/// <summary>
/// Truncates all previous events for instances when a state change occurs
/// </summary>
public void Truncate()
{
HashSet <ModelInstance> removeEventInstances = new HashSet <ModelInstance>();
for (var transaction = this; transaction != null; transaction = transaction.PreviousTransaction)
{
// Process the transaction log in reverse order, searching for changes to remove
var node = events.Last;
while (node != null)
{
var evt = node.Value;
var previous = node.Previous;
if (evt is ModelSaveEvent)
{
ModelSaveEvent saveEvent = (ModelSaveEvent)evt;
removeEventInstances.UnionWith(saveEvent.Added);
removeEventInstances.UnionWith(saveEvent.Deleted);
removeEventInstances.UnionWith(saveEvent.Modified);
transaction.events.Remove(node);
}
else if (removeEventInstances.Contains(evt.Instance))
{
transaction.events.Remove(node);
}
node = previous;
}
}
}
/// <summary>
/// Records <see cref="ModelEvent"/> occurences within the current context.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
void context_Event(object sender, ModelEvent e)
{
// Only track events that change the model.
// Don't track changes to cached objects.
if (e is ITransactedModelEvent && !e.Instance.IsCached)
{
// Track id mappings for new instances created during the transaction
if (e is ModelInitEvent.InitNew)
{
RegisterNewInstance(e.Instance);
}
// Populate save events with ids that have changed during the transaction
else if (e is ModelSaveEvent)
{
HashSet <ModelInstance> added = new HashSet <ModelInstance>();
HashSet <ModelInstance> modified = new HashSet <ModelInstance>();
HashSet <ModelInstance> deleted = new HashSet <ModelInstance>();
for (var transaction = this; transaction != null; transaction = transaction.PreviousTransaction)
{
// Process the transaction log in reverse order, searching for instances
// that were persisted by the save event
for (var node = transaction.events.Last; node != null; node = node.Previous)
{
var evt = node.Value;
// Stop processing if a previous save event is encountered
if (evt is ModelSaveEvent)
{
goto UpdateSave;
}
// Deleted
if (evt.Instance.IsDeleted)
{
deleted.Add(evt.Instance);
}
// Added
else if (evt is ModelInitEvent.InitNew && !evt.Instance.IsNew)
{
added.Add(evt.Instance);
}
// Modified
else if (!evt.Instance.IsNew && !evt.Instance.IsModified)
{
modified.Add(evt.Instance);
}
}
}
UpdateSave : ModelSaveEvent saveEvent = (ModelSaveEvent)e;
saveEvent.Added = added.ToArray();
saveEvent.Deleted = deleted.ToArray();
saveEvent.Modified = modified.Except(saveEvent.Added).Except(saveEvent.Deleted).ToArray();
}
// Add the transacted event to the list of events for the transaction
events.AddLast(e);
}
}
