seed

type BaseInfo struct {
	// the url of seed file.
	URL string

	// the taskID of seed file.
	TaskID string

	// the header of seed file.
	Header map[string][]string

	// URL may contains some changeful query parameters such as authentication parameters. Dragonfly will
	// filter these parameter via 'filter'. The usage of it is that different URL may generate the same
	// download url.
	Filters []string

	// the full length of seed file.
	FullLength int64

	// Seed will download data from rss which is divided by blocks.
	// And block size is defined by BlockOrder. It should be limited [10, 31].
	BlockOrder uint32

	// expire time duration of seed file.
	ExpireTimeDur time.Duration
}

type Manager interface {
	// Register a seed.
	Register(key string, info BaseInfo) (Seed, error)

	// UnRegister seed by key.
	UnRegister(key string) error

	// RefreshExpireTime refreshes expire time of seed.
	RefreshExpireTime(key string, expireTimeDur time.Duration) error

	// NotifyExpired get the expired chan of seed, it will be notified if seed expired.
	NotifyExpired(key string) (<-chan struct{}, error)

	// Prefetch will add seed to the prefetch list, and then prefetch by the concurrent limit.
	Prefetch(key string, perDownloadSize int64) (<-chan struct{}, error)

	// GetPrefetchResult should be called after notify by prefetch chan.
	GetPrefetchResult(key string) (PreFetchResult, error)

	// SetPrefetchLimit limits the concurrency of prefetching seed.
	// Default is defaultDownloadConcurrency.
	SetConcurrentLimit(limit int) (validLimit int)

	// Get gets the seed by key.
	Get(key string) (Seed, error)

	// List lists the seeds.
	List() ([]Seed, error)

	// Stop stops the SeedManager.
	Stop()
}

type PreFetchResult struct {
	Success bool
	Err     error
	// if canceled, caller need not to do other.
	Canceled bool
}

type Seed interface {
	// Prefetch will start to download seed file to local cache.
	Prefetch(perDownloadSize int64) (<-chan struct{}, error)

	// GetPrefetchResult should be called after notify by prefetch chan.
	GetPrefetchResult() (PreFetchResult, error)

	// Delete will delete the local cache and release the resource.
	Delete() error

	// Download providers the range download, if local cache of seed do not include the range,
	// it will download the range data from rss and reply to request.
	Download(off int64, size int64) (io.ReadCloser, error)

	// stop the internal loop and release execution resource.
	Stop()

	// GetFullSize gets the full size of seed file.
	GetFullSize() int64

	// GetStatus gets the status of seed file.
	GetStatus() string

	// GetURL gets the url of seed file.
	GetURL() string

	// GetHeaders gets the headers of seed file.
	GetHeaders() map[string][]string

	// GetHeaders gets the taskID of seed file.
	GetTaskID() string
}