"""
POST /api/chat_callback — 自定义 LLM 回调（SSE 流式响应）
"""

import json

from fastapi import APIRouter, Request
from fastapi.responses import StreamingResponse

from schemas.chat import ChatCallbackRequest
from services.local_llm_service import local_llm_service
from services.scene_service import ensure_custom_llm_authorized, get_custom_llm_callback_settings
from services.session_store import get_room_history
from utils.responses import custom_llm_error_response

router = APIRouter(tags=["LLM 回调"])


@router.post(
    "/api/chat_callback",
    summary="自定义 LLM 回调（SSE 流式）",
    description=(
        "由**火山引擎 RTC 平台**在用户发言后自动回调，返回 OpenAI 兼容格式的 SSE 流。\n\n"
        "处理逻辑：\n"
        "1. 校验 `Authorization: Bearer <CUSTOM_LLM_API_KEY>`\n"
        "2. 过滤掉 RTC 平台发送的 `欢迎语` 触发词（非真实用户输入）\n"
        "3. 若携带 `room_id` Query 参数，自动从缓存取历史并 prepend 到 messages 前\n"
        "4. 调用本地 LLM（工具调用 / RAG 按需触发），以 SSE 流返回结果\n\n"
        "**鉴权**：`Authorization: Bearer <CUSTOM_LLM_API_KEY>`"
    ),
    responses={
        401: {"description": "API Key 无效"},
        400: {"description": "messages 为空或最后一条不是 user 角色"},
        500: {"description": "LLM 初始化失败"},
    },
)
async def chat_callback(request: Request, body: ChatCallbackRequest):
    try:
        settings = get_custom_llm_callback_settings()
        ensure_custom_llm_authorized(request, settings["api_key"])
    except PermissionError as exc:
        return custom_llm_error_response(
            str(exc),
            code="AuthenticationError",
            status_code=401,
        )
    except ValueError as exc:
        return custom_llm_error_response(str(exc))
    except Exception as exc:
        return custom_llm_error_response(
            f"解析请求失败: {exc}",
            code="InternalError",
            status_code=500,
        )

    messages = [m.model_dump() for m in body.messages]
    if not messages:
        return custom_llm_error_response(
            "messages 不能为空",
            code="BadRequest",
            status_code=400,
        )

    # 过滤 RTC 平台的"欢迎语"触发词（不是真实用户输入）
    messages = [m for m in messages if not (m["role"] == "user" and m["content"] == "欢迎语")]

    # 注入历史对话上下文（prepend 到当前会话消息前）
    room_id = request.query_params.get("room_id", "")
    if room_id:
        history = get_room_history(room_id)
        if history:
            messages = history + messages

    if not messages:
        return custom_llm_error_response(
            "messages 不能为空",
            code="BadRequest",
            status_code=400,
        )

    last_message = messages[-1]
    if last_message.get("role") != "user":
        return custom_llm_error_response(
            "最后一条消息必须是用户消息",
            code="BadRequest",
            status_code=400,
        )

    # RAG 已改为 tool 按需调用，不再预检索

    try:
        stream_iterator = local_llm_service.chat_stream(
            history_messages=messages,
            request_options={
                "temperature": body.temperature,
                "max_tokens": body.max_tokens,
                "top_p": body.top_p,
            },
        )
    except Exception as exc:
        return custom_llm_error_response(
            f"初始化本地 LLM 流式调用失败: {exc}",
            code="InternalError",
            status_code=500,
        )

    def generate_sse():
        has_error = False
        try:
            for chunk in stream_iterator:
                if chunk is None:
                    continue

                if hasattr(chunk, "model_dump_json"):
                    chunk_json = chunk.model_dump_json()
                else:
                    chunk_json = json.dumps(chunk, ensure_ascii=False)
                yield f"data: {chunk_json}\n\n"
        except GeneratorExit:
            raise
        except Exception as exc:
            has_error = True
            print(f"❌ /api/chat_callback 流式输出失败: {exc}")

        if has_error:
            print("⚠️ 已提前结束当前 SSE 流")

        yield "data: [DONE]\n\n"

    return StreamingResponse(
        generate_sse(),
        status_code=200,
        media_type="text/event-stream",
        headers={
            "Cache-Control": "no-cache",
            "Connection": "keep-alive",
            "Access-Control-Allow-Origin": "*",
        },
    )