DESIGN_DOC.md

High-Level Design & Implementation Plan

Functional Requirements

1. Creating an Account

• Description: Users can create an account by providing a unique username and password. The password is hashed before transmission to ensure security.
• Implementation:
  • Client: The src/client/pages/signup_page.py file handles the UI for account creation and sends the request to the server.
  • Server: The src/server/api.py file processes the account creation request, checks for username availability, and stores the hashed password in the database (chat_app.db).
  • Database: The src/server/db_manager.py file manages user data storage and retrieval.

2. Logging In to an Account

• Description: Users can log in using their username and password. The server verifies the credentials and returns the number of unread messages.
• Implementation:
  • Client: The src/client/pages/login_page.py file handles the login UI and sends the credentials to the server.
  • Server: The src/server/api.py file verifies the credentials and retrieves the number of unread messages from the database.
  • Database: The src/server/db_manager.py file handles credential verification and message count retrieval.

3. Listing Accounts

• Description: Users can list all accounts or filter them using a wildcard pattern. The system supports scrolling pagination for large lists.
• Implementation:
  • Client: The src/client/pages/users_page.py file handles the UI for listing accounts and sends the filter request to the server.
  • Server: The src/server/api.py file processes the request and retrieves the list of accounts from the database.
  • Database: The src/server/db_manager.py file handles the query and pagination logic.

4. Sending a Message

• Description: Users can send messages to other users. If the recipient is offline, the message is stored until they log in. Messages will deliver immediately if the recipient is logged in and will dynamically update if two users are chatting at the same time. In order to update a user's home page with new messages, they can simply click any button to refresh, including the Home button.
• Implementation:
  • Client: The src/client/pages/chat_page.py file handles the UI for composing and sending messages.
  • Server: The src/server/api.py file processes the message and checks the recipient's status. If the recipient is offline, the message is stored in the database.
  • Database: The src/server/db_manager.py file manages message storage and retrieval.

5. Reading Messages

• Description: Users can read their messages. The system allows users to specify the number of messages that are "delivered" as unread messages to the user's home page at once to avoid overwhelming the client. Once users open a chat, those messages are "read", and the new, unread messages (up to the limit specified) will display if the user navigates back to the home page and requests to see their messages again. The messages will populate the user's inbox in order of oldest unreads (up to the limit specified) because we assume that users want to see the answers to whatever prior conversation they had. To prevent the client from being overwhelmed if there are a lot of messages, we allow the client to receive the number of new unread messages they see at once.

• Implementation:

  • Client: The chat_page.py and settings_page.py files handles the UI for displaying messages and allowing users to specify the number of unread messages to display at once.
  • Server: The api.py file processes the request and retrieves the specified number of messages from the database.
  • Database: The db_manager.py file handles message retrieval and marking messages as read.

6. Deleting Messages

• Description: Users can delete individual messages or a set of messages. Deleted messages are removed from both the client and server.
• Implementation:
  • Client: The chat_page.py file handles the UI for deleting messages.
  • Server: The api.py file processes the deletion request and removes the messages from the database.
  • Database: The db_manager.py file handles message deletion.

7. Deleting an Account

• Description: Users can delete their accounts. For accounts with unread messages, the system notifies the user before deletion. If a user tries to message a user with a deleted account, they'll see an error page and be unable to send messages.
• Implementation:
  • Client: The settings_page.py file handles the UI for account deletion.
  • Server: The api.py file processes the deletion request and removes the account and associated messages from the database.
  • Database: The db_manager.py file handles account and message deletion.

Wire Protocols

Custom Protocol: Designed for efficiency, our protocol minimizes the size of the data transmitted over the network. It uses binary encoding for messages and it's optimized for low latency and high throughput.

JSON Protocol: This protocol uses JSON for message serialization. It's easier to debug and human-readable, development and testing.

Initial UI Design Diagram