import logging
import os
from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse, Response
import httpx

try:
    from dotenv import load_dotenv

    load_dotenv()
except ImportError:
    pass

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

app = FastAPI()

UPSTREAM_URL = os.getenv(
    "LLM_UPSTREAM_URL",
    "https://llm.corp.septem.pro/v1/chat/completions",
).strip()
OPENROUTER_KEY = os.getenv("OPENROUTER_API_KEY", "").strip()


def _client_timeout() -> httpx.Timeout:
    total = float(os.getenv("LLM_PROXY_TIMEOUT_SECONDS", "120"))
    connect = float(os.getenv("LLM_PROXY_CONNECT_TIMEOUT", "15"))
    return httpx.Timeout(total, connect=connect)


@app.post("/v1/chat/completions")
async def proxy(req: Request):
    if not OPENROUTER_KEY:
        logger.error("OPENROUTER_API_KEY is not set (env or .env)")
        return JSONResponse(
            status_code=503,
            content={
                "error": "Service unavailable",
                "details": "Set OPENROUTER_API_KEY for the LLM proxy (or add it to .env).",
            },
        )

    try:
        body = await req.json()
    except Exception as e:
        return JSONResponse(
            status_code=400,
            content={"error": "Invalid JSON", "details": str(e)},
        )

    verify = os.getenv("HTTPX_VERIFY", "true").lower() not in ("0", "false", "no")

    async with httpx.AsyncClient(verify=verify) as client:
        try:
            r = await client.post(
                UPSTREAM_URL,
                headers={
                    "Authorization": f"Bearer {OPENROUTER_KEY}",
                    "HTTP-Referer": os.getenv("LLM_HTTP_REFERER", "http://localhost"),
                    "X-Title": os.getenv("LLM_PROXY_X_TITLE", "rag-engine"),
                },
                json=body,
                timeout=_client_timeout(),
            )
        except httpx.RequestError as e:
            logger.error(
                "LLM upstream unreachable (%s): %s",
                UPSTREAM_URL,
                e,
                exc_info=True,
            )
            return JSONResponse(
                status_code=502,
                content={
                    "error": "Bad gateway",
                    "details": str(e),
                    "upstream": UPSTREAM_URL,
                    "hint": "Проверьте VPN, DNS, доступность хоста и переменную LLM_UPSTREAM_URL.",
                },
            )

    if r.status_code >= 500:
        logger.warning(
            "LLM upstream HTTP %s, body (prefix): %s",
            r.status_code,
            (r.text or "")[:800],
        )

    return Response(
        content=r.content,
        status_code=r.status_code,
        media_type=r.headers.get("content-type", "application/json"),
    )