public bool TryAddOrUpdate(TEntity entity, out IEnumerable <TEntity> entitiesToAdd, out IEnumerable <TEntity> entitiesToRemove)
{
var newCellHash = this.GetHash(entity);
SpatialGridCell oldCell = null;
entitiesToAdd = Enumerable.Empty <TEntity>();
entitiesToRemove = Enumerable.Empty <TEntity>();
var regInfo = this.entities.AddOrUpdate(
entity.Id,
(id) => new EntityRegistrationInfo(entity, this.GetCell(newCellHash)),
(id, oldRegInfo) =>
{
oldCell = oldRegInfo.Cell;
if (newCellHash != oldCell.Hash)
{
oldRegInfo.Cell = this.GetCell(newCellHash);
}
return(oldRegInfo);
});
// At this point we have three possible states:
// 1. Entity was registered on the grid for the first time
// 2. Entity remains on the same cell
// 3. Entity moved to the other cell
if (oldCell != null && oldCell.Hash == newCellHash)
{
// Entity stays on the same cell, no need to update
return(false);
}
IEnumerable <SpatialGridCell> newCellBlock = this.GetCellWithNeighbors(newCellHash).ToList();
if (oldCell != null)
{
// Entity moved to the other cell
oldCell.Remove(entity);
var oldCellBlock = this.GetCellWithNeighbors(oldCell.Hash).ToList();
entitiesToRemove = oldCellBlock.Except(newCellBlock).SelectMany(cell => cell.Entities).ToList();
newCellBlock = newCellBlock.Except(oldCellBlock);
}
entitiesToAdd = newCellBlock.SelectMany(cell => cell.Entities).ToList();
regInfo.Cell.Register(entity);
if (oldCell == null)
{
// New entity registered on the grid
this.EntityRegistered?.Invoke(this, new EntityEventArgs <TEntityId, TEntity>(entity));
}
return(true);
}
public EntityRegistrationInfo(TEntity entity, SpatialGridCell cell)
{
this.Entity = entity;
this.Cell = cell;
}
