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());
}
private int GetCurrentPosition(ChangeAwareList <T> target, T item)
{
int index = _sortOptions == SortOptions.UseBinarySearch
? target.BinarySearch(item, _comparer)
: target.IndexOf(item);
if (index < 0)
{
throw new SortException("Current item cannot be found");
}
return(index);
}
private int GetCurrentPosition(ChangeAwareList <T> target, T item)
{
var index = _sortOptions == SortOptions.UseBinarySearch
? target.BinarySearch(item, _comparer)
: target.IndexOf(item);
if (index < 0)
{
throw new SortException($"Cannot find item: {typeof(T).Name} -> {item}");
}
return(index);
}
private int GetCurrentPosition(ChangeAwareList <T> target, T item)
{
int index;
if (_sortOptions == SortOptions.UseBinarySearch)
{
index = target.BinarySearch(item, _comparer);
}
else
{
var index1 = target.IndexOf(item);
index = target.IndexOf(item, _referencEqualityComparer);
Debug.Assert(index == index1);
}
if (index < 0)
{
throw new SortException("Current item cannot be found");
}
return(index);
}
private IChangeSet <T> Reorder(ChangeAwareList <T> target)
{
int index = -1;
foreach (var item in target.OrderBy(t => t, _comparer).ToList())
{
index++;
var existing = target[index];
// if item is in the same place,
if (ReferenceEquals(item, existing))
{
continue;
}
// Cannot use binary search as Resort is implicit of a mutable change
var old = target.IndexOf(item);
target.Move(old, index);
}
return(target.CaptureChanges());
}
private IChangeSet <T> ProcessImpl(ChangeAwareList <T> target, IChangeSet <T> changes)
{
var refreshes = new List <T>(changes.Refreshes);
foreach (var change in changes)
{
switch (change.Reason)
{
case ListChangeReason.Add:
{
var current = change.Item.Current;
Insert(target, current);
break;
}
case ListChangeReason.AddRange:
{
var ordered = change.Range.OrderBy(t => t, _comparer).ToList();
if (target.Count == 0)
{
target.AddRange(ordered);
}
else
{
ordered.ForEach(item => Insert(target, item));
}
break;
}
case ListChangeReason.Remove:
{
var current = change.Item.Current;
Remove(target, current);
break;
}
case ListChangeReason.Refresh:
{
// add to refresh list so position can be calculated
refreshes.Add(change.Item.Current);
// add to current list so downstream operators can receive a refresh
// notification, so get the latest index and pass the index up the chain
var indexed = target.IndexOfOptional(change.Item.Current).ValueOrThrow(() => new SortException($"Cannot find index of {typeof(T).Name} -> {change.Item.Current}. Expected to be in the list"));
target.Refresh(indexed.Item, indexed.Index);
break;
}
case ListChangeReason.Replace:
{
var current = change.Item.Current;
// TODO: check whether an item should stay in the same position
// i.e. update and move
Remove(target, change.Item.Previous.Value);
Insert(target, current);
break;
}
case ListChangeReason.RemoveRange:
{
target.RemoveMany(change.Range);
break;
}
case ListChangeReason.Clear:
{
target.Clear();
break;
}
}
}
// Now deal with refreshes [can be expensive]
foreach (var item in refreshes)
{
var old = target.IndexOf(item);
if (old == -1)
{
continue;
}
int newPosition = GetInsertPositionLinear(target, item);
if (old < newPosition)
{
newPosition--;
}
if (old == newPosition)
{
continue;
}
target.Move(old, newPosition);
}
return(target.CaptureChanges());
}
private PageChangeSet <T> Page(List <T> all, ChangeAwareList <T> paged, IPageRequest request, IChangeSet <T> changeset = null)
{
if (changeset != 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)));
}
