Merge pull request #794 from TechnologyEnhancedLearning/Develop/Fixes/TD-5176

TD-5176 file download refactor

Author: OluwatobiAwe

LearningHub.Nhs.WebUI/Services/FileService.cs

@@ -9,6 +9,7 @@
     using System.Threading.Tasks;
     using System.Threading.Tasks.Dataflow;
     using Azure;
+    using Azure.Storage;
     using Azure.Storage.Files.Shares;
     using Azure.Storage.Files.Shares.Models;
     using LearningHub.Nhs.Models.Resource;
@@ -133,10 +134,6 @@ public async Task DeleteChunkDirectory(string directoryRef, int chunks)
         /// <returns>The <see cref="Task{FileDownloadResponse}"/>.</returns>
         public async Task<FileDownloadResponse> DownloadFileAsync(string filePath, string fileName)
         {
-            const int ChunkSizeInMB = 100;
-            const int MaxParallelDownloads = 8;
-            int chunkSize = ChunkSizeInMB * 1024 * 1024;
-
             var file = await this.FindFileAsync(filePath, fileName);
             if (file == null)
             {
@@ -146,9 +143,9 @@ public async Task<FileDownloadResponse> DownloadFileAsync(string filePath, strin
             var properties = await file.GetPropertiesAsync();
             long fileSize = properties.Value.ContentLength;
 
-            // If the file size is less than 500 MB, download it directly
-            if (fileSize <= 500 * 1024 * 1024)
+            try
             {
+                // Directly download the entire file as a stream
                 var response = await file.DownloadAsync();
                 return new FileDownloadResponse
                 {
@@ -157,52 +154,10 @@ public async Task<FileDownloadResponse> DownloadFileAsync(string filePath, strin
                     ContentLength = fileSize,
                 };
             }
-
-            var pipe = new System.IO.Pipelines.Pipe();
-            var semaphore = new SemaphoreSlim(1, 1);
-
-            var downloadBlock = new ActionBlock<long>(
-                async offset =>
-                {
-                    long rangeSize = Math.Min(chunkSize, fileSize - offset);
-                    try
-                    {
-                        var response = await file.DownloadAsync(new HttpRange(offset, rangeSize));
-                        var buffer = new byte[rangeSize];
-                        await response.Value.Content.ReadAsync(buffer, 0, (int)rangeSize);
-
-                        await semaphore.WaitAsync();
-                        try
-                        {
-                            pipe.Writer.Write(buffer);
-                        }
-                        finally
-                        {
-                            semaphore.Release();
-                        }
-                    }
-                    catch (Exception ex)
-                    {
-                        throw new Exception($"Error downloading chunk at offset {offset}: {ex.Message}");
-                    }
-                },
-                new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = MaxParallelDownloads, EnsureOrdered = false });
-
-            for (long offset = 0; offset < fileSize; offset += chunkSize)
+            catch (Exception ex)
             {
-                downloadBlock.Post(offset);
+                throw new Exception($"Error downloading file: {ex.Message}");
             }
-
-            downloadBlock.Complete();
-            await downloadBlock.Completion;
-            await pipe.Writer.CompleteAsync();
-
-            return new FileDownloadResponse
-            {
-                Content = pipe.Reader.AsStream(),
-                ContentType = properties.Value.ContentType,
-                ContentLength = fileSize,
-            };
         }
 
         /// <summary>