// ReparentShard creates the reparenting action and launches a goroutine
// to coordinate the procedure.
//
//
// leaveMasterReadOnly: leave the master in read-only mode, even
//   though all the other necessary updates have been made.
// forceReparentToCurrentMaster: mostly for test setups, this can
//   cause data loss.
func (wr *Wrangler) ReparentShard(keyspace, shard string, masterElectTabletAlias topo.TabletAlias, leaveMasterReadOnly, forceReparentToCurrentMaster bool) error {
	// lock the shard
	actionNode := actionnode.ReparentShard(masterElectTabletAlias)
	lockPath, err := wr.lockShard(keyspace, shard, actionNode)
	if err != nil {
		return err
	}

	// do the work
	err = wr.reparentShardLocked(keyspace, shard, masterElectTabletAlias, leaveMasterReadOnly, forceReparentToCurrentMaster)

	// and unlock
	return wr.unlockShard(keyspace, shard, actionNode, lockPath, err)
}

// EmergencyReparentShard will make the provided tablet the master for
// the shard, when the old master is completely unreachable.
func (wr *Wrangler) EmergencyReparentShard(ctx context.Context, keyspace, shard string, masterElectTabletAlias *pb.TabletAlias, waitSlaveTimeout time.Duration) error {
	// lock the shard
	actionNode := actionnode.ReparentShard(emergencyReparentShardOperation, masterElectTabletAlias)
	lockPath, err := wr.lockShard(ctx, keyspace, shard, actionNode)
	if err != nil {
		return err
	}

	// Create reusable Reparent event with available info
	ev := &events.Reparent{}

	// do the work
	err = wr.emergencyReparentShardLocked(ctx, ev, keyspace, shard, masterElectTabletAlias, waitSlaveTimeout)
	if err != nil {
		event.DispatchUpdate(ev, "failed EmergencyReparentShard: "+err.Error())
	} else {
		event.DispatchUpdate(ev, "finished EmergencyReparentShard")
	}

	// and unlock
	return wr.unlockShard(ctx, keyspace, shard, actionNode, lockPath, err)
}