Merge feature/namegen-backend (FEAT-NAMEGEN-BE): GET /names/suggest via Gemini + LitterLetter

NameSuggestionService (bestehender OpenAiChatClient/Gemini, Fence-Strip, [{name,meaning,origin}]),
NamesEndpoints (503 NamesKeyMissing / 502 NamesUpstreamError), Litter.LitterLetter + Migration AddLitterLetter.
157/157, drift clean (Dwight). has-pending via CI (lokaler Build durch laufende App gesperrt).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

GerbilManager.Tests/NameSuggestionTests.cs

@@ -0,0 +1,208 @@
+using System.Net;
+using System.Text;
+using System.Text.Json;
+using GerbilManagerWebAPI.Names;
+using GerbilManagerWebAPI.SaleAd;
+using Microsoft.Extensions.Options;
+
+namespace GerbilManager.Tests
+{
+    /// <summary>
+    /// FEAT-NAMEGEN: NameSuggestionService — prompt assembly, JSON parse (incl. Markdown
+    /// fence strip), 503-not-configured path, upstream-error path.
+    /// </summary>
+    public class NameSuggestionTests
+    {
+        // ── Prompt assembly ───────────────────────────────────────────────────
+
+        [Fact]
+        public void SystemPrompt_verlangt_reines_JSON_ohne_Erklärungen()
+        {
+            var prompt = NameSuggestionService.BuildSystemPrompt();
+            Assert.Contains("reinen JSON-Array", prompt);
+            Assert.Contains("KEINE Markdown-Code-Blöcke", prompt);
+            Assert.Contains("name", prompt);
+            Assert.Contains("meaning", prompt);
+            Assert.Contains("origin", prompt);
+        }
+
+        [Fact]
+        public void UserPrompt_enthält_Anzahl_und_Anfangsbuchstaben()
+        {
+            var prompt = NameSuggestionService.BuildUserPrompt("A", "female", "norn,mythg", 6);
+            Assert.Contains("6", prompt);
+            Assert.Contains("\"A\"", prompt);
+            Assert.Contains("weibliche", prompt);
+            Assert.Contains("norn,mythg", prompt);
+        }
+
+        [Fact]
+        public void UserPrompt_ohne_optionale_Parameter_ist_gültig()
+        {
+            var prompt = NameSuggestionService.BuildUserPrompt(null, null, null, 5);
+            Assert.Contains("5", prompt);
+            Assert.DoesNotContain("Buchstaben", prompt);
+            Assert.DoesNotContain("weibliche", prompt);
+            Assert.DoesNotContain("männliche", prompt);
+        }
+
+        [Fact]
+        public void UserPrompt_gender_any_wird_nicht_im_Prompt_erwähnt()
+        {
+            var prompt = NameSuggestionService.BuildUserPrompt(null, "any", null, 3);
+            Assert.DoesNotContain("weibliche", prompt);
+            Assert.DoesNotContain("männliche", prompt);
+        }
+
+        // ── JSON parsing ──────────────────────────────────────────────────────
+
+        [Fact]
+        public void ParseSuggestions_verarbeitet_reines_JSON()
+        {
+            var json = """[{"name":"Astrid","meaning":"göttliche Stärke","origin":"Altnordisch"}]""";
+            var result = NameSuggestionService.ParseSuggestions(json);
+            Assert.NotNull(result);
+            Assert.Single(result);
+            Assert.Equal("Astrid", result[0].Name);
+            Assert.Equal("göttliche Stärke", result[0].Meaning);
+            Assert.Equal("Altnordisch", result[0].Origin);
+        }
+
+        [Fact]
+        public void ParseSuggestions_strippt_json_Markdown_Fence()
+        {
+            var fenced = "```json\n[{\"name\":\"Aiko\",\"meaning\":\"kleine Geliebte\",\"origin\":\"Japanisch\"}]\n```";
+            var result = NameSuggestionService.ParseSuggestions(fenced);
+            Assert.NotNull(result);
+            Assert.Equal("Aiko", result![0].Name);
+        }
+
+        [Fact]
+        public void ParseSuggestions_strippt_generische_Markdown_Fence()
+        {
+            var fenced = "```\n[{\"name\":\"Luna\",\"meaning\":\"Mond\",\"origin\":\"Lateinisch\"}]\n```";
+            var result = NameSuggestionService.ParseSuggestions(fenced);
+            Assert.NotNull(result);
+            Assert.Equal("Luna", result![0].Name);
+        }
+
+        [Fact]
+        public void ParseSuggestions_toleriert_umgebenden_Text_vor_Array()
+        {
+            var messy = "Hier sind die Namen:\n[{\"name\":\"Sol\",\"meaning\":\"Sonne\",\"origin\":\"Nordisch\"}]\nHoffnungslos.";
+            var result = NameSuggestionService.ParseSuggestions(messy);
+            Assert.NotNull(result);
+            Assert.Equal("Sol", result![0].Name);
+        }
+
+        [Fact]
+        public void ParseSuggestions_gibt_null_zurück_bei_ungültigem_JSON()
+        {
+            Assert.Null(NameSuggestionService.ParseSuggestions("kein json"));
+            Assert.Null(NameSuggestionService.ParseSuggestions("{\"name\":\"X\"}"));
+            Assert.Null(NameSuggestionService.ParseSuggestions(""));
+        }
+
+        // ── 503: nicht konfiguriert ───────────────────────────────────────────
+
+        [Theory]
+        [InlineData(null, "key", "model")]
+        [InlineData("https://api.example.com/v1", null, "model")]
+        [InlineData("https://api.example.com/v1", "key", null)]
+        [InlineData(null, null, null)]
+        public async Task SuggestAsync_gibt_NotConfigured_wenn_AI_Key_fehlt(
+            string? baseUrl, string? apiKey, string? model)
+        {
+            var service = CreateService(baseUrl, apiKey, model,
+                new StubHandler(_ => throw new InvalidOperationException("darf nicht aufgerufen werden")));
+
+            var result = await service.SuggestAsync(null, null, null, 5);
+
+            Assert.Equal(NameSuggestionStatus.NotConfigured, result.Status);
+            Assert.Null(result.Suggestions);
+        }
+
+        // ── Gemini-Antwort wird geparst ───────────────────────────────────────
+
+        [Fact]
+        public async Task SuggestAsync_parst_valide_JSON_Antwort()
+        {
+            var payload = """[{"name":"Astrid","meaning":"göttliche Stärke","origin":"Altnordisch"},{"name":"Aiko","meaning":"kleine Geliebte","origin":"Japanisch"}]""";
+            var handler = new StubHandler(_ => Canned(payload));
+            var service = CreateService("https://generativelanguage.googleapis.com/v1beta/openai", "k", "gemini-2.0-flash", handler);
+
+            var result = await service.SuggestAsync("A", "female", "norn,japa", 2);
+
+            Assert.Equal(NameSuggestionStatus.Ok, result.Status);
+            Assert.NotNull(result.Suggestions);
+            Assert.Equal(2, result.Suggestions!.Count);
+            Assert.Equal("Astrid", result.Suggestions[0].Name);
+        }
+
+        [Fact]
+        public async Task SuggestAsync_parst_JSON_in_Markdown_Fence()
+        {
+            var fenced = "```json\n[{\"name\":\"Luna\",\"meaning\":\"Mond\",\"origin\":\"Lateinisch\"}]\n```";
+            var handler = new StubHandler(_ => Canned(fenced));
+            var service = CreateService("https://api.example.com/v1", "k", "m", handler);
+
+            var result = await service.SuggestAsync(null, null, null, 1);
+
+            Assert.Equal(NameSuggestionStatus.Ok, result.Status);
+            Assert.Equal("Luna", result.Suggestions![0].Name);
+        }
+
+        [Fact]
+        public async Task SuggestAsync_gibt_UpstreamError_bei_ungültigem_JSON()
+        {
+            var handler = new StubHandler(_ => Canned("das ist kein json"));
+            var service = CreateService("https://api.example.com/v1", "k", "m", handler);
+
+            var result = await service.SuggestAsync(null, null, null, 3);
+
+            Assert.Equal(NameSuggestionStatus.UpstreamError, result.Status);
+            Assert.Null(result.Suggestions);
+        }
+
+        [Fact]
+        public async Task SuggestAsync_gibt_UpstreamError_bei_HTTP_Fehler()
+        {
+            var handler = new StubHandler(_ => new HttpResponseMessage(HttpStatusCode.TooManyRequests));
+            var service = CreateService("https://api.example.com/v1", "k", "m", handler);
+
+            var result = await service.SuggestAsync(null, null, null, 3);
+
+            Assert.Equal(NameSuggestionStatus.UpstreamError, result.Status);
+        }
+
+        // ── Helfer ────────────────────────────────────────────────────────────
+
+        private static NameSuggestionService CreateService(
+            string? baseUrl, string? apiKey, string? model, StubHandler handler)
+        {
+            var options = Options.Create(new AiOptions { BaseUrl = baseUrl, ApiKey = apiKey, Model = model });
+            return new NameSuggestionService(new HttpClient(handler), options);
+        }
+
+        private static HttpResponseMessage Canned(string content)
+        {
+            var completion = new
+            {
+                choices = new[] { new { message = new { role = "assistant", content } } },
+            };
+            return new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = new StringContent(JsonSerializer.Serialize(completion),
+                    Encoding.UTF8, "application/json"),
+            };
+        }
+
+        private sealed class StubHandler(Func<HttpRequestMessage, HttpResponseMessage> respond)
+            : HttpMessageHandler
+        {
+            protected override Task<HttpResponseMessage> SendAsync(
+                HttpRequestMessage request, CancellationToken cancellationToken)
+                => Task.FromResult(respond(request));
+        }
+    }
+}

GerbilManagerWebAPI/Endpoints/NamesEndpoints.cs

@@ -0,0 +1,38 @@
+using GerbilManagerWebAPI.Names;
+
+namespace GerbilManagerWebAPI.Endpoints
+{
+    /// <summary>
+    /// FEAT-NAMEGEN: GET /names/suggest — meaningful gerbil name suggestions via Gemini.
+    ///
+    /// 503 {code:"NamesKeyMissing"} while the AI section is unconfigured — the
+    /// frontend maps exactly this code to its German disabled-state hint.
+    /// </summary>
+    public static class NamesEndpoints
+    {
+        public static IEndpointRouteBuilder MapNamesEndpoints(this IEndpointRouteBuilder app)
+        {
+            app.MapGet("/names/suggest", async (
+                string? letter,
+                string? gender,
+                string? usages,
+                int count,
+                NameSuggestionService service,
+                CancellationToken ct) =>
+            {
+                var result = await service.SuggestAsync(letter, gender, usages, count, ct);
+                return result.Status switch
+                {
+                    NameSuggestionStatus.Ok => Results.Ok(result.Suggestions),
+                    NameSuggestionStatus.NotConfigured => Results.Json(
+                        new { code = "NamesKeyMissing", message = result.Error ?? "" }, statusCode: 503),
+                    _ => Results.Json(
+                        new { code = "NamesUpstreamError", message = result.Error ?? "" }, statusCode: 502),
+                };
+            })
+            .WithTags("Names");
+
+            return app;
+        }
+    }
+}

GerbilManagerWebAPI/Migrations/20260606185411_AddLitterLetter.cs

@@ -0,0 +1,28 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace GerbilManagerWebAPI.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddLitterLetter : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "LitterLetter",
+                table: "Litters",
+                type: "text",
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "LitterLetter",
+                table: "Litters");
+        }
+    }
+}

GerbilManagerWebAPI/Migrations/ApplicationContextModelSnapshot.cs

@@ -905,6 +905,9 @@ namespace GerbilManagerWebAPI.Migrations
                     b.Property<Guid?>("FatherId")
                         .HasColumnType("uuid");
 
+                    b.Property<string>("LitterLetter")
+                        .HasColumnType("text");
+
                     b.Property<Guid?>("MotherId")
                         .HasColumnType("uuid");
 

GerbilManagerWebAPI/Models/Litter.cs

@@ -30,5 +30,9 @@ namespace GerbilManagerWebAPI.Models
         /// nulls allowed for manually-entered litters). Primary idempotency key for re-imports;
         /// Name+Date is the fallback for litters created before this column existed.</summary>
         public string? ExternalRef { get; set; }
+
+        /// <summary>FEAT-NAMEGEN: Wurfbuchstabe (A, B, C … AA, AB …) — alle Welpen dieses
+        /// Wurfs erhalten Namen mit diesem Anfangsbuchstaben (gängige Zuchtkonvention).</summary>
+        public string? LitterLetter { get; set; }
     }
 }

GerbilManagerWebAPI/Names/NameSuggestion.cs

@@ -0,0 +1,5 @@
+namespace GerbilManagerWebAPI.Names
+{
+    /// <summary>FEAT-NAMEGEN: a single name suggestion returned by GET /names/suggest.</summary>
+    public sealed record NameSuggestion(string Name, string Meaning, string Origin);
+}

GerbilManagerWebAPI/Names/NameSuggestionService.cs

@@ -0,0 +1,107 @@
+using System.Text;
+using System.Text.Json;
+using GerbilManagerWebAPI.Ai;
+using GerbilManagerWebAPI.SaleAd;
+using Microsoft.Extensions.Options;
+
+namespace GerbilManagerWebAPI.Names
+{
+    /// <summary>
+    /// FEAT-NAMEGEN: generates meaningful gerbil name suggestions via Gemini
+    /// (the same OpenAiChatClient used by sale-ads and reply-drafts).
+    /// Returns NotConfigured when the AI section is missing — callers map to 503.
+    /// </summary>
+    public sealed class NameSuggestionService(HttpClient http, IOptions<AiOptions> options)
+    {
+        private readonly OpenAiChatClient _client = new(http, options);
+
+        private static readonly JsonSerializerOptions JsonOpts = new()
+        {
+            PropertyNameCaseInsensitive = true,
+        };
+
+        public async Task<NameSuggestionResult> SuggestAsync(
+            string? letter, string? gender, string? usages, int count,
+            CancellationToken ct = default)
+        {
+            var aiResult = await _client.CompleteAsync(
+                BuildSystemPrompt(),
+                BuildUserPrompt(letter, gender, usages, count),
+                ct);
+
+            if (aiResult.Status == AiCallStatus.NotConfigured)
+                return new NameSuggestionResult(NameSuggestionStatus.NotConfigured, null, aiResult.Error);
+            if (aiResult.Status != AiCallStatus.Ok || aiResult.Text is null)
+                return new NameSuggestionResult(NameSuggestionStatus.UpstreamError, null, aiResult.Error);
+
+            var suggestions = ParseSuggestions(aiResult.Text);
+            return suggestions is null
+                ? new NameSuggestionResult(NameSuggestionStatus.UpstreamError, null, "Ungültiges JSON in KI-Antwort.")
+                : new NameSuggestionResult(NameSuggestionStatus.Ok, suggestions, null);
+        }
+
+        internal static string BuildSystemPrompt() =>
+            "Du bist ein Helfer für Rennmaus-Züchter. " +
+            "Antworte IMMER mit einem reinen JSON-Array — KEINE Markdown-Code-Blöcke, " +
+            "KEINE Erklärungen, KEIN Text außerhalb des Arrays. " +
+            "Jedes Element hat genau die Felder: name, meaning, origin (alle Strings, alle auf Deutsch).";
+
+        internal static string BuildUserPrompt(string? letter, string? gender, string? usages, int count)
+        {
+            var sb = new StringBuilder();
+            sb.Append($"Schlage {count} Rennmaus-Namen vor");
+            if (!string.IsNullOrWhiteSpace(letter))
+                sb.Append($" die mit dem Buchstaben \"{letter.ToUpperInvariant()}\" beginnen");
+            if (!string.IsNullOrWhiteSpace(gender) &&
+                !gender.Equals("any", StringComparison.OrdinalIgnoreCase))
+                sb.Append($", passend für {(gender.Equals("female", StringComparison.OrdinalIgnoreCase) ? "weibliche" : "männliche")} Tiere");
+            if (!string.IsNullOrWhiteSpace(usages))
+                sb.Append($", aus den Kulturkreisen: {usages}");
+            sb.Append(". Jeder Name muss eine echte etymologische Bedeutung und Herkunft haben ");
+            sb.Append("(keine erfundenen oder zufälligen Namen). ");
+            sb.Append($"Antworte mit genau {count} Elementen als reines JSON-Array: ");
+            sb.Append("[{\"name\":\"...\",\"meaning\":\"...\",\"origin\":\"...\"}]");
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// Strips optional markdown fences (```json ... ```) Gemini sometimes wraps around
+        /// its JSON output, then deserialises the array.
+        /// </summary>
+        internal static List<NameSuggestion>? ParseSuggestions(string raw)
+        {
+            var text = raw.Trim();
+
+            // Strip ```json ... ``` or ``` ... ``` fences.
+            if (text.StartsWith("```", StringComparison.Ordinal))
+            {
+                var firstNewline = text.IndexOf('\n');
+                if (firstNewline >= 0) text = text[(firstNewline + 1)..];
+                if (text.EndsWith("```", StringComparison.Ordinal))
+                    text = text[..^3].TrimEnd();
+            }
+
+            // Find the JSON array bounds defensively.
+            var start = text.IndexOf('[');
+            var end = text.LastIndexOf(']');
+            if (start < 0 || end <= start) return null;
+            text = text[start..(end + 1)];
+
+            try
+            {
+                return JsonSerializer.Deserialize<List<NameSuggestion>>(text, JsonOpts);
+            }
+            catch (JsonException)
+            {
+                return null;
+            }
+        }
+    }
+
+    public enum NameSuggestionStatus { Ok, NotConfigured, UpstreamError }
+
+    public sealed record NameSuggestionResult(
+        NameSuggestionStatus Status,
+        List<NameSuggestion>? Suggestions,
+        string? Error);
+}

GerbilManagerWebAPI/Program.cs

@@ -45,6 +45,9 @@ builder.Services.AddHttpClient<GerbilManagerWebAPI.SaleAd.SaleAdService>(
 // INBOX-2: KI-Antwortentwurf (gleiche AI-Sektion, gleicher Wire-Client).
 builder.Services.AddHttpClient<GerbilManagerWebAPI.Inbox.DraftReplyService>(
     http => http.Timeout = TimeSpan.FromSeconds(60));
+// FEAT-NAMEGEN: Name suggestions via Gemini (same AI section, same wire client).
+builder.Services.AddHttpClient<GerbilManagerWebAPI.Names.NameSuggestionService>(
+    http => http.Timeout = TimeSpan.FromSeconds(60));
 
 // INBOX-0: Gmail inbox. App Password encrypted at rest via Data Protection.
 // AR-3: persist the key ring so encrypted passwords survive image redeployments.
@@ -100,6 +103,7 @@ app.MapSettingsEndpoints();
 app.MapExportEndpoints();
 app.MapCmsEndpoints();
 app.MapRequestEndpoints();
+app.MapNamesEndpoints();
 
 app.Run();