/// <summary>
/// Creates a new <see cref="IAsyncReadOnlyCollection{T}" /> that contains the sorted elements of the
/// <see cref="IAsyncEnumerable{T}" />.
/// </summary>
/// <param name="source">
/// The <see cref="IAsyncEnumerable{T}" /> to sort.
/// </param>
/// <param name="comparison">
/// The comparison to use while sorting.
/// </param>
/// <typeparam name="T">
/// The type of the items.
/// </typeparam>
/// <returns>
/// The sorted <see cref="IAsyncReadOnlyCollection{T}" />.
/// </returns>
public async Task <IAsyncReadOnlyCollection <T> > SortAsync <T>(IAsyncEnumerable <T> source, Comparison <T> comparison)
{
var chunks = new List <IAsyncReadOnlyCollection <T> >();
if (source.Policy != this)
{
source = await this.MaterializeAsync(source).ConfigureAwait(false);
}
await source.Batch(this.MaximumChunkSize).ForEachAsync(
async batch =>
{
var builder = await this.CreateBuilder <T>().AddAsync(await this.memPolicy.SortAsync(batch, comparison).ConfigureAwait(false));
chunks.Add(await builder.BuildAsync().ConfigureAwait(false));
});
var result = this.CreateBuilder <T>();
var enumerators = chunks.Select(c => c.GetAsyncEnumerator()).ToList();
foreach (var enumerator in enumerators.ToArray())
{
if (!enumerator.MoveNext() && !(await enumerator.NextBatchAsync().ConfigureAwait(false) && enumerator.MoveNext()))
{
enumerator.Dispose();
enumerators.Remove(enumerator);
}
}
enumerators.Sort((a, b) => comparison(a.Current, b.Current));
while (true)
{
await result.AddAsync(TemporaryFilePolicy.TakeItems(enumerators, comparison)).ConfigureAwait(false);
if (!(await enumerators[0].NextBatchAsync().ConfigureAwait(false) && enumerators[0].MoveNext()))
{
enumerators[0].Dispose();
enumerators.RemoveAt(0);
if (enumerators.Count == 0)
{
break;
}
}
else
{
TemporaryFilePolicy.SortEnumerators(enumerators, comparison);
}
}
foreach (var chunk in chunks)
{
chunk.Dispose();
}
return(await result.BuildAsync().ConfigureAwait(false));
}
