const (
	StateStart        = "start-container"
	StatePause        = "pause"
	StateResume       = "resume"
	StateExit         = "exit"
	StateRestart      = "restart"
	StateRestore      = "restore"
	StateStartProcess = "start-process"
	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 {
	Create(containerID string, spec 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) 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
}

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 StdioCallback func(IOPipe) error