",
+		Feature: feature.NewResourceFeature("any", nil).When(enabled),
+		Mutate: func(m *pod.Mutator) error {
+			m.EditObjectMetadata(func(meta *editors.ObjectMetaEditor) error {
+				meta.EnsureLabel("sidecar.jaegertracing.io/inject", "true")
+				return nil
+			})
+			return nil
+		},
+	}
+}
+
+// VersionFeature records the desired version on the pod as a label.
+// It avoids mutating container images directly; while Kubernetes allows
+// in-place image updates, this example keeps mutations in metadata only.
+func VersionFeature(version string) pod.Mutation {
+	return pod.Mutation{
+		Name:    "Version",
+		Feature: feature.NewResourceFeature(version, nil),
+		Mutate: func(m *pod.Mutator) error {
+			m.EditObjectMetadata(func(meta *editors.ObjectMetaEditor) error {
+				meta.EnsureLabel("app.kubernetes.io/version", version)
+				return nil
+			})
+			return nil
+		},
+	}
+}