Update API.md

Author: stepbystepcode

API.md

@@ -1,5 +1,6 @@
 # API Documentation
 ## User Management
+
 ```POST /api/signup```
 
 Register a new user account.
@@ -8,7 +9,7 @@ Register a new user account.
 
 username: Username string
 password: Password string
-other user info fields
+
 - Response:
 
 201: User created successfully
@@ -22,11 +23,26 @@ Login with username and password.
 
 username: Username string
 password: Password string
+
 - Response:
 
 200: Login succeeded
 401: Invalid credentials
-Chat
+
+```POST /api/avatar```
+
+Set user avatar.
+
+- Request Body:
+
+avatar: Avatar ID int
+
+- Response:
+
+200: Login succeeded
+401: Invalid credentials
+
+## Chat
 
 ```POST /api/chat```
 
@@ -35,61 +51,88 @@ Send a chat message.
 - Request Body:
 
 content: Chat message content
-userId: Sender user ID
-roomId: Chat room ID
+receiver: receiver username string
+
 - Response:
 
 200: Message sent
 404: User or chat room not found
-Friend Management
-POST /api/nfmgr
+
+```POST /api/check```
+
+Send a chat message.
+
+- Response:
+
+200: Message sent
+404: User or chat room not found
+
+## Friend Management
+
+```POST /api/nfmgr```
+
 Manage friend requests.
 
 - Request Body:
 
-action: add to send request, accept to accept request
-userId: Recipient user ID
+info: add string
+username: Recipient username
+
 - Response:
 
 200: Request success
 404: User not found
-GET /api/newfriends
+
+```GET /api/newfriends```
+
 Get list of pending friend requests.
 
 - Response:
+
 200: Array of friend request objects
 401: Unauthorized
+
 User Info
-GET /api/info
+
+```GET /api/info```
+
 Get user profile information.
 
 - Request Header:
 
 Authorization: JWT token
+
 - Response:
 
 200: User info object
 401: Invalid token
+
 File Management
-POST /api/file/save
+
+```POST /api/file/save```
+
 Save a file.
 
 - Request Body:
 
 file: File data
 path: File path
 filename: Filename
+
 - Response:
 
 201: File saved
 500: Error saving file
-GET /api/file/get
+
+```GET /api/file/get```
+
 Get a file.
 
 - Request Parameter:
 
 filePath: Path of file on server
+
 Response:
 
 200: File data
-404: File not found
+404: File not found