"""AI Research Agent API（Phase 5）。

POST /api/agent/chat {message} → {reply, actions:[{tool,args,output}]}
未配置 LLM Key 时返回 400 引导（不会崩溃）。
"""

from __future__ import annotations

from typing import Annotated

from fastapi import APIRouter, Depends, HTTPException
from pydantic import BaseModel, Field

from app.agent.llm import LLMClient, build_llm_from_settings
from app.agent.service import AgentService

router = APIRouter(prefix="/agent", tags=["agent"])


class AgentChatRequest(BaseModel):
    message: str = Field(min_length=1, max_length=2000)


def _llm_or_raise() -> LLMClient:
    llm = build_llm_from_settings()
    if llm is None:
        raise HTTPException(
            status_code=400,
            detail="未配置 LLM：请在根目录 .env 中设置 LLM_API_KEY（可选 LLM_BASE_URL / LLM_MODEL），"
            "参考 .env.example 与 AGENT.md §33",
        )
    return llm


@router.post("/chat", summary="与 AI 研究助手对话（受控工具）")
def agent_chat(
    body: AgentChatRequest,
    llm: Annotated[LLMClient, Depends(_llm_or_raise)],
) -> dict:
    return AgentService(llm).chat(body.message)