make sure network path substitution matches correctly

Emby.Server.Implementations/Library/LibraryManager.cs

@@ -2788,10 +2788,9 @@ namespace Emby.Server.Implementations.Library
                             continue;
                         }
 
-                        var substitutionResult = SubstitutePathInternal(path, pathInfo.Path, pathInfo.NetworkPath);
-                        if (substitutionResult.Item2)
+                        if (path.TryReplaceSubPath(pathInfo.Path, pathInfo.NetworkPath, out var newPath))
                         {
-                            return substitutionResult.Item1;
+                            return newPath;
                         }
                     }
                 }
@@ -2802,22 +2801,22 @@ namespace Emby.Server.Implementations.Library
 
             if (!string.IsNullOrWhiteSpace(metadataPath) && !string.IsNullOrWhiteSpace(metadataNetworkPath))
             {
-                var metadataSubstitutionResult = SubstitutePathInternal(path, metadataPath, metadataNetworkPath);
-                if (metadataSubstitutionResult.Item2)
+                if (path.TryReplaceSubPath(metadataPath, metadataNetworkPath, out var newPath))
                 {
-                    return metadataSubstitutionResult.Item1;
+                    return newPath;
                 }
             }
 
             foreach (var map in _configurationManager.Configuration.PathSubstitutions)
             {
-                if (!string.IsNullOrWhiteSpace(map.From))
+                if (string.IsNullOrWhiteSpace(map.From))
                 {
-                    var substitutionResult = SubstitutePathInternal(path, map.From, map.To);
-                    if (substitutionResult.Item2)
-                    {
-                        return substitutionResult.Item1;
+                    continue;
                 }
+
+                if (path.TryReplaceSubPath(map.From, map.To, out var newPath))
+                {
+                    return newPath;
                 }
             }
 
@@ -2826,47 +2825,12 @@ namespace Emby.Server.Implementations.Library
 
         public string SubstitutePath(string path, string from, string to)
         {
-            return SubstitutePathInternal(path, from, to).Item1;
+            if (path.TryReplaceSubPath(from, to, out var newPath))
+            {
+                return newPath;
             }
 
-        private Tuple<string, bool> SubstitutePathInternal(string path, string from, string to)
-        {
-            if (string.IsNullOrWhiteSpace(path))
-            {
-                throw new ArgumentNullException(nameof(path));
-            }
-
-            if (string.IsNullOrWhiteSpace(from))
-            {
-                throw new ArgumentNullException(nameof(from));
-            }
-
-            if (string.IsNullOrWhiteSpace(to))
-            {
-                throw new ArgumentNullException(nameof(to));
-            }
-
-            from = from.Trim();
-            to = to.Trim();
-
-            var newPath = path.Replace(from, to, StringComparison.OrdinalIgnoreCase);
-            var changed = false;
-
-            if (!string.Equals(newPath, path, StringComparison.Ordinal))
-            {
-                if (to.IndexOf('/', StringComparison.Ordinal) != -1)
-                {
-                    newPath = newPath.Replace('\\', '/');
-                }
-                else
-                {
-                    newPath = newPath.Replace('/', '\\');
-                }
-
-                changed = true;
-            }
-
-            return new Tuple<string, bool>(newPath, changed);
+            return path;
         }
 
         private void SetExtraTypeFromFilename(Video item)

Emby.Server.Implementations/Library/PathExtensions.cs

@@ -1,6 +1,7 @@
 #nullable enable
 
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Text.RegularExpressions;
 
 namespace Emby.Server.Implementations.Library
@@ -47,5 +48,84 @@ namespace Emby.Server.Implementations.Library
 
             return null;
         }
+
+        /// <summary>
+        /// Replaces a sub path with another sub path and normalizes the final path.
+        /// </summary>
+        /// <param name="path">The original path.</param>
+        /// <param name="subPath">The original sub path.</param>
+        /// <param name="newSubPath">The new sub path.</param>
+        /// <param name="newPath">The result of the sub path replacement</param>
+        /// <returns>The path after replacing the sub path.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="path" />, <paramref name="newSubPath" /> or <paramref name="newSubPath" /> is empty.</exception>
+        public static bool TryReplaceSubPath(this string path, string subPath, string newSubPath, [NotNullWhen(true)] out string? newPath)
+        {
+            if (string.IsNullOrWhiteSpace(path))
+            {
+                throw new ArgumentNullException(nameof(path));
+            }
+
+            if (string.IsNullOrWhiteSpace(subPath))
+            {
+                throw new ArgumentNullException(nameof(subPath));
+            }
+
+            if (string.IsNullOrWhiteSpace(newSubPath))
+            {
+                throw new ArgumentNullException(nameof(newSubPath));
+            }
+
+            char oldDirectorySeparatorChar;
+            char newDirectorySeparatorChar;
+            // True normalization is still not possible https://github.com/dotnet/runtime/issues/2162
+            // The reasoning behind this is that a forward slash likely means it's a Linux path and
+            // so the whole path should be normalized to use / and vice versa for Windows (although Windows doesn't care much).
+            if (newSubPath.Contains('/', StringComparison.Ordinal))
+            {
+                oldDirectorySeparatorChar = '\\';
+                newDirectorySeparatorChar = '/';
+            }
+            else
+            {
+                oldDirectorySeparatorChar = '/';
+                newDirectorySeparatorChar = '\\';
+            }
+
+            if (path.Contains(oldDirectorySeparatorChar, StringComparison.Ordinal))
+            {
+                path = path.Replace(oldDirectorySeparatorChar, newDirectorySeparatorChar);
+            }
+
+            if (subPath.Contains(oldDirectorySeparatorChar, StringComparison.Ordinal))
+            {
+                subPath = subPath.Replace(oldDirectorySeparatorChar, newDirectorySeparatorChar);
+            }
+
+            // We have to ensure that the sub path ends with a directory separator otherwise we'll get weird results
+            // when the sub path matches a similar but in-complete subpath
+            if (!subPath.EndsWith(newDirectorySeparatorChar))
+            {
+                subPath += newDirectorySeparatorChar;
+            }
+
+            if (newSubPath.Contains(oldDirectorySeparatorChar, StringComparison.Ordinal))
+            {
+                newSubPath = newSubPath.Replace(oldDirectorySeparatorChar, newDirectorySeparatorChar);
+            }
+
+            if (!newSubPath.EndsWith(newDirectorySeparatorChar))
+            {
+                newSubPath += newDirectorySeparatorChar;
+            }
+
+            if (!path.Contains(subPath, StringComparison.OrdinalIgnoreCase))
+            {
+                newPath = null;
+                return false;
+            }
+
+            newPath = path.Replace(subPath, newSubPath, StringComparison.OrdinalIgnoreCase);
+            return true;
+        }
     }
 }

tests/Jellyfin.Server.Implementations.Tests/Library/PathExtensionsTests.cs

@@ -24,5 +24,28 @@ namespace Jellyfin.Server.Implementations.Tests.Library
         {
             Assert.Throws<ArgumentException>(() => PathExtensions.GetAttributeValue(input, attribute));
         }
+
+        [Theory]
+        [InlineData("C:/Users/jeff/myfile.mkv", "C:/Users/jeff", "/home/jeff", true, "/home/jeff/myfile.mkv")]
+        [InlineData("C:/Users/jeff/myfile.mkv", "C:/Users/jeff/", "/home/jeff", true, "/home/jeff/myfile.mkv")]
+        [InlineData("/home/jeff/music/jeff's band/consistently inconsistent.mp3", "/home/jeff/music/not jeff's band", "/home/not jeff", false, null)]
+        [InlineData("/home/jeff/music/jeff's band/consistently inconsistent.mp3", "/home/jeff/music/jeff's band", "/home/not jeff", true, "/home/not jeff/consistently inconsistent.mp3")]
+        [InlineData("C:\\Users\\jeff\\myfile.mkv", "C:\\Users/jeff", "/home/jeff", true, "/home/jeff/myfile.mkv")]
+        public void TryReplaceSubPath_ValidArgs_Correct(string path, string subPath, string newSubPath, bool succeeded, string? expectedResult)
+        {
+            var status = PathExtensions.TryReplaceSubPath(path, subPath, newSubPath, out var result);
+            Assert.Equal(succeeded, status);
+            Assert.Equal(expectedResult, result);
+        }
+
+        [Theory]
+        [InlineData("", "", "")]
+        [InlineData("/my/path", "", "")]
+        [InlineData("", "/another/path", "")]
+        [InlineData("", "", "/new/subpath")]
+        public void TryReplaceSubPath_EmptyString_ThrowsArgumentNullException(string path, string subPath, string newSubPath)
+        {
+            Assert.Throws<ArgumentNullException>(() => PathExtensions.TryReplaceSubPath(path, subPath, newSubPath, out _));
+        }
     }
 }