fix: universal chat when default model invalid (#905)

api/core/tool/current_datetime_tool.py

@@ -0,0 +1,25 @@
+from datetime import datetime
+from typing import Type
+
+from langchain.tools import BaseTool
+from pydantic import Field, BaseModel
+
+
+class DatetimeToolInput(BaseModel):
+    type: str = Field(..., description="Type for current time, must be: datetime.")
+
+
+class DatetimeTool(BaseTool):
+    """Tool for querying current datetime."""
+    name: str = "current_datetime"
+    args_schema: Type[BaseModel] = DatetimeToolInput
+    description: str = "A tool when you want to get the current date, time, week, month or year, " \
+                       "and the time zone is UTC. Result is \"<date> <time> <timezone> <week>\"."
+
+    def _run(self, type: str) -> str:
+        # get current time
+        current_time = datetime.utcnow()
+        return current_time.strftime("%Y-%m-%d %H:%M:%S UTC+0000 %A")
+
+    async def _arun(self, tool_input: str) -> str:
+        raise NotImplementedError()