backend/app/api/chat.py

import logging

from fastapi import APIRouter, HTTPException, Request

from app.config import settings
from app.models.schemas import ChatRequest, ChatResponse
from app.services import rag_service
from app.services.limits import SlidingWindowLimiter

logger = logging.getLogger(__name__)
router = APIRouter()

_chat_limiter = SlidingWindowLimiter(settings.rate_limit_chat_per_minute, 60)


def _client_ip(request: Request) -> str:
    # Behind Vercel/HF proxies the real client is in X-Forwarded-For
    fwd = request.headers.get("x-forwarded-for")
    if fwd:
        return fwd.split(",")[0].strip()
    return request.client.host if request.client else "unknown"


@router.post("/chat", response_model=ChatResponse)
async def chat_endpoint(request: ChatRequest, http_request: Request):
    if not request.message.strip():
        raise HTTPException(status_code=400, detail="Message cannot be empty")

    if not _chat_limiter.allow(_client_ip(http_request)):
        raise HTTPException(
            status_code=429,
            detail="Too many requests — please wait a minute and try again.",
        )

    try:
        answer, sources, response_type, structured_data, token_usage, model_used, rate_limit = \
            await rag_service.chat(
                request.session_id,
                request.message,
                request.model,
                request.email_action,
                request.email_payload,
            )
        return ChatResponse(
            answer=answer,
            sources=sources,
            session_id=request.session_id,
            response_type=response_type,
            structured_data=structured_data,
            token_usage=token_usage,
            model_used=model_used,
            rate_limit=rate_limit,
        )
    except Exception:
        # Full details go to the server log only — never to the client.
        logger.exception("Chat request failed (session=%s)", request.session_id)
        raise HTTPException(
            status_code=500,
            detail="Something went wrong while processing your request. Please try again.",
        )


@router.delete("/chat/{session_id}")
async def clear_session(session_id: str):
    rag_service.clear_session(session_id)
    return {"cleared": session_id}