private bool CanMerge(HistoryPoint newPoint, Stack<HistoryPoint> undostack, TimeSpan mergeTime)
{
if (!undostack.Any())
return false;
var hp = undostack.Peek();
if (!ReferenceEquals(hp.Control, newPoint.Control))
return false;
var dt = newPoint.Timestamp - hp.Timestamp;
return dt < mergeTime;
}
private void Merge(HistoryPoint newPoint, Stack<HistoryPoint> undostack, TimeSpan mergeTime)
{
if (!CanMerge(newPoint, undostack, mergeTime))
throw new InvalidOperationException("Cannot merge call CanMerge() before");
var hp = undostack.Pop();
undostack.Push(newPoint);
}
internal void Update(HistoryPoint historyPoint)
{
var cv = _undoStack.FirstOrDefault(x => x.UpdateReason != UpdateReason.DataUpdated && ReferenceEquals(x.Control, historyPoint.Control));
if (cv != null && Equals(cv.Value, historyPoint.Value))
return;
if (_redoStack.Any())
{
HistoryPoint redoPoint = _redoStack.Peek();
if (ReferenceEquals(redoPoint.Control, historyPoint.Control) && Equals(redoPoint.Value, historyPoint.Value))
return;
}
if (CanMerge(historyPoint, UndoStack, _mergeTime))
{
Merge(historyPoint, UndoStack, _mergeTime);
return;
}
_undoStack.Push(historyPoint);
_redoStack.Clear();
OnOnChanged();
}