from fastapi import APIRouter, HTTPException
from fastapi.responses import StreamingResponse
import oss2
from app.utils.s3 import bucket  

router = APIRouter(prefix="/v1/media", tags=["Media"])

@router.get("/{file_path:path}")
async def get_avatar(file_path: str):
    """
    通过流式传输代理阿里云 OSS 中的图片
    file_path 接收 avatars/xxx/avatar.jpg 等任何相对路径
    """
    s3_key = file_path.lstrip("/")
    
    if not s3_key:
        raise HTTPException(status_code=400, detail="Invalid file path")
        
    try:
        # 从阿里云 OSS 获取对象
        # oss2 的 get_object 是同步阻塞的
        # 初期可以直接用，后续高并发可以放入 run_in_executor
        oss_object = bucket.get_object(s3_key)
        
        # 获取文件的 Content-Type
        content_type = oss_object.headers.get("Content-Type", "image/jpeg")
        
        # 创建一个生成器来分块读取 OSS 数据，防止大文件时撑爆内存
        def image_stream():
            while True:
                chunk = oss_object.read(1024 * 64)  # 每次读 64KB
                if not chunk:
                    break
                yield chunk
                
        # 流式返回给前端
        return StreamingResponse(image_stream(), media_type=content_type)
        
    except oss2.exceptions.NoSuchKey:
        # 阿里云 OSS 专属的 404 异常
        raise HTTPException(status_code=404, detail="Image not found in storage")
    except Exception as e:
        import traceback
        traceback.print_exc()
        raise HTTPException(status_code=500, detail="Internal storage service error")