var (
	ErrNoPluginType = errors.New("plugin: no type")
	ErrNoPluginID   = errors.New("plugin: no id")

	// SkipPlugin is used when a plugin is not initialized and should not be loaded,
	// this allows the plugin loader differentiate between a plugin which is configured
	// not to load and one that fails to load.
	SkipPlugin = errors.New("skip plugin")
)

type Differ interface {
	Apply(ctx context.Context, desc ocispec.Descriptor, mount []mount.Mount) (ocispec.Descriptor, error)
	DiffMounts(ctx context.Context, lower, upper []mount.Mount, media, ref string) (ocispec.Descriptor, error)
}

type InitContext struct {
	Root    string
	State   string
	Address string
	Context context.Context
	Config  interface{}
	Events  *events.Exchange
	// contains filtered or unexported fields
}

type PluginType string

const (
	RuntimePlugin     PluginType = "io.containerd.runtime.v1"
	GRPCPlugin        PluginType = "io.containerd.grpc.v1"
	SnapshotPlugin    PluginType = "io.containerd.snapshotter.v1"
	TaskMonitorPlugin PluginType = "io.containerd.monitor.v1"
	DiffPlugin        PluginType = "io.containerd.differ.v1"
	MetadataPlugin    PluginType = "io.containerd.metadata.v1"
	ContentPlugin     PluginType = "io.containerd.content.v1"
)

type Registration struct {
	Type     PluginType
	ID       string
	Config   interface{}
	Requires []PluginType
	Init     func(*InitContext) (interface{}, error)
	// contains filtered or unexported fields
}

type Service interface {
	Register(*grpc.Server) error
}