import json
import uuid
from pathlib import Path
from typing import Optional

from fastapi import APIRouter, File, Form, UploadFile
from sse_starlette.sse import EventSourceResponse

from app.agent.loop import run_agent_loop

router = APIRouter()

UPLOADS_DIR = Path(__file__).parent.parent.parent / "uploads"


async def _save_upload(file: UploadFile) -> str:
    """保存上传的参考图，返回可访问的 URL 路径。"""
    ext = Path(file.filename).suffix or ".png"
    filename = f"{uuid.uuid4().hex}{ext}"
    filepath = UPLOADS_DIR / filename
    content = await file.read()
    filepath.write_bytes(content)
    return f"/uploads/{filename}"


@router.post("/chat")
async def chat(
    messages: str = Form(...),
    ref_image: Optional[UploadFile] = File(None),
):
    """
    主对话端点。

    参数：
    - messages: JSON 字符串，对话历史 [{role, content}]
    - ref_image: 可选的参考图文件
    """
    parsed_messages = json.loads(messages)

    ref_image_url: Optional[str] = None
    if ref_image and ref_image.filename:
        ref_image_url = await _save_upload(ref_image)

    async def event_generator():
        async for event in run_agent_loop(parsed_messages, ref_image_url):
            yield {
                "event": event["type"],
                "data": json.dumps(event["data"], ensure_ascii=False),
            }

    return EventSourceResponse(event_generator())