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 IChangeSet <T> Virtualise(List <T> all, ChangeAwareList <T> virtualised, IChangeSet <T> changeset = null)
{
if (changeset != null)
{
all.Clone(changeset);
}
var previous = virtualised;
var current = all.Skip(_parameters.StartIndex)
.Take(_parameters.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(_parameters.StartIndex, _parameters.StartIndex + _parameters.Size));
foreach (var change in moves)
{
//check whether an item has moved within the same page
var currentIndex = change.Item.CurrentIndex - _parameters.StartIndex;
var previousIndex = change.Item.PreviousIndex - _parameters.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 void Transform(ChangeAwareList <TransformedItemContainer> transformed, IChangeSet <TSource> changes)
{
if (changes == null)
{
throw new ArgumentNullException(nameof(changes));
}
transformed.EnsureCapacityFor(changes);
foreach (var item in changes)
{
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;
}
}
}
}
private void Insert(ChangeAwareList <T> target, T item)
{
var index = GetInsertPosition(target, item);
target.Insert(index, item);
}
private void Insert(T item)
{
var index = GetInsertPosition(item);
_innerList.Insert(index, item);
}
