Make Task, Container, Image interface types

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

client.go

@@ -83,12 +83,12 @@ type Client struct {
 }
 
 // Containers returns all containers created in containerd
-func (c *Client) Containers(ctx context.Context) ([]*Container, error) {
+func (c *Client) Containers(ctx context.Context) ([]Container, error) {
 	r, err := c.containers().List(ctx, &containers.ListContainersRequest{})
 	if err != nil {
 		return nil, err
 	}
-	var out []*Container
+	var out []Container
 	for _, container := range r.Containers {
 		out = append(out, containerFromProto(c, container))
 	}
@@ -119,9 +119,9 @@ func WithExistingRootFS(id string) NewContainerOpts {
 
 // WithNewRootFS allocates a new snapshot to be used by the container as the
 // root filesystem in read-write mode
-func WithNewRootFS(id string, image *Image) NewContainerOpts {
+func WithNewRootFS(id string, i Image) NewContainerOpts {
 	return func(ctx context.Context, client *Client, c *containers.Container) error {
-		diffIDs, err := image.i.RootFS(ctx, client.content())
+		diffIDs, err := i.(*image).i.RootFS(ctx, client.content())
 		if err != nil {
 			return err
 		}
@@ -135,9 +135,9 @@ func WithNewRootFS(id string, image *Image) NewContainerOpts {
 
 // WithNewReadonlyRootFS allocates a new snapshot to be used by the container as the
 // root filesystem in read-only mode
-func WithNewReadonlyRootFS(id string, image *Image) NewContainerOpts {
+func WithNewReadonlyRootFS(id string, i Image) NewContainerOpts {
 	return func(ctx context.Context, client *Client, c *containers.Container) error {
-		diffIDs, err := image.i.RootFS(ctx, client.content())
+		diffIDs, err := i.(*image).i.RootFS(ctx, client.content())
 		if err != nil {
 			return err
 		}
@@ -158,7 +158,7 @@ func WithRuntime(name string) NewContainerOpts {
 
 // NewContainer will create a new container in container with the provided id
 // the id must be unique within the namespace
-func (c *Client) NewContainer(ctx context.Context, id string, spec *specs.Spec, opts ...NewContainerOpts) (*Container, error) {
+func (c *Client) NewContainer(ctx context.Context, id string, spec *specs.Spec, opts ...NewContainerOpts) (Container, error) {
 	data, err := json.Marshal(spec)
 	if err != nil {
 		return nil, err
@@ -258,7 +258,7 @@ func (s *snapshotUnpacker) getLayers(ctx context.Context, image images.Image) ([
 	return layers, nil
 }
 
-func (c *Client) Pull(ctx context.Context, ref string, opts ...PullOpts) (*Image, error) {
+func (c *Client) Pull(ctx context.Context, ref string, opts ...PullOpts) (Image, error) {
 	pullCtx := defaultPullContext()
 	for _, o := range opts {
 		if err := o(c, pullCtx); err != nil {
@@ -296,7 +296,7 @@ func (c *Client) Pull(ctx context.Context, ref string, opts ...PullOpts) (*Image
 			return nil, err
 		}
 	}
-	return &Image{
+	return &image{
 		client: c,
 		i:      i,
 	}, nil

container.go

@@ -10,27 +10,37 @@ import (
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 )
 
-func containerFromProto(client *Client, c containers.Container) *Container {
+type Container interface {
-	return &Container{
+	ID() string
+	Delete(context.Context) error
+	NewTask(context.Context, IOCreation) (Task, error)
+	Spec() (*specs.Spec, error)
+	Task() Task
+}
+
+func containerFromProto(client *Client, c containers.Container) *container {
+	return &container{
 		client: client,
 		c:      c,
 	}
 }
 
-type Container struct {
+var _ = (Container)(&container{})
+
+type container struct {
 	client *Client
 
 	c    containers.Container
-	task *Task
+	task *task
 }
 
 // ID returns the container's unique id
-func (c *Container) ID() string {
+func (c *container) ID() string {
 	return c.c.ID
 }
 
 // Spec returns the current OCI specification for the container
-func (c *Container) Spec() (*specs.Spec, error) {
+func (c *container) Spec() (*specs.Spec, error) {
 	var s specs.Spec
 	if err := json.Unmarshal(c.c.Spec.Value, &s); err != nil {
 		return nil, err
@@ -40,7 +50,7 @@ func (c *Container) Spec() (*specs.Spec, error) {
 
 // Delete deletes an existing container
 // an error is returned if the container has running tasks
-func (c *Container) Delete(ctx context.Context) error {
+func (c *container) Delete(ctx context.Context) error {
 	// TODO: should the client be the one removing resources attached
 	// to the container at the moment before we have GC?
 	err := c.client.snapshotter().Remove(ctx, c.c.RootFS)
@@ -53,11 +63,11 @@ func (c *Container) Delete(ctx context.Context) error {
 	return err
 }
 
-func (c *Container) Task() *Task {
+func (c *container) Task() Task {
 	return c.task
 }
 
-func (c *Container) NewTask(ctx context.Context, ioCreate IOCreation) (*Task, error) {
+func (c *container) NewTask(ctx context.Context, ioCreate IOCreation) (Task, error) {
 	i, err := ioCreate()
 	if err != nil {
 		return nil, err
@@ -85,7 +95,7 @@ func (c *Container) NewTask(ctx context.Context, ioCreate IOCreation) (*Task, er
 	if err != nil {
 		return nil, err
 	}
-	t := &Task{
+	t := &task{
 		client:      c.client,
 		io:          i,
 		containerID: response.ContainerID,

image.go

@@ -2,7 +2,12 @@ package containerd
 
 import "github.com/containerd/containerd/images"
 
-type Image struct {
+type Image interface {
+}
+
+var _ = (Image)(&image{})
+
+type image struct {
 	client *Client
 
 	i images.Image

spec_unix.go

@@ -183,8 +183,9 @@ func WithHostNamespace(ns specs.LinuxNamespaceType) SpecOpts {
 	}
 }
 
-func WithImage(ctx context.Context, image *Image) SpecOpts {
+func WithImage(ctx context.Context, i Image) SpecOpts {
 	return func(s *specs.Spec) error {
+		image := i.(*image)
 		store := image.client.content()
 		ic, err := image.i.Config(ctx, store)
 		if err != nil {

task.go

@@ -10,7 +10,7 @@ import (
 	"syscall"
 
 	"github.com/containerd/containerd/api/services/execution"
-	"github.com/containerd/containerd/api/types/task"
+	taskapi "github.com/containerd/containerd/api/types/task"
 	"github.com/containerd/fifo"
 )
 
@@ -158,7 +158,20 @@ func (g *wgCloser) Close() error {
 	return nil
 }
 
-type Task struct {
+type Task interface {
+	Delete(context.Context) (uint32, error)
+	Kill(context.Context, syscall.Signal) error
+	Pause(context.Context) error
+	Resume(context.Context) error
+	Pid() uint32
+	Start(context.Context) error
+	Status(context.Context) (string, error)
+	Wait(context.Context) (uint32, error)
+}
+
+var _ = (Task)(&task{})
+
+type task struct {
 	client *Client
 
 	io          *IO
@@ -167,18 +180,18 @@ type Task struct {
 }
 
 // Pid returns the pid or process id for the task
-func (t *Task) Pid() uint32 {
+func (t *task) Pid() uint32 {
 	return t.pid
 }
 
-func (t *Task) Start(ctx context.Context) error {
+func (t *task) Start(ctx context.Context) error {
 	_, err := t.client.tasks().Start(ctx, &execution.StartRequest{
 		ContainerID: t.containerID,
 	})
 	return err
 }
 
-func (t *Task) Kill(ctx context.Context, s syscall.Signal) error {
+func (t *task) Kill(ctx context.Context, s syscall.Signal) error {
 	_, err := t.client.tasks().Kill(ctx, &execution.KillRequest{
 		Signal:      uint32(s),
 		ContainerID: t.containerID,
@@ -189,21 +202,21 @@ func (t *Task) Kill(ctx context.Context, s syscall.Signal) error {
 	return err
 }
 
-func (t *Task) Pause(ctx context.Context) error {
+func (t *task) Pause(ctx context.Context) error {
 	_, err := t.client.tasks().Pause(ctx, &execution.PauseRequest{
 		ContainerID: t.containerID,
 	})
 	return err
 }
 
-func (t *Task) Resume(ctx context.Context) error {
+func (t *task) Resume(ctx context.Context) error {
 	_, err := t.client.tasks().Resume(ctx, &execution.ResumeRequest{
 		ContainerID: t.containerID,
 	})
 	return err
 }
 
-func (t *Task) Status(ctx context.Context) (string, error) {
+func (t *task) Status(ctx context.Context) (string, error) {
 	r, err := t.client.tasks().Info(ctx, &execution.InfoRequest{
 		ContainerID: t.containerID,
 	})
@@ -214,7 +227,7 @@ func (t *Task) Status(ctx context.Context) (string, error) {
 }
 
 // Wait is a blocking call that will wait for the task to exit and return the exit status
-func (t *Task) Wait(ctx context.Context) (uint32, error) {
+func (t *task) Wait(ctx context.Context) (uint32, error) {
 	events, err := t.client.tasks().Events(ctx, &execution.EventsRequest{})
 	if err != nil {
 		return 255, err
@@ -224,7 +237,7 @@ func (t *Task) Wait(ctx context.Context) (uint32, error) {
 		if err != nil {
 			return 255, err
 		}
-		if e.Type != task.Event_EXIT {
+		if e.Type != taskapi.Event_EXIT {
 			continue
 		}
 		if e.ID == t.containerID && e.Pid == t.pid {
@@ -236,7 +249,7 @@ func (t *Task) Wait(ctx context.Context) (uint32, error) {
 // Delete deletes the task and its runtime state
 // it returns the exit status of the task and any errors that were encountered
 // during cleanup
-func (t *Task) Delete(ctx context.Context) (uint32, error) {
+func (t *task) Delete(ctx context.Context) (uint32, error) {
 	cerr := t.io.Close()
 	r, err := t.client.tasks().Delete(ctx, &execution.DeleteRequest{
 		ContainerID: t.containerID,