/// <summary>
/// Constructs an instance of <see cref="VirtualizingCacheBlock{T}"/>.
/// </summary>
/// <param name="range">The range of the block.</param>
/// <param name="items">The items the block holds.</param>
public VirtualizingCacheBlock(IndexRange range, T[] items)
{
_items = items;
Range = range;
Requests = Enumerable.Empty <VirtualizingCacheBlockRequest <T> >();
}
/// <summary>
/// Gets a slice of the block's items based on a given subrange.
/// </summary>
/// <param name="subrange">The range describing the slice to get.</param>
/// <returns>A <see cref="Span{T}"/> holding the slice.</returns>
/// <exception cref="ArgumentOutOfRangeException"/>
public Span <T> Slice(IndexRange subrange) => Range.Slice(_items, subrange);
/// <summary>
/// Transfers to another request with a given effective range.
/// </summary>
/// <param name="effectiveRange">The effective range of the other request.</param>
/// <returns></returns>
public VirtualizingCacheBlockRequest <T> Transfer(IndexRange effectiveRange)
{
return(new VirtualizingCacheBlockRequest <T>(FullRange, effectiveRange, WhenItemsLoaded));
}
/// <summary>
/// Applies the change to an array of selected ranges.
/// </summary>
/// <param name="e">The change.</param>
/// <param name="oldSelection">The array of selection.</param>
/// <returns>A new array of selected ranges reflecting the change.</returns>
public static IndexRange[] ApplyToSelection(this NotifyCollectionChangedEventArgs e, IndexRange[] oldSelection)
{
if (oldSelection.Length == 0)
{
return(oldSelection);
}
var newSelection = new List <IndexRange>(oldSelection);
switch (e.Action)
{
case NotifyCollectionChangedAction.Add:
{
var searchResult = newSelection.Search(e.NewStartingIndex, IndexRangeSearchApproximation.NearestRight);
if (searchResult.IsFound)
{
var affectedRange = newSelection[searchResult.Index];
if (e.NewStartingIndex > affectedRange.FirstIndex)
{
newSelection[searchResult.Index] = new IndexRange(affectedRange.FirstIndex, e.NewStartingIndex - 1);
newSelection.Insert(searchResult.Index + 1, new IndexRange(e.NewStartingIndex + 1, affectedRange.LastIndex + 1));
newSelection.Shift(1, searchResult.Index + 2);
}
else
{
newSelection.Shift(1, searchResult.Index);
}
}
else
{
newSelection.Shift(1, searchResult.Index);
}
}
break;
case NotifyCollectionChangedAction.Remove:
{
var searchResult = newSelection.Search(e.OldStartingIndex, IndexRangeSearchApproximation.NearestRight);
if (searchResult.IsFound)
{
var affectedRange = newSelection[searchResult.Index];
if (affectedRange.Length > 1)
{
newSelection[searchResult.Index] = affectedRange.ShrinkLast(1);
}
else
{
newSelection.RemoveAt(searchResult.Index);
}
newSelection.Shift(-1, searchResult.Index + 1);
}
else
{
newSelection.Shift(-1, searchResult.Index);
if (searchResult.Index > 0)
{
var nearestLeftRange = newSelection[searchResult.Index - 1];
if (nearestLeftRange.TryUnion(newSelection[searchResult.Index], ref nearestLeftRange))
{
newSelection[searchResult.Index - 1] = nearestLeftRange;
newSelection.RemoveAt(searchResult.Index);
}
}
}
}
break;
case NotifyCollectionChangedAction.Move:
{
var searchResult = newSelection.Search(e.OldStartingIndex, IndexRangeSearchApproximation.NearestRight);
var previouslySelected = false;
if (searchResult.IsFound)
{
var affectedRange = newSelection[searchResult.Index];
if (affectedRange.Length > 1)
{
newSelection[searchResult.Index] = affectedRange.ShrinkLast(1);
}
else
{
newSelection.RemoveAt(searchResult.Index);
}
newSelection.Shift(-1, searchResult.Index + 1);
previouslySelected = true;
}
else
{
newSelection.Shift(-1, searchResult.Index);
if (searchResult.Index > 0)
{
var nearestLeftRange = newSelection[searchResult.Index - 1];
if (nearestLeftRange.TryUnion(newSelection[searchResult.Index], ref nearestLeftRange))
{
newSelection[searchResult.Index - 1] = nearestLeftRange;
newSelection.RemoveAt(searchResult.Index);
}
}
}
searchResult = newSelection.Search(e.NewStartingIndex, IndexRangeSearchApproximation.NearestRight);
if (searchResult.IsFound)
{
var affectedRange = newSelection[searchResult.Index];
if (previouslySelected)
{
newSelection[searchResult.Index] = affectedRange.ExpandLast(1);
newSelection.Shift(1, searchResult.Index + 1);
}
else
{
if (e.NewStartingIndex > affectedRange.FirstIndex)
{
newSelection[searchResult.Index] = new IndexRange(affectedRange.FirstIndex, e.NewStartingIndex - 1);
newSelection.Insert(searchResult.Index + 1, new IndexRange(e.NewStartingIndex + 1, affectedRange.LastIndex + 1));
newSelection.Shift(1, searchResult.Index + 2);
}
else
{
newSelection.Shift(1, searchResult.Index);
}
}
}
else
{
if (previouslySelected)
{
var newRange = new IndexRange(e.NewStartingIndex, e.NewStartingIndex);
if (searchResult.Index == -1 || searchResult.Index > 0)
{
var nearestLeftIndex = searchResult.Index == -1
? newSelection.Count - 1
: searchResult.Index - 1;
if (newRange.TryUnion(newSelection[nearestLeftIndex], ref newRange))
{
newSelection[nearestLeftIndex] = newRange;
newSelection.Shift(1, nearestLeftIndex + 1);
}
else
{
newSelection.Insert(nearestLeftIndex + 1, newRange);
newSelection.Shift(1, nearestLeftIndex + 2);
}
}
else
{
newSelection.Insert(searchResult.Index, newRange);
newSelection.Shift(1, searchResult.Index + 1);
}
}
else
{
newSelection.Shift(1, searchResult.Index);
}
}
}
break;
}
return(newSelection.ToArray());
}
/// <summary>
/// Constructs a new instance of <see cref="VirtualizingCacheItemsLoadedEvent{T}"/>.
/// </summary>
/// <param name="range"></param>
/// <param name="block"></param>
public VirtualizingCacheItemsLoadedEvent(IndexRange range, VirtualizingCacheBlock <T> block)
{
Range = range;
Block = block;
}
