Block duplicate-release uploads by (title, artist): pre-flight check + server 409 backstop, with within-batch Cut attach via releaseId

DeepDrftManager/Services/CmsTrackService.cs

@@ -68,6 +68,7 @@ public class CmsTrackService : ICmsTrackService
         ReleaseType releaseType,
         int trackNumber,
         ReleaseMedium medium = ReleaseMedium.Cut,
+        long? releaseId = null,
         IProgress<long>? progress = null,
         CancellationToken ct = default)
     {
@@ -91,6 +92,9 @@ public class CmsTrackService : ICmsTrackService
         // The upload endpoint binds "medium" to the created release's ReleaseMedium (defaulting to Cut
         // for an unrecognised value). Authoritative only when this upload creates the release.
         multipart.Add(new StringContent(medium.ToString()), "medium");
+        // releaseId present → ATTACH (rows 2..N of a within-batch Cut); absent → CREATE (server rejects a
+        // pre-existing (title, artist) as a duplicate). Only sent when set so the form omits it on row 1.
+        if (releaseId is { } rid) multipart.Add(new StringContent(rid.ToString()), "releaseId");
 
         var send = await phase.SendAsync(UploadPath, multipart, $"upload of {trackName}");
         if (send.Response is not { } response)
@@ -474,6 +478,53 @@ public class CmsTrackService : ICmsTrackService
         }
     }
 
+    public async Task<ResultContainer<ReleaseDto?>> GetExistingReleaseAsync(
+        string title, string artist, CancellationToken ct = default)
+    {
+        var client = _httpClientFactory.CreateClient(ContentCmsClientName);
+        var query = $"api/track/release/exists?title={Uri.EscapeDataString(title)}&artist={Uri.EscapeDataString(artist)}";
+
+        HttpResponseMessage response;
+        try
+        {
+            response = await client.GetAsync(query, ct);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Content API call failed for release existence check ({Title}, {Artist})", title, artist);
+            return ResultContainer<ReleaseDto?>.CreateFailResult("Content API is unreachable.");
+        }
+
+        using (response)
+        {
+            // 404 is the not-found (null) case, not a failure — no release matches this (title, artist).
+            if (response.StatusCode == HttpStatusCode.NotFound)
+            {
+                return ResultContainer<ReleaseDto?>.CreatePassResult(null);
+            }
+
+            if (!response.IsSuccessStatusCode)
+            {
+                _logger.LogError("Content API release existence check failed for ({Title}, {Artist}): {Status}",
+                    title, artist, (int)response.StatusCode);
+                return ResultContainer<ReleaseDto?>.CreateFailResult("Failed to check for an existing release.");
+            }
+
+            ReleaseDto? release;
+            try
+            {
+                release = await response.Content.ReadFromJsonAsync<ReleaseDto>(ct);
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Failed to deserialize ReleaseDto from release existence check");
+                return ResultContainer<ReleaseDto?>.CreateFailResult("Content API returned an unexpected response.");
+            }
+
+            return ResultContainer<ReleaseDto?>.CreatePassResult(release);
+        }
+    }
+
     private static readonly HashSet<string> KnownImageMimeTypes = new(StringComparer.OrdinalIgnoreCase)
     {
         "image/jpeg", "image/png", "image/gif", "image/webp", "image/svg+xml", "image/bmp"