private IChangeSet <IGrouping <TObject, TGroupKey> > Process(ChangeAwareList <IGrouping <TObject, TGroupKey> > result, IDictionary <TGroupKey, GroupContainer> allGroupings, IChangeSet <ItemWithGroupKey> changes)
{
//need to keep track of effected groups to calculate correct notifications
var initialStateOfGroups = new Dictionary <TGroupKey, IGrouping <TObject, TGroupKey> >();
foreach (var grouping in Enumerable.GroupBy(changes.Unified(), change => change.Current.Group))
{
//lookup group and if created, add to result set
var currentGroup = grouping.Key;
var groupContainer = GetGroup(allGroupings, currentGroup);
void GetInitialState()
{
if (!initialStateOfGroups.ContainsKey(grouping.Key))
{
initialStateOfGroups[grouping.Key] = GetGroupState(groupContainer);
}
}
var listToModify = groupContainer.List;
//iterate through the group's items and process
foreach (var change in grouping)
{
switch (change.Reason)
{
case ListChangeReason.Add:
{
GetInitialState();
listToModify.Add(change.Current.Item);
break;
}
case ListChangeReason.Refresh:
{
var previousItem = change.Current.Item;
var previousGroup = change.Current.PrevousGroup.Value;
var currentItem = change.Current.Item;
//check whether an item changing has resulted in a different group
if (!previousGroup.Equals(currentGroup))
{
GetInitialState();
//add to new group
listToModify.Add(currentItem);
//remove from old group
allGroupings.Lookup(previousGroup)
.IfHasValue(g =>
{
if (!initialStateOfGroups.ContainsKey(g.Key))
{
initialStateOfGroups[g.Key] = GetGroupState(g.Key, g.List);
}
g.List.Remove(previousItem);
});
}
break;
}
case ListChangeReason.Replace:
{
GetInitialState();
var previousItem = change.Previous.Value.Item;
var previousGroup = change.Previous.Value.Group;
//check whether an item changing has resulted in a different group
if (previousGroup.Equals(currentGroup))
{
//find and replace
var index = listToModify.IndexOf(previousItem);
listToModify[index] = change.Current.Item;
}
else
{
//add to new group
listToModify.Add(change.Current.Item);
//remove from old group
allGroupings.Lookup(previousGroup)
.IfHasValue(g =>
{
if (!initialStateOfGroups.ContainsKey(g.Key))
{
initialStateOfGroups[g.Key] = GetGroupState(g.Key, g.List);
}
g.List.Remove(previousItem);
});
}
break;
}
case ListChangeReason.Remove:
{
GetInitialState();
listToModify.Remove(change.Current.Item);
break;
}
case ListChangeReason.Clear:
{
GetInitialState();
listToModify.Clear();
break;
}
}
}
}
return(CreateChangeSet(result, allGroupings, initialStateOfGroups));
}
