storage

type CancelFunc func()

type ConsistentIndexGetter interface {
	// ConsistentIndex returns the consistent index of current executing entry.
	ConsistentIndex() uint64
}

type ConsistentWatchableKV interface {
	WatchableKV
}

type KV interface {
	// Rev returns the current revision of the KV.
	Rev() int64

	// Range gets the keys in the range at rangeRev.
	// If rangeRev <=0, range gets the keys at currentRev.
	// If `end` is nil, the request returns the key.
	// If `end` is not nil, it gets the keys in range [key, range_end).
	// Limit limits the number of keys returned.
	// If the required rev is compacted, ErrCompacted will be returned.
	Range(key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64, err error)

	// Put puts the given key,value into the store.
	// A put also increases the rev of the store, and generates one event in the event history.
	Put(key, value []byte) (rev int64)

	// DeleteRange deletes the given range from the store.
	// A deleteRange increases the rev of the store if any key in the range exists.
	// The number of key deleted will be returned.
	// It also generates one event for each key delete in the event history.
	// if the `end` is nil, deleteRange deletes the key.
	// if the `end` is not nil, deleteRange deletes the keys in range [key, range_end).
	DeleteRange(key, end []byte) (n, rev int64)

	// TxnBegin begins a txn. Only Txn prefixed operation can be executed, others will be blocked
	// until txn ends. Only one on-going txn is allowed.
	// TxnBegin returns an int64 txn ID.
	// All txn prefixed operations with same txn ID will be done with the same rev.
	TxnBegin() int64
	// TxnEnd ends the on-going txn with txn ID. If the on-going txn ID is not matched, error is returned.
	TxnEnd(txnID int64) error
	TxnRange(txnID int64, key, end []byte, limit, rangeRev int64) (kvs []storagepb.KeyValue, rev int64, err error)
	TxnPut(txnID int64, key, value []byte) (rev int64, err error)
	TxnDeleteRange(txnID int64, key, end []byte) (n, rev int64, err error)

	Compact(rev int64) error

	// Get the hash of KV state.
	// This method is designed for consistency checking purpose.
	Hash() (uint32, error)

	// Snapshot snapshots the full KV store.
	Snapshot() Snapshot

	// Commit commits txns into the underlying backend.
	Commit()

	Restore() error
	Close() error
}

type Snapshot backend.Snapshot

type Watchable interface {
	// NewWatcher returns a Watcher that can be used to
	// watch events happened or happending on the KV.
	NewWatcher() Watcher
}

type WatchableKV interface {
	KV
	Watchable
}

type Watcher interface {
	// Watch watches the events happening or happened on the given key
	// or key prefix from the given startRev.
	// The whole event history can be watched unless compacted.
	// If `prefix` is true, watch observes all events whose key prefix could be the given `key`.
	// If `startRev` <=0, watch observes events after currentRev.
	Watch(key []byte, prefix bool, startRev int64) CancelFunc

	// Chan returns a chan. All watched events will be sent to the returned chan.
	Chan() <-chan storagepb.Event

	// Close closes the WatchChan and release all related resources.
	Close()
}