TD-5348 azure file download service

Author: OluwatobiAwe

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

@@ -69,9 +69,10 @@ 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);
+                return !string.IsNullOrEmpty(file.DownloadUrl) ? this.Redirect(file.DownloadUrl) : this.File(file.Content, file.ContentType, fileName);
             }
             else
             {
@@ -106,7 +107,8 @@ public async Task<IActionResult> DownloadResourceAndRecordActivity(int resourceV
                     ActivityStatus = ActivityStatusEnum.Completed,
                 };
                 await this.activityService.CreateResourceActivityAsync(activity);
-                return this.File(file.Content, file.ContentType, fileName);
+
+                return !string.IsNullOrEmpty(file.DownloadUrl) ? this.Redirect(file.DownloadUrl) : this.File(file.Content, file.ContentType, fileName);
             }
             else
             {

LearningHub.Nhs.WebUI/Models/FileDownloadResponse.cs

@@ -21,5 +21,10 @@ public class FileDownloadResponse
         /// Gets or sets the ContentType.
         /// </summary>
         public long ContentLength { get; set; }
+
+        /// <summary>
+        /// Gets or sets when downloading large files, a SAS URL is returned so the client can download directly from Azure Files.
+        /// </summary>
+        public string DownloadUrl { get; set; }
     }
 }

LearningHub.Nhs.WebUI/Services/FileService.cs

@@ -1,17 +1,13 @@
 namespace LearningHub.Nhs.WebUI.Services
 {
     using System;
-    using System.Buffers;
     using System.Collections.Generic;
     using System.IO;
     using System.Linq;
-    using System.Threading;
     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 Azure.Storage.Sas;
     using LearningHub.Nhs.Models.Resource;
     using LearningHub.Nhs.WebUI.Configuration;
     using LearningHub.Nhs.WebUI.Interfaces;
@@ -145,26 +141,19 @@ public async Task<FileDownloadResponse> DownloadFileAsync(string filePath, strin
 
             try
             {
-                if (fileSize <= 900 * 1024 * 1024)
+                var response = new FileDownloadResponse
                 {
-                    // Directly 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
+                    ContentType = properties.Value.ContentType,
+                    ContentLength = fileSize,
+                    Content = await file.OpenReadAsync(),
+                };
+
+                if (fileSize >= 999 * 1024 * 1024)
                 {
-                    return new FileDownloadResponse
-                    {
-                        Content = await file.OpenReadAsync(),
-                        ContentType = properties.Value.ContentType,
-                        ContentLength = fileSize,
-                    };
+                    response.DownloadUrl = this.GenerateSasUriForFile(file);
                 }
+
+                return response;
             }
             catch (Exception ex)
             {
@@ -460,5 +449,23 @@ private async Task<ShareFileClient> FindFileAsync(string filePath, string fileNa
 
             return null;
         }
+
+        private string GenerateSasUriForFile(ShareFileClient fileClient)
+        {
+            if (fileClient.CanGenerateSasUri)
+            {
+                ShareSasBuilder sasBuilder = new ShareSasBuilder(ShareFileSasPermissions.Read, DateTimeOffset.UtcNow.AddMinutes(20))
+                {
+                    Protocol = SasProtocol.Https,
+                };
+
+                Uri sasUri = fileClient.GenerateSasUri(sasBuilder);
+                return sasUri.ToString();
+            }
+            else
+            {
+                throw new InvalidOperationException("Unable to generate SAS URI for the file.");
+            }
+        }
     }
 }