feat(lobby): start round with selected category

lobby/tests.py

@@ -2,7 +2,7 @@ from django.contrib.auth import get_user_model
 from django.test import TestCase
 from django.urls import reverse
 
-from fupogfakta.models import GameSession, Player
+from fupogfakta.models import Category, GameSession, Player, Question, RoundConfig
 
 User = get_user_model()
 
@@ -81,3 +81,82 @@ class LobbyFlowTests(TestCase):
         payload = response.json()
         self.assertEqual(payload["session"]["players_count"], 2)
         self.assertEqual([p["nickname"] for p in payload["players"]], ["Bo", "Mia"])
+
+
+class StartRoundTests(TestCase):
+    def setUp(self):
+        self.host = User.objects.create_user(username="host", password="secret123")
+        self.other_user = User.objects.create_user(username="other", password="secret123")
+        self.session = GameSession.objects.create(host=self.host, code="ABCD23")
+        self.category = Category.objects.create(name="Historie", slug="historie", is_active=True)
+        Question.objects.create(
+            category=self.category,
+            prompt="Hvilket år faldt muren?",
+            correct_answer="1989",
+            is_active=True,
+        )
+
+    def test_host_can_start_round_with_selected_category(self):
+        self.client.login(username="host", password="secret123")
+
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": self.category.slug},
+            content_type="application/json",
+        )
+
+        self.assertEqual(response.status_code, 201)
+        body = response.json()
+        self.assertEqual(body["session"]["status"], GameSession.Status.LIE)
+        self.assertEqual(body["round"]["number"], 1)
+        self.assertEqual(body["round"]["category"]["slug"], self.category.slug)
+
+        self.session.refresh_from_db()
+        self.assertEqual(self.session.status, GameSession.Status.LIE)
+        round_config = RoundConfig.objects.get(session=self.session, number=1)
+        self.assertEqual(round_config.category, self.category)
+
+    def test_start_round_requires_host(self):
+        self.client.login(username="other", password="secret123")
+
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": self.category.slug},
+            content_type="application/json",
+        )
+
+        self.assertEqual(response.status_code, 403)
+        self.assertEqual(response.json()["error"], "Only host can start round")
+
+    def test_start_round_requires_existing_active_category_with_questions(self):
+        self.client.login(username="host", password="secret123")
+
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": "ukendt"},
+            content_type="application/json",
+        )
+        self.assertEqual(response.status_code, 404)
+
+        empty_category = Category.objects.create(name="Sport", slug="sport", is_active=True)
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": empty_category.slug},
+            content_type="application/json",
+        )
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.json()["error"], "Category has no active questions")
+
+    def test_start_round_rejects_non_lobby_session(self):
+        self.client.login(username="host", password="secret123")
+        self.session.status = GameSession.Status.GUESS
+        self.session.save(update_fields=["status"])
+
+        response = self.client.post(
+            reverse("lobby:start_round", kwargs={"code": self.session.code}),
+            data={"category_slug": self.category.slug},
+            content_type="application/json",
+        )
+
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.json()["error"], "Round can only be started from lobby")

lobby/urls.py

@@ -8,4 +8,5 @@ urlpatterns = [
     path("sessions/create", views.create_session, name="create_session"),
     path("sessions/join", views.join_session, name="join_session"),
     path("sessions/<str:code>", views.session_detail, name="session_detail"),
+    path("sessions/<str:code>/rounds/start", views.start_round, name="start_round"),
 ]

lobby/views.py

@@ -2,10 +2,11 @@ import json
 import random
 
 from django.contrib.auth.decorators import login_required
+from django.db import transaction
 from django.http import HttpRequest, JsonResponse
 from django.views.decorators.http import require_GET, require_POST
 
-from fupogfakta.models import GameSession, Player
+from fupogfakta.models import Category, GameSession, Player, Question, RoundConfig
 
 SESSION_CODE_ALPHABET = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"
 SESSION_CODE_LENGTH = 6
@@ -132,3 +133,68 @@ def session_detail(request: HttpRequest, code: str) -> JsonResponse:
             "players": players,
         }
     )
+
+
+@require_POST
+@login_required
+def start_round(request: HttpRequest, code: str) -> JsonResponse:
+    payload = _json_body(request)
+    category_slug = str(payload.get("category_slug", "")).strip()
+
+    if not category_slug:
+        return JsonResponse({"error": "category_slug is required"}, status=400)
+
+    session_code = code.strip().upper()
+
+    try:
+        session = GameSession.objects.get(code=session_code)
+    except GameSession.DoesNotExist:
+        return JsonResponse({"error": "Session not found"}, status=404)
+
+    if session.host_id != request.user.id:
+        return JsonResponse({"error": "Only host can start round"}, status=403)
+
+    if session.status != GameSession.Status.LOBBY:
+        return JsonResponse({"error": "Round can only be started from lobby"}, status=400)
+
+    try:
+        category = Category.objects.get(slug=category_slug, is_active=True)
+    except Category.DoesNotExist:
+        return JsonResponse({"error": "Category not found"}, status=404)
+
+    if not Question.objects.filter(category=category, is_active=True).exists():
+        return JsonResponse({"error": "Category has no active questions"}, status=400)
+
+    with transaction.atomic():
+        session = GameSession.objects.select_for_update().get(pk=session.pk)
+        if session.status != GameSession.Status.LOBBY:
+            return JsonResponse({"error": "Round can only be started from lobby"}, status=400)
+
+        round_config, created = RoundConfig.objects.get_or_create(
+            session=session,
+            number=session.current_round,
+            defaults={"category": category},
+        )
+        if not created:
+            return JsonResponse({"error": "Round already configured"}, status=409)
+
+        session.status = GameSession.Status.LIE
+        session.save(update_fields=["status"])
+
+    return JsonResponse(
+        {
+            "session": {
+                "code": session.code,
+                "status": session.status,
+                "current_round": session.current_round,
+            },
+            "round": {
+                "number": round_config.number,
+                "category": {
+                    "slug": round_config.category.slug,
+                    "name": round_config.category.name,
+                },
+            },
+        },
+        status=201,
+    )