Langchain-Chatchat/server/callback_handler/agent_callback_handler.py

from __future__ import annotations
from uuid import UUID
import json
import asyncio
from typing import Any, Dict, List, Optional

from langchain.callbacks import AsyncIteratorCallbackHandler
from langchain.schema import AgentFinish, AgentAction
from langchain_core.outputs import LLMResult


def dumps(obj: Dict) -> str:
    return json.dumps(obj, ensure_ascii=False)


class Status:
    start: int = 1
    running: int = 2
    complete: int = 3
    agent_action: int = 4
    agent_finish: int = 5
    error: int = 6
    tool_finish: int = 7


class CustomAsyncIteratorCallbackHandler(AsyncIteratorCallbackHandler):
    def __init__(self):
        super().__init__()
        self.queue = asyncio.Queue()
        self.done = asyncio.Event()
        self.cur_tool = {}
        self.out = True

    async def on_tool_start(self, serialized: Dict[str, Any], input_str: str, *, run_id: UUID,
                            parent_run_id: UUID | None = None, tags: List[str] | None = None,
                            metadata: Dict[str, Any] | None = None, **kwargs: Any) -> None:
        self.cur_tool = {
            "tool_name": serialized["name"],
            "input_str": input_str,
            "output_str": "",
            "status": Status.agent_action,
            "run_id": run_id.hex,
            "llm_token": "",
            "final_answer": "",
            "error": "",
        }
        self.queue.put_nowait(dumps(self.cur_tool))

    async def on_tool_end(self, output: str, *, run_id: UUID, parent_run_id: UUID | None = None,
                          tags: List[str] | None = None, **kwargs: Any) -> None:

        self.out = True
        self.cur_tool.update(
            status=Status.tool_finish,
            output_str=output.replace("Answer:", ""),
        )
        self.queue.put_nowait(dumps(self.cur_tool))

    async def on_tool_error(self, error: Exception | KeyboardInterrupt, *, run_id: UUID,
                            parent_run_id: UUID | None = None, tags: List[str] | None = None, **kwargs: Any) -> None:
        self.cur_tool.update(
            status=Status.error,
            error=str(error),
        )
        self.queue.put_nowait(dumps(self.cur_tool))

    async def on_llm_new_token(self, token: str, **kwargs: Any) -> None:
        special_tokens = ["Action", "<|observation|>"]
        for stoken in special_tokens:
            if stoken in token:
                before_action = token.split(stoken)[0]
                self.cur_tool.update(
                    status=Status.running,
                    llm_token=before_action + "\n",
                )
                self.queue.put_nowait(dumps(self.cur_tool))
                self.out = False
                break

        if token is not None and token != "" and self.out:
            self.cur_tool.update(
                status=Status.running,
                llm_token=token,
            )
            self.queue.put_nowait(dumps(self.cur_tool))

    async def on_llm_start(self, serialized: Dict[str, Any], prompts: List[str], **kwargs: Any) -> None:
        self.cur_tool.update(
            status=Status.start,
            llm_token="",
        )
        self.queue.put_nowait(dumps(self.cur_tool))

    async def on_chat_model_start(
            self,
            serialized: Dict[str, Any],
            messages: List[List],
            *,
            run_id: UUID,
            parent_run_id: Optional[UUID] = None,
            tags: Optional[List[str]] = None,
            metadata: Optional[Dict[str, Any]] = None,
            **kwargs: Any,
    ) -> None:
        self.cur_tool.update(
            status=Status.start,
            llm_token="",
        )
        self.queue.put_nowait(dumps(self.cur_tool))

    async def on_llm_end(self, response: LLMResult, **kwargs: Any) -> None:
        self.cur_tool.update(
            status=Status.complete,
            llm_token="",
        )
        self.out = True
        self.queue.put_nowait(dumps(self.cur_tool))

    async def on_llm_error(self, error: Exception | KeyboardInterrupt, **kwargs: Any) -> None:
        self.cur_tool.update(
            status=Status.error,
            error=str(error),
        )
        self.queue.put_nowait(dumps(self.cur_tool))

    async def on_agent_action(
            self,
            action: AgentAction,
            *,
            run_id: UUID,
            parent_run_id: Optional[UUID] = None,
            tags: Optional[List[str]] = None,
            **kwargs: Any,
    ) -> None:
        self.cur_tool.update(
            status=Status.agent_action,
            tool_name=action.tool,
            tool_input=action.tool_input,
        )
        self.queue.put_nowait(dumps(self.cur_tool))

    async def on_agent_finish(
            self, finish: AgentFinish, *, run_id: UUID, parent_run_id: Optional[UUID] = None,
            tags: Optional[List[str]] = None,
            **kwargs: Any,
    ) -> None:
        if "Thought:" in finish.return_values["output"]:
            finish.return_values["output"] = finish.return_values["output"].replace("Thought:", "")

        self.cur_tool.update(
            status=Status.agent_finish,
            agent_finish=finish.return_values["output"],
        )
        self.queue.put_nowait(dumps(self.cur_tool))