/// <summary>
/// Roll back the versions of the last changed tiles
/// </summary>
public void Undo()
{
// for multi-undo, we could store prev. changed tiles set in the metadata store, or stack up change sets in ram.
var changed = _lastChangedTiles.ToArray();
var changesMade = false;
foreach (var tile in changed)
{
// if tiles exist for version-1:
// - roll the version back in meta
// - reload tile (purge from cache and flip the reload trigger)
var path = tile.ToString();
var node = _tileStore.Exists(path);
if (node.IsFailure)
{
continue;
}
if (node.ResultData == null)
{
continue;
}
var prevVersion = node.ResultData.CurrentVersion - 1;
if (prevVersion < 1)
{
// undoing the first stroke. Mark it deleted.
var deadNode = new StorageNode {
CurrentVersion = node.ResultData.CurrentVersion, Id = node.ResultData.Id, IsDeleted = true
};
_tileStore.UpdateNode(path, deadNode);
changesMade = true;
}
else
{
var ok = _tileStore.Read(path, "img", prevVersion);
if (ok.IsFailure)
{
continue;
}
var newNode = new StorageNode {
CurrentVersion = prevVersion, Id = node.ResultData.Id, IsDeleted = false
};
_tileStore.UpdateNode(path, newNode);
changesMade = true;
}
}
if (changesMade)
{
ResetCache();
}
// Reset the last update set
// For multi-undo, we should roll back to a previous undo set.
_lastChangedTiles.Clear();
}