const MaxLeaseTTL = 9000000000

const NoLease = LeaseID(0)

var (
	ErrNotPrimary       = errors.New("not a primary lessor")
	ErrLeaseNotFound    = errors.New("lease not found")
	ErrLeaseExists      = errors.New("lease already exists")
	ErrLeaseTTLTooLarge = errors.New("too large lease TTL")
)

type FakeLessor struct{}

type Lease struct {
	ID LeaseID
	// contains filtered or unexported fields
}

type LeaseID int64

type LeaseItem struct {
	Key string
}

type Lessor interface {
	// SetRangeDeleter lets the lessor create TxnDeletes to the store.
	// Lessor deletes the items in the revoked or expired lease by creating
	// new TxnDeletes.
	SetRangeDeleter(rd RangeDeleter)

	// Grant grants a lease that expires at least after TTL seconds.
	Grant(id LeaseID, ttl int64) (*Lease, error)
	// Revoke revokes a lease with given ID. The item attached to the
	// given lease will be removed. If the ID does not exist, an error
	// will be returned.
	Revoke(id LeaseID) error

	// Attach attaches given leaseItem to the lease with given LeaseID.
	// If the lease does not exist, an error will be returned.
	Attach(id LeaseID, items []LeaseItem) error

	// GetLease returns LeaseID for given item.
	// If no lease found, NoLease value will be returned.
	GetLease(item LeaseItem) LeaseID

	// Detach detaches given leaseItem from the lease with given LeaseID.
	// If the lease does not exist, an error will be returned.
	Detach(id LeaseID, items []LeaseItem) error

	// Promote promotes the lessor to be the primary lessor. Primary lessor manages
	// the expiration and renew of leases.
	// Newly promoted lessor renew the TTL of all lease to extend + previous TTL.
	Promote(extend time.Duration)

	// Demote demotes the lessor from being the primary lessor.
	Demote()

	// Renew renews a lease with given ID. It returns the renewed TTL. If the ID does not exist,
	// an error will be returned.
	Renew(id LeaseID) (int64, error)

	// Lookup gives the lease at a given lease id, if any
	Lookup(id LeaseID) *Lease

	// Leases lists all leases.
	Leases() []*Lease

	// ExpiredLeasesC returns a chan that is used to receive expired leases.
	ExpiredLeasesC() <-chan []*Lease

	// Recover recovers the lessor state from the given backend and RangeDeleter.
	Recover(b backend.Backend, rd RangeDeleter)

	// Stop stops the lessor for managing leases. The behavior of calling Stop multiple
	// times is undefined.
	Stop()
}

type RangeDeleter func() TxnDelete

type TxnDelete interface {
	DeleteRange(key, end []byte) (n, rev int64)
	End()
}