import asyncio
import logging
from collections.abc import Awaitable, Callable
from dataclasses import replace as dc_replace
from typing import NotRequired, override

from langchain.agents import AgentState
from langchain.agents.middleware import AgentMiddleware
from langchain_core.messages import ToolMessage
from langgraph.prebuilt.tool_node import ToolCallRequest
from langgraph.runtime import Runtime
from langgraph.types import Command

from deerflow.agents.thread_state import SandboxStateField, ThreadDataState
from deerflow.sandbox import get_sandbox_provider

logger = logging.getLogger(__name__)


class SandboxMiddlewareState(AgentState):
    """Compatible with the `ThreadState` schema."""

    sandbox: SandboxStateField
    thread_data: NotRequired[ThreadDataState | None]


class SandboxMiddleware(AgentMiddleware[SandboxMiddlewareState]):
    """Create a sandbox environment and assign it to an agent.

    Lifecycle Management:
    - With lazy_init=True (default): Sandbox is acquired on first tool call
    - With lazy_init=False: Sandbox is acquired on first agent invocation (before_agent)
    - Sandbox is reused across multiple turns within the same thread
    - Sandbox is NOT released after each agent call to avoid wasteful recreation
    - Cleanup happens at application shutdown via SandboxProvider.shutdown()
    """

    state_schema = SandboxMiddlewareState

    def __init__(self, lazy_init: bool = True):
        """Initialize sandbox middleware.

        Args:
            lazy_init: If True, defer sandbox acquisition until first tool call.
                      If False, acquire sandbox eagerly in before_agent().
                      Default is True for optimal performance.
        """
        super().__init__()
        self._lazy_init = lazy_init

    def _acquire_sandbox(self, thread_id: str) -> str:
        provider = get_sandbox_provider()
        sandbox_id = provider.acquire(thread_id)
        logger.info(f"Acquiring sandbox {sandbox_id}")
        return sandbox_id

    async def _acquire_sandbox_async(self, thread_id: str) -> str:
        provider = get_sandbox_provider()
        sandbox_id = await provider.acquire_async(thread_id)
        logger.info(f"Acquiring sandbox {sandbox_id}")
        return sandbox_id

    async def _release_sandbox_async(self, sandbox_id: str) -> None:
        await asyncio.to_thread(get_sandbox_provider().release, sandbox_id)

    @override
    def before_agent(self, state: SandboxMiddlewareState, runtime: Runtime) -> dict | None:
        # Skip acquisition if lazy_init is enabled
        if self._lazy_init:
            return super().before_agent(state, runtime)

        # Eager initialization (original behavior)
        if "sandbox" not in state or state["sandbox"] is None:
            thread_id = (runtime.context or {}).get("thread_id")
            if thread_id is None:
                return super().before_agent(state, runtime)
            sandbox_id = self._acquire_sandbox(thread_id)
            logger.info(f"Assigned sandbox {sandbox_id} to thread {thread_id}")
            return {"sandbox": {"sandbox_id": sandbox_id}}
        return super().before_agent(state, runtime)

    @override
    async def abefore_agent(self, state: SandboxMiddlewareState, runtime: Runtime) -> dict | None:
        # Skip acquisition if lazy_init is enabled
        if self._lazy_init:
            return await super().abefore_agent(state, runtime)

        # Eager initialization (original behavior), but use the async provider
        # hook so blocking sandbox startup/polling runs outside the event loop.
        if "sandbox" not in state or state["sandbox"] is None:
            thread_id = (runtime.context or {}).get("thread_id")
            if thread_id is None:
                return await super().abefore_agent(state, runtime)
            sandbox_id = await self._acquire_sandbox_async(thread_id)
            logger.info(f"Assigned sandbox {sandbox_id} to thread {thread_id}")
            return {"sandbox": {"sandbox_id": sandbox_id}}
        return await super().abefore_agent(state, runtime)

    @override
    def after_agent(self, state: SandboxMiddlewareState, runtime: Runtime) -> dict | None:
        sandbox = state.get("sandbox")
        if sandbox is not None:
            sandbox_id = sandbox["sandbox_id"]
            logger.info(f"Releasing sandbox {sandbox_id}")
            get_sandbox_provider().release(sandbox_id)
            return None

        if (runtime.context or {}).get("sandbox_id") is not None:
            sandbox_id = runtime.context.get("sandbox_id")
            logger.info(f"Releasing sandbox {sandbox_id} from context")
            get_sandbox_provider().release(sandbox_id)
            return None

        # No sandbox to release
        return super().after_agent(state, runtime)

    @override
    async def aafter_agent(self, state: SandboxMiddlewareState, runtime: Runtime) -> dict | None:
        sandbox = state.get("sandbox")
        if sandbox is not None:
            sandbox_id = sandbox["sandbox_id"]
            logger.info(f"Releasing sandbox {sandbox_id}")
            await self._release_sandbox_async(sandbox_id)
            return None

        if (runtime.context or {}).get("sandbox_id") is not None:
            sandbox_id = runtime.context.get("sandbox_id")
            logger.info(f"Releasing sandbox {sandbox_id} from context")
            await self._release_sandbox_async(sandbox_id)
            return None

        # No sandbox to release
        return await super().aafter_agent(state, runtime)

    # ------------------------------------------------------------------
    # Tool-call wrappers: persist lazily-acquired sandbox state into the
    # graph state via Command(update=...).
    #
    # Background:
    #   ``ensure_sandbox_initialized*`` in ``deerflow.sandbox.tools`` mutates
    #   ``runtime.state["sandbox"]`` directly. That mutation is local to the
    #   current tool invocation and is NOT picked up by LangGraph's channel
    #   reducer, so subsequent graph steps (and downstream consumers such as
    #   ``ToolOutputBudgetMiddleware`` and the sub-agent ``task_tool``)
    #   cannot observe the sandbox id. Wrapping the tool call lets us detect
    #   a fresh lazy init by diffing the state snapshot before/after the
    #   handler and emit a proper state update via ``Command``.
    # ------------------------------------------------------------------

    @staticmethod
    def _read_sandbox_id_from_state(state: object) -> str | None:
        if not isinstance(state, dict):
            return None
        sandbox_state = state.get("sandbox")
        if not isinstance(sandbox_state, dict):
            return None
        sandbox_id = sandbox_state.get("sandbox_id")
        return sandbox_id if isinstance(sandbox_id, str) else None

    @staticmethod
    def _attach_sandbox_update(result: ToolMessage | Command, sandbox_id: str) -> ToolMessage | Command:
        """Wrap or merge ``result`` so that ``sandbox.sandbox_id`` is persisted.

        - ``ToolMessage`` -> ``Command(update={"sandbox": ..., "messages": [msg]})``
        - ``Command`` with dict update -> merge ``sandbox`` key, preserve all
          existing fields (``messages``, ``goto``, ``graph``, ``resume``, ...).
        - ``Command`` with non-dict / None update -> leave it untouched to
          avoid silent data loss on unknown update shapes.
        """
        sandbox_update = {"sandbox": {"sandbox_id": sandbox_id}}

        if isinstance(result, ToolMessage):
            return Command(update={**sandbox_update, "messages": [result]})

        existing_update = result.update
        if isinstance(existing_update, dict):
            merged_update = {**existing_update, **sandbox_update}
            return dc_replace(result, update=merged_update)
        return result

    @staticmethod
    def _read_sandbox_id_from_request(request: ToolCallRequest) -> str | None:
        """Read sandbox_id from runtime.state (where ensure_sandbox_initialized writes)."""
        runtime = request.runtime
        if runtime is None or runtime.state is None:
            return None
        return SandboxMiddleware._read_sandbox_id_from_state(runtime.state)

    @override
    def wrap_tool_call(
        self,
        request: ToolCallRequest,
        handler: Callable[[ToolCallRequest], ToolMessage | Command],
    ) -> ToolMessage | Command:
        prev_sandbox_id = self._read_sandbox_id_from_request(request)
        result = handler(request)
        if prev_sandbox_id is not None:
            return result
        curr_sandbox_id = self._read_sandbox_id_from_request(request)
        if curr_sandbox_id is None:
            return result
        return self._attach_sandbox_update(result, curr_sandbox_id)

    @override
    async def awrap_tool_call(
        self,
        request: ToolCallRequest,
        handler: Callable[[ToolCallRequest], Awaitable[ToolMessage | Command]],
    ) -> ToolMessage | Command:
        prev_sandbox_id = self._read_sandbox_id_from_request(request)
        result = await handler(request)
        if prev_sandbox_id is not None:
            return result
        curr_sandbox_id = self._read_sandbox_id_from_request(request)
        if curr_sandbox_id is None:
            return result
        return self._attach_sandbox_update(result, curr_sandbox_id)
