TD-5348 stream files with keep alive.

Author: OluwatobiAwe

LearningHub.Nhs.WebUI/Controllers/Api/ResourceController.cs

@@ -2,13 +2,18 @@ namespace LearningHub.Nhs.WebUI.Controllers.Api
 {
     using System;
     using System.Collections.Generic;
+    using System.IO;
+    using System.Linq;
+    using System.Net.Http.Headers;
+    using System.Threading;
     using System.Threading.Tasks;
     using LearningHub.Nhs.Models.Enums;
     using LearningHub.Nhs.Models.Resource;
     using LearningHub.Nhs.Models.Resource.Activity;
     using LearningHub.Nhs.Models.Resource.Contribute;
     using LearningHub.Nhs.WebUI.Interfaces;
     using Microsoft.AspNetCore.Authorization;
+    using Microsoft.AspNetCore.Http;
     using Microsoft.AspNetCore.Mvc;
     using Microsoft.Extensions.Configuration;
 
@@ -70,7 +75,15 @@ public async Task<IActionResult> DownloadResource(string filePath, string fileNa
             var file = await this.fileService.DownloadFileAsync(filePath, fileName);
             if (file != null)
             {
-                return this.File(file.Content, file.ContentType, fileName);
+                // Set response headers.
+                this.Response.ContentType = file.ContentType;
+                this.Response.ContentLength = file.ContentLength;
+                var contentDisposition = new ContentDispositionHeaderValue("attachment") { FileNameStar = fileName };
+                this.Response.Headers["Content-Disposition"] = contentDisposition.ToString();
+
+                // Stream the file in chunks with periodic flushes to keep the connection active.
+                await this.StreamFileWithKeepAliveAsync(file.Content, this.Response.Body, this.HttpContext.RequestAborted);
+                return this.Ok();
             }
             else
             {
@@ -105,7 +118,16 @@ public async Task<IActionResult> DownloadResourceAndRecordActivity(int resourceV
                     ActivityStatus = ActivityStatusEnum.Completed,
                 };
                 await this.activityService.CreateResourceActivityAsync(activity);
-                return this.File(file.Content, file.ContentType, fileName);
+
+                // Set response headers.
+                this.Response.ContentType = file.ContentType;
+                this.Response.ContentLength = file.ContentLength;
+                var contentDisposition = new ContentDispositionHeaderValue("attachment") { FileNameStar = fileName };
+                this.Response.Headers["Content-Disposition"] = contentDisposition.ToString();
+
+                // Stream the file in chunks with periodic flushes to keep the connection active.
+                await this.StreamFileWithKeepAliveAsync(file.Content, this.Response.Body, this.HttpContext.RequestAborted);
+                return this.Ok();
             }
             else
             {
@@ -584,5 +606,20 @@ public async Task<List<string>> GetObsoleteResourceFile(int resourceVersionId, b
             var result = await this.resourceService.GetObsoleteResourceFile(resourceVersionId, deletedResource);
             return result;
         }
+
+        /// <summary>
+        /// Reads from the source stream in chunks and writes to the destination stream,
+        /// flushing after each chunk to help keep the connection active.
+        /// </summary>
+        private async Task StreamFileWithKeepAliveAsync(Stream source, Stream destination, CancellationToken cancellationToken)
+        {
+            byte[] buffer = new byte[8192];
+            int bytesRead;
+            while ((bytesRead = await source.ReadAsync(buffer, 0, buffer.Length, cancellationToken)) > 0)
+            {
+                await destination.WriteAsync(buffer, 0, bytesRead, cancellationToken);
+                await destination.FlushAsync(cancellationToken);
+            }
+        }
     }
 }

LearningHub.Nhs.WebUI/Services/FileService.cs

@@ -135,20 +135,37 @@ public async Task<ShareFileDownloadInfo> DownloadFileAsync(string filePath, stri
             {
                 var file = directory.GetFileClient(fileName);
 
-                if (await file.ExistsAsync())
+            var properties = await file.GetPropertiesAsync();
+            long fileSize = properties.Value.ContentLength;
+
+            try
+            {
+                if (fileSize <= 900 * 1024 * 1024)
                 {
-                    return await file.DownloadAsync();
+                    // For smaller files, download the entire file as a stream.
+                    var response = await file.DownloadAsync();
+                    return new FileDownloadResponse
+                    {
+                        Content = response.Value.Content,
+                        ContentType = properties.Value.ContentType,
+                        ContentLength = fileSize,
+                    };
                 }
-            }
-            else if (await sourceDirectory.ExistsAsync())
-            {
-                var file = sourceDirectory.GetFileClient(fileName);
-
-                if (await file.ExistsAsync())
+                else
                 {
-                    return await file.DownloadAsync();
+                    // For large files, open a read stream
+                    return new FileDownloadResponse
+                    {
+                        Content = await file.OpenReadAsync(),
+                        ContentType = properties.Value.ContentType,
+                        ContentLength = fileSize,
+                    };
                 }
             }
+            catch (Exception ex)
+            {
+                throw new Exception($"Error downloading file: {ex.Message}");
+            }
 
             return null;
         }