from fastapi import APIRouter, Depends
from sqlalchemy.orm import Session
from starlette.responses import StreamingResponse

from app.core.response import ApiResponse, ok
from app.core.user_context import UserContext, get_user_context
from app.db.session import get_db
from app.schemas.learning_assistant import (
    LearningAssistantChatRequest,
    LearningAssistantSessionCreateRequest,
    LearningAssistantSessionResponse,
)
from app.services.learning_assistant_service import LearningAssistantService

router = APIRouter()


@router.post("/sessions", response_model=ApiResponse[LearningAssistantSessionResponse])
async def create_learning_assistant_session(
    payload: LearningAssistantSessionCreateRequest,
    ctx: UserContext = Depends(get_user_context),
    db: Session = Depends(get_db),
):
    """学习助手会话创建：进入 AI 学习助手页面时生成短期会话 ID。"""
    result = LearningAssistantService(db).create_session(ctx, payload)
    return ok(result)


@router.post("/sessions/{assistant_session_id}/chat/stream", response_class=StreamingResponse)
async def stream_learning_assistant_session_chat(
    assistant_session_id: str,
    payload: LearningAssistantChatRequest,
    ctx: UserContext = Depends(get_user_context),
    db: Session = Depends(get_db),
):
    """学习助手会话式流式问答：绑定短期会话上下文，返回 SSE 增量回答。"""
    service = LearningAssistantService(db)
    assistant_session = service.validate_session(ctx, assistant_session_id)
    stream = service.stream_session_chat(ctx, payload, assistant_session)
    return _sse_response(stream)


def _sse_response(stream) -> StreamingResponse:
    """SSE 响应封装：关闭代理缓冲，避免前端长时间看不到增量内容。"""
    return StreamingResponse(
        stream,
        media_type="text/event-stream",
        headers={"Cache-Control": "no-cache", "Connection": "keep-alive", "X-Accel-Buffering": "no"},
    )