public Connection(
IReadOnlyCollection <Edge <T> > edges,
ConnectionPageInfo info,
Func <CancellationToken, ValueTask <int> > getTotalCount)
: base(edges, info, getTotalCount)
{
Edges = edges;
}
public void CreateConnection_EdgesNull_ArgumentNullException()
{
// arrange
var pageInfo = new ConnectionPageInfo(true, true, "a", "b", null);
// act
Action a = () => new Connection <string>(
null, pageInfo, ct => throw new NotSupportedException());
// assert
Assert.Throws <ArgumentNullException>(a);
}
public void CreateConnection_CountIsNull_ArgumentNullException()
{
// arrange
var pageInfo = new ConnectionPageInfo(true, true, "a", "b", null);
var edges = new List <Edge <string> >();
// act
Action a = () => new Connection <string>(
edges, pageInfo, null);
// assert
Assert.Throws <ArgumentNullException>(a);
}
public void CreateConnection_PageInfoAndEdges_PassedCorrectly()
{
// arrange
var pageInfo = new ConnectionPageInfo(true, true, "a", "b", null);
var edges = new List <Edge <string> >();
// act
var connection = new Connection(
edges,
pageInfo,
_ => throw new NotSupportedException());
// assert
Assert.Equal(pageInfo, connection.Info);
Assert.Equal(edges, connection.Edges);
}
public void CreatePageInfo_ArgumentsArePassedCorrectly(
bool hasNextPage, bool hasPreviousPage,
string startCursor, string endCursor,
int?totalCount)
{
// arrange
// act
var pageInfo = new ConnectionPageInfo(
hasNextPage, hasPreviousPage,
startCursor, endCursor,
totalCount);
// assert
Assert.Equal(hasNextPage, pageInfo.HasNextPage);
Assert.Equal(hasPreviousPage, pageInfo.HasPreviousPage);
Assert.Equal(startCursor, pageInfo.StartCursor);
Assert.Equal(endCursor, pageInfo.EndCursor);
Assert.Equal(totalCount, pageInfo.TotalCount);
}
private async ValueTask <Connection> ResolveAsync(
IQueryable <TEntity> source,
CursorPagingArguments arguments = default,
CancellationToken cancellationToken = default)
{
var count = await Task.Run(source.Count, cancellationToken)
.ConfigureAwait(false);
int?after = arguments.After is { } a
? (int?)IndexEdge <TEntity> .DeserializeCursor(a)
: null;
int?before = arguments.Before is { } b
? (int?)IndexEdge <TEntity> .DeserializeCursor(b)
: null;
IReadOnlyList <IndexEdge <TEntity> > selectedEdges =
await GetSelectedEdgesAsync(
source, arguments.First, arguments.Last, after, before, cancellationToken)
.ConfigureAwait(false);
IndexEdge <TEntity>?firstEdge = selectedEdges.Count == 0
? null
: selectedEdges[0];
IndexEdge <TEntity>?lastEdge = selectedEdges.Count == 0
? null
: selectedEdges[selectedEdges.Count - 1];
var pageInfo = new ConnectionPageInfo(
lastEdge?.Index < count - 1,
firstEdge?.Index > 0,
firstEdge?.Cursor,
lastEdge?.Cursor,
count);
return(new Connection <TEntity>(
selectedEdges,
pageInfo,
ct => new ValueTask <int>(pageInfo.TotalCount ?? 0)));
}
/// <summary>
/// Applies the pagination algorithm to the provided query.
/// </summary>
/// <param name="query">The query builder.</param>
/// <param name="arguments">The paging arguments.</param>
/// <param name="totalCount">Specify the total amount of elements</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>
/// Returns the connection.
/// </returns>
public async ValueTask <Connection <TEntity> > ApplyPaginationAsync(
TQuery query,
CursorPagingArguments arguments,
int?totalCount,
CancellationToken cancellationToken)
{
if (query is null)
{
throw new ArgumentNullException(nameof(query));
}
var maxElementCount = int.MaxValue;
Func <CancellationToken, ValueTask <int> > executeCount = totalCount is null ?
ct => CountAsync(query, ct)
: _ => new ValueTask <int>(totalCount.Value);
// We only need the maximal element count if no `before` counter is set and no `first`
// argument is provided.
if (arguments.Before is null && arguments.First is null)
{
var count = await executeCount(cancellationToken);
maxElementCount = count;
// in case we already know the total count, we override the countAsync parameter
// so that we do not have to fetch the count twice
executeCount = _ => new ValueTask <int>(count);
}
CursorPagingRange range = SliceRange(arguments, maxElementCount);
var skip = range.Start;
var take = range.Count();
// we fetch one element more than we requested
if (take != maxElementCount)
{
take++;
}
TQuery slicedSource = query;
if (skip != 0)
{
slicedSource = ApplySkip(query, skip);
}
if (take != maxElementCount)
{
slicedSource = ApplyTake(slicedSource, take);
}
IReadOnlyList <Edge <TEntity> > selectedEdges =
await ExecuteAsync(slicedSource, skip, cancellationToken);
var moreItemsReturnedThanRequested = selectedEdges.Count > range.Count();
var isSequenceFromStart = range.Start == 0;
selectedEdges = new SkipLastCollection <Edge <TEntity> >(
selectedEdges,
moreItemsReturnedThanRequested);
ConnectionPageInfo pageInfo =
CreatePageInfo(isSequenceFromStart, moreItemsReturnedThanRequested, selectedEdges);
return(new Connection <TEntity>(selectedEdges, pageInfo, executeCount));
}