"""FluentGerman.ai — Chat router with SSE streaming."""

import json
import logging

from fastapi import APIRouter, Depends
from fastapi.responses import StreamingResponse
from sqlalchemy.ext.asyncio import AsyncSession

from app.auth import get_current_user
from app.database import get_db
from app.models import User
from app.schemas import ChatRequest
from app.services.instruction_service import get_system_prompt
from app.services.llm_service import chat_stream

logger = logging.getLogger("fluentgerman.chat")

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


@router.post("/")
async def chat(
    body: ChatRequest,
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Send a message and receive a streamed SSE response."""
    logger.info("Chat request from user=%s message_len=%d history=%d",
                user.username, len(body.message), len(body.history))

    system_prompt = await get_system_prompt(db, user.id)

    messages = [{"role": "system", "content": system_prompt}]
    for msg in body.history:
        messages.append({"role": msg.role, "content": msg.content})
    messages.append({"role": "user", "content": body.message})

    async def event_generator():
        try:
            async for token in chat_stream(messages):
                yield f"data: {json.dumps({'token': token})}\n\n"
            yield "data: [DONE]\n\n"
        except Exception as e:
            logger.error("LLM streaming error: %s", e, exc_info=True)
            yield f"data: {json.dumps({'error': str(e)})}\n\n"

    return StreamingResponse(event_generator(), media_type="text/event-stream")