From f4025e3cbb3814819e6bfbfb0909f9f122108ff8 Mon Sep 17 00:00:00 2001
From: Giorgio Gilestro <giorgio@gilest.ro>
Date: Wed, 27 May 2026 17:16:17 +0200
Subject: [PATCH] settings: PATCH /api/settings/language with ACTIVE_LANGUAGES
 gate

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 app/routers/api.py                     | 36 +++++++++++++++
 tests/test_localization_integration.py | 61 ++++++++++++++++++++++++++
 2 files changed, 97 insertions(+)

diff --git a/app/routers/api.py b/app/routers/api.py
index 5e06090..0b23d57 100644
--- a/app/routers/api.py
+++ b/app/routers/api.py
@@ -21,6 +21,7 @@ import httpx
 from pydantic import BaseModel, Field
 
 from app.auth import require_token, maybe_current_user, CurrentUser
+from app.services.i18n import ACTIVE_LANGUAGES
 from app.config import get_settings
 from app.db import get_session, utcnow
 from app.services.openrouter import (
@@ -895,3 +896,38 @@ async def patch_digest_prefs(
     user.digest_tone = payload.tone
     await session.commit()
     return DigestPrefsOut(opt_in=payload.opt_in, tone=payload.tone)
+
+
+# ---------------------------------------------------------------------------
+# Settings — language preference
+# ---------------------------------------------------------------------------
+
+
+class LanguagePrefsIn(BaseModel):
+    lang: str
+
+
+class LanguagePrefsOut(BaseModel):
+    lang: str
+
+
+@router.patch("/settings/language", response_model=LanguagePrefsOut)
+async def patch_language_prefs(
+    payload: LanguagePrefsIn,
+    principal: CurrentUser = Depends(require_token),
+    session: AsyncSession = Depends(get_session),
+) -> LanguagePrefsOut:
+    if principal.user is None:
+        raise HTTPException(status_code=400, detail="no_user_context")
+    lang = (payload.lang or "").strip().lower()
+    if lang not in ACTIVE_LANGUAGES:
+        raise HTTPException(
+            status_code=400,
+            detail=f"unsupported language: {payload.lang!r}",
+        )
+    user = await session.get(User, principal.user.id)
+    if user is None:
+        raise HTTPException(status_code=404, detail="user_not_found")
+    user.lang = lang
+    await session.commit()
+    return LanguagePrefsOut(lang=lang)
diff --git a/tests/test_localization_integration.py b/tests/test_localization_integration.py
index ae74a53..c5cf92c 100644
--- a/tests/test_localization_integration.py
+++ b/tests/test_localization_integration.py
@@ -395,3 +395,64 @@ async def test_log_endpoint_falls_back_to_english_when_no_translation(tmp_path):
         user = await session.get(User, 11)
         content = await _resolve_log_content(session, log_id, user.lang)
     assert "Open" in content
+
+
+@pytest.mark.asyncio
+async def test_patch_language_accepts_active(tmp_path):
+    """PATCH /api/settings/language accepts 'en' and 'it' and persists."""
+    from app.models import User
+    from app.routers.api import patch_language_prefs, LanguagePrefsIn
+
+    _, factory, setup = _build_session_factory(tmp_path)
+    await setup()
+
+    async with factory() as session:
+        session.add(User(id=20, email="u@x", tier="paid", lang="en"))
+        await session.commit()
+
+    class _P:
+        is_admin = False
+        def __init__(self, u): self.user = u
+
+    async with factory() as session:
+        user = await session.get(User, 20)
+        result = await patch_language_prefs(
+            payload=LanguagePrefsIn(lang="it"),
+            principal=_P(user),
+            session=session,
+        )
+        assert result.lang == "it"
+
+    async with factory() as session:
+        user = await session.get(User, 20)
+    assert user.lang == "it"
+
+
+@pytest.mark.asyncio
+async def test_patch_language_rejects_wip(tmp_path):
+    """PATCH rejects 'es'/'fr'/'de'/'xx' with 400 — ACTIVE_LANGUAGES gate."""
+    from fastapi import HTTPException
+    from app.models import User
+    from app.routers.api import patch_language_prefs, LanguagePrefsIn
+
+    _, factory, setup = _build_session_factory(tmp_path)
+    await setup()
+
+    async with factory() as session:
+        session.add(User(id=21, email="u2@x", tier="paid", lang="en"))
+        await session.commit()
+
+    class _P:
+        is_admin = False
+        def __init__(self, u): self.user = u
+
+    for bad in ("es", "fr", "de", "xx"):
+        async with factory() as session:
+            user = await session.get(User, 21)
+            with pytest.raises(HTTPException) as exc:
+                await patch_language_prefs(
+                    payload=LanguagePrefsIn(lang=bad),
+                    principal=_P(user),
+                    session=session,
+                )
+            assert exc.value.status_code == 400