remote

type Backend interface {
	Put(ctx context.Context, key string, r io.Reader, size int64) error
	Get(ctx context.Context, key string) (io.ReadCloser, error)
	List(ctx context.Context, prefix string) ([]Object, error)
	Exists(ctx context.Context, key string) (bool, error)
	Close() error
}

type Object struct {
	Key  string
	Size int64
	// Modified is when the store last wrote this object, when the backend
	// reports it (S3, GCS) and the zero time when it does not. It is how the
	// hub decides an object can no longer change — see RemoteSource.verify.
	Modified time.Time
}

type PutSigner interface {
	SignPut(ctx context.Context, key string, size int64, ttl time.Duration) (*SignedPut, error)
}

type ReadEvent struct {
	Path string `json:"path"`
	// Session is the agent session the read happened in, so the hub can join
	// a run's reads to the writes journal.Op.Session carries. A client string
	// — the hub pins each recorded row to the device it validated, never to
	// anything in this body (see handleReadReport).
	Session string    `json:"session,omitempty"`
	Time    time.Time `json:"time,omitzero"`
}

type ReadReporter interface {
	ReportReads(ctx context.Context, reads []ReadEvent) error
}

type SignedPut struct {
	URL     string            // upload here
	Method  string            // always "PUT"
	Headers map[string]string // headers that must be sent verbatim (they are signed)
	Expires time.Time
}