feat(private-api): add check friend relationship api

app/router/private/cover.py

@@ -28,7 +28,7 @@ async def upload_cover(
 ):
     """上传用户头图
 
-    接收图片数据，验证图片格式和大小后存储到存储服务，并更新用户的头像 URL
+    接收图片数据，验证图片格式和大小后存储到存储服务，并更新用户的头图 URL
 
     限制条件:
     - 支持的图片格式: PNG、JPEG、GIF
@@ -36,7 +36,7 @@ async def upload_cover(
     - 最大图片尺寸: 3000x2000 像素
 
     返回:
-    - 头像 URL 和文件哈希值
+    - 头图 URL 和文件哈希值
     """
 
     # check file

app/router/private/relationship.py

@@ -0,0 +1,65 @@
+from __future__ import annotations
+
+from app.database import Relationship, User
+from app.database.relationship import RelationshipType
+from app.dependencies.database import get_db
+from app.dependencies.user import get_client_user
+
+from .router import router
+
+from fastapi import Depends, HTTPException, Path, Security
+from pydantic import BaseModel, Field
+from sqlmodel import select
+from sqlmodel.ext.asyncio.session import AsyncSession
+
+
+class CheckResponse(BaseModel):
+    is_followed: bool = Field(..., description="对方是否关注了当前用户")
+    is_following: bool = Field(..., description="当前用户是否关注了对方")
+    mutual: bool = Field(..., description="当前用户与对方是否互相关注")
+
+
+@router.get(
+    "/relationship/check/{user_id}",
+    name="检查关系状态",
+    description="检查当前用户与指定用户的关系状态",
+    response_model=CheckResponse,
+)
+async def check_user_relationship(
+    user_id: int = Path(..., description="目标用户的 ID"),
+    current_user: User = Security(get_client_user),
+    db: AsyncSession = Depends(get_db),
+):
+    if user_id == current_user.id:
+        raise HTTPException(422, "Cannot check relationship with yourself")
+
+    my_relationship = (
+        await db.exec(
+            select(Relationship).where(
+                Relationship.user_id == current_user.id,
+                Relationship.target_id == user_id,
+            )
+        )
+    ).first()
+
+    target_relationship = (
+        await db.exec(
+            select(Relationship).where(
+                Relationship.user_id == user_id,
+                Relationship.target_id == current_user.id,
+            )
+        )
+    ).first()
+
+    is_followed = bool(
+        target_relationship and target_relationship.type == RelationshipType.FOLLOW
+    )
+    is_following = bool(
+        my_relationship and my_relationship.type == RelationshipType.FOLLOW
+    )
+
+    return CheckResponse(
+        is_followed=is_followed,
+        is_following=is_following,
+        mutual=is_followed and is_following,
+    )