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Add Online Chat solution

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Donne Martin 2017-03-03 18:54:08 -08:00
parent ae9832c6b7
commit 616710f42e
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solutions/object_oriented_design/online_chat/__init__.py Normal file
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solutions/object_oriented_design/online_chat/online_chat.ipynb Normal file
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{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-primer)."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Design an online chat"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Constraints and assumptions\n",
"\n",
"* Assume we'll focus on the following workflows:\n",
" * Text conversations only\n",
" * Users\n",
" * Add a user\n",
" * Remove a user\n",
" * Update a user\n",
" * Add to a user's friends list\n",
" * Add friend request\n",
" * Approve friend request\n",
" * Reject friend request\n",
" * Remove from a user's friends list\n",
" * Create a group chat\n",
" * Invite friends to a group chat\n",
" * Post a message to a group chat\n",
" * Private 1-1 chat\n",
" * Invite a friend to a private chat\n",
" * Post a meesage to a private chat\n",
"* No need to worry about scaling initially"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Solution"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Overwriting online_chat.py\n"
]
}
],
"source": [
"%%writefile online_chat.py\n",
"from abc import ABCMeta\n",
"\n",
"\n",
"class UserService(object):\n",
"\n",
" __metaclass__ = Singleton\n",
"\n",
" def __init__(self):\n",
" self.users_by_id = {} # key: user id, value: User\n",
"\n",
" def add_user(self, user_id, name, pass_hash): # ...\n",
" def remove_user(self, user_id): # ...\n",
" def add_friend_request(self, from_user_id, to_user_id): # ...\n",
" def approve_friend_request(self, from_user_id, to_user_id): # ...\n",
" def reject_friend_request(self, from_user_id, to_user_id): # ...\n",
"\n",
"\n",
"class User(object):\n",
"\n",
" def __init__(self, user_id, name, pass_hash):\n",
" self.user_id = user_id\n",
" self.name = name\n",
" self.pass_hash = pass_hash\n",
" self.friends_by_id = {} # key: friend id, value: User\n",
" self.friend_ids_to_private_chats = {} # key: friend id, value: private chats\n",
" self.group_chats_by_id = {} # key: chat id, value: GroupChat\n",
" self.received_friend_requests_by_friend_id = {} # key: friend id, value: AddRequest\n",
" self.sent_friend_requests_by_friend_id = {} # key: friend id, value: AddRequest\n",
"\n",
" def message_user(self, friend_id, message): # ...\n",
" def message_group(self, group_id, message): # ...\n",
" def send_friend_request(self, friend_id): # ...\n",
" def receive_friend_request(self, friend_id): # ...\n",
" def approve_friend_request(self, friend_id): # ...\n",
" def reject_friend_request(self, friend_id): # ...\n",
"\n",
"\n",
"class Chat(metaclass=ABCMeta):\n",
"\n",
" def __init__(self, chat_id):\n",
" self.chat_id = chat_id\n",
" self.users = []\n",
" self.messages = []\n",
"\n",
"\n",
"class PrivateChat(Chat):\n",
"\n",
" def __init__(self, first_user, second_user):\n",
" super(PrivateChat, self).__init__()\n",
" self.users.append(first_user)\n",
" self.users.append(second_user)\n",
"\n",
"\n",
"class GroupChat(Chat):\n",
"\n",
" def add_user(self, user): # ...\n",
" def remove_user(self, user): # ... \n",
"\n",
"\n",
"class Message(object):\n",
"\n",
" def __init__(self, message_id, message, timestamp):\n",
" self.message_id = message_id\n",
" self.message = message\n",
" self.timestamp = timestamp\n",
"\n",
"\n",
"class AddRequest(object):\n",
"\n",
" def __init__(self, from_user_id, to_user_id, request_status, timestamp):\n",
" self.from_user_id = from_user_id\n",
" self.to_user_id = to_user_id\n",
" self.request_status = request_status\n",
" self.timestamp = timestamp\n",
"\n",
"\n",
"class RequestStatus(Enum):\n",
"\n",
" UNREAD = 0\n",
" READ = 1\n",
" ACCEPTED = 2\n",
" REJECTED = 3\n",
"\n",
"\n",
"class Singleton(type):\n",
"\n",
" _instances = {}\n",
" def __call__(cls, *args, **kwargs):\n",
" if cls not in cls._instances:\n",
" cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)\n",
" return cls._instances[cls]"
]
}
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solutions/object_oriented_design/online_chat/online_chat.py Normal file
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from abc import ABCMeta
class UserService(object):
__metaclass__ = Singleton
def __init__(self):
self.users_by_id = {} # key: user id, value: User
def add_user(self, user_id, name, pass_hash): # ...
def remove_user(self, user_id): # ...
def add_friend_request(self, from_user_id, to_user_id): # ...
def approve_friend_request(self, from_user_id, to_user_id): # ...
def reject_friend_request(self, from_user_id, to_user_id): # ...
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 = {} # key: friend id, value: User
self.friend_ids_to_private_chats = {} # key: friend id, value: private chats
self.group_chats_by_id = {} # key: chat id, value: GroupChat
self.received_friend_requests_by_friend_id = {} # key: friend id, value: AddRequest
self.sent_friend_requests_by_friend_id = {} # key: friend id, value: AddRequest
def message_user(self, friend_id, message): # ...
def message_group(self, group_id, message): # ...
def send_friend_request(self, friend_id): # ...
def receive_friend_request(self, friend_id): # ...
def approve_friend_request(self, friend_id): # ...
def reject_friend_request(self, friend_id): # ...
class Chat(metaclass=ABCMeta):
def __init__(self, chat_id):
self.users = []
self.chat_id = chat_id
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): # ...
def remove_user(self, user): # ...
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
class RequestStatus(Enum):
UNREAD = 0
READ = 1
ACCEPTED = 2
REJECTED = 3
class Singleton(type):
_instances = {}
def __call__(cls, *args, **kwargs):
if cls not in cls._instances:
cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
return cls._instances[cls]