1 files changed, 162 insertions, 0 deletions
diff --git a/Jellyfin.Server.Implementations/Item/LinkedChildrenService.cs b/Jellyfin.Server.Implementations/Item/LinkedChildrenService.cs
new file mode 100644
index 0000000000..415510b2f4
--- /dev/null
+++ b/Jellyfin.Server.Implementations/Item/LinkedChildrenService.cs
@@ -0,0 +1,162 @@
+#pragma warning disable RS0030 // Do not use banned APIs
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Jellyfin.Data.Enums;
+using Jellyfin.Database.Implementations;
+using MediaBrowser.Controller.Entities.Audio;
+using MediaBrowser.Controller.Persistence;
+using Microsoft.EntityFrameworkCore;
+using DbLinkedChildType = Jellyfin.Database.Implementations.Entities.LinkedChildType;
+using LinkedChildType = MediaBrowser.Controller.Entities.LinkedChildType;
+
+namespace Jellyfin.Server.Implementations.Item;
+
+/// <summary>
+/// Provides linked children query and manipulation operations.
+/// </summary>
+public class LinkedChildrenService : ILinkedChildrenService
+{
+    private readonly IDbContextFactory<JellyfinDbContext> _dbProvider;
+    private readonly IItemTypeLookup _itemTypeLookup;
+    private readonly IItemQueryHelpers _queryHelpers;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="LinkedChildrenService"/> class.
+    /// </summary>
+    /// <param name="dbProvider">The database context factory.</param>
+    /// <param name="itemTypeLookup">The item type lookup.</param>
+    /// <param name="queryHelpers">The shared query helpers.</param>
+    public LinkedChildrenService(
+        IDbContextFactory<JellyfinDbContext> dbProvider,
+        IItemTypeLookup itemTypeLookup,
+        IItemQueryHelpers queryHelpers)
+    {
+        _dbProvider = dbProvider;
+        _itemTypeLookup = itemTypeLookup;
+        _queryHelpers = queryHelpers;
+    }
+
+    /// <inheritdoc/>
+    public IReadOnlyList<Guid> GetLinkedChildrenIds(Guid parentId, int? childType = null)
+    {
+        using var dbContext = _dbProvider.CreateDbContext();
+
+        var query = dbContext.LinkedChildren
+            .Where(lc => lc.ParentId.Equals(parentId));
+
+        if (childType.HasValue)
+        {
+            query = query.Where(lc => (int)lc.ChildType == childType.Value);
+        }
+
+        return query
+            .OrderBy(lc => lc.SortOrder)
+            .Select(lc => lc.ChildId)
+            .ToArray();
+    }
+
+    /// <inheritdoc/>
+    public IReadOnlyDictionary<string, MusicArtist[]> FindArtists(IReadOnlyList<string> artistNames)
+    {
+        using var dbContext = _dbProvider.CreateDbContext();
+
+        var artists = dbContext.BaseItems
+            .AsNoTracking()
+            .Where(e => e.Type == _itemTypeLookup.BaseItemKindNames[BaseItemKind.MusicArtist]!)
+            .Where(e => artistNames.Contains(e.Name))
+            .ToArray();
+
+        var lookup = artists
+            .GroupBy(e => e.Name!)
+            .ToDictionary(
+                g => g.Key,
+                g => g.Select(f => _queryHelpers.DeserializeBaseItem(f)).Where(dto => dto is not null).Cast<MusicArtist>().ToArray());
+
+        var result = new Dictionary<string, MusicArtist[]>(artistNames.Count);
+        foreach (var name in artistNames)
+        {
+            if (lookup.TryGetValue(name, out var artistArray))
+            {
+                result[name] = artistArray;
+            }
+        }
+
+        return result;
+    }
+
+    /// <inheritdoc/>
+    public IReadOnlyList<Guid> GetManualLinkedParentIds(Guid childId)
+    {
+        using var context = _dbProvider.CreateDbContext();
+        return context.LinkedChildren
+            .Where(lc => lc.ChildId == childId && lc.ChildType == DbLinkedChildType.Manual)
+            .Select(lc => lc.ParentId)
+            .Distinct()
+            .ToList();
+    }
+
+    /// <inheritdoc/>
+    public IReadOnlyList<Guid> RerouteLinkedChildren(Guid fromChildId, Guid toChildId)
+    {
+        using var context = _dbProvider.CreateDbContext();
+
+        var affectedParentIds = context.LinkedChildren
+            .Where(lc => lc.ChildId == fromChildId && lc.ChildType == DbLinkedChildType.Manual)
+            .Select(lc => lc.ParentId)
+            .Distinct()
+            .ToList();
+
+        if (affectedParentIds.Count == 0)
+        {
+            return affectedParentIds;
+        }
+
+        var parentsWithTarget = context.LinkedChildren
+            .Where(lc => lc.ChildId == toChildId && lc.ChildType == DbLinkedChildType.Manual)
+            .Select(lc => lc.ParentId)
+            .ToHashSet();
+
+        context.LinkedChildren
+            .Where(lc => lc.ChildId == fromChildId
+                && lc.ChildType == DbLinkedChildType.Manual
+                && !parentsWithTarget.Contains(lc.ParentId))
+            .ExecuteUpdate(s => s.SetProperty(e => e.ChildId, toChildId));
+
+        context.LinkedChildren
+            .Where(lc => lc.ChildId == fromChildId
+                && lc.ChildType == DbLinkedChildType.Manual
+                && parentsWithTarget.Contains(lc.ParentId))
+            .ExecuteDelete();
+
+        return affectedParentIds;
+    }
+
+    /// <inheritdoc/>
+    public void UpsertLinkedChild(Guid parentId, Guid childId, LinkedChildType childType)
+    {
+        using var context = _dbProvider.CreateDbContext();
+
+        var dbChildType = (DbLinkedChildType)childType;
+        var existingLink = context.LinkedChildren
+            .FirstOrDefault(lc => lc.ParentId == parentId && lc.ChildId == childId);
+
+        if (existingLink is null)
+        {
+            context.LinkedChildren.Add(new Jellyfin.Database.Implementations.Entities.LinkedChildEntity
+            {
+                ParentId = parentId,
+                ChildId = childId,
+                ChildType = dbChildType,
+                SortOrder = null
+            });
+        }
+        else
+        {
+            existingLink.ChildType = dbChildType;
+        }
+
+        context.SaveChanges();
+    }
+}