Add export download endpoint

src/Gameboard.Api/Features/Game/GameController.cs

@@ -154,6 +154,14 @@ public Task<GamePlayState> GetGamePlayState(string gameId)
         public Task<ExportGamesResult> ExportGames([FromBody] ExportGameCommand request, CancellationToken cancellationToken)
             => _mediator.Send(request, cancellationToken);
 
+        [HttpGet("/api/games/export/{exportBatchId}")]
+        [ProducesResponseType(typeof(FileContentResult), 200)]
+        public async Task<FileContentResult> DownloadExportPackage(string exportBatchId, CancellationToken cancellationToken)
+        {
+            var bytes = await _mediator.Send(new DownloadExportPackageRequest(exportBatchId), cancellationToken);
+            return new FileContentResult(bytes, "application/zip");
+        }
+
         [HttpPost("/api/games/import")]
         public async Task<ImportedGame[]> ImportGames([FromForm] IFormFile packageFile, CancellationToken cancellationToken)
         {

src/Gameboard.Api/Features/Game/ImportExport/GameImportExportModels.cs

@@ -124,3 +124,8 @@ public sealed class ImportedGame
     public required string Id { get; set; }
     public required string Name { get; set; }
 }
+
+public sealed class ExportPackageNotFound : GameboardException
+{
+    public ExportPackageNotFound(string exportBatchId) : base($"Export package {exportBatchId} doesn't exist.") { }
+}

src/Gameboard.Api/Features/Game/ImportExport/GameImportExportService.cs

@@ -2,7 +2,6 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
 using Gameboard.Api.Common.Services;
@@ -19,6 +18,7 @@ namespace Gameboard.Api.Features.Games;
 
 public interface IGameImportExportService
 {
+    Task<byte[]> GetExportedPackageContent(string exportBatchId, CancellationToken cancellationToken);
     Task<GameImportExportBatch> ExportPackage(string[] gameIds, bool includePracticeAreaTemplate, CancellationToken cancellationToken);
     Task<ImportedGame[]> ImportPackage(byte[] package, CancellationToken cancellationToken);
 }
@@ -28,21 +28,28 @@ internal sealed class GameImportExportService
     IActingUserService actingUser,
     CoreOptions coreOptions,
     IGuidService guids,
-    HttpClient http,
     IJsonService json,
     IPracticeService practice,
-    IStore store,
-    IZipService zip
+    IStore store
 ) : IGameImportExportService
 {
     private readonly IActingUserService _actingUser = actingUser;
     private readonly CoreOptions _coreOptions = coreOptions;
     private readonly IGuidService _guids = guids;
-    private readonly HttpClient _http = http;
     private readonly IJsonService _json = json;
     private readonly IPracticeService _practice = practice;
     private readonly IStore _store = store;
-    private readonly IZipService _zip = zip;
+
+    public async Task<byte[]> GetExportedPackageContent(string exportBatchId, CancellationToken cancellationToken)
+    {
+        var path = GetExportBatchPackagePath(exportBatchId);
+        if (!File.Exists(path))
+        {
+            throw new ExportPackageNotFound(exportBatchId);
+        }
+
+        return await File.ReadAllBytesAsync(path, cancellationToken);
+    }
 
     public async Task<GameImportExportBatch> ExportPackage(string[] gameIds, bool includePracticeAreaTemplate, CancellationToken cancellationToken)
     {

src/Gameboard.Api/Features/Game/ImportExport/Requests/DownloadExportPackage/DownloadExportPackage.cs

@@ -0,0 +1,28 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Gameboard.Api.Features.Users;
+using Gameboard.Api.Structure.MediatR;
+using MediatR;
+
+namespace Gameboard.Api.Features.Games;
+
+public record DownloadExportPackageRequest(string ExportBatchId) : IRequest<byte[]>;
+
+internal sealed class DownloadExportPackageHandler
+(
+    IGameImportExportService importExport,
+    IValidatorService validator
+) : IRequestHandler<DownloadExportPackageRequest, byte[]>
+{
+    private readonly IGameImportExportService _importExport = importExport;
+    private readonly IValidatorService _validator = validator;
+
+    public async Task<byte[]> Handle(DownloadExportPackageRequest request, CancellationToken cancellationToken)
+    {
+        await _validator
+            .Auth(c => c.Require(PermissionKey.Games_CreateEditDelete))
+            .Validate(cancellationToken);
+
+        return await _importExport.GetExportedPackageContent(request.ExportBatchId, cancellationToken);
+    }
+}