Extract some Controller methods into extensions

src/Tgstation.Server.Host/Controllers/AdministrationController.cs

@@ -19,6 +19,7 @@ using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.Core;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.IO;
 using Tgstation.Server.Host.Security;
 using Tgstation.Server.Host.System;
@@ -173,7 +174,7 @@ namespace Tgstation.Server.Host.Controllers
 			catch (ApiException e)
 			{
 				Logger.LogWarning(e, OctokitException);
-				return StatusCode(HttpStatusCode.FailedDependency, new ErrorMessageResponse(ErrorCode.RemoteApiError)
+				return this.StatusCode(HttpStatusCode.FailedDependency, new ErrorMessageResponse(ErrorCode.RemoteApiError)
 				{
 					AdditionalData = e.Message,
 				});
@@ -224,9 +225,9 @@ namespace Tgstation.Server.Host.Controllers
 					{
 						NewVersion = model.NewVersion,
 					}),
-					ServerUpdateResult.ReleaseMissing => Gone(),
+					ServerUpdateResult.ReleaseMissing => this.Gone(),
 					ServerUpdateResult.UpdateInProgress => BadRequest(new ErrorMessageResponse(ErrorCode.ServerUpdateInProgress)),
-					ServerUpdateResult.SwarmIntegrityCheckFailed => StatusCode(HttpStatusCode.FailedDependency, new ErrorMessageResponse(ErrorCode.SwarmIntegrityCheckFailed)),
+					ServerUpdateResult.SwarmIntegrityCheckFailed => this.StatusCode(HttpStatusCode.FailedDependency, new ErrorMessageResponse(ErrorCode.SwarmIntegrityCheckFailed)),
 					_ => throw new InvalidOperationException($"Unexpected ServerUpdateResult: {updateResult}"),
 				};
 			}
@@ -237,7 +238,7 @@ namespace Tgstation.Server.Host.Controllers
 			catch (ApiException e)
 			{
 				Logger.LogWarning(e, OctokitException);
-				return StatusCode(HttpStatusCode.FailedDependency, new ErrorMessageResponse(ErrorCode.RemoteApiError)
+				return this.StatusCode(HttpStatusCode.FailedDependency, new ErrorMessageResponse(ErrorCode.RemoteApiError)
 				{
 					AdditionalData = e.Message,
 				});

src/Tgstation.Server.Host/Controllers/ApiController.cs

@@ -14,13 +14,16 @@ using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Query;
 using Microsoft.Extensions.Logging;
 using Microsoft.Net.Http.Headers;
+
 using Octokit;
+
 using Serilog.Context;
 
 using Tgstation.Server.Api;
 using Tgstation.Server.Api.Models;
 using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
 using Tgstation.Server.Host.Utils;
@@ -119,7 +122,7 @@ namespace Tgstation.Server.Host.Controllers
 
 				if (!ApiHeaders.Compatible())
 				{
-					await StatusCode(
+					await this.StatusCode(
 						HttpStatusCode.UpgradeRequired,
 						new ErrorMessageResponse(ErrorCode.ApiMismatch))
 						.ExecuteResultAsync(context)
@@ -206,12 +209,6 @@ namespace Tgstation.Server.Host.Controllers
 		}
 #pragma warning restore CA1506
 
-		/// <summary>
-		/// Generic 410 response.
-		/// </summary>
-		/// <returns>An <see cref="ObjectResult"/> with <see cref="HttpStatusCode.Gone"/>.</returns>
-		protected ObjectResult Gone() => StatusCode(HttpStatusCode.Gone, new ErrorMessageResponse(ErrorCode.ResourceNotPresent));
-
 		/// <summary>
 		/// Generic 404 response.
 		/// </summary>
@@ -222,7 +219,7 @@ namespace Tgstation.Server.Host.Controllers
 		/// Generic 501 response.
 		/// </summary>
 		/// <returns>An <see cref="ObjectResult"/> with <see cref="HttpStatusCode.NotImplemented"/>.</returns>
-		protected ObjectResult RequiresPosixSystemIdentity() => StatusCode(HttpStatusCode.NotImplemented, new ErrorMessageResponse(ErrorCode.RequiresPosixSystemIdentity));
+		protected ObjectResult RequiresPosixSystemIdentity() => this.StatusCode(HttpStatusCode.NotImplemented, new ErrorMessageResponse(ErrorCode.RequiresPosixSystemIdentity));
 
 		/// <summary>
 		/// Strongly type calls to <see cref="ControllerBase.StatusCode(int)"/>.
@@ -231,14 +228,6 @@ namespace Tgstation.Server.Host.Controllers
 		/// <returns>A <see cref="StatusCodeResult"/> with the given <paramref name="statusCode"/>.</returns>
 		protected StatusCodeResult StatusCode(HttpStatusCode statusCode) => StatusCode((int)statusCode);
 
-		/// <summary>
-		/// Strongly type calls to <see cref="ControllerBase.StatusCode(int, object)"/>.
-		/// </summary>
-		/// <param name="statusCode">The <see cref="HttpStatusCode"/>.</param>
-		/// <param name="errorMessage">The accompanying <see cref="ErrorMessageResponse"/> payload.</param>
-		/// <returns>A <see cref="StatusCodeResult"/> with the given <paramref name="statusCode"/>.</returns>
-		protected ObjectResult StatusCode(HttpStatusCode statusCode, object errorMessage) => StatusCode((int)statusCode, errorMessage);
-
 		/// <summary>
 		/// Generic 201 response with a given <paramref name="payload"/>.
 		/// </summary>
@@ -260,7 +249,7 @@ namespace Tgstation.Server.Host.Controllers
 
 			var secondsString = Math.Ceiling(rateLimitException.GetRetryAfterTimeSpan().TotalSeconds).ToString(CultureInfo.InvariantCulture);
 			Response.Headers.Add(HeaderNames.RetryAfter, secondsString);
-			return StatusCode(HttpStatusCode.TooManyRequests, new ErrorMessageResponse(ErrorCode.GitHubApiRateLimit));
+			return this.StatusCode(HttpStatusCode.TooManyRequests, new ErrorMessageResponse(ErrorCode.GitHubApiRateLimit));
 		}
 
 		/// <summary>
@@ -295,7 +284,7 @@ namespace Tgstation.Server.Host.Controllers
 			};
 
 			if (headersException.MissingOrMalformedHeaders.HasFlag(HeaderTypes.Accept))
-				return StatusCode(HttpStatusCode.NotAcceptable, errorMessage);
+				return this.StatusCode(HttpStatusCode.NotAcceptable, errorMessage);
 
 			return BadRequest(errorMessage);
 		}

src/Tgstation.Server.Host/Controllers/ByondController.cs

@@ -14,6 +14,7 @@ using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Components;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Jobs;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
@@ -290,7 +291,7 @@ namespace Tgstation.Server.Host.Controllers
 
 					return Task.FromResult<IActionResult>(
 						versionNotInstalled
-							? Gone()
+							? this.Gone()
 							: null);
 				});
 

src/Tgstation.Server.Host/Controllers/ChatController.cs

@@ -20,6 +20,7 @@ using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Components;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
 
@@ -165,7 +166,7 @@ namespace Tgstation.Server.Host.Controllers
 					return null;
 				})
 
-				?? StatusCode(HttpStatusCode.Created, dbModel.ToApi());
+				?? this.StatusCode(HttpStatusCode.Created, dbModel.ToApi());
 		}
 
 		/// <summary>
@@ -251,7 +252,7 @@ namespace Tgstation.Server.Host.Controllers
 
 			var results = await query.FirstOrDefaultAsync(cancellationToken);
 			if (results == default)
-				return Gone();
+				return this.Gone();
 
 			var connectionStrings = (AuthenticationContext.GetRight(RightsType.ChatBots) & (ulong)ChatBotRights.ReadConnectionString) != 0;
 
@@ -295,7 +296,7 @@ namespace Tgstation.Server.Host.Controllers
 			var current = await query.FirstOrDefaultAsync(cancellationToken);
 
 			if (current == default)
-				return Gone();
+				return this.Gone();
 
 			if ((model.Channels?.Count ?? current.Channels.Count) > (model.ChannelLimit ?? current.ChannelLimit.Value))
 			{

src/Tgstation.Server.Host/Controllers/ConfigurationController.cs

@@ -14,6 +14,7 @@ using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Components;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.IO;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
@@ -132,7 +133,7 @@ namespace Tgstation.Server.Host.Controllers
 							.Read(filePath, systemIdentity, cancellationToken)
 							;
 						if (result == null)
-							return Gone();
+							return this.Gone();
 
 						return Json(result);
 					})
@@ -186,7 +187,7 @@ namespace Tgstation.Server.Host.Controllers
 								.ListDirectory(directoryPath, systemIdentity, cancellationToken)
 								;
 							if (result == null)
-								return new PaginatableResult<ConfigurationFileResponse>(Gone());
+								return new PaginatableResult<ConfigurationFileResponse>(this.Gone());
 
 							return new PaginatableResult<ConfigurationFileResponse>(
 								result

src/Tgstation.Server.Host/Controllers/DreamDaemonController.cs

@@ -17,6 +17,7 @@ using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Components;
 using Tgstation.Server.Host.Components.Session;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Jobs;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
@@ -173,7 +174,7 @@ namespace Tgstation.Server.Host.Controllers
 				.FirstOrDefaultAsync(cancellationToken);
 
 			if (current == default)
-				return Gone();
+				return this.Gone();
 
 			if (model.Port.HasValue && model.Port.Value != current.Port.Value)
 			{
@@ -339,7 +340,7 @@ namespace Tgstation.Server.Host.Controllers
 						.FirstOrDefaultAsync(cancellationToken)
 						;
 					if (settings == default)
-						return Gone();
+						return this.Gone();
 				}
 
 				var result = new DreamDaemonResponse();

src/Tgstation.Server.Host/Controllers/DreamMakerController.cs

@@ -14,6 +14,7 @@ using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Components;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Jobs;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
@@ -191,7 +192,7 @@ namespace Tgstation.Server.Host.Controllers
 				.FirstOrDefaultAsync(cancellationToken)
 				;
 			if (hostModel == null)
-				return Gone();
+				return this.Gone();
 
 			if (model.ProjectName != null)
 			{

src/Tgstation.Server.Host/Controllers/HomeController.cs

@@ -21,6 +21,7 @@ using Tgstation.Server.Host.Components.Interop;
 using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.Core;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
 using Tgstation.Server.Host.Security.OAuth;
@@ -178,7 +179,7 @@ namespace Tgstation.Server.Host.Controllers
 					// we only allow authorization header issues
 					var headers = new ApiHeaders(Request.GetTypedHeaders(), true);
 					if (!headers.Compatible())
-						return StatusCode(
+						return this.StatusCode(
 							HttpStatusCode.UpgradeRequired,
 							new ErrorMessageResponse(ErrorCode.ApiMismatch));
 				}

src/Tgstation.Server.Host/Controllers/InstanceController.cs

@@ -20,6 +20,7 @@ using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Components;
 using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.IO;
 using Tgstation.Server.Host.Jobs;
 using Tgstation.Server.Host.Models;
@@ -288,7 +289,7 @@ namespace Tgstation.Server.Host.Controllers
 				.Where(x => x.Id == id && x.SwarmIdentifer == swarmConfiguration.Identifier)
 				.FirstOrDefaultAsync(cancellationToken);
 			if (originalModel == default)
-				return Gone();
+				return this.Gone();
 			if (originalModel.Online.Value)
 				return Conflict(new ErrorMessageResponse(ErrorCode.InstanceDetachOnline));
 
@@ -359,7 +360,7 @@ namespace Tgstation.Server.Host.Controllers
 				.Include(x => x.DreamDaemonSettings) // need these for onlining
 				.FirstOrDefaultAsync(cancellationToken);
 			if (originalModel == default(Models.Instance))
-				return Gone();
+				return this.Gone();
 
 			if (ValidateInstanceOnlineStatus(originalModel))
 				await DatabaseContext.Save(cancellationToken);
@@ -604,7 +605,7 @@ namespace Tgstation.Server.Host.Controllers
 			var instance = await QueryForUser().FirstOrDefaultAsync(cancellationToken);
 
 			if (instance == null)
-				return Gone();
+				return this.Gone();
 
 			if (ValidateInstanceOnlineStatus(instance))
 				await DatabaseContext.Save(cancellationToken);
@@ -664,7 +665,7 @@ namespace Tgstation.Server.Host.Controllers
 					;
 
 				if (!instanceExists)
-					return Gone();
+					return this.Gone();
 
 				var instanceAdminUser = InstanceAdminPermissionSet(null);
 				instanceAdminUser.InstanceId = id;

src/Tgstation.Server.Host/Controllers/InstancePermissionSetController.cs

@@ -14,6 +14,7 @@ using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Components;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
 
@@ -77,7 +78,7 @@ namespace Tgstation.Server.Host.Controllers
 				;
 
 			if (existingPermissionSet == default)
-				return Gone();
+				return this.Gone();
 
 			if (existingPermissionSet.UserId.HasValue)
 			{
@@ -140,7 +141,7 @@ namespace Tgstation.Server.Host.Controllers
 				.FirstOrDefaultAsync(cancellationToken)
 				;
 			if (originalPermissionSet == null)
-				return Gone();
+				return this.Gone();
 
 			originalPermissionSet.ByondRights = RightsHelper.Clamp(model.ByondRights ?? originalPermissionSet.ByondRights.Value);
 			originalPermissionSet.RepositoryRights = RightsHelper.Clamp(model.RepositoryRights ?? originalPermissionSet.RepositoryRights.Value);
@@ -222,7 +223,7 @@ namespace Tgstation.Server.Host.Controllers
 				.FirstOrDefaultAsync(cancellationToken)
 				;
 			if (permissionSet == default)
-				return Gone();
+				return this.Gone();
 			return Json(permissionSet.ToApi());
 		}
 
@@ -248,7 +249,7 @@ namespace Tgstation.Server.Host.Controllers
 				.Where(x => x.PermissionSetId == id)
 				.DeleteAsync(cancellationToken)
 				;
-			return numDeleted > 0 ? NoContent() : Gone();
+			return numDeleted > 0 ? NoContent() : this.Gone();
 		}
 	}
 }

src/Tgstation.Server.Host/Controllers/JobController.cs

@@ -12,6 +12,7 @@ using Tgstation.Server.Api.Models;
 using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Host.Components;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Jobs;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
@@ -139,7 +140,7 @@ namespace Tgstation.Server.Host.Controllers
 				return Forbid();
 
 			var updatedJob = await jobManager.CancelJob(job, AuthenticationContext.User, false, cancellationToken);
-			return updatedJob != null ? Accepted(updatedJob.ToApi()) : Gone();
+			return updatedJob != null ? Accepted(updatedJob.ToApi()) : this.Gone();
 		}
 
 		/// <summary>

src/Tgstation.Server.Host/Controllers/RepositoryController.cs

@@ -18,6 +18,7 @@ using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Components;
 using Tgstation.Server.Host.Components.Repository;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Jobs;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
@@ -107,7 +108,7 @@ namespace Tgstation.Server.Host.Controllers
 				;
 
 			if (currentModel == default)
-				return Gone();
+				return this.Gone();
 
 			currentModel.UpdateSubmodules = model.UpdateSubmodules ?? true;
 			currentModel.AccessToken = model.AccessToken;
@@ -214,7 +215,7 @@ namespace Tgstation.Server.Host.Controllers
 				;
 
 			if (currentModel == default)
-				return Gone();
+				return this.Gone();
 
 			currentModel.AccessToken = null;
 			currentModel.AccessUser = null;
@@ -262,7 +263,7 @@ namespace Tgstation.Server.Host.Controllers
 				;
 
 			if (currentModel == default)
-				return Gone();
+				return this.Gone();
 
 			var api = currentModel.ToApi();
 
@@ -351,7 +352,7 @@ namespace Tgstation.Server.Host.Controllers
 				;
 
 			if (currentModel == default)
-				return Gone();
+				return this.Gone();
 
 			bool CheckModified<T>(Expression<Func<Api.Models.Internal.RepositorySettings, T>> expression, RepositoryRights requiredRight)
 			{

src/Tgstation.Server.Host/Controllers/TransferController.cs

@@ -1,20 +1,16 @@
 using System;
 using System.ComponentModel.DataAnnotations;
-using System.Linq;
-using System.Net;
-using System.Net.Mime;
 using System.Threading;
 using System.Threading.Tasks;
 
-using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Extensions.Logging;
-using Microsoft.Net.Http.Headers;
 
 using Tgstation.Server.Api;
 using Tgstation.Server.Api.Models;
 using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Security;
 using Tgstation.Server.Host.Transfer;
 
@@ -65,41 +61,8 @@ namespace Tgstation.Server.Host.Controllers
 		[HttpGet]
 		[ProducesResponseType(200, Type = typeof(LimitedStreamResult))]
 		[ProducesResponseType(410, Type = typeof(ErrorMessageResponse))]
-		public async Task<IActionResult> Download([Required, FromQuery] string ticket, CancellationToken cancellationToken)
-		{
-			if (ticket == null)
-				return BadRequest(new ErrorMessageResponse(ErrorCode.ModelValidationFailure));
-
-			var streamAccept = new MediaTypeHeaderValue(MediaTypeNames.Application.Octet);
-			if (!Request.GetTypedHeaders().Accept.Any(x => streamAccept.IsSubsetOf(x)))
-				return StatusCode(HttpStatusCode.NotAcceptable, new ErrorMessageResponse(ErrorCode.BadHeaders)
-				{
-					AdditionalData = $"File downloads must accept both {MediaTypeNames.Application.Octet} and {MediaTypeNames.Application.Json}!",
-				});
-
-			var fileTicketResult = new FileTicketResponse
-			{
-				FileTicket = ticket,
-			};
-
-			var tuple = await fileTransferService.RetrieveDownloadStream(fileTicketResult, cancellationToken);
-			var stream = tuple.Item1;
-			try
-			{
-				if (tuple.Item2 != null)
-					return Conflict(tuple.Item2);
-
-				if (stream == null)
-					return Gone();
-
-				return new LimitedStreamResult(stream);
-			}
-			catch
-			{
-				await stream.DisposeAsync();
-				throw;
-			}
-		}
+		public Task<IActionResult> Download([Required, FromQuery] string ticket, CancellationToken cancellationToken)
+			=> fileTransferService.GenerateDownloadResponse(this, ticket, cancellationToken);
 
 		/// <summary>
 		/// Uploads a file with a given <paramref name="ticket"/>.
@@ -127,7 +90,7 @@ namespace Tgstation.Server.Host.Controllers
 			var result = await fileTransferService.SetUploadStream(fileTicketResult, Request.Body, cancellationToken);
 			if (result != null)
 				return result.ErrorCode == ErrorCode.ResourceNotPresent
-					? Gone()
+					? this.Gone()
 					: Conflict(result);
 
 			return NoContent();

src/Tgstation.Server.Host/Controllers/UserController.cs

@@ -16,6 +16,7 @@ using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
 
@@ -116,14 +117,14 @@ namespace Tgstation.Server.Host.Controllers
 
 			var dbUser = await CreateNewUserFromModel(model, cancellationToken);
 			if (dbUser == null)
-				return Gone();
+				return this.Gone();
 
 			if (model.SystemIdentifier != null)
 				try
 				{
 					using var sysIdentity = await systemIdentityFactory.CreateSystemIdentity(dbUser, cancellationToken);
 					if (sysIdentity == null)
-						return Gone();
+						return this.Gone();
 					dbUser.Name = sysIdentity.Username;
 					dbUser.SystemIdentifier = sysIdentity.Uid;
 				}
@@ -269,7 +270,7 @@ namespace Tgstation.Server.Host.Controllers
 					;
 
 				if (originalUser.Group == default)
-					return Gone();
+					return this.Gone();
 
 				DatabaseContext.Groups.Attach(originalUser.Group);
 				if (originalUser.PermissionSet != null)

src/Tgstation.Server.Host/Controllers/UserGroupController.cs

@@ -15,6 +15,7 @@ using Tgstation.Server.Api.Models.Response;
 using Tgstation.Server.Api.Rights;
 using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.Database;
+using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.Models;
 using Tgstation.Server.Host.Security;
 
@@ -125,7 +126,7 @@ namespace Tgstation.Server.Host.Controllers
 				;
 
 			if (currentGroup == default)
-				return Gone();
+				return this.Gone();
 
 			if (model.PermissionSet != null)
 			{
@@ -170,7 +171,7 @@ namespace Tgstation.Server.Host.Controllers
 				.FirstOrDefaultAsync(cancellationToken)
 				;
 			if (group == default)
-				return Gone();
+				return this.Gone();
 			return Json(group.ToApi(true));
 		}
 
@@ -236,7 +237,7 @@ namespace Tgstation.Server.Host.Controllers
 
 			return groupExists
 				? Conflict(new ErrorMessageResponse(ErrorCode.UserGroupNotEmpty))
-				: Gone();
+				: this.Gone();
 		}
 	}
 }

src/Tgstation.Server.Host/Extensions/ControllerBaseExtensions.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Net;
+
+using Microsoft.AspNetCore.Mvc;
+
+using Tgstation.Server.Api.Models;
+using Tgstation.Server.Api.Models.Response;
+
+namespace Tgstation.Server.Host.Extensions
+{
+	/// <summary>
+	/// Extension methods for <see cref="ControllerBase"/>.
+	/// </summary>
+	static class ControllerBaseExtensions
+	{
+		/// <summary>
+		/// Generic 410 response.
+		/// </summary>
+		/// <param name="controller">The <see cref="ControllerBase"/> the request is coming from.</param>
+		/// <returns>An <see cref="ObjectResult"/> with <see cref="HttpStatusCode.Gone"/>.</returns>
+		public static ObjectResult Gone(this ControllerBase controller)
+			=> controller?.StatusCode(HttpStatusCode.Gone, new ErrorMessageResponse(ErrorCode.ResourceNotPresent)) ?? throw new ArgumentNullException(nameof(controller));
+
+		/// <summary>
+		/// Strongly type calls to <see cref="ControllerBase.StatusCode(int, object)"/>.
+		/// </summary>
+		/// <param name="controller">The <see cref="ControllerBase"/> the request is coming from.</param>
+		/// <param name="statusCode">The <see cref="HttpStatusCode"/>.</param>
+		/// <param name="errorMessage">The accompanying <see cref="ErrorMessageResponse"/> payload.</param>
+		/// <returns>A <see cref="StatusCodeResult"/> with the given <paramref name="statusCode"/>.</returns>
+		public static ObjectResult StatusCode(this ControllerBase controller, HttpStatusCode statusCode, object errorMessage)
+			=> controller?.StatusCode((int)statusCode, errorMessage) ?? throw new ArgumentNullException(nameof(controller));
+	}
+}

src/Tgstation.Server.Host/Extensions/FileTransferStreamHandlerExtensions.cs

@@ -0,0 +1,78 @@
+using System;
+using System.Linq;
+using System.Net;
+using System.Net.Mime;
+using System.Threading;
+using System.Threading.Tasks;
+
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Net.Http.Headers;
+
+using Tgstation.Server.Api.Models;
+using Tgstation.Server.Api.Models.Response;
+using Tgstation.Server.Host.Controllers;
+using Tgstation.Server.Host.Transfer;
+
+namespace Tgstation.Server.Host.Extensions
+{
+	/// <summary>
+	/// Extension methods for <see cref="IFileTransferStreamHandler"/>.
+	/// </summary>
+	static class FileTransferStreamHandlerExtensions
+	{
+		/// <summary>
+		/// Downloads a file with a given <paramref name="ticket"/>.
+		/// </summary>
+		/// <param name="fileTransferService">The <see cref="IFileTransferStreamHandler"/>.</param>
+		/// <param name="controller">The <see cref="ControllerBase"/> the request is coming from.</param>
+		/// <param name="ticket">The <see cref="FileTicketResponse.FileTicket"/> for the download.</param>
+		/// <param name="cancellationToken">The <see cref="CancellationToken"/> for the operation.</param>
+		/// <returns>A <see cref="Task{TResult}"/> resulting in the <see cref="IActionResult"/> of the method.</returns>
+		public static async Task<IActionResult> GenerateDownloadResponse(
+			this IFileTransferStreamHandler fileTransferService,
+			ControllerBase controller,
+			string ticket,
+			CancellationToken cancellationToken)
+		{
+			if (fileTransferService == null)
+				throw new ArgumentNullException(nameof(fileTransferService));
+
+			if (controller == null)
+				throw new ArgumentNullException(nameof(controller));
+
+			if (ticket == null)
+				return controller.BadRequest(new ErrorMessageResponse(ErrorCode.ModelValidationFailure));
+
+			var streamAccept = new MediaTypeHeaderValue(MediaTypeNames.Application.Octet);
+			if (!controller.Request.GetTypedHeaders().Accept.Any(streamAccept.IsSubsetOf))
+				return controller.StatusCode((int)HttpStatusCode.NotAcceptable, new ErrorMessageResponse(ErrorCode.BadHeaders)
+				{
+					AdditionalData = $"File downloads must accept both {MediaTypeNames.Application.Octet} and {MediaTypeNames.Application.Json}!",
+				});
+
+			var fileTicketResult = new FileTicketResponse
+			{
+				FileTicket = ticket,
+			};
+
+			var tuple = await fileTransferService.RetrieveDownloadStream(fileTicketResult, cancellationToken);
+			var stream = tuple.Item1;
+			try
+			{
+				if (tuple.Item2 != null)
+					return controller.Conflict(tuple.Item2);
+
+				if (stream == null)
+					return controller.Gone();
+
+				return new LimitedStreamResult(stream);
+			}
+			catch
+			{
+				await stream.DisposeAsync();
+				throw;
+			}
+		}
+	}
+}