/// <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 ??
throw new ArgumentNullException(nameof(info));
_getTotalCount = getTotalCount ??
throw new ArgumentNullException(nameof(getTotalCount));
}
protected override ValueTask <CollectionSegment> SliceAsync(IResolverContext context, object source, OffsetPagingArguments arguments)
{
//If Appropriate we handle the values here to ensure that no post-processing is done other than
// correctly mapping the results into a GraphQL Collection Segment with appropriate Paging Details...
if (source is IPreProcessedOffsetPageResults <TEntity> pagedResults)
{
bool includeTotalCountEnabled = this.PagingOptions.IncludeTotalCount ?? PagingDefaults.IncludeTotalCount;
var graphQLParamsContext = new GraphQLParamsContext(context);
//Optimized to only require TotalCount value if the query actually requested it!
if (includeTotalCountEnabled && graphQLParamsContext.IsTotalCountRequested && pagedResults.TotalCount == null)
{
throw new InvalidOperationException($"Total Count is requested in the query, but was not provided with the results [{this.GetType().GetTypeName()}] from the resolvers pre-processing logic; TotalCount is null.");
}
int?totalCount = pagedResults.TotalCount;
//Ensure we are null safe and return a valid empty list by default.
var segmentResults = pagedResults?.ToList() ?? new List <TEntity>();
var collectionSegmentInfo = new CollectionSegmentInfo(
hasNextPage: pagedResults?.HasNextPage ?? false,
hasPreviousPage: pagedResults?.HasPreviousPage ?? false
);
var graphQLConnection = new CollectionSegment(
(IReadOnlyCollection <object>)segmentResults,
collectionSegmentInfo,
ct => new ValueTask <int>(totalCount ?? throw new InvalidOperationException())
);
return(new ValueTask <CollectionSegment>(graphQLConnection));
}
throw new GraphQLException($"[{nameof(PreProcessedOffsetPagingHandler<TEntity>)}] cannot handle the specified data source of type [{source.GetType().Name}].");
}
