navigate_back.py

from __future__ import annotations

from typing import Optional, Type

from langchain_core.callbacks import (
    AsyncCallbackManagerForToolRun,
    CallbackManagerForToolRun,
)
from pydantic import BaseModel

from langchain_community.tools.playwright.base import BaseBrowserTool
from langchain_community.tools.playwright.utils import (
    aget_current_page,
    get_current_page,
)


class NavigateBackToolInput(BaseModel):
    """Explicit no-args input for NavigateBackTool."""


class NavigateBackTool(BaseBrowserTool):  # type: ignore[override, override]
    """Navigate back to the previous page in the browser history."""

    name: str = "previous_webpage"
    description: str = "Navigate back to the previous page in the browser history"
    args_schema: Type[BaseModel] = NavigateBackToolInput

    def _run(self, run_manager: Optional[CallbackManagerForToolRun] = None) -> str:
        """Use the tool."""
        if self.sync_browser is None:
            raise ValueError(f"Synchronous browser not provided to {self.name}")
        page = get_current_page(self.sync_browser)
        response = page.go_back()

        if response:
            return (
                f"Navigated back to the previous page with URL '{response.url}'."
                f" Status code {response.status}"
            )
        else:
            return "Unable to navigate back; no previous page in the history"

    async def _arun(
        self,
        run_manager: Optional[AsyncCallbackManagerForToolRun] = None,
    ) -> str:
        """Use the tool."""
        if self.async_browser is None:
            raise ValueError(f"Asynchronous browser not provided to {self.name}")
        page = await aget_current_page(self.async_browser)
        response = await page.go_back()

        if response:
            return (
                f"Navigated back to the previous page with URL '{response.url}'."
                f" Status code {response.status}"
            )
        else:
            return "Unable to navigate back; no previous page in the history"