// Licensed to the .NET Foundation under one or more agreements. // The .NET Foundation licenses this file to you under the Apache 2.0 License. // See the LICENSE file in the project root for more information. using System.Collections.Generic; using System.Threading; using System.Threading.Tasks; namespace System.Linq { public static partial class AsyncEnumerableEx { public static ValueTask> MinByAsync(this IAsyncEnumerable source, Func keySelector, CancellationToken cancellationToken = default) { if (source == null) throw Error.ArgumentNull(nameof(source)); if (keySelector == null) throw Error.ArgumentNull(nameof(keySelector)); return MinByCore(source, keySelector, comparer: null, cancellationToken); } public static ValueTask> MinByAsync(this IAsyncEnumerable source, Func keySelector, IComparer? comparer, CancellationToken cancellationToken = default) { if (source == null) throw Error.ArgumentNull(nameof(source)); if (keySelector == null) throw Error.ArgumentNull(nameof(keySelector)); return MinByCore(source, keySelector, comparer, cancellationToken); } public static ValueTask> MinByAsync(this IAsyncEnumerable source, Func> keySelector, CancellationToken cancellationToken = default) { if (source == null) throw Error.ArgumentNull(nameof(source)); if (keySelector == null) throw Error.ArgumentNull(nameof(keySelector)); return MinByCore(source, keySelector, comparer: null, cancellationToken); } #if !NO_DEEP_CANCELLATION public static ValueTask> MinByAsync(this IAsyncEnumerable source, Func> keySelector, CancellationToken cancellationToken = default) { if (source == null) throw Error.ArgumentNull(nameof(source)); if (keySelector == null) throw Error.ArgumentNull(nameof(keySelector)); return MinByCore(source, keySelector, comparer: null, cancellationToken); } #endif public static ValueTask> MinByAsync(this IAsyncEnumerable source, Func> keySelector, IComparer? comparer, CancellationToken cancellationToken = default) { if (source == null) throw Error.ArgumentNull(nameof(source)); if (keySelector == null) throw Error.ArgumentNull(nameof(keySelector)); return MinByCore(source, keySelector, comparer, cancellationToken); } #if !NO_DEEP_CANCELLATION public static ValueTask> MinByAsync(this IAsyncEnumerable source, Func> keySelector, IComparer comparer, CancellationToken cancellationToken = default) { if (source == null) throw Error.ArgumentNull(nameof(source)); if (keySelector == null) throw Error.ArgumentNull(nameof(keySelector)); return MinByCore(source, keySelector, comparer, cancellationToken); } #endif private static ValueTask> MinByCore(IAsyncEnumerable source, Func keySelector, IComparer? comparer, CancellationToken cancellationToken) { comparer ??= Comparer.Default; return ExtremaBy(source, keySelector, (key, minValue) => -comparer.Compare(key, minValue), cancellationToken); } private static ValueTask> MinByCore(IAsyncEnumerable source, Func> keySelector, IComparer? comparer, CancellationToken cancellationToken) { comparer ??= Comparer.Default; return ExtremaBy(source, keySelector, (key, minValue) => -comparer.Compare(key, minValue), cancellationToken); } #if !NO_DEEP_CANCELLATION private static ValueTask> MinByCore(IAsyncEnumerable source, Func> keySelector, IComparer? comparer, CancellationToken cancellationToken) { comparer ??= Comparer.Default; return ExtremaBy(source, keySelector, (key, minValue) => -comparer.Compare(key, minValue), cancellationToken); } #endif private static async ValueTask> ExtremaBy(IAsyncEnumerable source, Func keySelector, Func compare, CancellationToken cancellationToken) { var result = new List(); await using (var e = source.GetConfiguredAsyncEnumerator(cancellationToken, false)) { if (!await e.MoveNextAsync()) throw Error.NoElements(); var current = e.Current; var resKey = keySelector(current); result.Add(current); while (await e.MoveNextAsync()) { var cur = e.Current; var key = keySelector(cur); var cmp = compare(key, resKey); if (cmp == 0) { result.Add(cur); } else if (cmp > 0) { result = new List { cur }; resKey = key; } } } return result; } private static async ValueTask> ExtremaBy(IAsyncEnumerable source, Func> keySelector, Func compare, CancellationToken cancellationToken) { var result = new List(); await using (var e = source.GetConfiguredAsyncEnumerator(cancellationToken, false)) { if (!await e.MoveNextAsync()) throw Error.NoElements(); var current = e.Current; var resKey = await keySelector(current).ConfigureAwait(false); result.Add(current); while (await e.MoveNextAsync()) { var cur = e.Current; var key = await keySelector(cur).ConfigureAwait(false); var cmp = compare(key, resKey); if (cmp == 0) { result.Add(cur); } else if (cmp > 0) { result = new List { cur }; resKey = key; } } } return result; } #if !NO_DEEP_CANCELLATION private static async ValueTask> ExtremaBy(IAsyncEnumerable source, Func> keySelector, Func compare, CancellationToken cancellationToken) { var result = new List(); await using (var e = source.GetConfiguredAsyncEnumerator(cancellationToken, false)) { if (!await e.MoveNextAsync()) throw Error.NoElements(); var current = e.Current; var resKey = await keySelector(current, cancellationToken).ConfigureAwait(false); result.Add(current); while (await e.MoveNextAsync()) { var cur = e.Current; var key = await keySelector(cur, cancellationToken).ConfigureAwait(false); var cmp = compare(key, resKey); if (cmp == 0) { result.Add(cur); } else if (cmp > 0) { result = new List { cur }; resKey = key; } } } return result; } #endif } }