这份 notebook 由 Donne Martin 准备。Source 和 license info 在 GitHub。

设计 Online Chat

Constraints & assumptions

只聚焦以下 workflows：
- Text conversations only
- 用户：
  - Add / Remove / Update user
  - Add friend request → approve / reject
  - Remove friend
- Group chat：create / invite / post message
- Private 1-1 chat：invite / post message
暂时不考虑 scaling

Solution

设计目标是把用户关系、聊天房间、消息拆清楚，便于扩展到 group / private chat。

核心对象

UserService：用户管理、好友请求处理
User：包含 friend list、private chats、group chats
Chat（abstract）：chat_id + users + messages
PrivateChat：1-1 chat
GroupChat：多人 chat，可 add/remove users
Message：消息体 + timestamp
AddRequest：好友请求 + status
RequestStatus：UNREAD / READ / ACCEPTED / REJECTED

主要流程

Add user：写入 users_by_id
Friend request：创建 AddRequest，写入 sender/receiver 的 request map
Approve：把双方加入 friend list，并创建/绑定 private chat
Group chat：创建 GroupChat，邀请朋友加入，发消息追加到 messages list

Class 设计（示例）

class UserService(object):
    def __init__(self):
        self.users_by_id = {}

    def add_user(self, user_id, name, pass_hash):
        pass

    def add_friend_request(self, from_user_id, to_user_id):
        pass

    def approve_friend_request(self, from_user_id, to_user_id):
        pass

class User(object):
    def __init__(self, user_id, name, pass_hash):
        self.user_id = user_id
        self.name = name
        self.pass_hash = pass_hash
        self.friends_by_id = {}
        self.friend_ids_to_private_chats = {}
        self.group_chats_by_id = {}
        self.received_friend_requests_by_friend_id = {}
        self.sent_friend_requests_by_friend_id = {}

    def message_user(self, friend_id, message):
        pass

    def message_group(self, group_id, message):
        pass

class Chat(metaclass=ABCMeta):
    def __init__(self, chat_id):
        self.chat_id = chat_id
        self.users = []
        self.messages = []

class PrivateChat(Chat):
    def __init__(self, first_user, second_user):
        super(PrivateChat, self).__init__()
        self.users.append(first_user)
        self.users.append(second_user)

class GroupChat(Chat):
    def add_user(self, user):
        pass

    def remove_user(self, user):
        pass

class Message(object):
    def __init__(self, message_id, message, timestamp):
        self.message_id = message_id
        self.message = message
        self.timestamp = timestamp

class AddRequest(object):
    def __init__(self, from_user_id, to_user_id, request_status, timestamp):
        self.from_user_id = from_user_id
        self.to_user_id = to_user_id
        self.request_status = request_status
        self.timestamp = timestamp

可以扩展的点

Message delivery：ack / retry / offline queue
Presence：online/offline 状态
Typing indicator：临时状态更新
Search：message search + indexing
Moderation：content filtering

参考与下载

下载 Python 源码