"""Chat endpoint — POST /api/v1/chat with SSE streaming response.

Accepts a query and optional creator filter, returns a Server-Sent Events
stream with sources, token, done, and error events.
"""

from __future__ import annotations

import logging

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

from chat_service import ChatService
from config import Settings, get_settings
from database import get_session
from redis_client import get_redis

logger = logging.getLogger("chrysopedia.chat.router")

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


class ChatRequest(BaseModel):
    """Request body for the chat endpoint."""

    query: str = Field(..., min_length=1, max_length=1000)
    creator: str | None = None
    conversation_id: str | None = None
    personality_weight: float = Field(default=0.0, ge=0.0, le=1.0)


@router.post("")
async def chat(
    body: ChatRequest,
    db: AsyncSession = Depends(get_session),
    settings: Settings = Depends(get_settings),
) -> StreamingResponse:
    """Stream a chat response as Server-Sent Events.

    SSE protocol:
    - ``event: sources`` — citation metadata array (sent first)
    - ``event: token``   — streamed text chunk (repeated)
    - ``event: done``    — completion metadata with cascade_tier, conversation_id
    - ``event: error``   — error message (on failure)
    """
    logger.info("chat_request query=%r creator=%r cid=%r weight=%.2f", body.query, body.creator, body.conversation_id, body.personality_weight)

    redis = await get_redis()
    service = ChatService(settings, redis=redis)

    return StreamingResponse(
        service.stream_response(
            query=body.query,
            db=db,
            creator=body.creator,
            conversation_id=body.conversation_id,
            personality_weight=body.personality_weight,
        ),
        media_type="text/event-stream",
        headers={
            "Cache-Control": "no-cache",
            "X-Accel-Buffering": "no",
        },
    )