Backport pull request #15263 from jellyfin/release-10.11.z

Resolve symlinks for static media source infos

Original-merge: 3b2d64995a

Merged-by: crobibero <cody@robibe.ro>

Backported-by: Bond_009 <bond.009@outlook.com>

MediaBrowser.Controller/IO/FileSystemHelper.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using MediaBrowser.Model.IO;
@@ -61,4 +62,77 @@ public static class FileSystemHelper
             }
         }
     }
+
+    /// <summary>
+    /// Gets the target of the specified file link.
+    /// </summary>
+    /// <remarks>
+    /// This helper exists because of this upstream runtime issue; https://github.com/dotnet/runtime/issues/92128.
+    /// </remarks>
+    /// <param name="linkPath">The path of the file link.</param>
+    /// <param name="returnFinalTarget">true to follow links to the final target; false to return the immediate next link.</param>
+    /// <returns>
+    /// A <see cref="FileInfo"/> if the <paramref name="linkPath"/> is a link, regardless of if the target exists; otherwise, <c>null</c>.
+    /// </returns>
+    public static FileInfo? ResolveLinkTarget(string linkPath, bool returnFinalTarget = false)
+    {
+        // Check if the file exists so the native resolve handler won't throw at us.
+        if (!File.Exists(linkPath))
+        {
+            return null;
+        }
+
+        if (!returnFinalTarget)
+        {
+            return File.ResolveLinkTarget(linkPath, returnFinalTarget: false) as FileInfo;
+        }
+
+        if (File.ResolveLinkTarget(linkPath, returnFinalTarget: false) is not FileInfo targetInfo)
+        {
+            return null;
+        }
+
+        var currentPath = targetInfo.FullName;
+        var visited = new HashSet<string>(StringComparer.Ordinal) { linkPath, currentPath };
+        while (File.ResolveLinkTarget(currentPath, returnFinalTarget: false) is FileInfo linkInfo)
+        {
+            var targetPath = linkInfo.FullName;
+
+            // If an infinite loop is detected, return the file info for the
+            // first link in the loop we encountered.
+            if (!visited.Add(targetPath))
+            {
+                return new FileInfo(targetPath);
+            }
+
+            targetInfo = linkInfo;
+            currentPath = targetPath;
+
+            // Exit if the target doesn't exist, so the native resolve handler won't throw at us.
+            if (!targetInfo.Exists)
+            {
+                break;
+            }
+        }
+
+        return targetInfo;
+    }
+
+    /// <summary>
+    /// Gets the target of the specified file link.
+    /// </summary>
+    /// <remarks>
+    /// This helper exists because of this upstream runtime issue; https://github.com/dotnet/runtime/issues/92128.
+    /// </remarks>
+    /// <param name="fileInfo">The file info of the file link.</param>
+    /// <param name="returnFinalTarget">true to follow links to the final target; false to return the immediate next link.</param>
+    /// <returns>
+    /// A <see cref="FileInfo"/> if the <paramref name="fileInfo"/> is a link, regardless of if the target exists; otherwise, <c>null</c>.
+    /// </returns>
+    public static FileInfo? ResolveLinkTarget(FileInfo fileInfo, bool returnFinalTarget = false)
+    {
+        ArgumentNullException.ThrowIfNull(fileInfo);
+
+        return ResolveLinkTarget(fileInfo.FullName, returnFinalTarget);
+    }
 }