const (
	StateStart       = "start-container"
	StatePause       = "pause"
	StateResume      = "resume"
	StateExit        = "exit"
	StateRestore     = "restore"
	StateExitProcess = "exit-process"
	StateOOM         = "oom" // fake state
)

const (
	// InitFriendlyName is the name given in the lookup map of processes
	// for the first process started in a container.
	InitFriendlyName = "init"
)

type Backend interface {
	StateChanged(containerID string, state StateInfo) error
}

type Client interface {
	GetServerVersion(ctx context.Context) (*ServerVersion, error)
	Create(containerID string, checkpoint string, checkpointDir string, spec specs.Spec, attachStdio StdioCallback, options ...CreateOption) error
	Signal(containerID string, sig int) error
	SignalProcess(containerID string, processFriendlyName string, sig int) error
	AddProcess(ctx context.Context, containerID, processFriendlyName string, process Process, attachStdio StdioCallback) (int, error)
	Resize(containerID, processFriendlyName string, width, height int) error
	Pause(containerID string) error
	Resume(containerID string) error
	Restore(containerID string, attachStdio StdioCallback, options ...CreateOption) error
	Stats(containerID string) (*Stats, error)
	GetPidsForContainer(containerID string) ([]int, error)
	Summary(containerID string) ([]Summary, error)
	UpdateResources(containerID string, resources Resources) error
	CreateCheckpoint(containerID string, checkpointID string, checkpointDir string, exit bool) error
	DeleteCheckpoint(containerID string, checkpointID string, checkpointDir string) error
	ListCheckpoints(containerID string, checkpointDir string) (*Checkpoints, error)
}

type CommonStateInfo struct {
	State     string
	Pid       uint32
	ExitCode  uint32
	ProcessID string
}

type CreateOption interface {
	Apply(interface{}) error
}

type IOPipe struct {
	Stdin    io.WriteCloser
	Stdout   io.ReadCloser
	Stderr   io.ReadCloser
	Terminal bool // Whether stderr is connected on Windows
}

type Remote interface {
	// Client returns a new Client instance connected with given Backend.
	Client(Backend) (Client, error)
	// Cleanup stops containerd if it was started by libcontainerd.
	// Note this is not used on Windows as there is no remote containerd.
	Cleanup()
	// UpdateOptions allows various remote options to be updated at runtime.
	UpdateOptions(...RemoteOption) error
}

type RemoteOption interface {
	Apply(Remote) error
}

type ServerVersion struct {
	containerd.GetServerVersionResponse
}

type StdioCallback func(IOPipe) error