/// <summary>Perform removal of the specified thing from our Children.</summary>
/// <param name="thingToRemove">The thing to remove from our Children.</param>
/// <param name="removalEvent">The removal event to work with; must have previously been sent as the request.</param>
/// <param name="multipleParentsBehavior">The multipleParentsBehavior, if applicable.</param>
/// <returns>True if the thing has been successfully removed, else false.</returns>
private bool PerformRemoval(Thing thingToRemove, RemoveChildEvent removalEvent, MultipleParentsBehavior multipleParentsBehavior)
{
if (removalEvent.IsCancelled)
{
return(false);
}
// Send the removal event.
this.Eventing.OnMovementEvent(removalEvent, EventScope.SelfDown);
// If the thing to remove was in our Children collection, remove it.
if (this.Children.Contains(thingToRemove))
{
this.Children.Remove(thingToRemove);
}
// If we don't have a MultipleParentsBehavior, directly remove the one-allowed
// parent ourselves, else use the behavior's logic for adjusting the parents.
if (multipleParentsBehavior == null)
{
thingToRemove.Parent = null;
}
else
{
multipleParentsBehavior.RemoveParent(this);
}
return(true);
}
private RemoveChildEvent RequestRemoval(Thing thingToRemove)
{
// Create and raise a removal event request.
var removeChildEvent = new RemoveChildEvent(thingToRemove);
this.Eventing.OnMovementRequest(removeChildEvent, EventScope.SelfDown);
return(removeChildEvent);
}
// TODO: All things (world, room, item, mob, etc), should all potentially have sub-things
// but it should be up to the code which moves things about to do so intelligently
// (IE should not allow adding an Area inside a Room, etc.) These can be prevented
// either explicitly here, or preferably via event request cancellation.
public bool Add(Thing thing)
{
// No two threads may add/remove any combination of the parent/sub-thing at the same time,
// in order to prevent race conditions resulting in thing-disconnection/duplication/etc.
// TODO: May need to pick a consistent order to apply the locks (like locking the lowest
// alphabetical thing ID's lock first) to prevent possible deadlocks.
// TODO: The whole MultipleParentsBehavior may be too complicated for our actual use cases,
// and we should consider a lighter approach that doesn't track multiple parents, but
// simply lets the thing be a child of multiple locations.
lock (lockObject)
{
lock (thing.lockObject)
{
// If the thing already has a parent, ensure we have permission to continue.
// Presence of MultipleParentsBehavior means we can always add more parents, but
// if it's not present, we have to see if removal would be accepted first.
var multipleParentsBehavior = thing.Behaviors.FindFirst <MultipleParentsBehavior>();
RemoveChildEvent removalRequest = null;
var oldParent = thing.Parent;
if (oldParent != null && multipleParentsBehavior == null)
{
removalRequest = oldParent.RequestRemoval(thing);
if (removalRequest.IsCancelled)
{
return(false);
}
}
var addRequest = RequestAdd(thing);
if (addRequest.IsCancelled)
{
return(false);
}
// If we got this far, both removal (if needed) and add requests were accepted, so
// perform both now and send the confirmation events for any listeners. Removal is
// first, since we don't want to risk accidentally removing from the new parent, etc.
if (removalRequest != null)
{
oldParent.PerformRemoval(thing, removalRequest, multipleParentsBehavior);
}
PerformAdd(thing, addRequest, multipleParentsBehavior);
}
return(true);
}
}
// @@@ All things (world, room, item, mob, etc), should all potentially have sub-things
// but it should be up to the code which moves things about to do so intelligently
// (IE should not allow adding an Area inside a Room, etc.) These can be prevented
// either explicitly here, or preferably via event request cancellation.
public bool Add(Thing thing)
{
// No two threads may add/remove any combination of the parent/sub-thing at the same time,
// in order to prevent race conditions resulting in thing-disconnection/duplication/etc.
lock (this.lockObject)
{
lock (thing.lockObject)
{
// If the thing already has a parent, ensure we have permission to continue.
// Presence of MultipleParentsBehavior means we can always add more parents, but
// if it's not present, we have to see if removal would be accepted first.
var multipleParentsBehavior = thing.Behaviors.FindFirst <MultipleParentsBehavior>();
RemoveChildEvent removalRequest = null;
var oldParent = thing.Parent;
if (oldParent != null && multipleParentsBehavior == null)
{
removalRequest = oldParent.RequestRemoval(thing);
if (removalRequest.IsCancelled)
{
return(false);
}
}
var addRequest = this.RequestAdd(thing);
if (addRequest.IsCancelled)
{
return(false);
}
// If we got this far, both removal (if needed) and add requests were accepted, so
// perform both now and send the confirmation events for any listeners. Removal is
// first, since we don't want to risk accidentally removing from the new parent, etc.
if (removalRequest != null)
{
oldParent.PerformRemoval(thing, removalRequest, multipleParentsBehavior);
}
this.PerformAdd(thing, addRequest, multipleParentsBehavior);
}
return(true);
}
}
