private IChangeSet <T> Page(IChangeSet <T> changeset = null)
{
if (changeset != null)
{
_all.Clone(changeset);
}
var previous = _paged;
int pages = CalculatePages();
int page = _parameters.Page > pages ? pages : _parameters.Page;
int skip = _parameters.Size * (page - 1);
var current = _all.Skip(skip)
.Take(_parameters.Size)
.ToList();
var adds = current.Except(previous);
var removes = previous.Except(current);
_paged.RemoveMany(removes);
adds.ForEach(t =>
{
var index = current.IndexOf(t);
_paged.Insert(index, t);
});
var startIndex = skip;
var moves = changeset.EmptyIfNull()
.Where(change => change.Reason == ListChangeReason.Moved &&
change.MovedWithinRange(startIndex, startIndex + _parameters.Size));
foreach (var change in moves)
{
//check whether an item has moved within the same page
var currentIndex = change.Item.CurrentIndex - startIndex;
var previousIndex = change.Item.PreviousIndex - startIndex;
_paged.Move(previousIndex, currentIndex);
}
//find replaces [Is this ever the case that it can be reached]
for (int i = 0; i < current.Count; i++)
{
var currentItem = current[i];
var previousItem = previous[i];
if (ReferenceEquals(currentItem, previousItem))
{
continue;
}
var index = _paged.IndexOf(currentItem);
_paged.Move(i, index);
}
return(_paged.CaptureChanges());
}
private static IChangeSet <T> Virtualise(List <T> all, ChangeAwareList <T> virtualised, IVirtualRequest request, IChangeSet <T> changeset = null)
{
if (changeset != null)
{
all.Clone(changeset);
}
var previous = virtualised;
var current = all.Skip(request.StartIndex)
.Take(request.Size)
.ToList();
var adds = current.Except(previous);
var removes = previous.Except(current);
virtualised.RemoveMany(removes);
adds.ForEach(t =>
{
var index = current.IndexOf(t);
virtualised.Insert(index, t);
});
var moves = changeset.EmptyIfNull()
.Where(change => change.Reason == ListChangeReason.Moved &&
change.MovedWithinRange(request.StartIndex, request.StartIndex + request.Size));
foreach (var change in moves)
{
//check whether an item has moved within the same page
var currentIndex = change.Item.CurrentIndex - request.StartIndex;
var previousIndex = change.Item.PreviousIndex - request.StartIndex;
virtualised.Move(previousIndex, currentIndex);
}
//find replaces [Is this ever the case that it can be reached]
for (var i = 0; i < current.Count; i++)
{
var currentItem = current[i];
var previousItem = previous[i];
if (ReferenceEquals(currentItem, previousItem))
{
continue;
}
var index = virtualised.IndexOf(currentItem);
virtualised.Move(i, index);
}
return(virtualised.CaptureChanges());
}
public IList <Change <TObject, TKey> > Calculate(IKeyValueCollection <TObject, TKey> currentItems,
IKeyValueCollection <TObject, TKey> previousItems, IChangeSet <TObject, TKey> sourceUpdates)
{
if (currentItems.SortReason == SortReason.ComparerChanged)
{
//clear collection and rebuild
var removed = previousItems.Select((item, index) => new Change <TObject, TKey>(ChangeReason.Remove, item.Key, item.Value, index));
var newitems = currentItems.Select((item, index) => new Change <TObject, TKey>(ChangeReason.Add, item.Key, item.Value, index));
return(new List <Change <TObject, TKey> >(removed.Union(newitems)));
}
var previousList = previousItems.ToList();
var keyComparer = new KeyComparer <TObject, TKey>();
var removes = previousItems.Except(currentItems, keyComparer).ToList();
var adds = currentItems.Except(previousItems, keyComparer).ToList();
var inbothKeys = previousItems.Intersect(currentItems, keyComparer)
.Select(x => x.Key).ToHashSet();
var result = new List <Change <TObject, TKey> >();
foreach (var remove in removes)
{
int index = previousList.IndexOf(remove);
previousList.RemoveAt(index);
result.Add(new Change <TObject, TKey>(ChangeReason.Remove, remove.Key, remove.Value, index));
}
foreach (var add in adds)
{
//find new insert position
int index = previousList.BinarySearch(add, currentItems.Comparer);
int insertIndex = ~index;
previousList.Insert(insertIndex, add);
result.Add(new Change <TObject, TKey>(ChangeReason.Add, add.Key, add.Value, insertIndex));
}
//Adds and removes ahave been accounted for
//so check whether anything in the remaining change set have been moved ot updated
var remainingItems = sourceUpdates
.EmptyIfNull()
.Where(u => inbothKeys.Contains(u.Key) &&
(u.Reason == ChangeReason.Update ||
u.Reason == ChangeReason.Moved ||
u.Reason == ChangeReason.Evaluate))
.ToList();
foreach (var change in remainingItems)
{
if (change.Reason == ChangeReason.Update)
{
var current = new KeyValuePair <TKey, TObject>(change.Key, change.Current);
var previous = new KeyValuePair <TKey, TObject>(change.Key, change.Previous.Value);
//remove from the actual index
var removeIndex = previousList.IndexOf(previous);
previousList.RemoveAt(removeIndex);
//insert into the desired index
int desiredIndex = previousList.BinarySearch(current, currentItems.Comparer);
int insertIndex = ~desiredIndex;
previousList.Insert(insertIndex, current);
result.Add(new Change <TObject, TKey>(ChangeReason.Update, current.Key, current.Value,
previous.Value, insertIndex, removeIndex));
}
else if (change.Reason == ChangeReason.Moved)
{
//TODO: We have the index already, would be more efficient to calculate new position from the original index
var current = new KeyValuePair <TKey, TObject>(change.Key, change.Current);
var previousindex = previousList.IndexOf(current);
int desiredIndex = previousList.BinarySearch(current, currentItems.Comparer);
int insertIndex = ~desiredIndex;
//this should never be the case, but check anyway
if (previousindex == insertIndex)
{
continue;
}
if (insertIndex < 0)
{
throw new SortException("Cannot determine current index");
}
previousList.RemoveAt(previousindex);
previousList.Insert(insertIndex, current);
result.Add(new Change <TObject, TKey>(current.Key, current.Value, insertIndex, previousindex));
}
else
{
//TODO: re-evaluate to check whether item should be moved
result.Add(change);
}
}
//Alternative to evaluate is to check order
var evaluates = remainingItems.Where(c => c.Reason == ChangeReason.Evaluate)
.OrderByDescending(x => new KeyValuePair <TKey, TObject>(x.Key, x.Current), currentItems.Comparer)
.ToList();
//calculate moves. Very expensive operation
//TODO: Try and make this better
foreach (var u in evaluates)
{
var current = new KeyValuePair <TKey, TObject>(u.Key, u.Current);
var old = previousList.IndexOf(current);
if (old == -1)
{
continue;
}
int newposition = GetInsertPositionLinear(previousList, current, currentItems.Comparer);
if (old < newposition)
{
newposition--;
}
if (old == newposition)
{
continue;
}
previousList.RemoveAt(old);
previousList.Insert(newposition, current);
result.Add(new Change <TObject, TKey>(u.Key, u.Current, newposition, old));
}
return(result);
}
private static PageChangeSet <T> Page(List <T> all, ChangeAwareList <T> paged, IPageRequest request, IChangeSet <T>?changeSet = null)
{
if (changeSet is not null)
{
all.Clone(changeSet);
}
var previous = paged;
int pages = CalculatePages(all, request);
int page = request.Page > pages ? pages : request.Page;
int skip = request.Size * (page - 1);
var current = all.Skip(skip)
.Take(request.Size)
.ToList();
var adds = current.Except(previous);
var removes = previous.Except(current);
paged.RemoveMany(removes);
adds.ForEach(t =>
{
var index = current.IndexOf(t);
paged.Insert(index, t);
});
var startIndex = skip;
var moves = changeSet.EmptyIfNull()
.Where(change => change.Reason == ListChangeReason.Moved &&
change.MovedWithinRange(startIndex, startIndex + request.Size));
foreach (var change in moves)
{
// check whether an item has moved within the same page
var currentIndex = change.Item.CurrentIndex - startIndex;
var previousIndex = change.Item.PreviousIndex - startIndex;
paged.Move(previousIndex, currentIndex);
}
// find replaces [Is this ever the case that it can be reached]
for (int i = 0; i < current.Count; i++)
{
var currentItem = current[i];
var previousItem = previous[i];
if (ReferenceEquals(currentItem, previousItem))
{
continue;
}
var index = paged.IndexOf(currentItem);
paged.Move(i, index);
}
var changed = paged.CaptureChanges();
return(new PageChangeSet <T>(changed, new PageResponse(paged.Count, page, all.Count, pages)));
}
