comms DBMS

SessionId Class Structure and Workflow

The SessionId class manages user sessions with database support using MariaDB/MySQL through the mysql2/promise library in Node.js. This class allows you to create, update, and delete sessions, manage user lists, and store session-specific settings in the database.

Table of Contents

1. Overview
2. Constructor Properties and Methods
3. Database Operations
4. Class Diagram (Mermaid)
5. Usage and Execution Flow

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1. Overview

The SessionId class is designed to handle user session information, including:

• Session Code: Unique identifier for each session.
• Username List: Stores users within the session.
• Settings: Configurable settings for each session.
• Admin: The primary user with control over the session settings.

The class ensures that session data is persistent in the database and can be modified by users (admin) or other instances of the session.

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2. Constructor Properties and Methods

Constructor

The constructor initializes essential properties and connects to the database:

• sessionCode: A unique code for identifying the session.
• usernameList: An array storing usernames of active participants.
• settings: Stores settings specific to each session (e.g., preferences).
• admin: The primary user of the session with admin rights.

constructor(sessionCode, user) { ... }

Key Properties

• sessionCode: Unique session code (passed during initialization).
• usernameList: List of usernames in the session.
• settings: Private settings object with session-specific configurations.
• admin: Initially set to null, updated when an admin is assigned.

Main Methods

• initDb(): Connects to the database and checks for an existing session.
• checkAndCreateSession(): Checks if a session exists, else creates a new one.
• createSession(): Inserts a new session into the database.
• joinSession(username): Adds a username to the session.
• leaveSession(username): Removes a username from the session.
• updateDb(): Updates session details in the database.
• deleteSession(): Deletes the session from the database.

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3. Database Operations

Each method handling session management involves querying the database to ensure data persistence:

Database Methods:

1. initDb():

   • Establishes a database connection using mysql2/promise.

2. checkAndCreateSession(user):

   • Executes a SELECT query to check for an existing session.
   • Loads session data if found; else, calls createSession().

3. createSession(user):

   • Creates a unique session ID and inserts a new session record into the sessions table.

4. updateDb():

   • Updates usernames, admin, and settings in the database for the current session.

5. deleteSession():

   • Deletes the session row from the sessions table based on the session_id.

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4. Class Diagram

Here’s a visual overview of the SessionId class structure and its methods using Mermaid for easier visualization.

classDiagram
    class SessionId {
        - String sessionCode
        - Array usernameList
        - Object settings
        - String admin
        - Object connection
        + constructor(sessionCode, user)
        + async initDb()
        + async checkAndCreateSession(user)
        + async createSession(user)
        + generateSessionId() String
        + joinSession(username)
        + leaveSession(username)
        + async updateDb()
        + async deleteSession()
        + getSettings() Object
        + updateSettings(newSettings)
    }
    
    SessionId : + initDb() void
    SessionId : + checkAndCreateSession(user) void
    SessionId : + createSession(user) void
    SessionId : + generateSessionId() String
    SessionId : + joinSession(username) void
    SessionId : + leaveSession(username) void
    SessionId : + updateDb() void
    SessionId : + deleteSession() void

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5. Usage and Execution Flow

Usage Example

Here’s an example of creating a new session and managing settings:

const SessionId = require('./SessionId');
const session = new SessionId('12345ABC', 'adminUser');
 
// Add a new user to the session
session.joinSession('newUser');
 
// Update session settings
session.updateSettings({ theme: 'dark' });
 
// Delete session
session.deleteSession();

Execution Flow

1. Instance Creation: new SessionId('code', 'user') initializes a session with a session code and user.
2. Database Initialization: initDb() is called to set up the database connection.
3. Session Check: checkAndCreateSession(user) verifies if a session exists or creates a new one.
4. Session Modifications: Methods like joinSession(username) and leaveSession(username) manage user lists, while updateSettings(newSettings) modifies session settings.
5. Database Update: updateDb() ensures all changes are saved.
6. Session Deletion: deleteSession() removes the session from the database, cleaning up data.

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This documentation explains the structure, methods, and execution of the SessionId class and provides insight into each method’s role in managing session data effectively.q

erDiagram
    USER {
        string _id
        string username
        string profile_picture_url
    }

    SESSION {
        string _id
        string code
        Map session_settings
    }

    USER_SESSION {
        string _id
        string user_id
        string session_id
        boolean is_admin
    }

    MESSAGE {
        string _id
        string user_id
        string session_id
        string content
        string file_url
        Date timestamp
        string message_type
    }

    USER ||--o{ USER_SESSION : "has"
    SESSION ||--o{ USER_SESSION : "contains"
    USER ||--o{ MESSAGE : "sends"
    SESSION ||--o{ MESSAGE : "contains"

flowchart TD
    A[Start] --> B[User accesses StartSession component];
    B --> C{User submits form};
    C --> D{Is username provided?};
    D -- No --> E[Generate random username];
    D -- Yes --> F{Is session code provided?};
    F -- No --> G[Generate random session code];
    F -- Yes --> H{Is session code valid?};
    H -- No --> I[Animate input shake];
    H -- Yes --> J{Does user exist in cookies?};
    J -- Yes --> K[Join session with existing user];
    J -- No --> L[Create new user];
    L --> M[Join session with new user];
    M --> N[Store user and session data in cookies];
    K --> N;
    N --> P[Move to chat page];
    P --> Q[Retrieve chat for session ID];
    Q --> R{Is userId in session?};
    R -- Yes --> S[Retrieve chat history based on settings];
    R -- No --> T[Notify user: No chat history available];
    S --> U[Display chat history];
    U --> V{User sends a message?};
    V -- Yes --> W[Encrypt message];
    W --> X[Send message];
    X --> Y[Broadcast message to users];
    Y --> Z[Store message in database];
    V -- No --> AA{User exits?};
    AA -- Yes --> AB[Confirm user exit];
    AB --> AC[Delete userId from session];
    AC --> AD{Are all users gone?};
    AD -- Yes --> AE[Session will be deleted in 30 minutes];
    AD -- No --> O[End];
    AE --> O[End];