Fix GetOrderBy and add tests

Jellyfin.Api/Helpers/RequestHelpers.cs

@@ -25,22 +25,25 @@ namespace Jellyfin.Api.Helpers
         /// <param name="sortBy">Sort By. Comma delimited string.</param>
         /// <param name="requestedSortOrder">Sort Order. Comma delimited string.</param>
         /// <returns>Order By.</returns>
-        public static ValueTuple<string, SortOrder>[] GetOrderBy(IReadOnlyList<string> sortBy, IReadOnlyList<SortOrder> requestedSortOrder)
+        public static (string, SortOrder)[] GetOrderBy(IReadOnlyList<string> sortBy, IReadOnlyList<SortOrder> requestedSortOrder)
         {
             if (sortBy.Count == 0)
             {
                 return Array.Empty<ValueTuple<string, SortOrder>>();
             }
 
-            var result = new ValueTuple<string, SortOrder>[sortBy.Count];
-            for (var i = 0; i < sortBy.Count; i++)
+            var result = new (string, SortOrder)[sortBy.Count];
+            var i = 0;
+            // Add elements which have a SortOrder specified
+            for (; i < requestedSortOrder.Count; i++)
             {
-                var sortOrderIndex = requestedSortOrder.Count > i ? i : 0;
+                result[i] = (sortBy[i], requestedSortOrder[i]);
+            }
 
-                var sortOrder = requestedSortOrder.Count > sortOrderIndex
-                    ? requestedSortOrder[sortOrderIndex]
-                    : SortOrder.Ascending;
-                result[i] = new ValueTuple<string, SortOrder>(sortBy[i], sortOrder);
+            // Add remaining elements with the default SortOrder
+            for (; i < sortBy.Count; i++)
+            {
+                result[i] = (sortBy[i], SortOrder.Ascending);
             }
 
             return result;

tests/Jellyfin.Api.Tests/Helpers/RequestHelpersTests.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+using Jellyfin.Api.Helpers;
+using Jellyfin.Data.Enums;
+using Xunit;
+
+namespace Jellyfin.Api.Tests.Helpers
+{
+    public class RequestHelpersTests
+    {
+        [Theory]
+        [MemberData(nameof(GetOrderBy_Success_TestData))]
+        public void GetOrderBy_Success(IReadOnlyList<string> sortBy, IReadOnlyList<SortOrder> requestedSortOrder, (string, SortOrder)[] expected)
+        {
+            Assert.Equal(expected, RequestHelpers.GetOrderBy(sortBy, requestedSortOrder));
+        }
+
+        public static IEnumerable<object[]> GetOrderBy_Success_TestData()
+        {
+            yield return new object[]
+            {
+                Array.Empty<string>(),
+                Array.Empty<SortOrder>(),
+                Array.Empty<(string, SortOrder)>()
+            };
+            yield return new object[]
+            {
+                new string[]
+                {
+                    "IsFavoriteOrLiked",
+                    "Random"
+                },
+                Array.Empty<SortOrder>(),
+                new (string, SortOrder)[]
+                {
+                    ("IsFavoriteOrLiked", SortOrder.Ascending),
+                    ("Random", SortOrder.Ascending),
+                }
+            };
+            yield return new object[]
+            {
+                new string[]
+                {
+                    "SortName",
+                    "ProductionYear"
+                },
+                new SortOrder[]
+                {
+                    SortOrder.Descending
+                },
+                new (string, SortOrder)[]
+                {
+                    ("SortName", SortOrder.Descending),
+                    ("ProductionYear", SortOrder.Ascending),
+                }
+            };
+        }
+    }
+}