resource

type Cache struct {
	Dir       string
	HttpDo    func(req *http.Request) (*http.Response, error)
	Progress  Progress
	RetryWait time.Duration
	Writer    io.Writer
}

type Catalog struct {
	Items []Item
}

type Item struct {
	URL   string
	Name  string
	MD5   string
	Size  uint64
	InUse bool
}

type Progress interface {
	io.Writer
	Start(total uint64)
	Add(add uint64)
	End()
	SetLastCompleted()
	ResetCurrent()
}