/// <summary>
/// Initializes <see cref="CollectionSegment" />.
/// </summary>
/// <param name="items">
/// The items that belong to this page.
/// </param>
/// <param name="info">
/// Additional information about this page.
/// </param>
/// <param name="getTotalCount">
/// A delegate to request the the total count.
/// </param>
public CollectionSegment(
IReadOnlyCollection<T> items,
CollectionSegmentInfo info,
Func<CancellationToken, ValueTask<int>> getTotalCount)
: base(new CollectionWrapper(items), info, getTotalCount)
{
Items = items;
}
/// <summary>
/// Initializes <see cref="CollectionSegment" />.
/// </summary>
/// <param name="items">
/// The items that belong to this page.
/// </param>
/// <param name="info">
/// Additional information about this page.
/// </param>
/// <param name="getTotalCount">
/// A delegate to request the the total count.
/// </param>
public CollectionSegment(
IReadOnlyCollection <object> items,
CollectionSegmentInfo info,
Func <CancellationToken, ValueTask <int> > getTotalCount)
{
Items = items ??
throw new ArgumentNullException(nameof(items));
Info = info;
_getTotalCount = getTotalCount ??
throw new ArgumentNullException(nameof(getTotalCount));
}
public void CreateCollectionSegment_ItemsNull_ArgumentNullException()
{
// arrange
var pageInfo = new CollectionSegmentInfo(true, true);
// act
Action a = () => new CollectionSegment <string>(
null, pageInfo, ct => throw new NotSupportedException());
// assert
Assert.Throws <ArgumentNullException>(a);
}
public void CreateCollectionSegment_PageInfoAndItems_PassedCorrectly()
{
// arrange
var pageInfo = new CollectionSegmentInfo(true, true);
var items = new List <string>();
// act
var collection = new CollectionSegment(
items,
pageInfo,
ct => throw new NotSupportedException());
// assert
Assert.Equal(pageInfo, collection.Info);
Assert.Equal(items, collection.Items);
}
protected override async ValueTask <CollectionSegment> SliceAsync(
IResolverContext context,
object source,
OffsetPagingArguments arguments)
{
IQueryable <TItemType> queryable = source switch
{
IQueryable <TItemType> q => q,
IEnumerable <TItemType> e => e.AsQueryable(),
_ => throw new GraphQLException("Cannot handle the specified data source.")
};
IQueryable <TItemType> original = queryable;
if (arguments.Skip.HasValue)
{
queryable = queryable.Skip(arguments.Skip.Value);
}
queryable = queryable.Take(arguments.Take + 1);
List <TItemType> items =
await ExecuteQueryableAsync(queryable, context.RequestAborted)
.ConfigureAwait(false);
var pageInfo = new CollectionSegmentInfo(
items.Count == arguments.Take + 1,
(arguments.Skip ?? 0) > 0);
if (items.Count > arguments.Take)
{
items.RemoveAt(arguments.Take);
}
return(new CollectionSegment((IReadOnlyCollection <object>)items, pageInfo, CountAsync));
async ValueTask <int> CountAsync(CancellationToken cancellationToken) =>
await Task.Run(original.Count, cancellationToken).ConfigureAwait(false);
}
protected override async ValueTask <CollectionSegment> SliceAsync(
IResolverContext context,
object source,
OffsetPagingArguments arguments)
{
IQueryable <TItemType> queryable = source switch
{
IQueryable <TItemType> q => q,
IEnumerable <TItemType> e => e.AsQueryable(),
_ => throw new GraphQLException("Cannot handle the specified data source.")
};
IQueryable <TItemType> original = queryable;
if (arguments.Skip.HasValue)
{
queryable = queryable.Skip(arguments.Skip.Value);
}
queryable = queryable.Take(arguments.Take + 1);
List <TItemType> items =
await ExecuteQueryableAsync(queryable, context.RequestAborted)
.ConfigureAwait(false);
var pageInfo = new CollectionSegmentInfo(
items.Count == arguments.Take + 1,
(arguments.Skip ?? 0) > 0);
if (items.Count > arguments.Take)
{
items.RemoveAt(arguments.Take);
}
Func <CancellationToken, ValueTask <int> > getTotalCount =
ct => throw new InvalidOperationException();
// TotalCount is one of the heaviest operations. It is only necessary to load totalCount
// when it is enabled (IncludeTotalCount) and when it is contained in the selection set.
if (IncludeTotalCount &&
context.Field.Type is ObjectType objectType &&
context.FieldSelection.SelectionSet is {} selectionSet)
{
IReadOnlyList <IFieldSelection> selections = context
.GetSelections(objectType, selectionSet, true);
var includeTotalCount = false;
for (var i = 0; i < selections.Count; i++)
{
if (selections[i].Field.Name.Value is "totalCount")
{
includeTotalCount = true;
break;
}
}
// When totalCount is included in the selection set we prefetch it, then capture the
// count in a variable, to pass it into the clojure
if (includeTotalCount)
{
var captureCount = original.Count();
getTotalCount = ct => new ValueTask <int>(captureCount);
}
}
return(new CollectionSegment(
(IReadOnlyCollection <object>)items,
pageInfo,
getTotalCount));
}
