Add upload retries and richer errors

clients/photobooth-uploader/PhotoboothUploader/MainWindow.axaml.cs

@@ -304,14 +304,14 @@ public partial class MainWindow : Window
         UpdateLiveStatus();
     }
 
-    private void OnFailure(string path)
+    private void OnFailure(string path, string message)
     {
         _failedPaths.Add(path);
         Interlocked.Decrement(ref _uploadingCount);
         Interlocked.Increment(ref _failedCount);
         UpdateUpload(path, UploadStatus.Failed);
         UpdateStatusIfAllowed($"Upload fehlgeschlagen: {Path.GetFileName(path)}", true);
-        SetLastError($"Upload fehlgeschlagen: {Path.GetFileName(path)}");
+        SetLastError($"{Path.GetFileName(path)} – {message}");
         UpdateRetryButton();
         UpdateCountersText();
     }

clients/photobooth-uploader/PhotoboothUploader/Services/UploadService.cs

@@ -14,6 +14,8 @@ namespace PhotoboothUploader.Services;
 public sealed class UploadService
 {
     private static readonly TimeSpan DefaultTimeout = TimeSpan.FromSeconds(20);
+    private static readonly TimeSpan RetryBaseDelay = TimeSpan.FromSeconds(2);
+    private const int MaxRetries = 2;
     private readonly Channel<string> _queue = Channel.CreateUnbounded<string>();
     private readonly ConcurrentDictionary<string, byte> _pending = new(StringComparer.OrdinalIgnoreCase);
     private string _userAgent = "FotospielPhotoboothUploader";
@@ -33,7 +35,7 @@ public sealed class UploadService
         Action<string> onQueued,
         Action<string> onUploading,
         Action<string> onSuccess,
-        Action<string> onFailure)
+        Action<string, string> onFailure)
     {
         Stop();
 
@@ -69,7 +71,7 @@ public sealed class UploadService
         Action<string> onQueued,
         Action<string> onUploading,
         Action<string> onSuccess,
-        Action<string> onFailure,
+        Action<string, string> onFailure,
         CancellationToken token)
     {
         if (string.IsNullOrWhiteSpace(settings.UploadUrl))
@@ -89,18 +91,20 @@ public sealed class UploadService
                 try
                 {
                     onUploading(path);
-                    await WaitForFileReadyAsync(path, token);
-                    await UploadAsync(client, settings, path, token);
-                    onSuccess(path);
+                    var error = await UploadWithRetryAsync(client, settings, path, token);
+                    if (error is null)
+                    {
+                        onSuccess(path);
+                    }
+                    else
+                    {
+                        onFailure(path, error);
+                    }
                 }
                 catch (OperationCanceledException)
                 {
                     return;
                 }
-                catch
-                {
-                    onFailure(path);
-                }
                 finally
                 {
                     _pending.TryRemove(path, out _);
@@ -109,38 +113,46 @@ public sealed class UploadService
         }
     }
 
-    private static async Task WaitForFileReadyAsync(string path, CancellationToken token)
+    private static async Task<string?> UploadWithRetryAsync(
+        HttpClient client,
+        PhotoboothSettings settings,
+        string path,
+        CancellationToken token)
     {
-        var lastSize = -1L;
-
-        for (var attempts = 0; attempts < 10; attempts++)
+        for (var attempt = 0; attempt <= MaxRetries; attempt++)
         {
-            token.ThrowIfCancellationRequested();
-
-            if (!File.Exists(path))
+            var attemptError = await UploadOnceAsync(client, settings, path, token);
+            if (attemptError.Success)
             {
-                await Task.Delay(500, token);
-                continue;
+                return null;
             }
 
-            var info = new FileInfo(path);
-            var size = info.Length;
-
-            if (size > 0 && size == lastSize)
+            if (!attemptError.Retryable || attempt >= MaxRetries)
             {
-                return;
+                return attemptError.Error ?? "Upload fehlgeschlagen.";
             }
 
-            lastSize = size;
-            await Task.Delay(700, token);
+            await Task.Delay(GetRetryDelay(attempt), token);
         }
+
+        return "Upload fehlgeschlagen.";
     }
 
-    private static async Task UploadAsync(HttpClient client, PhotoboothSettings settings, string path, CancellationToken token)
+    private static async Task<UploadAttempt> UploadOnceAsync(
+        HttpClient client,
+        PhotoboothSettings settings,
+        string path,
+        CancellationToken token)
     {
+        var readyError = await WaitForFileReadyAsync(path, token);
+        if (readyError is not null)
+        {
+            return UploadAttempt.Fail(readyError, retryable: false);
+        }
+
         if (!File.Exists(path))
         {
-            return;
+            return UploadAttempt.Fail("Datei nicht gefunden.", retryable: false);
         }
 
         using var content = new MultipartFormDataContent();
@@ -165,8 +177,61 @@ public sealed class UploadService
         fileContent.Headers.ContentType = new MediaTypeHeaderValue(ResolveContentType(path));
         content.Add(fileContent, "media", Path.GetFileName(path));
 
-        var response = await client.PostAsync(settings.UploadUrl, content, token);
-        response.EnsureSuccessStatusCode();
+        try
+        {
+            var response = await client.PostAsync(settings.UploadUrl, content, token);
+
+            if (response.IsSuccessStatusCode)
+            {
+                return UploadAttempt.Ok();
+            }
+
+            var body = await ReadResponseBodyAsync(response, token);
+            var status = $"{(int)response.StatusCode} {response.ReasonPhrase}".Trim();
+            var message = string.IsNullOrWhiteSpace(body) ? status : $"{status} – {body}";
+            return UploadAttempt.Fail(message, IsRetryableStatus(response.StatusCode));
+        }
+        catch (TaskCanceledException) when (!token.IsCancellationRequested)
+        {
+            return UploadAttempt.Fail("Zeitüberschreitung beim Upload.", retryable: true);
+        }
+        catch (HttpRequestException)
+        {
+            return UploadAttempt.Fail("Netzwerkfehler beim Upload.", retryable: true);
+        }
+        catch (IOException)
+        {
+            return UploadAttempt.Fail("Datei konnte nicht gelesen werden.", retryable: false);
+        }
+    }
+
+    private static async Task<string?> WaitForFileReadyAsync(string path, CancellationToken token)
+    {
+        var lastSize = -1L;
+
+        for (var attempts = 0; attempts < 10; attempts++)
+        {
+            token.ThrowIfCancellationRequested();
+
+            if (!File.Exists(path))
+            {
+                await Task.Delay(500, token);
+                continue;
+            }
+
+            var info = new FileInfo(path);
+            var size = info.Length;
+
+            if (size > 0 && size == lastSize)
+            {
+                return null;
+            }
+
+            lastSize = size;
+            await Task.Delay(700, token);
+        }
+
+        return "Datei ist noch in Bearbeitung.";
     }
 
     private static string ResolveContentType(string path)
@@ -179,6 +244,35 @@ public sealed class UploadService
         };
     }
 
+    private static bool IsRetryableStatus(System.Net.HttpStatusCode statusCode)
+    {
+        var numeric = (int)statusCode;
+        return numeric >= 500 || statusCode is System.Net.HttpStatusCode.RequestTimeout or System.Net.HttpStatusCode.TooManyRequests;
+    }
+
+    private static TimeSpan GetRetryDelay(int attempt)
+    {
+        var jitter = TimeSpan.FromMilliseconds(Random.Shared.Next(100, 350));
+        return TimeSpan.FromMilliseconds(RetryBaseDelay.TotalMilliseconds * Math.Pow(2, attempt)) + jitter;
+    }
+
+    private static async Task<string?> ReadResponseBodyAsync(HttpResponseMessage response, CancellationToken token)
+    {
+        if (response.Content is null)
+        {
+            return null;
+        }
+
+        var body = await response.Content.ReadAsStringAsync(token);
+        if (string.IsNullOrWhiteSpace(body))
+        {
+            return null;
+        }
+
+        body = body.Trim();
+        return body.Length > 200 ? body[..200] + "…" : body;
+    }
+
     private static int GetWorkerCount(PhotoboothSettings settings)
     {
         var count = settings.MaxConcurrentUploads;
@@ -189,4 +283,11 @@ public sealed class UploadService
 
         return count > 5 ? 5 : count;
     }
+
+    private readonly record struct UploadAttempt(bool Success, bool Retryable, string? Error)
+    {
+        public static UploadAttempt Ok() => new(true, false, null);
+
+        public static UploadAttempt Fail(string error, bool retryable) => new(false, retryable, error);
+    }
 }