const (
	// DefaultQuotaBytes is the number of bytes the backend Size may
	// consume before exceeding the space quota.
	DefaultQuotaBytes = int64(2 * 1024 * 1024 * 1024) // 2GB
	// MaxQuotaBytes is the maximum number of bytes suggested for a backend
	// quota. A larger quota may lead to degraded performance.
	MaxQuotaBytes = int64(8 * 1024 * 1024 * 1024) // 8GB
)

var (

	// InitialMmapSize is the initial size of the mmapped region. Setting this larger than
	// the potential max db size can prevent writer from blocking reader.
	// This only works for linux.
	InitialMmapSize = int64(10 * 1024 * 1024 * 1024)
)

type Backend interface {
	BatchTx() BatchTx
	Snapshot() Snapshot
	Hash(ignores map[IgnoreKey]struct{}) (uint32, error)
	// Size returns the current size of the backend.
	Size() int64
	Defrag() error
	ForceCommit()
	Close() error
}

type BatchTx interface {
	Lock()
	Unlock()
	UnsafeCreateBucket(name []byte)
	UnsafePut(bucketName []byte, key []byte, value []byte)
	UnsafeSeqPut(bucketName []byte, key []byte, value []byte)
	UnsafeRange(bucketName []byte, key, endKey []byte, limit int64) (keys [][]byte, vals [][]byte)
	UnsafeDelete(bucketName []byte, key []byte)
	UnsafeForEach(bucketName []byte, visitor func(k, v []byte) error) error
	Commit()
	CommitAndStop()
}

type IgnoreKey struct {
	Bucket string
	Key    string
}

type Snapshot interface {
	// Size gets the size of the snapshot.
	Size() int64
	// WriteTo writes the snapshot into the given writer.
	WriteTo(w io.Writer) (n int64, err error)
	// Close closes the snapshot.
	Close() error
}