From 1a8737ffa5933cfa96b36eb9d56fc9c41492ea26 Mon Sep 17 00:00:00 2001
From: Louis Seubert <louis.seubert.ls@gmail.com>
Date: Wed, 1 May 2024 17:48:11 +0200
Subject: [PATCH] feat: add join for list of `Task<Result<T>>`

Allow joining `IEnumerable<Task<Result<T>>>` to one single `Task<Result<IReadOnlyList<T>>>` contains the success value of each result.
---
 .../Extensions/Extensions.Enumerable.cs       | 50 +++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/src/Result/Extensions/Extensions.Enumerable.cs b/src/Result/Extensions/Extensions.Enumerable.cs
index b1791fb..cbaf3d8 100644
--- a/src/Result/Extensions/Extensions.Enumerable.cs
+++ b/src/Result/Extensions/Extensions.Enumerable.cs
@@ -34,4 +34,54 @@ public static partial class Extensions
 
 		return list;
 	}
+
+	/// <inheritdoc cref="Join{T}(System.Collections.Generic.IEnumerable{Geekeey.Extensions.Result.Result{T}})"/>
+	/// <remarks>
+	/// For parallel execution of the async tasks, one should await the <c>Task.WhenAll()</c> of the provided list
+	/// before calling this function
+	/// </remarks>
+	/// <seealso cref="Join{T}(System.Collections.Generic.IEnumerable{Geekeey.Extensions.Result.Result{T}})"/>
+	// ReSharper disable once InconsistentNaming
+	public static async Task<Result<IReadOnlyList<T>>> Join<T>(this IEnumerable<Task<Result<T>>> results)
+	{
+		_ = results.TryGetNonEnumeratedCount(out var count);
+		var list = new List<T>(count);
+
+		foreach (var result in results)
+		{
+			if (!(await result).TryGetValue(out var value, out var error))
+			{
+				return new Result<IReadOnlyList<T>>(error);
+			}
+
+			list.Add(value);
+		}
+
+		return list;
+	}
+
+	/// <inheritdoc cref="Join{T}(System.Collections.Generic.IEnumerable{Geekeey.Extensions.Result.Result{T}})"/>
+	/// <remarks>
+	/// For parallel execution of the async tasks, one should await the <c>Task.WhenAll()</c> of the provided list
+	/// before calling this function
+	/// </remarks>
+	/// <seealso cref="Join{T}(System.Collections.Generic.IEnumerable{Geekeey.Extensions.Result.Result{T}})"/>
+	// ReSharper disable once InconsistentNaming
+	public static async ValueTask<Result<IReadOnlyList<T>>> Join<T>(this IEnumerable<ValueTask<Result<T>>> results)
+	{
+		_ = results.TryGetNonEnumeratedCount(out var count);
+		var list = new List<T>(count);
+
+		foreach (var result in results)
+		{
+			if (!(await result).TryGetValue(out var value, out var error))
+			{
+				return new Result<IReadOnlyList<T>>(error);
+			}
+
+			list.Add(value);
+		}
+
+		return list;
+	}
 }
\ No newline at end of file