Move to UniqueMediaPathScheme

src/Umbraco.Core/Composing/CompositionExtensions/FileSystems.cs

@@ -79,7 +79,7 @@ namespace Umbraco.Core.Composing.CompositionExtensions
             composition.RegisterUnique<IFileSystems>(factory => factory.GetInstance<IO.FileSystems>());
 
             // register the scheme for media paths
-            composition.RegisterUnique<IMediaPathScheme, CombinedGuidsMediaPathScheme>();
+            composition.RegisterUnique<IMediaPathScheme, UniqueMediaPathScheme>();
 
             // register the IMediaFileSystem implementation
             composition.RegisterFileSystem<IMediaFileSystem, MediaFileSystem>();

src/Umbraco.Core/IO/MediaPathSchemes/CombinedGuidsMediaPathScheme.cs

@@ -8,6 +8,7 @@ namespace Umbraco.Core.IO.MediaPathSchemes
     /// </summary>
     /// <remarks>
     /// <para>Path is "{combinedGuid}/{filename}" where combinedGuid is a combination of itemGuid and propertyGuid.</para>
+    /// <para>This scheme is dangerous, as it does not prevent potential collisions.</para>
     /// </remarks>
     public class CombinedGuidsMediaPathScheme : IMediaPathScheme
     {

src/Umbraco.Core/IO/MediaPathSchemes/UniqueMediaPathScheme.cs

@@ -0,0 +1,38 @@
+using System;
+using System.IO;
+
+namespace Umbraco.Core.IO.MediaPathSchemes
+{
+    /// <summary>
+    /// Implements a unique directory media path scheme.
+    /// </summary>
+    /// <remarks>
+    /// <para>This scheme provides short paths, yet handle potential collisions.</para>
+    /// </remarks>
+    public class UniqueMediaPathScheme : IMediaPathScheme
+    {
+        private const int DirectoryLength = 8;
+
+        /// <inheritdoc />
+        public string GetFilePath(IMediaFileSystem fileSystem, Guid itemGuid, Guid propertyGuid, string filename, string previous = null)
+        {
+            string directory;
+
+            // no point "combining" guids if all we want is some random guid - just get a new one
+            // and then, because we don't want collisions, ensure that the directory does not already exist
+            // (should be quite rare, but eh...)
+
+            do
+            {
+                var combinedGuid = Guid.NewGuid();
+                directory = GuidUtils.ToBase32String(combinedGuid, DirectoryLength); // see also HexEncoder, we may want to fragment path eg 12/e4/f3...
+
+            } while (fileSystem.DirectoryExists(directory));
+
+            return Path.Combine(directory, filename).Replace('\\', '/');
+        }
+
+        /// <inheritdoc />
+        public string GetDeleteDirectory(IMediaFileSystem fileSystem, string filepath) => Path.GetDirectoryName(filepath);
+    }
+}

src/Umbraco.Core/Umbraco.Core.csproj

@@ -207,6 +207,7 @@
     <Compile Include="Composing\TypeFinder.cs" />
     <Compile Include="Composing\TypeHelper.cs" />
     <Compile Include="Composing\TypeLoader.cs" />
+    <Compile Include="IO\MediaPathSchemes\UniqueMediaPathScheme.cs" />
     <Compile Include="Migrations\Upgrade\V_8_0_0\MergeDateAndDateTimePropertyEditor.cs" />
     <Compile Include="PropertyEditors\DateTimeConfiguration.cs" />
     <Compile Include="Migrations\Upgrade\V_8_0_0\RenameLabelAndRichTextPropertyEditorAliases.cs" />

src/Umbraco.Tests/IO/FileSystemsTests.cs

@@ -33,7 +33,7 @@ namespace Umbraco.Tests.IO
             composition.Register(_ => Mock.Of<ILogger>());
             composition.Register(_ => Mock.Of<IDataTypeService>());
             composition.Register(_ => Mock.Of<IContentSection>());
-            composition.RegisterUnique<IMediaPathScheme, CombinedGuidsMediaPathScheme>();
+            composition.RegisterUnique<IMediaPathScheme, UniqueMediaPathScheme>();
 
             composition.Configs.Add(SettingsForTests.GetDefaultGlobalSettings);
             composition.Configs.Add(SettingsForTests.GetDefaultUmbracoSettings);

src/Umbraco.Tests/Testing/UmbracoTestBase.cs

@@ -243,7 +243,7 @@ namespace Umbraco.Tests.Testing
             Composition.WithCollectionBuilder<PropertyValueConverterCollectionBuilder>();
             Composition.RegisterUnique<IPublishedContentTypeFactory, PublishedContentTypeFactory>();
 
-            Composition.RegisterUnique<IMediaPathScheme, CombinedGuidsMediaPathScheme>();
+            Composition.RegisterUnique<IMediaPathScheme, UniqueMediaPathScheme>();
 
             // register empty content apps collection
             Composition.WithCollectionBuilder<ContentAppFactoryCollectionBuilder>();