const (
	// Use ConcurrentReadTx and the txReadBuffer is copied
	ConcurrentReadTxMode = ReadTxMode(1)
	// Use backend ReadTx and txReadBuffer is not copied
	SharedBufReadTxMode = ReadTxMode(2)
)

var (
	ErrCompacted = errors.New("mvcc: required revision has been compacted")
	ErrFutureRev = errors.New("mvcc: required revision is a future revision")
)

var (
	ErrWatcherNotExist    = errors.New("mvcc: watcher does not exist")
	ErrEmptyWatcherRange  = errors.New("mvcc: watcher range is empty")
	ErrWatcherDuplicateID = errors.New("mvcc: duplicate watch ID provided on the WatchStream")
)

var ErrRevisionNotFound = errors.New("mvcc: revision not found")

type BucketKey struct {
	Revision
	// contains filtered or unexported fields
}

type FilterFunc func(e *mvccpb.Event) bool

type HashStorage interface {
	// Hash computes the hash of the whole backend keyspace,
	// including key, lease, and other buckets in storage.
	// This is designed for testing ONLY!
	// Do not rely on this in production with ongoing transactions,
	// since Hash operation does not hold MVCC locks.
	// Use "HashByRev" method instead for "key" bucket consistency checks.
	Hash() (hash uint32, revision int64, err error)

	// HashByRev computes the hash of all MVCC revisions up to a given revision.
	HashByRev(rev int64) (hash KeyValueHash, currentRev int64, err error)

	// Store adds hash value in local cache, allowing it to be returned by HashByRev.
	Store(valueHash KeyValueHash)

	// Hashes returns list of up to `hashStorageMaxSize` newest previously stored hashes.
	Hashes() []KeyValueHash
}

type KV interface {
	ReadView
	WriteView

	// Read creates a read transaction.
	Read(mode ReadTxMode, trace *traceutil.Trace) TxnRead

	// Write creates a write transaction.
	Write(trace *traceutil.Trace) TxnWrite

	// HashStorage returns HashStorage interface for KV storage.
	HashStorage() HashStorage

	// Compact frees all superseded keys with revisions less than rev.
	Compact(trace *traceutil.Trace, rev int64) (<-chan struct{}, error)

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

	// Restore restores the KV store from a backend.
	Restore(b backend.Backend) error
	Close() error
}

type KeyValueHash struct {
	Hash            uint32
	CompactRevision int64
	Revision        int64
}

type RangeOptions struct {
	Limit          int64
	Rev            int64
	CountOnly      bool
	FastKeysOnly   bool
	WithTotalCount bool
}

type RangeResult struct {
	KVs   []*mvccpb.KeyValue
	Rev   int64
	Count int
}

type ReadTxMode uint32

type ReadView interface {
	// FirstRev returns the first KV revision at the time of opening the txn.
	// After a compaction, the first revision increases to the compaction
	// revision.
	FirstRev() int64

	// Rev returns the revision of the KV at the time of opening the txn.
	Rev() int64

	// Range gets the keys in the range at rangeRev.
	// The returned rev is the current revision of the KV when the operation is executed.
	// If rangeRev <=0, range gets the keys at currentRev.
	// If `end` is nil, the request returns the key.
	// If `end` is not nil and not empty, it gets the keys in range [key, range_end).
	// If `end` is not nil and empty, it gets the keys greater than or equal to key.
	// Limit limits the number of keys returned.
	// If the required rev is compacted, ErrCompacted will be returned.
	Range(ctx context.Context, key, end []byte, ro RangeOptions) (r *RangeResult, err error)
}

type Revision struct {
	// Main is the main revision of a set of changes that happen atomically.
	Main int64
	// Sub is the sub revision of a change in a set of changes that happen
	// atomically. Each change has different increasing sub revision in that
	// set.
	Sub int64
}

type StoreConfig struct {
	CompactionBatchLimit    int
	CompactionSleepInterval time.Duration
}

type TxnRead interface {
	ReadView
	// End marks the transaction is complete and ready to commit.
	End()
}

type TxnWrite interface {
	TxnRead
	WriteView
	// Changes gets the changes made since opening the write txn.
	Changes() []*mvccpb.KeyValue
}

type WatchID int64

type WatchResponse struct {
	// WatchID is the WatchID of the watcher this response sent to.
	WatchID WatchID

	// Events contains all the events that needs to send.
	Events []*mvccpb.Event

	// Revision is the revision of the KV when the watchResponse is created.
	// For a normal response, the revision should be the same as the last
	// modified revision inside Events. For a delayed response to a unsynced
	// watcher, the revision is greater than the last modified revision
	// inside Events.
	Revision int64

	// CompactRevision is set when the watcher is cancelled due to compaction.
	CompactRevision int64
}

type WatchStream interface {
	// Watch creates a watcher. The watcher watches the events happening or
	// happened on the given key or range [key, end) from the given startRev.
	//
	// The whole event history can be watched unless compacted.
	// If "startRev" <=0, watch observes events after currentRev.
	//
	// The returned "id" is the ID of this watcher. It appears as WatchID
	// in events that are sent to the created watcher through stream channel.
	// The watch ID is used when it's not equal to AutoWatchID. Otherwise,
	// an auto-generated watch ID is returned.
	Watch(ctx context.Context, id WatchID, key, end []byte, startRev int64, fcs ...FilterFunc) (WatchID, error)

	// Chan returns a chan. All watch response will be sent to the returned chan.
	Chan() <-chan WatchResponse

	// RequestProgress requests the progress of the watcher with given ID. The response
	// will only be sent if the watcher is currently synced.
	// The responses will be sent through the WatchRespone Chan attached
	// with this stream to ensure correct ordering.
	// The responses contains no events. The revision in the response is the progress
	// of the watchers since the watcher is currently synced.
	RequestProgress(id WatchID)

	// RequestProgressAll requests a progress notification for all
	// watchers sharing the stream.  If all watchers are synced, a
	// progress notification with watch ID -1 will be sent to an
	// arbitrary watcher of this stream, and the function returns
	// true.
	RequestProgressAll() bool

	// Cancel cancels a watcher by giving its ID. If watcher does not exist, an error will be
	// returned.
	Cancel(id WatchID) error

	// Close closes Chan and release all related resources.
	Close()

	// Rev returns the current revision of the KV the stream watches on.
	Rev() int64
}

type Watchable interface {
	// NewWatchStream returns a WatchStream that can be used to
	// watch events happened or happening on the KV.
	NewWatchStream() WatchStream
}

type WatchableKV interface {
	KV
	Watchable
}

type WriteView interface {
	// 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.
	// The returned rev is the current revision of the KV when the operation is executed.
	// 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)

	// Put puts the given key, value into the store. Put also takes additional argument lease to
	// attach a lease to a key-value pair as meta-data. KV implementation does not validate the lease
	// id.
	// A put also increases the rev of the store, and generates one event in the event history.
	// The returned rev is the current revision of the KV when the operation is executed.
	Put(key, value []byte, lease lease.LeaseID) (rev int64)
}