Phase 1 fix auth redirect API handling and route issues

app/core/http_responses.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+from fastapi import Request
+from fastapi.responses import JSONResponse, RedirectResponse, Response
+
+
+def wants_json(request: Request) -> bool:
+    path = request.url.path or ""
+    accept = (request.headers.get("accept") or "").lower()
+    requested_with = (request.headers.get("x-requested-with") or "").lower()
+    return path.startswith("/api") or "application/json" in accept or requested_with == "xmlhttprequest"
+
+
+def ui_access_denied(message: str = "Access denied") -> Response:
+    return Response(
+        content=f"403 Forbidden: {message}",
+        status_code=403,
+        media_type="text/plain; charset=utf-8",
+    )
+
+
+def ui_not_found(message: str = "Not found") -> Response:
+    return Response(
+        content=f"404 Not Found: {message}",
+        status_code=404,
+        media_type="text/plain; charset=utf-8",
+    )
+
+
+def auth_required_response(request: Request):
+    if wants_json(request):
+        return JSONResponse({"detail": "Not authenticated"}, status_code=401)
+    return RedirectResponse(url="/login", status_code=303)
+
+
+def forbidden_response(request: Request, message: str = "Access denied"):
+    if wants_json(request):
+        return JSONResponse({"detail": message}, status_code=403)
+    return ui_access_denied(message)
+
+
+def not_found_response(request: Request, message: str = "Not found"):
+    if wants_json(request):
+        return JSONResponse({"detail": message}, status_code=404)
+    return ui_not_found(message)