/// <summary>
/// Sorts using the specified sorter. Will return null if there are no changes
/// </summary>
/// <param name="sortReason">The sort reason.</param>
/// <param name="changes">The changes.</param>
/// <returns></returns>
private ISortedChangeSet <TObject, TKey> DoSort(SortReason sortReason, IChangeSet <TObject, TKey> changes = null)
{
if (changes != null)
{
_cache.Clone(changes);
changes = _cache.CaptureChanges();
_haveReceivedData = true;
if (_comparer == null)
{
return(null);
}
}
//if the comparer is not set, return nothing
if (_comparer == null || !_haveReceivedData)
{
return(null);
}
if (!_initialised)
{
sortReason = SortReason.InitialLoad;
_initialised = true;
}
else if (changes != null && (_resetThreshold > 0 && changes.Count >= _resetThreshold))
{
sortReason = SortReason.Reset;
}
IChangeSet <TObject, TKey> changeSet;
switch (sortReason)
{
case SortReason.InitialLoad:
{
//For the first batch, changes may have arrived before the comparer was set.
//therefore infer the first batch of changes from the cache
_calculator = new IndexCalculator <TObject, TKey>(_comparer, _optimisations);
changeSet = _calculator.Load(_cache);
}
break;
case SortReason.Reset:
{
_calculator.Reset(_cache);
changeSet = changes;
}
break;
case SortReason.DataChanged:
{
changeSet = _calculator.Calculate(changes);
}
break;
case SortReason.ComparerChanged:
{
changeSet = _calculator.ChangeComparer(_comparer);
if (_resetThreshold > 0 && _cache.Count >= _resetThreshold)
{
sortReason = SortReason.Reset;
_calculator.Reset(_cache);
}
else
{
sortReason = SortReason.Reorder;
changeSet = _calculator.Reorder();
}
}
break;
case SortReason.Reorder:
{
changeSet = _calculator.Reorder();
}
break;
default:
throw new ArgumentOutOfRangeException(nameof(sortReason));
}
Debug.Assert(changeSet != null, "changeSet != null");
if ((sortReason == SortReason.InitialLoad || sortReason == SortReason.DataChanged) &&
changeSet.Count == 0)
{
return(null);
}
if (sortReason == SortReason.Reorder && changeSet.Count == 0)
{
return(null);
}
_sorted = new KeyValueCollection <TObject, TKey>(_calculator.List, _comparer, sortReason, _optimisations);
return(new SortedChangeSet <TObject, TKey>(_sorted, changeSet));
}
