private IChangeSet <IGroup <TObject, TGroupKey> > Process(ChangeAwareList <IGroup <TObject, TGroupKey> > result, IDictionary <TGroupKey, Group <TObject, TGroupKey> > groupCollection, IChangeSet <ItemWithValue <TObject, TGroupKey> > changes)
{
//TODO.This flattened enumerator is inefficient as range operations are lost.
//maybe can infer within each grouping whether we can regroup i.e. Another enumerator!!!
foreach (var grouping in changes.Unified().GroupBy(change => change.Current.Value))
{
//lookup group and if created, add to result set
var currentGroup = grouping.Key;
var lookup = GetCache(groupCollection, currentGroup);
var groupCache = lookup.Group;
if (lookup.WasCreated)
{
result.Add(groupCache);
}
//start a group edit session, so all changes are batched
groupCache.Edit(
list =>
{
//iterate through the group's items and process
foreach (var change in grouping)
{
switch (change.Reason)
{
case ListChangeReason.Add:
{
list.Add(change.Current.Item);
break;
}
case ListChangeReason.Replace:
{
var previousItem = change.Previous.Value.Item;
var previousGroup = change.Previous.Value.Value;
//check whether an item changing has resulted in a different group
if (previousGroup.Equals(currentGroup))
{
//find and replace
var index = list.IndexOf(previousItem);
list[index] = change.Current.Item;
}
else
{
//add to new group
list.Add(change.Current.Item);
//remove from old group
groupCollection.Lookup(previousGroup)
.IfHasValue(g =>
{
g.Edit(oldList => oldList.Remove(previousItem));
if (g.List.Count != 0)
{
return;
}
groupCollection.Remove(g.GroupKey);
result.Remove(g);
});
}
break;
}
case ListChangeReason.Remove:
{
list.Remove(change.Current.Item);
break;
}
case ListChangeReason.Clear:
{
list.Clear();
break;
}
}
}
});
if (groupCache.List.Count == 0)
{
groupCollection.Remove(groupCache.GroupKey);
result.Remove(groupCache);
}
}
return(result.CaptureChanges());
}
private void Transform(IChangeSet <TSource> changes)
{
if (changes == null)
{
throw new ArgumentNullException(nameof(changes));
}
_transformed.EnsureCapacityFor(changes);
changes.ForEach(item =>
{
switch (item.Reason)
{
case ListChangeReason.Add:
{
var change = item.Item;
if (change.CurrentIndex < 0 | change.CurrentIndex >= _transformed.Count)
{
_transformed.Add(_containerFactory(change.Current));
}
else
{
_transformed.Insert(change.CurrentIndex, _containerFactory(change.Current));
}
break;
}
case ListChangeReason.AddRange:
{
_transformed.AddOrInsertRange(item.Range.Select(_containerFactory), item.Range.Index);
break;
}
case ListChangeReason.Replace:
{
var change = item.Item;
if (change.CurrentIndex == change.PreviousIndex)
{
_transformed[change.CurrentIndex] = _containerFactory(change.Current);
}
else
{
_transformed.RemoveAt(change.PreviousIndex);
_transformed.Insert(change.CurrentIndex, _containerFactory(change.Current));
}
}
break;
case ListChangeReason.Remove:
{
var change = item.Item;
bool hasIndex = change.CurrentIndex >= 0;
if (hasIndex)
{
_transformed.RemoveAt(item.Item.CurrentIndex);
}
else
{
var toremove = _transformed.FirstOrDefault(t => ReferenceEquals(t.Source, t));
if (toremove != null)
{
_transformed.Remove(toremove);
}
}
}
break;
case ListChangeReason.RemoveRange:
{
if (item.Range.Index >= 0)
{
_transformed.RemoveRange(item.Range.Index, item.Range.Count);
}
else
{
var toremove = _transformed.Where(t => ReferenceEquals(t.Source, t)).ToArray();
_transformed.RemoveMany(toremove);
}
}
break;
case ListChangeReason.Clear:
{
//i.e. need to store transformed reference so we can correctly clear
var toClear = new Change <TransformedItemContainer>(ListChangeReason.Clear, _transformed);
_transformed.ClearOrRemoveMany(toClear);
}
break;
case ListChangeReason.Moved:
{
var change = item.Item;
bool hasIndex = change.CurrentIndex >= 0;
if (!hasIndex)
{
throw new UnspecifiedIndexException("Cannot move as an index was not specified");
}
var collection = _transformed as IExtendedList <TransformedItemContainer>;
if (collection != null)
{
collection.Move(change.PreviousIndex, change.CurrentIndex);
}
else
{
var current = _transformed[change.PreviousIndex];
_transformed.RemoveAt(change.PreviousIndex);
_transformed.Insert(change.CurrentIndex, current);
}
break;
}
}
});
}
