make a media api, encapsulate the original S3 bucket address

there are 3 parts, from back to head, url inside the bucket -> url of backend media api -> backend domain, only the last part is spliced by frontend, the other two parts are spliced with sqlalchemy

app/graphql/types.py

@@ -4,15 +4,19 @@ from datetime import datetime
 from strawberry.types import Info
 
 from app.utils.format import get_image_url
+from app.models.user import User
 
 @strawberry.type
 class UserType:
     id: str
     email: str
     name: str
-    avatar: str
     handle: Optional[str]
     
+    @strawberry.field
+    def avatar(self, root: User) -> Optional[str]:
+        return root.avatar_url
+    
     # 互动统计字段
     following_count: int
     follower_count: int

app/main.py

@@ -6,6 +6,7 @@ from strawberry.fastapi import GraphQLRouter
 from dotenv import load_dotenv
 
 from auth import router as auth_router
+from app.media.router import router as media_router
 
 from app.db import engine, SessionLocal
 from app.models import Base, User
@@ -44,6 +45,7 @@ graphql_router = GraphQLRouter(schema, context_getter=get_context)
 
 # 挂载路由
 app.include_router(auth_router)                         # 保留现有的 auth 路由供 Google OAuth 回调使用
+app.include_router(media_router)                        # 挂载媒体路由，提供头像代理访问等等
 app.include_router(graphql_router, prefix="/graphql")   # 挂载 GraphQL 终点，前端以后只需要请求 /graphql
 
 # 打印路由测试

app/media/router.py

@@ -0,0 +1,45 @@
+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")

app/models/user.py

@@ -17,6 +17,19 @@ class User(Base, AutoID):
     handle = Column(String, unique=True, index=True, nullable=True)
     avatar = Column(String)
     
+    @property
+    def avatar_url(self) -> str | None:
+        if not self.avatar:
+            return None
+            
+        # 如果是第三方（如未迁移成功时降级的 Google 原始链接），直接返回
+        if self.avatar.startswith(("http://", "https://")):
+            return self.avatar
+        
+        path = self.avatar.lstrip("/")
+        
+        return f"/v1/media/{path}"
+    
     # ---- 互动统计字段 ----
     following_count = Column(Integer, default=0, nullable=False, server_default="0")            # 关注了多少人
     follower_count = Column(Integer, default=0, nullable=False, server_default="0")             # 粉丝数