"""Independent LangChain ReAct host for find_agent_v2.

The host owns model construction, retries, usage accounting, tool adaptation and
controlled nested-agent delegation.  It never imports the legacy find-agent package.
"""

from __future__ import annotations

import asyncio
import json
import os
from collections.abc import Iterable
from typing import Any

from langchain.agents import create_agent
from langchain.agents.middleware import ModelFallbackMiddleware, ModelRetryMiddleware, ToolRetryMiddleware
from langchain_core.messages import AIMessage, BaseMessage, ToolMessage
from langchain_core.tools import StructuredTool
from langchain_openai import ChatOpenAI
from pydantic import BaseModel, Field

from find_agent_v2.observability import InputSlot, ObagentObserver
from find_agent_v2.state import NodeRun
from find_agent_v2.tools import ToolFn
from supply_agent.config import Settings, get_settings


class DelegateRequest(BaseModel):
    task: str = Field(description="交给子 Agent 的完整、独立任务")


class DelegateArgs(BaseModel):
    requests: list[DelegateRequest] = Field(
        min_length=1, max_length=8,
        description="可并发执行的子 Agent 任务；有依赖的任务不要放在同一批",
    )


def _tool_name(fn: ToolFn) -> str:
    return str(getattr(fn, "_tool_name", fn.__name__))


def _as_langchain_tool(fn: ToolFn) -> StructuredTool:
    kwargs = {
        "name": _tool_name(fn),
        "description": str(getattr(fn, "_tool_description", fn.__doc__ or "")),
    }
    if asyncio.iscoroutinefunction(fn):
        return StructuredTool.from_function(coroutine=fn, **kwargs)
    return StructuredTool.from_function(func=fn, **kwargs)


def _message_dict(message: BaseMessage) -> dict[str, Any]:
    data = message.model_dump(mode="json")
    data["type"] = message.type
    return data


def _usage(messages: list[BaseMessage]) -> dict[str, int | float]:
    totals: dict[str, int | float] = {
        "input_tokens": 0, "output_tokens": 0, "total_tokens": 0, "cost": 0.0,
    }
    for message in messages:
        usage = getattr(message, "usage_metadata", None) or {}
        totals["input_tokens"] += int(usage.get("input_tokens") or 0)
        totals["output_tokens"] += int(usage.get("output_tokens") or 0)
        totals["total_tokens"] += int(usage.get("total_tokens") or 0)
        response = getattr(message, "response_metadata", None) or {}
        cost = response.get("cost") or (response.get("usage") or {}).get("cost")
        if cost is not None:
            totals["cost"] += float(cost)
    totals["cost"] = round(float(totals["cost"]), 8)
    return totals


def _events(messages: list[BaseMessage]) -> list[dict[str, Any]]:
    events: list[dict[str, Any]] = []
    for message in messages:
        if isinstance(message, AIMessage):
            events.append({
                "type": "llm_output",
                "content": message.content,
                "tool_calls": message.tool_calls,
                "usage": message.usage_metadata,
            })
        elif isinstance(message, ToolMessage):
            events.append({
                "type": "tool_call",
                "name": message.name,
                "tool_call_id": message.tool_call_id,
                "result": message.content,
                "status": message.status,
            })
    return events


class FindAgentNodeHost:
    """Create a fresh LangChain Agent for every workflow or delegated node."""

    def __init__(
        self,
        *,
        settings: Settings | None = None,
        models_by_role: dict[str, str] | None = None,
        default_model: str = "google/gemini-3-flash-preview",
        observer: ObagentObserver | None = None,
    ) -> None:
        self.settings = settings or get_settings()
        self.models_by_role = dict(models_by_role or {})
        self.default_model = default_model
        self.observer = observer or ObagentObserver()
        self.usage = {"input_tokens": 0, "output_tokens": 0, "total_tokens": 0, "cost": 0.0}

    def reset_usage(self) -> None:
        self.usage = {
            "input_tokens": 0,
            "output_tokens": 0,
            "total_tokens": 0,
            "cost": 0.0,
        }

    def _model(self, role: str) -> ChatOpenAI:
        model_name = self.models_by_role.get(role, self.default_model)
        return ChatOpenAI(
            model=model_name,
            api_key=self.settings.openrouter_api_key,
            base_url=self.settings.openrouter_base_url,
            timeout=self.settings.openrouter_timeout_seconds,
            temperature=0.2,
            max_retries=0,  # retries are observable LangChain middleware below
            default_headers={
                "HTTP-Referer": self.settings.openrouter_site_url,
                "X-Title": self.settings.openrouter_site_name,
            },
        )

    def _middleware(self, role: str):
        items: list[Any] = [
            ModelRetryMiddleware(max_retries=2, on_failure="error"),
            ToolRetryMiddleware(max_retries=2, on_failure="continue"),
        ]
        fallback = os.getenv("FIND_AGENT_V2_FALLBACK_MODEL", "").strip()
        if fallback and fallback != self.models_by_role.get(role, self.default_model):
            items.insert(0, ModelFallbackMiddleware(self._model_for_name(fallback)))
        return items

    def _model_for_name(self, model_name: str) -> ChatOpenAI:
        return ChatOpenAI(
            model=model_name,
            api_key=self.settings.openrouter_api_key,
            base_url=self.settings.openrouter_base_url,
            timeout=self.settings.openrouter_timeout_seconds,
            temperature=0.2,
            max_retries=0,
        )

    def _delegate_tool(
        self,
        *,
        parent_node: str,
        round_index: int,
        system_prompt: str,
        tools: tuple[ToolFn, ...],
        max_iterations: int,
        slots: tuple[InputSlot, ...],
    ) -> StructuredTool:
        async def delegate_agents_v2(requests: list[DelegateRequest]) -> str:
            """并发委派多个相互独立的任务给同阶段子 Agent。"""
            normalized = [
                item if isinstance(item, DelegateRequest) else DelegateRequest.model_validate(item)
                for item in requests
            ]

            async def run_one(index: int, request: DelegateRequest) -> dict[str, Any]:
                result = await self.run_node(
                    node=parent_node,
                    round_index=round_index,
                    system_prompt=system_prompt,
                    user_content=request.task,
                    tools=tools,
                    max_iterations=max_iterations,
                    slots=slots,
                    branch_key=f"delegate-{index}",
                    allow_delegation=False,
                )
                return {
                    "branch": index,
                    "content": result.content,
                    "iterations": result.iterations,
                    "tool_calls_made": result.tool_calls_made,
                }

            results = await asyncio.gather(*(
                run_one(index, request) for index, request in enumerate(normalized, start=1)
            ), return_exceptions=True)
            output = []
            for index, result in enumerate(results, start=1):
                if isinstance(result, BaseException):
                    output.append({"branch": index, "error": f"{type(result).__name__}: {result}"})
                else:
                    output.append(result)
            return json.dumps({"delegated": output}, ensure_ascii=False)

        return StructuredTool.from_function(
            coroutine=delegate_agents_v2,
            name="delegate_agents_v2",
            description="将多个无依赖任务并发委派给拥有相同阶段工具权限的子 Agent。",
            args_schema=DelegateArgs,
        )

    async def run_node(
        self,
        *,
        node: str,
        round_index: int,
        system_prompt: str,
        user_content: str,
        tools: Iterable[ToolFn] = (),
        max_iterations: int = 12,
        slots: tuple[InputSlot, ...] = (),
        branch_key: str = "",
        allow_delegation: bool = True,
    ) -> NodeRun:
        tool_functions = tuple(tools)
        model_name = self.models_by_role.get(node, self.default_model)
        langchain_tools = [_as_langchain_tool(fn) for fn in tool_functions]
        if allow_delegation and node in {"search", "evidence", "evaluator"}:
            langchain_tools.append(self._delegate_tool(
                parent_node=node,
                round_index=round_index,
                system_prompt=system_prompt,
                tools=tool_functions,
                max_iterations=max_iterations,
                slots=slots,
            ))
        agent = create_agent(
            model=self._model(node),
            tools=langchain_tools,
            system_prompt=system_prompt,
            middleware=self._middleware(node),
            name=f"find_agent_v2_{node}",
        )
        with self.observer.node(node=node, branch_key=branch_key) as observation:
            actual_user_content = observation.declare(
                fallback=user_content,
                system_prompt=system_prompt,
                slots=slots,
                tools=tuple(langchain_tools),
                model=model_name,
                refs=({"delegate": "same-stage-worker"} if allow_delegation else None),
            )
            result = await agent.ainvoke(
                {"messages": [{"role": "user", "content": actual_user_content}]},
                # create_agent counts model and tool nodes separately, and middleware
                # retries also consume supersteps. Keep this budget distinct from
                # the business-level no-progress guard in graph.py.
                config={"recursion_limit": max(64, max_iterations * 6)},
            )
            messages: list[BaseMessage] = list(result.get("messages") or [])
            usage = _usage(messages)
            for key in ("input_tokens", "output_tokens", "total_tokens"):
                self.usage[key] = int(self.usage[key]) + int(usage[key])
            self.usage["cost"] = round(float(self.usage["cost"]) + float(usage["cost"]), 8)
            process = {
                "messages": [_message_dict(message) for message in messages],
                "events": _events(messages),
                "usage": usage,
                "iterations": sum(isinstance(message, AIMessage) for message in messages),
                "tool_calls_made": sum(
                    len(message.tool_calls) for message in messages if isinstance(message, AIMessage)
                ),
            }
            last_ai = next((message for message in reversed(messages) if isinstance(message, AIMessage)), None)
            content = str(last_ai.content if last_ai is not None else "")
            observation.record_react(output=process, ok=True)
            observation.set_output({"agent输出": content, **process}, ok=True)
            return NodeRun(
                node=node,
                round_index=round_index,
                content=content,
                iterations=int(process["iterations"]),
                tool_calls_made=int(process["tool_calls_made"]),
            )


def normalize_models(
    *,
    model: str | None = None,
    planning: str | None = None,
    search: str | None = None,
    evidence: str | None = None,
    evaluation: str | None = None,
    report: str | None = None,
) -> dict[str, str]:
    base = model or "google/gemini-3-flash-preview"
    return {
        "supervisor": planning or base,
        "search": search or base,
        "evidence": evidence or base,
        "evaluator": evaluation or base,
        "report": report or base,
    }