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 IChangeSet <T> Reorder(ChangeAwareList <T> target)
{
int index = -1;
var sorted = target.OrderBy(t => t, _comparer).ToList();
foreach (var item in sorted)
{
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());
}
