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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
namespace System.Linq
{
public static partial class AsyncEnumerable
{
/// <summary>Correlates the elements of two sequences based on key equality and groups the results. If <paramref name="comparer" /> is <see langword="null" /> or omitted, the default equality comparer is used to compare keys.</summary>
/// <typeparam name="TOuter">The type of the elements of the first sequence.</typeparam>
/// <typeparam name="TInner">The type of the elements of the second sequence.</typeparam>
/// <typeparam name="TKey">The type of the keys returned by the key selector functions.</typeparam>
/// <param name="outer">The first sequence to join.</param>
/// <param name="inner">The sequence to join to the first sequence.</param>
/// <param name="outerKeySelector">A function to extract the join key from each element of the first sequence.</param>
/// <param name="innerKeySelector">A function to extract the join key from each element of the second sequence.</param>
/// <param name="comparer">An <see cref="IEqualityComparer{T}"/> to hash and compare keys, or <see langword="null" /> to use <see cref="EqualityComparer{T}.Default" />.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> that contains elements of type <see cref="IGrouping{TOuter, TInner}"/>
/// where each grouping contains the outer element as the key and the matching inner elements.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="outer" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="inner" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="outerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="innerKeySelector" /> is <see langword="null" />.</exception>
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer = null)
{
ArgumentNullException.ThrowIfNull(outer);
ArgumentNullException.ThrowIfNull(inner);
ArgumentNullException.ThrowIfNull(outerKeySelector);
ArgumentNullException.ThrowIfNull(innerKeySelector);
return
outer.IsKnownEmpty() ? Empty<IGrouping<TOuter, TInner>>() :
Impl(outer, inner, outerKeySelector, innerKeySelector, comparer, default);
static async IAsyncEnumerable<IGrouping<TOuter, TInner>> Impl(
IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
IEqualityComparer<TKey>? comparer,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await using IAsyncEnumerator<TOuter> e = outer.GetAsyncEnumerator(cancellationToken);
if (await e.MoveNextAsync())
{
AsyncLookup<TKey, TInner> lookup = await AsyncLookup<TKey, TInner>.CreateForJoinAsync(inner, innerKeySelector, comparer, cancellationToken);
do
{
TOuter item = e.Current;
yield return new AsyncGroupJoinGrouping<TOuter, TInner>(item, lookup[outerKeySelector(item)]);
}
while (await e.MoveNextAsync());
}
}
}
/// <summary>Correlates the elements of two sequences based on key equality and groups the results. If <paramref name="comparer" /> is <see langword="null" /> or omitted, the default equality comparer is used to compare keys.</summary>
/// <typeparam name="TOuter">The type of the elements of the first sequence.</typeparam>
/// <typeparam name="TInner">The type of the elements of the second sequence.</typeparam>
/// <typeparam name="TKey">The type of the keys returned by the key selector functions.</typeparam>
/// <param name="outer">The first sequence to join.</param>
/// <param name="inner">The sequence to join to the first sequence.</param>
/// <param name="outerKeySelector">A function to extract the join key from each element of the first sequence.</param>
/// <param name="innerKeySelector">A function to extract the join key from each element of the second sequence.</param>
/// <param name="comparer">An <see cref="IEqualityComparer{T}"/> to hash and compare keys, or <see langword="null" /> to use <see cref="EqualityComparer{T}.Default" />.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> that contains elements of type <see cref="IGrouping{TOuter, TInner}"/>
/// where each grouping contains the outer element as the key and the matching inner elements.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="outer" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="inner" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="outerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="innerKeySelector" /> is <see langword="null" />.</exception>
public static IAsyncEnumerable<IGrouping<TOuter, TInner>> GroupJoin<TOuter, TInner, TKey>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer = null)
{
ArgumentNullException.ThrowIfNull(outer);
ArgumentNullException.ThrowIfNull(inner);
ArgumentNullException.ThrowIfNull(outerKeySelector);
ArgumentNullException.ThrowIfNull(innerKeySelector);
return
outer.IsKnownEmpty() ? Empty<IGrouping<TOuter, TInner>>() :
Impl(outer, inner, outerKeySelector, innerKeySelector, comparer, default);
static async IAsyncEnumerable<IGrouping<TOuter, TInner>> Impl(
IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
IEqualityComparer<TKey>? comparer,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await using IAsyncEnumerator<TOuter> e = outer.GetAsyncEnumerator(cancellationToken);
if (await e.MoveNextAsync())
{
AsyncLookup<TKey, TInner> lookup = await AsyncLookup<TKey, TInner>.CreateForJoinAsync(inner, innerKeySelector, comparer, cancellationToken);
do
{
TOuter item = e.Current;
yield return new AsyncGroupJoinGrouping<TOuter, TInner>(
item,
lookup[await outerKeySelector(item, cancellationToken)]);
}
while (await e.MoveNextAsync());
}
}
}
/// <summary>Correlates the elements of two sequences based on key equality and groups the results.</summary>
/// <typeparam name="TOuter"></typeparam>
/// <typeparam name="TInner"></typeparam>
/// <typeparam name="TKey"></typeparam>
/// <typeparam name="TResult"></typeparam>
/// <param name="outer">The first sequence to join.</param>
/// <param name="inner">The sequence to join to the first sequence.</param>
/// <param name="outerKeySelector">A function to extract the join key from each element of the first sequence.</param>
/// <param name="innerKeySelector">A function to extract the join key from each element of the second sequence.</param>
/// <param name="resultSelector">
/// A function to create a result element from an element from the first sequence
/// and a collection of matching elements from the second sequence.
/// </param>
/// <param name="comparer">An <see cref="IEqualityComparer{T}"/> to use to hash and compare keys.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> that contains elements of type <typeparamref name="TResult"/>
/// that are obtained by performing a grouped join on two sequences.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="outer" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="inner" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="outerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="innerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector" /> is <see langword="null" />.</exception>
public static IAsyncEnumerable<TResult> GroupJoin<TOuter, TInner, TKey, TResult>( // satisfies the C# query-expression pattern
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
Func<TOuter, IEnumerable<TInner>, TResult> resultSelector,
IEqualityComparer<TKey>? comparer = null)
{
ArgumentNullException.ThrowIfNull(outer);
ArgumentNullException.ThrowIfNull(inner);
ArgumentNullException.ThrowIfNull(outerKeySelector);
ArgumentNullException.ThrowIfNull(innerKeySelector);
ArgumentNullException.ThrowIfNull(resultSelector);
return
outer.IsKnownEmpty() ? Empty<TResult>() :
Impl(outer, inner, outerKeySelector, innerKeySelector, resultSelector, comparer, default);
static async IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
Func<TOuter, IEnumerable<TInner>, TResult> resultSelector,
IEqualityComparer<TKey>? comparer,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await using IAsyncEnumerator<TOuter> e = outer.GetAsyncEnumerator(cancellationToken);
if (await e.MoveNextAsync())
{
AsyncLookup<TKey, TInner> lookup = await AsyncLookup<TKey, TInner>.CreateForJoinAsync(inner, innerKeySelector, comparer, cancellationToken);
do
{
TOuter item = e.Current;
yield return resultSelector(item, lookup[outerKeySelector(item)]);
}
while (await e.MoveNextAsync());
}
}
}
/// <summary>Correlates the elements of two sequences based on key equality and groups the results.</summary>
/// <typeparam name="TOuter"></typeparam>
/// <typeparam name="TInner"></typeparam>
/// <typeparam name="TKey"></typeparam>
/// <typeparam name="TResult"></typeparam>
/// <param name="outer">The first sequence to join.</param>
/// <param name="inner">The sequence to join to the first sequence.</param>
/// <param name="outerKeySelector">A function to extract the join key from each element of the first sequence.</param>
/// <param name="innerKeySelector">A function to extract the join key from each element of the second sequence.</param>
/// <param name="resultSelector">
/// A function to create a result element from an element from the first sequence
/// and a collection of matching elements from the second sequence.
/// </param>
/// <param name="comparer">An <see cref="IEqualityComparer{T}"/> to use to hash and compare keys.</param>
/// <returns>
/// An <see cref="IAsyncEnumerable{T}"/> that contains elements of type <typeparamref name="TResult"/>
/// that are obtained by performing a grouped join on two sequences.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="outer" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="inner" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="outerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="innerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector" /> is <see langword="null" />.</exception>
public static IAsyncEnumerable<TResult> GroupJoin<TOuter, TInner, TKey, TResult>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
Func<TOuter, IEnumerable<TInner>, CancellationToken, ValueTask<TResult>> resultSelector,
IEqualityComparer<TKey>? comparer = null)
{
ArgumentNullException.ThrowIfNull(outer);
ArgumentNullException.ThrowIfNull(inner);
ArgumentNullException.ThrowIfNull(outerKeySelector);
ArgumentNullException.ThrowIfNull(innerKeySelector);
ArgumentNullException.ThrowIfNull(resultSelector);
return
outer.IsKnownEmpty() ? Empty<TResult>() :
Impl(outer, inner, outerKeySelector, innerKeySelector, resultSelector, comparer, default);
static async IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
Func<TOuter, IEnumerable<TInner>, CancellationToken, ValueTask<TResult>> resultSelector,
IEqualityComparer<TKey>? comparer,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await using IAsyncEnumerator<TOuter> e = outer.GetAsyncEnumerator(cancellationToken);
if (await e.MoveNextAsync())
{
AsyncLookup<TKey, TInner> lookup = await AsyncLookup<TKey, TInner>.CreateForJoinAsync(inner, innerKeySelector, comparer, cancellationToken);
do
{
TOuter item = e.Current;
yield return await resultSelector(
item,
lookup[await outerKeySelector(item, cancellationToken)],
cancellationToken);
}
while (await e.MoveNextAsync());
}
}
}
}
internal sealed class AsyncGroupJoinGrouping<TKey, TElement> : IGrouping<TKey, TElement>
{
private readonly TKey _key;
private readonly IEnumerable<TElement> _elements;
public AsyncGroupJoinGrouping(TKey key, IEnumerable<TElement> elements)
{
_key = key;
_elements = elements;
}
public TKey Key => _key;
public IEnumerator<TElement> GetEnumerator() => _elements.GetEnumerator();
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}
}
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