HTTP File Response Improvements (#4465)

* Make local temp path configurable

* Generate entity tag based on file content hash instead of modified date

src/modules/Elsa.Http/Activities/WriteFileHttpResponse.cs

@@ -1,3 +1,4 @@
+using System.Security.Cryptography;
 using Elsa.Extensions;
 using Elsa.Http.Contracts;
 using Elsa.Http.Models;
@@ -8,6 +9,7 @@ using Elsa.Workflows.Core.Attributes;
 using Elsa.Workflows.Core.Exceptions;
 using Elsa.Workflows.Core.Models;
 using FluentStorage.Blobs;
+using FluentStorage.Utils.Extensions;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.Abstractions;
@@ -141,10 +143,11 @@ public class WriteFileHttpResponse : Activity
 
         try
         {
-            // Send the zip stream the temporary file back to the client.
+            // Send the temporary file back to the client.
             var contentType = zipBlob.Metadata["ContentType"];
             var downloadAsFilename = zipBlob.Metadata["Filename"];
-            var eTag = $"\"{zipBlob.LastModificationTime?.ToString("O")}\"";
+            var hash = ComputeHash(zipStream);
+            var eTag = $"\"{hash}\"";
             var eTagHeaderValue = new EntityTagHeaderValue(eTag);
             await SendFileStream(context, httpContext, zipStream, contentType, downloadAsFilename, eTagHeaderValue);
 
@@ -162,6 +165,16 @@ public class WriteFileHttpResponse : Activity
         }
     }
 
+    private string ComputeHash(Stream stream)
+    {
+        stream.Seek(0, SeekOrigin.Begin);
+        var bytes = stream.ToByteArray()!;
+        using var md5Hash = MD5.Create();
+        var hash = md5Hash.ComputeHash(bytes);
+        stream.Seek(0, SeekOrigin.Begin);
+        return Convert.ToBase64String(hash);
+    }
+
     private async Task<(Blob, Stream, Func<ValueTask>)> GenerateZipFileAsync(ActivityExecutionContext context, HttpContext httpContext, ICollection<Func<ValueTask<Downloadable>>> downloadables)
     {
         var cancellationToken = context.CancellationToken;

src/modules/Elsa.Http/Features/HttpFeature.cs

@@ -27,6 +27,7 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.StaticFiles;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
 
 namespace Elsa.Http.Features;
 
@@ -71,9 +72,10 @@ public class HttpFeature : FeatureBase
     /// <summary>
     /// A delegate to configure the <see cref="IFileCacheStorageProvider"/>.
     /// </summary>
-    public Func<IServiceProvider, IFileCacheStorageProvider> FileCache { get; set; } = _ =>
+    public Func<IServiceProvider, IFileCacheStorageProvider> FileCache { get; set; } = sp =>
     {
-        var blobStorage = StorageFactory.Blobs.DirectoryFiles(Path.GetTempPath());
+        var options = sp.GetRequiredService<IOptions<HttpFileCacheOptions>>().Value;
+        var blobStorage = StorageFactory.Blobs.DirectoryFiles(options.LocalCacheDirectory);
         return new BlobFileCacheStorageProvider(blobStorage);
     };
 

src/modules/Elsa.Http/Options/HttpFileCacheOptions.cs

@@ -9,4 +9,9 @@ public class HttpFileCacheOptions
     /// The time to live for cached files.
     /// </summary>
     public TimeSpan TimeToLive { get; set; } = TimeSpan.FromDays(7);
+
+    /// <summary>
+    /// The local cache directory. Defaults to the system's temp directory.
+    /// </summary>
+    public string LocalCacheDirectory { get; set; } = Path.GetTempPath();
 }

src/modules/Elsa.Http/Services/ZipManager.cs

@@ -39,7 +39,7 @@ internal class ZipManager
         CancellationToken cancellationToken = default)
     {
         // Create a temporary file.
-        var tempFilePath = Path.GetTempFileName();
+        var tempFilePath = GetTempFilePath();
 
         // Create a zip archive from the downloadables.
         await CreateZipArchiveAsync(tempFilePath, downloadables, cancellationToken);
@@ -54,7 +54,7 @@ internal class ZipManager
         var zipStream = File.OpenRead(tempFilePath);
         return (zipBlob, zipStream, () => Cleanup(tempFilePath));
     }
-    
+
     /// <summary>
     /// Loads a cached zip blob for the specified download correlation ID.
     /// </summary>
@@ -174,6 +174,13 @@ internal class ZipManager
         return (downloadAsFilename, contentType);
     }
     
+    private string GetTempFilePath()
+    {
+        var tempFileName = Path.GetRandomFileName();
+        var tempFilePath = Path.Combine(_fileCacheOptions.Value.LocalCacheDirectory, tempFileName);
+        return tempFilePath;
+    }
+    
     private void Cleanup(string filePath)
     {
         try