feat: may_ask (#981)

* feat: u may ask

* chore: adjust code according to CR

* chore: adjust code according to CR

* ut: test for suggestions.py

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/tests/test_suggestions_router.py

@@ -0,0 +1,66 @@
+import asyncio
+from unittest.mock import MagicMock
+
+from src.gateway.routers import suggestions
+
+
+def test_strip_markdown_code_fence_removes_wrapping():
+    text = "```json\n[\"a\"]\n```"
+    assert suggestions._strip_markdown_code_fence(text) == "[\"a\"]"
+
+
+def test_strip_markdown_code_fence_no_fence_keeps_content():
+    text = "  [\"a\"]  "
+    assert suggestions._strip_markdown_code_fence(text) == "[\"a\"]"
+
+
+def test_parse_json_string_list_filters_invalid_items():
+    text = "```json\n[\"a\", \" \", 1, \"b\"]\n```"
+    assert suggestions._parse_json_string_list(text) == ["a", "b"]
+
+
+def test_parse_json_string_list_rejects_non_list():
+    text = "{\"a\": 1}"
+    assert suggestions._parse_json_string_list(text) is None
+
+
+def test_format_conversation_formats_roles():
+    messages = [
+        suggestions.SuggestionMessage(role="User", content="Hi"),
+        suggestions.SuggestionMessage(role="assistant", content="Hello"),
+        suggestions.SuggestionMessage(role="system", content="note"),
+    ]
+    assert suggestions._format_conversation(messages) == "User: Hi\nAssistant: Hello\nsystem: note"
+
+
+def test_generate_suggestions_parses_and_limits(monkeypatch):
+    req = suggestions.SuggestionsRequest(
+        messages=[
+            suggestions.SuggestionMessage(role="user", content="Hi"),
+            suggestions.SuggestionMessage(role="assistant", content="Hello"),
+        ],
+        n=3,
+        model_name=None,
+    )
+    fake_model = MagicMock()
+    fake_model.invoke.return_value = MagicMock(content="```json\n[\"Q1\", \"Q2\", \"Q3\", \"Q4\"]\n```")
+    monkeypatch.setattr(suggestions, "create_chat_model", lambda **kwargs: fake_model)
+
+    result = asyncio.run(suggestions.generate_suggestions("t1", req))
+
+    assert result.suggestions == ["Q1", "Q2", "Q3"]
+
+
+def test_generate_suggestions_returns_empty_on_model_error(monkeypatch):
+    req = suggestions.SuggestionsRequest(
+        messages=[suggestions.SuggestionMessage(role="user", content="Hi")],
+        n=2,
+        model_name=None,
+    )
+    fake_model = MagicMock()
+    fake_model.invoke.side_effect = RuntimeError("boom")
+    monkeypatch.setattr(suggestions, "create_chat_model", lambda **kwargs: fake_model)
+
+    result = asyncio.run(suggestions.generate_suggestions("t1", req))
+
+    assert result.suggestions == []